Fundamentals of Chiropractic

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Chiropractic Technique, Second Edition is the one (cxt that provides a solid foundation in both joint examination and hands-on chiropractic adjusancnI­ and S(:rves as an ongoing clinical rc:ferc:n~ as well! Call1-800-!>4S-2S22. VISit www.elseviefheotth..com·Visit

~~~ Mosby

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CONP-fRKJB UTORS

Gerard W. Clum, DC President, Life Chiropractic College West Hayward, California

Joel Alcantara, BsC, DC Research director, International Chiropractic Pediatric Association Media, Pennsylvania Private practice San Jose, California

Robert Cooperstein, MA, DC DirectoT of technique and research, Palmer College of Chiropractic West San Jose, California

Claudia A. Anrig, DC Private practice Fresno, California Postgraduate faculty, Life Chiropractic College West Hayward, California Postgraduate faculty, Life Chiropractic College Marietta, Georgia Postgraduate faculty, Cleveland Chiropractic College Kansas City, Missouri Los Angeles, California Postgraduate faculty, Parlier Chiropractic College Dallas, Texas Postgraduate faculty, Northwestern Health Sciences University Bloomington, Minnesota

Patrick Coughlin, PhD Professor, Department of Anatomy Coordinator, Distance and Distributed Learning Systems Philadelphia College of Osteopathic Meclicine Philadelphia, Pennsylvania

Alan Dumoff. JD. MSW Attorney-at-law, private practice President, LifeTree Consulting Rockville, Maryland Leonard Jobn B'aye, DC, FCCSS (Canada) Honorary affiliated Postgraduate faculty, Clevelaod Chiropractic College, Kansas City, Missouri and Los A{lgeles, California Private practice,

Los Angeles, California

Geoffrey Bove, DC. PhD Assistant professor, Beth Israel Deaconess Medical Center and Harvard Medical School, Department of Anesthesia and Critical Care Boston, Massachusetts

David P. Gilkey. DC, PhD, DACBO.

DACBOH, FICC

Assistant professor and director of

undergraduate education, The Department

of Environmental and Radiological Health Sciences Colorado State University Fort Collins, Colorado

Carol Claus, l\1A, DC, FICPA Chair, Chiropractic Sciences Department, Cleveland Chiropractic College Los Angeles, California Ashley Cleveland, MA, DC Associate dean and associate professor, Cleveland Chiropractic College Kansas City, Missouri

Gary Guebert, DC, DABCR Associate professor of radiology, Logan Coltege of Chiropractic Maryland Heights, Missouri

Carl S. Cleveland Ill, DC President, Cleveland Chiropractic College Kansas City, Missouri Los Angeles, California

v

vi

Contribu tors

Warren Hammer, DC, MS, nABCO Postgraduate faculty, National University of Health Sciences Postgraduate faculty, Northwestern Health Sciences University Postgraduate faculty, Cleveland Chiropractic College, Kansas City, Missouri and Los Angeles, California Private Practice Norwalk, Connecticut Jennifer Jamison, MBBCh, PhD. EdD Professor of diagnostic sciences, Department of Complementary Medicine, RMIT University, Melbourne, Australia Lisa Zaynab Killinger, DC Assistant professor of research and diagnosis, Palmer College of Chiropractic Davenport, Iowa William J. LaurettL DC Private practice Bethesda, Maryland Craig Liebenson, DC Private practice Postgraduate faculty, Sout11ern California University of Health Sciences Postgraduate faculty, Murdoch University Postgraduate faculty, Anglo-European College of Chiropractic Los Angeles, California Charles S. Masarsky, DC Private practice Vienna, Virginia Co-director, Neurological Fitness Postgraduate faculty, Cleveland Chiropractic College Kansas City, Missouri and Los Angeles, California Jerome F. McAndrews, DC Board of directors, NCMIC Insurance Company National spokesperson, American Chiropractic Association Past president, Palmer College of Chiropractic Claremore, Oklahoma

William Meeker, DC, MPH Vice president for research, Palmer Chiropractic University Foundation Director, Palmer Center for Chiropractic Research National Advisory CowlCil, National Institutes of Health, National Center for Complementary and Alternative Medicine Davenport, Iowa Joseph Morley. DC. PhD, PO Cert (Oxford) Youngstown, Ohio Marino Passero, DC Senior vice president, NCMIC Insurance Company New Canaan, Connecticut Stephen M. Perle. MS, DC Associate professor of clinical sciences, College of Chiropractic Adjunct professor of mechanical engineering, School of Engineering, University of Bridgeport Bridgeport, Connecticut Reed Phillips, DC, PhD P(esident, Southern California University of Health Sciences Whittier, CaJifornia Gregory Plaugher, DC Director of research, Life Chiropractic College West Director of research, Gonstead Clinical Studies Society Hayward, Calfornia Daniel Redwood, DC Private practice Vi(ginia Beach, Virginia Anthony L. Rosner, PhD, LL.D. (Honorary) Director of research and education, Foundation for Chiropractic Education and Research Brookline, Massachusetts

Contributors

John G. Scaringe. DC, DACBSP Dean of Clinical Education, Chief of StaJf, Southern California University of Health Sciences Whittier, California

Howard Vernon DC. FCCS. PhD (candidate) Director, Center for Studies of the Cervical Spine, Canadian Memorial Chiropractic College Toronto, Ontario, Canada

Clayton Skaggs, DC Research associate, Logan College of Chiropractic Adjunct faculty, Washington University School of Medicine Private practice St. Louis, Missouri

Glenda C. Wiese. MA Special collections librarian and archivist, David D. Palmer Health Sciences Library, Palmer College of Chiropractic Davenport, Iowa

Louis Sportelli. DC President, NCMIC Insurance Company Former chairman of the board, American Chiropractic Association Palmerton, Pennsylvania Rand Swenson. DC, MD. PhD Associate professor of medicine, neurology and anatomy. Dartmouth Medical School Hanover, New Hampshire Marion Todres-Masarsky. DC Private practice Co-director, Neurological Fitness Vienna, Virginia

vii

Johu C. Willis. MA. DC Editor, Chiropractic History, The Archives and Journal of the Association for the History of Chiropractic Private practice Richlands, Virginia Terry Yochum, DC, DACBR. FICC, Fellow. ACCR Director, Rocky Mountain Chiropractic Radiological Center Denver, Colorado Adjunct professor of radiology, Southern California University of Health Sciences Los Angeles, California Instructor, skeletal radiology. University of Colorado School of Medicine Denver, Colorado

BOUT THE AUTHORS

CARL S. CLEVELAND III Carl S. Cleveland III is president of the Cleveland Chiropractic College with campuses in Kansas City and Los Angeles. He has served as president of both the Association of Chiropractic Colleges (ACC) and the Council on Chiro­ practic Education. Dr. Cleveland has been the National Spokesperson for the Alliance for Chiro­ practic Progress of the American Chiropractic Association (ACA), International Chiropractors Association (lOA), and ACC, and has served as chair of the Philosophy Council of the California Chiropractic Association. He presently chairs tlle Unity Committee of the National Chiropractic Leadership Forum and is a board member of the Association for the History of Chiropractic, the Chiropractic Centennial Foundation, and the New Zealand College of Chiropractic. Dr. Cleveland has taught in the classroom for over 3 decades and is internation­ ally known as a chiropractic lecturer, author, and educator. He is a fourth-generation doctor of chiropractic.

DANIEL REDWOOD Daniel Redwood serves on the editorial board of the Journal of the A'I1terican Chiropractic Association and is associate editor of The Journal qf Altentative and Complementary Medicine. He has lectured on chiropractic at the National Institutes of Health and at the Medical College of Virginia. He has been widely published in both professional and lay publications. Churchill Livingstone published his text, Contemporary

Chimpractic, in 1997.

A 1979 graduate of Palmer College of Chiro­

practic, where he was student council president,

Dr. Redwood is a former vice president and leg­ islative committee chair for the chiropractic state association in the District of Columbia. He has a private practice in Virginia Beach, Virginia.

viii

FORE\VORID

Fundamentals of Chiropractic is a high-quality textbook that we strongly recommend to chiro­ practors, chiropractic students, and educators, as well as members of other health care profes­ sions. It fills a need in chiropractic education for a comprehensive, entry-level textbook designed to introduce readers to the key principles and practices of the profession. We have great respect for this text-its conception, its contributors, and its editors. Dr. Daniel Redwood is a skiUed organizer, author, and editor with outstanding dedication to his chosen profession. Through recent contri­ butions to a variety of scholarly and general readership publications, he has emerged as one of the foremost writers on chiropractic and inte­ grative health care, effectively translating and interpreting chiropractic to members of other health care professions and to tbe general pub­ lic. Among chiropractors in full-time private practice, he is arguably the most prolific writer in the profession. Dr. Carl Cleveland III is a fourth-generation chiropractor and a third-generation chiropractic college president, serving in this role for the Cleveland Chiropractic College with campuses in Kansas City and Los Angeles. In a profession with a broad diversity of opinion, Dr. Cleveland has always served as a unifying Jorce and is highly respected across the chiropractic spec­ tmm. Aside from his leadership at Cleveland College, his tireless efforts on behalf of the pro­ fession have included extensive work for national and state chiropractic associations, countless spealting engagements, and the authorship of numerous journal articles and book chapters. He has served as president of both the Association of Chiropractic Colleges and the Council on Chiropractic Education and has taught in the classroom for over 3 decades, playing a central role in the remarkable educational advances of the past generation. The combined breadth of skills and experience represented by Drs. Redwood and Cleveland has resulted in an exceptional textbook that intra-

duces the reader to the fundamentals of the sci­ ence, philosophy, and art of chiropractic. Terms are carefully defined in the text and in the exten­ sive glossary. Concepts are explained, enabling first- and second-year students to grasp them readily. Facts on anatomy and physiology, palpa­ tion and technique, patient care, research, safety, legal and ethical issues, and much more are pre­ sented in a logical progression that is extremely user-friendly Jor both faculty and students. Fundamentals of Chiropractic will become a standard entry-level text for the chiropractic profession. Chiropractic started a century ago as an alter­ native to the medical mainstream with a focus on the relationship of the spine and nervous system to overall function and health. The chi­ ropractic profession is now in the process of becoming mainstream in the early twenty-first century, as the social movement behind popular medicille recognizes health care alternatives in a renewed and positive light. Many of the chap­ ters in this text illustrate the basic and clinical science research that is fundamental to under­ standing the effectiveness of chiropractic proce­ dures. Such research has been a primary driving force behind the recent enhanced interprofes­ sional cooperation between doctors of chiroprac­ tic and medical physicians. It is no coincidence that chiropractic's most Jmpressive strides toward acceptance and inte­ gration have occurred between 1970 and the present-the era of the profession's great leap forward in the quality of its education and research. Starting around 1970, leaders in the profession embarked on an intensive project of educational and professional advancement. Numerous acbievements are the result: the expansion of chiropractic licensure that includes all of North America and many other nations; the governmental recognition of the Council on Chiropractic Education; the development of chi­ ropractic programs in universities in several nations; the inclusion of chiropractic in Medicare; the first conference on spinal manipulation

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x

Foreword

offered by the National Institutes of Health; and the aclmowledgment of spinal manipulation by the Agency for Healtll Care Policy and Research as one of the most effective procedures in the management low back pain. Landmarl{ events since the mid-1990s have included the initiation of an annual national Research Agenda Conference, the Chiropractic Demonstration Grants Program at the U.S. Health Resources and Services Administration, the first research funding of chiropractic institutions by the ational Institutes of Health's National Center for Complementary and Alternative Medicine, inclusion of chiropractic in U.S. Department of Defense and Veterans Administration health care, and the demonstration project under which chi­ ropractic students are eligible for student Loan reimbursement through the National Health Services Corps program for graduates committing to practice in underserved areas of the United States. The remarkable achievements of tllis era continue today. As it is for all professions, ever-increasing qual­ ity of its educational institutions is crucial to the further development of chiropractic. Both in the colleges and in the profession at large, a height­ ened understaIldiI~and appreciation of tlle scien­ tific process and endorsement of evidence-based practice must be encouraged, with doctors at all stages of their careers committed to changing and updating their practices when newty emerging evi­ dence clearly calls for such changes. Aside from its value as a teaching tool in chiropractic colleges worldWide, one of the most important uses of Fundamentals of Chiropractic will be as a source of informed guidance-a software update as it were-for practicing chiropractors. A new health care paradigm is on the horizon that can include the core concepts of chiroprac~ tic-the link between structure and function, the effectiveness of manual adjustment/manipu­ lation, and the cnlcial mediating role of the nervous system. This new perspective may allow consideration of various nonallopathic methods as part of a more inclusive and expansive model of health care that accommodates rather than subsumes these alternatives. Chiropractic is on the cusp of this significant transition in tbe new millennium.

For example, tbe high cost of medical liability insurance has reached a crisis point in many places. Low back pain is the most common cause of disability in American workers. Those practitioners performing surgery on the spine carry liability insurance that, in some cases, costs hundreds of thousands of dollars per year, requiring hundreds of such procedures to be per­ fonned annually simply to offset the cost of this insurance. Public policy discussion has focused on how we pay for health care rather than how it is practiced. The high costs and risks of health care, however, reSide not only in providing new drugs, technologies, and procedures through sci­ entific innovation, but also in the management of tlle known and accepted side effects of these powerful protocols. Although health care technology has advanced, renewed interest in methods once known as alternative or complementary has led to increas­ ing research, establishing their safety and effec­ tiveness. Along these lines, it is useful to arrange various practices according to their degree of invasiveness, because this characteristic is strongly associated with both risks and costs. From least invasive to most invasive, these prac­ tices would be meditation, talk therapies, hands­ on healing, massage, adjustment/manipulation, insertion, ingestion, injection, and surgery (see Appendix II). To illustrate how the level of invasiveness applies in the real world, consider the aforemen­ tioned case of back surgery where inherent risks have led to the unacceptably high cost of insur­ ance. It is possible that inappropriate proce­ dures may be perfonned simply to enable the practitioner to offer the service, or such proce­ dures may be ultimately priced out of the mar­ ket. By comparison, proven alternatives for the treatment of back pain are available at lower cost with lower risk. For example, spinal adjust.­ ment/manipulation prOVided by chiropractors and certain other profeSSionals is effective at reducing pain and restoring function in many people with low back pain. In addition, liabil­ ity insurance for chiropractors in the United States averages only $1500 annually. Pro­ cedures that work effectively at lower risk and with lower cost are not complementary or

Foreword

alternative; rather, they are simply good health care that make good public policy. William Meeker, DC, MPH Vice President of Research at Palmer College of Chiropractic Principal Investigator at the Consortia! Center for Chiropractic Research

Marc Micozzi,MD, PhD Director of the Policy Institute for Integrative Medicine ThomasJefferson University Hospital Editor, Medical Guides to Complementary & Altl.m1ahve Medicine Editor of the quarterly review journal, Seminars in Integrative Medicine

PREFACE

Fundamentals 0/ Chiropractic meets a long­ standing need in chiropractic education for a wide-ranging, introductory textbook con­ stmcted in a format fully accessible to first- and second-year students; one that presents the fun­ damental paradigm of chiropractic with its bis­ tory, its principles and practices, and its science and research; and one with an overview of tbe most significant contemporary issues in the professi 0 n. Fundamentals of Chiropractic is designed to serve as an effective core textbook that intro­ duces the beginning chiropractic student or interested health science practitioner to the cen­ tral elements of chiropractic practice and its emerging role as part of tbe mainstream health delivery system. Faculty will find multiple appli­ cations for Fundamentals of Chiropractic as a required text for class instruction in the intro­ ductory chiropractic principles and practices, all effective resource for national and state exami­ nation review, and a valuable compendium for introducing other healtb care practitioners to the concepts of chiropractic. In this era of accelerating change, grounding a book in its historical context is essential. The opening section of Fundamentals o/Chiropractic, "History, Philosophy, and Sociology," has three chapters that trace the origins and development of chiropractic. In "Forerunners of the Chiropractic Adjustment," John WilliS, editor of the journal Chiropractic History, surveys and examines fonus of manual manipulation before Daniel David Palmer's discovery of chiropractic. This chapter is followed by "The Chiropractic Paradigm," a unique collaboration by Ashley Cleveland, associ­ ate dean of instmction for Cleveland Chiropractic College, Kansas City campus, the profession's fust fifth-generation chiropractor, and two chiropractic college presidents, Reed Phillips of Southern California University of Health Sciences and Gerard Clum of Life Cbiropractic College West. These authors, representing diverse perspectives, have jointly crafted an introduction to the science, art, and philosophy of chiropractic that will be

of value to all who wish to understand chiro­ practic. In the third chapter in this section, "Major Themes in Chiropractic History," Glenda Wiese, special collections librarian and archivist at the David D. Palmer Health Sciences Library and co-autbor of Chiropractic: An Illustrated History, describes the profession's landmarl< his­ torical events and the individuals and groups that helped shape them. The "Anatomy, Biomechanics, and Physiology" section is made up of six chapters that provide students with the means to begin the daunting task of understanding the basic functions of the human body, with special emphasis on chiro­ practic applications. Although a general text such as this cannot replace the great classics such as Grays Anatomy or Gu),ton's Physiology, it does provide a focused and well-contextualized introduction for entry-level students, a concen­ trated review for national board examinations in these fundanlental subjects, and a useful "back to basics" resource for the practicing doctor of chiropractic. The "Spinal Anatomy" and "Spinal Neurology" chapters written by Patrick Coughlin, professor of anatomy at the Philadelphia College of Osteopathic Medicine, offer a clear, well-organ­ ized presentation of this core chiropractic mate­ rial with helpful explanations of its clinical relevance. Space did not allow us to include detailed information on spine-related muscula­ ture and fascial anatomy. For these topics, we refer readers to the many available standard texts. Joseph Morley's chapter "Basic Biomechanics" expands on the foundations presented in the anatomy and neurology chapters, introdUCing the basic temlS and concepts of this central element of the chiropractor's specialty. Carl Cleveland's chap­ ter, "Vertebral Subluxation" follows and describes the development of this essential chiropractic con­ struct through the profession's history, up to and including contemporary models of the vertebral subluxation complex. Clevelmld's "Neurobiologic RelatiOlJS and Chiropractic Applications" offers a wide-ranging presentation of the chiropractic

xii

Preface

theories and research that are opening new vis­ tas of understanding and possibilities for inter­ disciplinary study at the dawn of the twenty-first century. The final chapter in this section, Geoffrey Bove and Rand Swenson's "Nociceptors, Pain, and Chiropractic," provides a detailed intro­ duction to the neurophysiology of pain, with par­ ticular emphflsis on the International Association for the Study of Pain definitions and nociceptive and neuroint1ammatory processes. Dr. Rove is assistant professor in anesthesia and critical care at Harvard Medical School, and Dr. Swenson is associate professor of anatomy and medicine (neurology) at Dartmouth Medical School. 1\\'0 chapters make up the "Spinal Analysis and Diagnostic Procedures" section. In "Palpation: The Art of .Manual Assessment," John Scaringe, dean of clinical education and chief of staff at the Southern California University of Health Sciences, and Leonard John Faye, who serves on the post­ graduate faculty at Cleveland Chiropractic College, describe the manual examination pro­ cedures central to chiropractic practice. Particular emphasis is given to the role of palpation in eval­ uating the mechanics of spinal and extraspinal joints. In "Introduction to Diagnostic Imaging," chiropractic radiologists Gary Guebert, assistant professor of radiology at Logan College of Chiropractic, and Terry Yochum, director of the Rocky Mountain Chiropractic Radiological Center, and instructor in skeletal radiology at University of Colorado School of Medicine, Sur­ vey the uses of the various imaging techniques commonly in use today. We believe it is impor­ tant to note that the chiropractor's diagnostic process involves more than palpation and diag­ nostic imaging. Orthopedic and neurologic test­ ing and laboratory procedures are essential components of chiropractic training and prac­ tice. For discussions on these topics, we refer the reader to the many available standard texts. "Chiropractic Care" is the largest section in Fundamentals oj Ghiropmctic with 10 chapters whose primary goal is to offer the reader a solid introduction to the key areas of focus in the typ­ ical chiropractic practice. John Scaringe, serving as co-author with innovative technique author and instructor Robert Cooperstein, director of

xiii

technique and research at Palmer College of Chiropractic West, begin this section with a dis­ cussion on the cornerstones of chirorractic the manual adjustment and related hands-on proce­ dures. "Manual Soft Tissue Procedures" follows, in wblch Warren Hammer, who serves on the postgraduate faculties of the National University of Health SCiences, Northwestern Health Sciences University, and Cleveland Chiropractic College, proVides both the rationale for soft tis­ sue work and a well-guided tour through many of the most Widely used contemporary methods. Next, in "Reactivation and Rehabilitation," Craig Liebenson, who serves on the Murdoch University, Anglo-European College of Chiro­ practic, and Southern California University of Health Sciences postgraduate faculties, and Clayton Skaggs, an adjunct faculty member at the Washington University School of Medicine and Southern California University of Health SCiences, describe contemporary methods of reha­ bilitation through which patients become active participants in their own recovery. The care of children and older adults has been part of chiropractic practice sillce the profes­ sion's inception. The "Pediatrics" chapter by Joel Alcantara, Gregory Plaugher, and Claudia Anrig describes the biornechanical features unique to the pediatric spine. This chapter pro­ vides the rationale and foundation for their dis­ cussion of pediatric adjusting. Alcantara is research director of tbe International Chiropractic Pediatric Association, Plaug.her serves as director of Research at Life Chiropractic College West, and Anrig is on the postgraduate faculties of the follOWing chiropractic colleges: Life, Life West, Cleveland, Parker, and Northwestern. This chap­ ter is followed by "Caring for the Aging Patient" by Lisa Zaynab IGllinger, assistant professor of diagnosis at Palmer College of Chiropractic, which addresses the special needs of older patients. Her chapter emphasizes the appropri­ ate choice of case management methods and counseling on age-related changes. Killinger and Carol Claus, associate professor and chair of the Los Angeles campus of the Chiropractic Sciences department at the Cleveland Chiro­ practic College, collaborated on "Adjusting the Aging Patient," which describes the ways

.xiv

Preface

chiropractors can adapt adjustive tecbniques to accommodate the degenerative and osteoporotic changes that are more common with increased age, in the interest of enhanced patient comfort and safety. "Occupational Health," by David Gilkey, a past president of the American Chiropractic Association's Council on Occupational Health, a.nd currently assistant professor and director of undergraduate education, The Department of Environmental and Radiological Health Sciences, Colorado State University, offers a thorough discussion of occupational health. This chapter demonstrates that the traditional chiro­ practic emphasis on the treatment of work­ related injuries has been expanded to include prevention, ergonomic analysis, and inter­ disciplinary case management. In "Sports Chiropractic," Stephen Perle, associate profes­ sor of clinical sciences at the University of Dridgeport-College of Chiropractic, discusses the important roles chiropractors play in helping athletes to perfoml safely and to recover from injuries. In "Wellness: A Lifestyle," Jennifer Jamison, professor of diagnostic sciences at RMIT University in Australia and author of Maintaining Health in Primary Care, explains the crucial roles of diet, exercise, and stress man­ agement in chiropractic practice. Louis Sportelli, president of the National Chiropractic Mutual Insurance Company, fanner chairperson of tbe board of the American Chiropractic Association, and author of introduction to Chiropractic, demonstrates in "A Patient's Introduction to Chiropractic" that explaining chiropractic prin­ ciples and practices to patients and potential patients is a crucial skill for students to master. ThiS chapter offers the reader a basic outline for introducing the patient to chiropractic's role in health care and to the importance of proper spinal he31th. Because research is a linchpin of professional growtb and development, we have devoted four extensive chapters to this topic, providing up-to­ date summaries of the relevant literature, along with interpretations of its significance. For the entry-level student, a solid, step-by-step intro­ duction to the terminology and to the purposes and types of research is an absolute necessity.

"Research Essentials" by Daniel Redwood and William Meeker, vice president for Research of the Palmer Chiropractic University and direc­ tor of research at the Palmer Center for Chiropractic Research, offers this introduction. "Musculoskeletal Disorders Research" by Anthony Rosner, director of research and education for the Foundation for Chiropractic Education and Research, demonstrates the dramatic progress in chiropractic research over the past genera­ tion. Howard Vernon's chapter on headaches fol­ lows, which thoroughly discusses research on headaches, as well as providing a valuable intro­ duction to differential diagnosis and case man­ agement options. Chiropractic research on visceral conditions is currently at an earlier stage of development than research on muscu­ loskeletal disorders, but as Charles Masarsky and Marion Todres-Masarsky, postgraduate fac­ ulty members at Cleveland Chiropractic College and authors of Somatovisceral Aspects of Chiropractic: An E'Vidence-Based Approach, discuss in "Somatovisceral Research," a promis­ ing basis exists for what may prove a fertile area for chiropractic research in the coming years. The closing section, "Contemporary Issues in Chiropractic Practice," is intended to stimulate thought and discussion. William Laurettj's "The Comparative Safety of Chiropractic," is a solidly documented summary of critical safety issues by one of the profession's leading authorities on thiS subject, with special emphasis on cerebrovas­ cular accidents. Lametti's key original contri­ bution is his comparison between chiropractic neck adjustments and the most common medical treatment for neck pain-the use of nonsteroidal antiintlammatory drugs. Lauretti powerfully demonstrates the relative safety of chiropractic while offering cautionary instruction on how to minimize the likelihood of negative reactions to chiropractic care. Attorney Alan Dumoff's "Chiropractic and the Law" discusses the essen­ tials of legal matters, including licensure, scope of practice, insurance reimbursement, and mal­ practice, as well as the landmark case of Wilk 'Ll. AMA. J.F. McAndrews, a past president of Palmer College who has also held leadership positions for both the American Chiropractic Association alld the International Chiropractors Association,

Preface

has been one of the chiropractic profession's lead­ ing spokespersons for decades. In "Appropriate Care, Ethics, and Practice GUidelines," McAndrews contends that although the profession has made great strides toward maturity, subsmntial improve­ ment is still required in two pivotal areas: (1) respect for reasonable, objectively based prac­ tice gUidelines and (2) the development of a pro­ fession-wide ethic of financial fairness. "M'11laged Care" by Marino Passero of NCMIC Insurance Company and Daniel Redwood addresses issues central to delivery of care and reimbursement for services. Daniel Redwood's closing chapter, "Pathways for an Evolving Profession," begins with the question, "How can chiropractors and chiro­ practic students help the profession evolve so that it more fully reOects our noblest aspira­ tions?" Redwood offers 10 touchstones to guide the process, including distinguishing clearly among the proven, the probable, and the specu­ lative; promoting a heaUng partnership with

xv

patients; recognizing that the doctor must strive to model the healthy lifestyle choices he or she recommends; cultivating all attitude of tol­ erance and openmindedness; minimizing patient dependency; and serving those who cannot afford our services. Each chapter begins with a list of key terms to help readers focus on its essentiaJ points. All key terms are defined in the glossary at the back of the book. At the close of each chapter review and concept questions are proVided. We are aware that readers outside the United States will have to contend with parts of a few chapters (particularly those relating to legal mat­ ters and managed care) in which the focus is on issues specific to chiropractic in the United States. However, the vast majority of the text should be directly relevant to students and prac­ titioners from all nations. Daniel Redwood, DC CuI S. Cleveland III, DC

------

ACKNOWLEDGMENTS

I dedicate my role in the development of this text to the three generations of chiropractic family members who have stood before me. I aclmowl­ edge my great grandmother, Sylva L. Ashworth, DC, a 19.10 Palmer graduate, who became the first woman to practice chiropractic in the state of Nebrasl
I wish to thank my parents, Nonnrm and Jewel, for sharing my passion for chiropractic and other health-affirming endeavors; my wife, Beth, for her loving encouragement, thoughtfulness, and com­ panionship on our journey through life; my chil­ dren, Reuben and Jessica, for following their dreams as I have tried to follow mine; Marc Micozzi, for years of friendship and collaboration and his pioneering role in bridging the gap between alternative and mainstream health care; William Meeker, for his patience, good humor, and dedication to chiropractic research; Dana Lawrence, for his level-headed editorial judgment and prompt and remarkably helpful responses to my questions; and the late Jing­ Nuao Wu, for always encouraging me to look more deeply and to focus on what matters most. Thanks as well to Ron Hendrickson, Mac McClelland, J.F. McAndrews, Joseph Keating, Christopher Kent, and Claire Cassidy.

-DR

-csc Drs. Redwood and Cleveland both wish to thank all the chapter authors for their e..,,<:pertise and hard work and to gratefully acknowledge Keltic White, Christie Hart, and Julie Eddy, of Mosby and its parent company Elsevier, for their enthusiastic support of this textbook.

x~i

TS

PART ONE

PART THREE

HITSTORY, PJflllLOSOPH'Y;

SPiNAL ANALYSJ[S AJ\'D D1AGNOSTiC

AND SOCIOLOG ,1

PROCEDURES, 209

1 Forerunners of the Chiropractic Adjustment, J JOlLV WfLMS,

10 Palpation: The Art of Manual

DC

2 The Chiropractic Paradigm,

Assessment, 211 lS

JOHN

MA, DC

DC, PuD

DC

ASHLEY Cl,EVE[.AJ'YV, REED P1Jll-MPS, GEflAJW CUlM,

1 JL

DC

Introduction to Diagnostic Imaging, 237

;) Major Themes in Chiropractic History, 29 CaNDA WIESE,

G. SCARlNGE, DC, DACBSP

LEONARD JOHN FAYE,

GARY M. GUE8ERT, TERRY

R.

YOCHUM,

DC, DACBR DC, DACBR, FACCR

MA

PART FOUR PART TWO

CBITROJPRACTITC CARE, 255

A~AT01\IY,

12 Chiropractic Manual Procedures,

JIHOlo/lECHA.'\lHCS, Ai JD PHYSIOLOGY, 43

JOHN

ROBERT COOPERSTEIN,

WARREN HA.\f,WER, DC, DABCa

PATRICK COUGHLIN, PHD

PilTRlCK COUGHLIN,

14 Reactivation and Rehabilitation. 311

91

CRAfG LfEBeNsoN,

PHD

CLAYTON SKAGGS,

6 Basic Biomechanics, 117 JOSEPH MORLEY,

S.

DC

A. ANRJo, DC

GREGORY hAUGHEN., DC

JOEL, ALCANTAJ/i\,

CLJlUl>lA

Ill, DC

CLEVELAND

8 Neurobiologic Relations and

16 Caring for Aging Patients, 365

Chiropractic Applications, 155 CARL

S.

LISA ZAYJVAB

Ill, DC

Cf,EVELJlND

LISA ZAYNAB KiUINGER,

Chiropractic, 187

CAROL Cf."WS,

DC, PHD DC, MD, PHD

GWFFREY.V!. BOVE,

S.

SWENSON,

KiUINGER,

DC

lL 7 Adjusting the Aging Patient,

9 Nociceptors, Pain, and RAND

DC

DC

JL5 Pediatrics, 349

DC, PIlD

7 Vertebral Subluxation. 129 C,iRL

DC

13 Manual Soft TIssue Procedures. 293

~ Spinal Anatomy. 45

5 Spinal Neurology,

257

G. SCARlNGE, DC, DACBSP

DC

18 Occupational Health, DAVID

P.

GIL,KEY,

xvii

389

DC, PHD, DACBO, DACBOH

19 Sports Chiropractic. STEPHEN M.

381

DC

409 PeRLE, MS, DC, CCSP

Contents

20 WelIness: A Lifestyle, 423 JEN!'.7FER JAMISON,

MB BCH, PND, EdD, FACNEM.

:2 Jl A Patient's Introduction to DC

581

ALAN DUMOFF, JD, MSW

28 Appropriate Care, Ethics, and Practice Guidelines,

Chiropractic, 437 LOUTS SPORTEU,T,

27 Chiropractic and the Law,

J.F.

603

McANDREWS,

DC

29 Managed Care, 613 MARINO PASSERO, DC

PART FIVE

DANIEL REDWOOD,

RESEARCH, 447

DC

30 Pathways for an Evolving

22 Research Essentials. 449

Profession, 623 DANIEL REmH iQD,

DC

DANIEL REDWOOD, DC WILLIAM

C. MEEKER, DC, MPH

23 Musculoskeletal Disorders Research, 465

Appendix I: Statistical Methods for Determining Reliability, 629 John G. Scaringe, DC, DAGBSP

A'\'THOl\'Y L. ROSl.lER, PHD

24

Headaches, 497 HOlVARD VERNON,

DC, FeCS

Appendix II: Relative Physical Invasiveness of Selected Techniques, 631

25 Somatovisceral Research. 531 CHARLES

S.

MASARSKY, DC

M,\RlON TODRES-MASARSKY,

DC

Appendix III: The ACC Chiropractic Paradigm,6JJ Glossary, 637

PART SIX

CONTEMPORARY iSSUES IN CHIIROPRi\CTllC PRACTXCE, 559 26 Comparative Safety of Chiropractic, 561 WIU.lA.\1

J.

LAURETTf,

DC

PART ONE

HKSTOR~

PHKLOSO PH~

A D SOCIOLOGY

CHAPTER

"

1

Forerunners of the Chiropractic Adjustment John Willis, DC

Key Tenns

_

ADJUSTMENT

HIPPOCRATES

MAGNETIC HEALING

ANDREW TAYLOR PALMER

HUMORS

MANIPULATION

AYURVEDfC MEDICINE

LAYING ON OF HANDS

MASSAGE

BONESE1T1NG

LESION

Nel

BROAD OSTEOPATHS

LESION Osn:OPATHS

OSTEOPATHY

D.O.

LUMBAGO

PALMER

A

lthough its origins are lost deep in history, the practice of manipulation is close to being universal, 1 because "to massage and manip­ ulate an aching, muscle and limb"2 is a natural tendency. Only a small step separates adding pressure from rubbing an aching joint, especially when a popping noise and some degree of relief is often the reward. The first episodes of spinal manipulation certainly occurred well before tbe first known recordings of its use. What had been performed and orally passed on for unlmown years was eventually written' down. Sociologist Walter I. Wardwell, a pre-eminent observer of chiropractic, warns about the prob­ lems of language when studying the forerunners of the chiropractic adjustment. 3 Although D.D. Palmer and chiropractors termed chiropractic manipulation the adjustment and gave it a rela­ tivdy precise meaning, manipulation itself is a generic term. At various times, manipulation may refer to the reduction of a fracture, mas­ sage, mobilization, and other related activities. Unlike the chiropractic adjustment, manipula­ tion is not limited to the spine. Ancient and modern documents frequently fail to specify the type of manipulation to which they refer. Wardwell provides an excellent categorization system for the study of prechiropractic spinal manipulation:

JING

The pre-Palmer literature on spinal manipulation can be put in several categories. First would he manipula­ tive practices of ancient ciVilizations-Chinese, Japanese, Indian, Egyptian, Greek, Roman, and oth­ ers. Second would be the often similar practices of primitive peoples. Third would be the bonesetters and similar folk practitioners in Western societies, some of whom practiced well into the present century. ~'Ollrth, mention will be made of the orthodox medical litera­ ture on "spinal irritation" which appeared in the nine­ teenth century, Finally there is osteopathy, which beg1ln pre-Palmer lind is unquestionably similar to chiropractic though not identical in theory or tech­ nique. As is well known, both Palmers took great pains to differentiate chiropractic from it. J

MANIPULATIVE PRACTICES OF ANCIENT CIVILIZATIONS Joint manipulation seems to have always been II part of Chinese medicine. 4 From the beginning it was linked to massage; only rather recently was joint manipulation separated as a distinct disci­ pline. As in other geographic areas, its use was based on the results of empirical findings. It was perpetuated from generation to generation through the heritage and teachings of its disci­ ples; consequently, early records of its use are fragmentary.

3

4

PART ONE

HISTORY, PHlLOSOI'HY, AND SocrOLOGY

The first bool, pertaining to manipulation was briefly mentioned in the Nei Jing (The Yellow Emperor's Classi.c afMedicine) about three cen­ turies Be; unfortunately, the book was lost. Early practitioners of the manipulative arts performed massage, reduced dislocations and fractures, and manipulated joints for traumatic injuries, such as those seen in war. However, from a chiroprac­ tic perspective, it is interesting that from the outset, Chinese manipulative arts were used to treat some internal disorders. The first known description of manipulation is recorded in the writings of Pien Chiao in about the fifth century Be. In his writings, he recommended manipula­ tion for fatigue, rheumatism, nervous disorders, insomnia, lumbago, and for some forms of paral­ ysis. As with most fonns of the healing arts, manipulation had its periods of exaltation, as dUring the Tang dynasty, and periods during which it was held in low esteem. Especially dur­ ing periods of high use, it was used not only curatively but also as an aid in preventing dis­ ease. However, most of its use may have been soft tissue worl, or massage. The :Mongol conquest strongly influenced Chinese manipulation. The wandering, warlike Mongols developed sl,ills necessitated by their active way of life, including the ubiqUitous horseback riding involved in their far-ranging wars. HO',vever, as with any forerunner, tech­ niques used by the ancient (and even relatively recent) Chinese practitioners would seem cum­ bersome or even harsh to the current chiroprac­ tor. For example, one technique for tort.icollis used one hand to steady the head while the other held the chin, thereby extending the neck in a gross maneuver4 (Fig. 1-1). D.D. Palmer waS aware of Chinese medicine. He recorded an incident involVing a Chinese "houseboy" suffering from cholera. He stated that the Chinese healer "was prodding him [the hOllseboy] under the tongue with a long needle,"s and he also recorded haVing seen a physiologic chart used in Chinese medicine. Nevertheless, no definitive evidence suggests that the Chinese influenced Palmer's adjusting. Other Eastern medical traditions, including those of India, also contained forms of spinal manipulation. However, manipulation of joints

Fig. 1-1 Lumbar manipulation during the use of graVity traction as practiced in ancient China. (From The Golden Mirror ofMedicine.)

was usually performed by bath attendants, because it was considered a part of hygiene, not a medical procedure. 6 In fairness, it should be noted that preventive measures such as hygiene, diet, and proper liVing are of great importance in Ayurvedic (Indian) medicine, not simply periph­ eral items as observed during periods of recent history. Although most modem chiropractors, osteo­ pathic practitioners, and medical manipulators are proud to trace their lineage to Hippocrates (fifth century), the techniques he used bear little resemblance to modern methods. A minority opinion advanced by K.A. Ligeros, MD, PhD, claims that Hippocrates and Greek physicians of Hippocrates' day actually performed manipula­ tion of the spine in a manner similar to that per­ formed by chiropractors today.6 Ligeros appears to extrapolate the facts of Hippocrates' knowledge

CHAPTER 1

Forerunners of tbe Chiropractic Adjustment

of the spine and nervous system, as well as his recorded use of manipulation, to a point in which similarities to modern chiropractic manipulation seem inevitable. Ligeros states that the methods rediscovered and known as chiropractic were also known and practiced by Aesculapius and his followers 420 years before the Christian era. A famous votive relief depict­ ing Aesculapius manipulating a person's upper thoracic spine serves as part of Ligeros' proof. 7 However, little further evidence supports the view of a proto-chiropractic discipline during that era. Most historians might agree with Elizabeth Lomax who states, "Only further scholarly research could establish whether the Greeks merely attempted to reposition vertebrae

5

displaced through trauma, the conventional interpretation, or indeed frequently manipulated spines as therapy for a wide variety of dysfunc­ tions."8 It is still interesting to note that D.D. Palmer referred to Aesculapius and his teachings as a foundation for what he termed chiropractic 5 (Fig. 1-2). The Persian physician and philosopher Avicenna (AD 980-1037), lmown as Ibn Sina, aJso used and wrote of manipulation. His work was, for all practical purposes, a rewrite of Galen's that, in turn, was descended from that of Hippocrates. 9 Pierre Gaucher-Peslherbe wrote, "Well into the seventeenth century and regardless of whether they were Greek, Roman, Byzantine, Cretan,

A

B

s

e

Fig. 1-2 A, Typical spinal manipulation from classical Greek period into the seventeenth century. B. Votive relief depicting Aesculapius manipulating an individual's upper thoracic spine. (A courtesy Biblioteca Universitaria, i'\archiginnas, Bologna. Italy. B courtesy Palmer College of Chiropractic, Ubrmy Special Collections.)

6

PART OXE

HISTORY. PHILOSOPHY, AND SOCIOLOGY

Arabic, Spanish, Turkish, Italian, French, or German, all published authors resorted to the same method. The patient was bandaged illId lay on a board; traction was applied toward the head and feet while pressure was exerted onto a selected spinal area."6 The pressure or thrust was delivered by using the practitioner's hands, feet, or even buttocks by simply sitting on the patient's spine. Occasionally, a piece of wood might have also been used as a lever. Forms of manipulation practiced among prim­ itive peoples were similar to these practiced in ancient civilizations, but they were often accom­ panied by more extensive religious ritual or magic. The interconnection of religion illId heal­ ing was always present. In reference to manipu­ lation, Gaucher-Peslherbe quotes the noted anthropologist, Mircea Eliade, "... throughout history bones and joints have been invested with a symbolic and mystical significance."lO Chester Wilk in his book Chimpractic Speaks Out recounts Captain Cook's story of how the techniques of "pummeling and squeeZing" used by Tahitian women relieved his crippling rheumatism. l1 The ancient custom of children and small adults walking on an individual's back has been documented in many areas of the world, including North and South America, Polynesia, Asia, and Bohemia, where it was known as a "peasant practice."12 The use of manipulation has also been documented in the Americas. From the records of the early Spanish Friars of the sixteenth century, chiropractor and anthropologist C.w. Weiant relates that Aztecs distinguished between what they called a "tme doctor" and a "false doctor" or witch doctor. One of the qualifications for true doctors was their knowledge of how the joints worked properly. 1:3 North American Indians predating the Jamestown settlement (1607) used forms of manipulation as a part of daily life. Stories of their appreciation of spinal manipulation have become so commonplace that they have crept into popular literature. In a novel on Lewis and Clark's early nineteenth century expedition, James Alexander Thom relates how Clark kept the Nez Perce busy for most of a day "adjusting" their spines, anachronistically using Palmer's

word for spinal manipulation, which would not come into common usage until after another century had passed. 14 In South America, Ronald L. Firestone cites evidence of extensive use of manipulation in pre­ Columbian culture (Firestone R, e-mail commu­ nication to author, 11/19/01). "One of the best indicators of such would be the prevalence of this method in the current practices of the Quechua and Aymara traditional practitioners." Firestone shows great respect for these practi­ tioners, known as Callahullas or Yatiri (Fig. 1-3). Describing the work of these practitioners from an innovative perspective, he suggests, "1 actu­ ally think that we in chiropractic should begin referring to those who practice, or have prac­ ticed, in thiS manner as traditional chiropractors since medicine refers to its empirical practition­ ers as traditional medicine."

BONESETTING The earliest l
CHAPT8R 1

Forenmoers of the Chiropractic Adjustment

7

Fig. 1-3 The Callahullas, or Yatiri, of South Amedca. (Courtesy Ronald Firestone, D.C.)

deformities should be rest and induced local ulceration. Not all historians agree with Lomax as to the reason manipulation fell from grace; they only agree that it did. Johan Schultes, who died in 1645, was the last published author to teach spinal manipulation as a part of regular medi­ cine. 15 Although the discontinuation of manipu­ lation by medical physicians took place over a period of more than 100 years, no evidence of its usc after the end of the seventeenth century can be found. Johannes Fossgreen suggests another cause may have been fear of contagious con­ taet. 15 This argument is supported by evidence from physicians in the seventeenth and eigh­ teenth centuries, distancing themselves from their patients in the wake of such contagious dis­ eases as the highly virulent form of syphilis brought back to Europe from the Americas by the adventurers who had themselves introduced smallpox to the American Indians. In his seminal 1993 work, Chiropractic: Early Concepts in Their Historical Setting, Pierre ~ucher-Peslherbe discusses a more compli­ cated and subtle scenario. 6 To oversimplify Gaucher's work, culture changed. In medicine, the soft tissue and particularly the muscle

became the center of attention, and vertebral dislocations and subluxations were discarded from medical attention. AB a result, massage became a recommended treatment, and manip­ ulation or reduction was condemned because of the supposed progress in therapy. These changes fit the cultural image of the time. Medicine was becoming professionalized. Anything traditional, such as bonesetting, was associated with lay practitioners and thus rejected. A remark~lbly effective process had begun following the surgeons' condemnation of those practices they did not wish to see continued; incidentally, more to mark their newly acquired professional status by set­ ting themselves apart, than because of any real objec­ tion to the practices themselves, which they now dismissed on the grounds that they were unprofes­ sional. 16

The bonesetter or layperson's speech was crit­ icized. Greater importance was placed on how an individual communicated (flowery imagery often became more important than what it rep­ resented). It followed that the plain speech of laypeople was of little value because it laclied eloquence and was therefore unprofes­ sional. Because manipulation was performed by

8

PART ONE

HISTORY, PHILOSOPHY,.AND SOCIOLOGY

nonprofessionals who could not speaJ{ as profes­ sionals spoke, it followed that manipulation could not and should not be a part of the profession of medicine. Anderson and Gaucher-Peslherbe are in agreement that pompous arguments concern­ ing theory are diversionary and explain little of why physicians abandoned manipulation and then castigated the bonesetters \\'ho filled the void they had left.)6 Essentially, bonesetters based their practices on pragmatism. What was deemed to work was used. Attempts to explain the reasons procedures worked were often inadequate and, by statldards of that society, considered unprofessional. Largely because of this failure to articulate theories in a manner acceptable to the medical profession, boneset­ ter procedures were rejected. One is reminded of C.S. Lewis' discussion of scientists' depiction of the atom. He describes how the scientists' belief of a mathematical formula is given in such a manner that the layperson can create a mental picture. The mental picture is meant to be helpful; however, if it ceases to be helpful, it should be dropped, not confused with what it symbolizes. 17 Apparently, the flowery language of individuals such as Pouteau, with its love of imagery and metaphor, was carried so far that critical sense was sometimes lost.1 6 ThiS was the language that the lay manipulators could not duplicate. When medical physicians abandoned manipu­ lation in the seventeenth century, it became identified with the humble oral traditions of the uneducated ordinary people. IS As members of the ruling class, traditional physicians had no desire to emulate the common folk, even when manipulation showed success. The physicians and other members of the ruling class "... ded­ icated themselves to their whole body of custom as symbolic of discreteness from other classes of society. They took pride in being different, and by definition of different, superior."18 Excellent examples of this phenomenon can be found in the stories of matlY bonesetters of medieval France. When their successes becatne well­ known, t11ey were often summoned to serve the French Court. Once ensconced inside the soci­ ety of the day, these bonesetters had opportuni­

ties to advance academic studies and solidify bonesetting into a profession. Instead, they moved quicldy to separate t11emselves from their common past and dedicated themselves to becoming part of the elite. In so doing, they abandoned bonesetting, and many became " 'hereditary [passed from parent to child by virtue of birth] physicians' whose families 110ur­ ished in France until the seventeenth century and who touched for dog bites and other mishaps.,,(j A number of well-known bonesetters prac­ ticed in Great Britain and the United States. They seemed to arise in their communities when the need arose. Although most perfonned other jobs for their livelihood (as did many early chi­ ropractors), some were full-time practitioners. Among the more fatnous was Sir Herbert Barker (d.1950), a British bonesetter knighted for help­ ing humanity I9 (Fig. 1-4). Although the son of a solicitor, Barker learned bonesetting through a tutorship under his cousin. He reportedly refined and developed his techniques to a higher

Fig. 1-4 The British bonesetter Sir Herbert Barker. (Courtesy David D. Palmer Health Sciences Library, Palmer College of Chiropractic, Davenport, Iowa.)

CHAPTER 1 Forerunners of the ChiropnlCtic Adjustment

standard, eventually coining the term "manipula­ tive surgery" as an accurate description of his work. He often invited physicians to witness his work, but few accepted his offers. After a mal­ practice case that Barker suspected was "tnunped­ up" by physicians, the bonesetter's reputation and practice grew, although he lost the case. As an old man, he was invited by the British Orthopaedic Association to demonstrate his tec11l1iques. Although Barker believed the demonstration capped his career with a crowning victory, it had little or no effect on the medical profession during the years that followed (Fig. 1-5). The history of bonesetting as observed in Barker's case is important to the history of fore­ runners of the chiropractic adjustment, not only from the aspect of manipulative technique but also (and possibly more significantly) in the man­ ner in which it "demonstrates the obvious depth of feeling by organized m.edicine against health practitioners outside the medical establishment on grounds which are, in principle, understand­ able. "20 The Barker episode was used by the 1979 New Zealand government commission's report on chiropractic to help explain the attitude of New Zealand's organized medicine toward chiroprac­ tic. The commission believed that many clear par­ allels existed between Barll,er's episode and

9

chiropractic, including the lack of fonnal medical qualifications and Barker's inability to explain his methods. The commission went on to point out that the latter problem should not be considered as only an elitist way of separating the profes­ sional from the nonprofessional. Accepting Barker's unexplained method, even had he been a qualified medical practitioner, would have placed the medical profession in a difficult position were it to be faced with "the claims of anyone else who might say that he had discovered a miracle cure by using a technique that could not adequately be explained: The typical equipment of the quack."20 In other words, there was no doubt that prejudice eXisted, but there was also no doubt that bOlleset­ tees, as many other healers before and after them, must be able to explain tllemselves. However, the stigma of bOllesetting's associa­ tion with the humble and uneducated could not be overcome even when physicians such as Dr. Edward Harrison used its techniques, Although well educated and articulate, he could not over­ come the emotional resistance of the medical profession. His reputation among them was at best tenuous. One anonymous colleague would not go so far as to call Harrison a charlatan but would say that what he was doing was certainly well adapted to charlatanism. s

Fig. 1-5 A bonesetter practicing near Cedar Rapids, Iowa, at the tum of the twentieth century. (From Smith OG, Langworthy SM, Paxson MC: Modernized chiropractic, Cedar Rapids, Iowa, 1906, American School of Chiropractic.)

10

PART ONE

HISTORY, PHILOSOPHY. AND SOCIOLOGY

Some of the more famous names among American bonesetters are Reese, Sweet, Tiesten, and Orton. As bonesetting with its lack of forma] education and credentialing began to fade, entire families adopted the professions. The Sweets

Fig. 1-6 An example of magnetic healing. (From Weltmer SA.. Revised illustrated mail course of instruction in magnetic healing, 19U1, self-published.)

became orthopedists, whereas the Tiestens and Orton8 became chiropractors. 2J • 23 An often-overlooked antecedent of the c1uro­ practic adjustment is magnetic healing, the form of healing that D.O. Palmer practiced for 9 years before founding the chiropractic profession (Fig. 1-6). Andrew Taylor Still, the founder of osteopathy, also was a magnetic healer in and around 1875 (Fig. 1-7). The hands-on tech· nique of magnetic healing often involved vigor· ous rubbing and probably manipulation of various kinds. J Wardwell was intrigued when learning that often the practitioners of magnet­ ism, faith healing, and mental healing did more than simply the laying 00 of hands. Gevitz describes how Andrew Jackson Davis, a leading nineteenth century exponent of spiritualism, and Warren Felt Evans emphasized "vigorous rubbing along the spinal coluOln."24 Homola adds: The Mormon leader, Joseph Smith, Jr., practiced faith healing employing the use of bonesetting. One of his elders advertised to "set bones through faith in Christ" stating that "while commanding the bones, they came together, making a noise like the crushing of an old bas­ ket." Only (he joints of the spine can be made (0 give out with such sounds as the "crushing of an old basket."

Fig. 1-7 Andrew Taylor Still with his friend Elbert Hubbard, an author who was also a friend of B.J. Palmer. (Courtesy Still Osteopathic Museum and National Center fOT Osteopathic History.)

CHAPTER 1

Forerunners of the Chiroprnctic Adjustment

11

Obviollsly, the laying on of hands In this faith-healing procedure was performed with considerable force. 2

sized physical diagnosis. He emphasized that other methods were necessary.Z5

Gevitz st<1tes that Still was able to synthesize many of the m<1jor aspects of magnetic healing and bonesetting into "one unified doctrine," and the same could be said of Palmer. Far from attempting to hide his background in magnetic healing, Palmer wrote that "quite a portion of that which now constitutes Chiropractic I had col­ lected during the previous nine years" (the years spent practicing magnetic healing).s Again, as noted earlier, a natural tendency to rub an aching joint exists, and from there, it takes only a small step to add the necessary pressure to the joint to move it. Both Still and Palmer took that step.

Th<1t Still's osteopathy, like Palmer's chiroprac­ tic, was not confined to low back pain, stiff necks, and typical musculoskeletal complaints is as much a cause for celebration of their similar­ ities as is the fact that both use manipulation. Neither man intended to simply add the modal­ ity of manipulation to the accepted system. Both meant to establish a new and superior system that dealt with the entire person. It was not a wryneck or the proverbial "hitch-in-your-get­ along" that motivated Still; it was the dysentery and sl?inal meningitis that ravaged his family. Neither Still nor Palmer considered his system as merely manual medicine. Chiropractic and osteopathy have always emphasized their differences. The reasons for this emphasis are varied, ranging from political to personal to economic. Both were evangelistic in their desire to spread the good news of the new professions. An early osteopath from North Carolina quoted a Moravian tenet, Wishing it to be adopted by osteopaths: "Go as a missionary yourself, or take the fruits of your own labor and support someone else in the field of missionary endeavor. "26 When Still "flung to the breeze the banner of osteopathy" in 1889, it was an act against the primitive state of medicine as he saw it, as well as the hubris of the physicians themselves. 27 The same could be said of Palmer. Whether Palmer took from StUt or Still from Palmer or both from each other, the debate has been taken on by many including Brantingham, Gaucher-Peslherbe, and others but to the full sat­ isfaction of few. 28 Both the founders and their pro­ fessions had always significant differences, as well as similarities. Although different terminology was used, both professions initially emphasized the body's inherent ability to maintain health and the use of manipulation as a primary technique. Osteopathy's focus was 011 "the rule of the artery" and the use of nonspecific manipulation to enhance the flow of blood. Gaucher-Peslherbe mal{es the argument of osteopathy's ties with the ancient Greek doctrine of body humors, the pre­ dominant medical philosophy into the nineteenth

OSTEOPATHY Finally, the last of chiropractic's antecedents, osteopathy, is reached in this discussion. Osteopathy's position as a forerunner of chiro­ practic, based on its common use of m<1nipula­ tion, may be a contentious one for the OSleOPllth and, at least at times, an unappreciated one. When this author wrote to a renowned Virginia osteopath, he was firmly told that the osteopaths were complete physicians and that he, for one, performed no manipulation at all. When Still first announced his philosophy a mere 21 years before D.O. Palmer's founding of chiropractic, he did not mention manipulation. It was not until 1879 that Still began using manipulation and stmctural diagnosis in the manner associated with classical osteopathy.25 However, even in his time, Still \vas a complete physician. Siehl explains the founding: Remember, Dr. StilI founded osteopathy to improve upon the present practice of medicine, surgery, and obstetrics. He did not say "no drugs." He merely Slated that the drugs then in vogue were harmful and largely useless. He did not say "no surgery." In fact, the A80 (American School of Osteopathy) Hospital had a surgery suite and relatives of Dr. Still were the early chief surgeons in the ASO Hospital. KirksviUe became quite a surgical center as well as a center for osteopathic manipulative treatment at the turn of the century. Dr. Still did not say to avoid diagnostic pro­ cedures other than palpatory diagnosis. He empha­

12

PART ONE

HISTORY, PHILOSOPHY. AND SOCIOLOGY

century. (In medieval physiology, a humor one of the four elemental tluids of the body-blood, phlegm, black bile and yellow bile-and the flu­ ids' relative proportions determined an individ­ lUll's physical and mental makeup.) Chiropractic, on the other hand, gave emphasis to the specific spinal adjustment, which meant to release energy that traveled through the nervous system, a break from the humoral doctrine. However, caution must be used in these debates because neither profession sprang forth from Oleir respec­ tive shells in full-blown maturity. Both profes­ sions underwent considerable legal trauma, which helped define them. The early inclusion of drugs and surgery into osteopathy also made Ole debates about the differences between the pro­ fessions more obvious. Indeed, Palmer's first the­ ory of manipulation was as much concerned with circulation as it was with the nervous system. Debates between the lesion osteopaths, those most closely adhering to manipulation and Still's early tenets, and the broad osteopaths, those aligned more strongly with drugs and surgery, have also declined with time. The osteopathic lesion, later called somatic dysfunction, is a dis­ turbance of musculoskeletal structure and/or function, which may include accompanying dis­ turbances of other biological mechanisms. Early legal battles that were used to show osteopathy's distinctness from medicine, thereby establishing it as a separate healing art, later turned to battles that were used to show it equal and similar to medicine. Ironically, a 1982 study in Ohio, surveying osteopathic practitioners found that they viewed osteopathic manipulative treatments as the least important of the five main concepts stressed by osteopathy: (1) holistic medicine, (2) doctor­ patient relations, (3) emphasis on general prac­ tice, (4) the body's ability to heal itself, and (5) manipulation. Yet, from the patient's per­ spective, the study showed the more that indi­ viduals favored osteopathic manipulative therapy (OMT), the greater their tendency to rate osteopaths as well qualified, at least as well qual­ ified as medical physicians. 29 The same study showed that most osteopaths surveyed believed that patients receive less OMT in osteopathic hospitals than they need. This comes at a time

when there are no longer any chiropractic hos­ pitals, and the number of osteopathic hospitals (there are approximately 140 in the United States) appears to be waning. However, as Westview Hospital in Indiana is discovering, the reason for this reduction may not be that osteo­ pathic hospitals are too different; rather, it may be because they do not prOVide enough differ­ ence to acquire speciaJ status. 30 Without special status, they are similar to most small hospitals, which cannot absorb the discounts demanded by aggreSSive third party payers and therefore Hnd survival difficult.

CONCLUSION The forerunners of the chiropractic adjustment have been many and varied. Most in 'Vestern culture have managed musculoskeletal prob­ lems such as fractures, sprains, and strains. This is probably true of most cultures. If Ligeros is correct, some ancient Greeks may have prac­ ticed as proto-chiropractors. The evidence is strong that the Chinese also saw merit for manipulative treatment of nonmusculoskeletal illnesses, but it appears that this area was not much more than an aside to the mainstream of manipulation. The Middle Ages in Europe were preoccupied with the straightness of the spine as a sign of virtue and knightly stature, and the treatments proVided, both regular and other­ wise, were primarily aimed toward orthopediC problems. Practices of primitive peoples, though more steeped in religious aspects, still aimed predominately at helping structure, dislocations, and related ailments, such as Captain Cooli's rheumatism. Only osteopathy (or magnetic heal­ ing, if it can be considered a manipulative healing art) has a philosophy of care, which, like chiro­ practic, definitively goes beyond the muscu­ loskeletal system to the management of visceral problems. Both osteopathy and chiropractic aimed at being independent health care systems, not merely adjuncts to regular medicine. In addi­ tion, both, after achieving positions of relative esteem, continue to find themselves still battered by old prejudices and the ubiquitous stmggle for the health-care dollar. Yet, with the revival of pub­ lic demand for spinal manipuJation, osteopaths

CHAPTER 1

Forerunners of thc Chiropractic Adjustment

are enjoying a renaissance in the heritage and application of Dr. Still's favorite modality, a heritage chiropractic has never abandoned.

Review Questions 1. What manual methods may be included under the generic term manipulation? 2. What are some of the health conditions for which joint manipulation was used in ancient China? 3. Who were the "bonesetters;' and how were they trained? 4. What were the relations between British bonesetters and medical physicians in the seventeenth and eighteenth centuries? 5. To what does historian Elizabeth Lomax attribute manipulation's falling out of favor in the eighteenth century? 6. Why did bonesetting fail to move toward full professional status after bonesetters were invited to serve the French Court? 7. To what extent did social class (commoners versus professionals) influence the acceptance or rejection of joint manipulation in Europe? 8. Some of the best-established families

of American bonesetters joined which

two professions when bonesetting

declined?

9. In what ways was magnetic healing similar to chiropractic? In what ways did the two differ? 10. What were the similarities between early osteopathy and chiropractic? What were the differences?

Concept Questions 1. A.T. Still, the founder of osteopathy, was originally a medical physician, whereas D.O. Palmer, the founder of chiropractic, was originally a magnetic healer. In what ways does the evolution of the professions they founded reflect the different backgrounds of the founders? 2. Do you agree or disagree with Ronald

Firestone's suggestion that ancient or

indigenous practitioners of spinal

manipulation should be referred to as

"traditional chiropractors:' Why?

13

REFERENCES 1. Dlntenfass J: Chiropractic: a modem way to health,

New York, 1995, Pyramid Books. 2. Homola S: BUllesetting, chiropractic and cultism, Panama City, Fla, 1963, Critique Books. 3. Wardwell \:1,,1: Before the Palmers: an overview of chi­ ropractic antecedents, Chiropr Hist 7(2):27, 1987. 4. Shu Yan Ng: A brief review of manipulation in Chine e history, Eur J Chiropr 34(1-2):24, 1986. S. Palmer DD: The science, art, and philosophy Qf chi­ ropractic, PortJand, Ore, 191 0, Portland Printi ng ]-louse. 6. Gaucher-Peslherbe PL: Antecedents to chiroprac­ tic: a cultural approach from ancient mytl\s to mod­ em mythologies. In Petersen D, Wiese G, editors: Chiropractic: anillustmted hi,<;tory, St Louis, 1995, Mosby. 7. The ancient art of manipulation depicted in 5th cen· tury votive tablet, Chiropr ffist 7(2):26. 1987. 8. Lomax E: Mflnipulative therapy: an historical appronch. In Burger AA, Thhis JS, editors: Approaches to the 'Validation ofmanipulation thera.p:>\ Springfield, m, 1977, Charles C Thomas. 9. Victory KS: Spinal manipulation in the 11th century Middle East, Chiropr Hist 13(1):12. 1970. 10. Gaucher-Peslherbe PL: Chiropractic: early concepts in their historical setti7¥:!, Lomhard, III, 1993, National College of Chiropractic. 11. Wi.lk CA: Chiropractic speaks out: a reply to med­ ical propaganda, bigotry and ignorance, Park Ridge, JII, 1973, Wilk Publishing. 12. ZlItbuch MV: A profession for "bohemian chiroprac­ tic": Oakley Smith and the evolution of naprapathy, Chiropr Hist 7:77, 1986. 13. Thom JA: Sign-talker: the advencu:re of George Drouillard on the L<.-wis and Clark expedition, New' York, 2000, Ba.llentine Bool\5. 14. Weiant CW: Medicine and chiropractic, Lombard, ill, 1975, National College of Chiropractic. 15. Anderson R'r: On doctors and bonesetters in the 16th and 17th centuries, Chiropr Hist 3(1):12, 1983. 16. Anderson RT: BonesetUng: a medical bone of con­ tention, JAm Chiropr Assoc 15: 5, 1981. 17. Lewis CS: Mere Chri,~tianity, New York, 1975, Simon & Schuster. 18. Anderson RT: Traditional Europe: a Stuely ofanthro· pology and history, Belmont, Calif, 1971, Wadsworth Publishhlg. 19. Taylor HH: Sir Herbert Baker: bone-setter and early advocate of "hJoodless surgery," JAm Chiropr Assoc 32(7):27, 1995. 20. Chiropractic in New Zealand: report of the commi.s­ sian of irn,uiry, Wellington, New Zealand, 1979, PD Hasselberg, Government Printer. 21. Janse J: Principles and practices of chiropractiC, Lombard, Ill, 1976, National College of Cbiropractic. 22. Orton E: A touching story, the Ca1lasrota (South Dakota) clipper, 1985.

14

PART ONE

HISTORY. PHILOSOPHY. AND SOCIOLOGY

23. Master RO Sr: A hiStory of the chiropractic adjust­ ment, Dig Chiropr Econ 3(a):24, 1998. 24. Gevitz N: The DO's osteopathic medic-ine 'in America, Baltimore, 1982, Johns Hopkins University. 25. Siehl 0: The osteopathic differences: is it only manip­ ulation? JAm OsteaputhAssoc 101(10):630, 2001. 26. Meachum ':VB: Destiny of the osteopathic profession, JAm OsteopatltAssoc 101(10):621, 2001. 27. Klafhom \VK, Dodson JL: Osteopathic medicine: a photographic history, Greenwich, Conn, 1995, Greenwich Press.

28. Brantingham J\V: Still and Palmer: the impact of the first osteopath and the first chiropractor, ChinJpr Hist 6:12,1986. 29. Culbertson HM, Stompel GH Ill: A study of the public relations posture of osteopathic medicine in Ohio, Columbus, Ohio, 1982, Ohio Osteopathic Association. 30. Swiatek J: Beyond osteopathy-hospital looks for health-care niche, The Indianapolis Star, Sunda}', 30 September 2001, sec. El.

CHAPTER

The Chiropractic Paradigm

Ashley Cleveland, MA, DC, Reed Phillips, DC, PhD, Gerard Clum, DC

Key Terms,

_

ACliPUNCTURE

DANIEL DAVID PALMER

ADJUSTMENT

DIAGNOSIS

PHYSIOTHERAPY

ALLOPATHIC

HOMEOPATHY

SAM.UEL HAHNEMANN

HYDROTHERAPY

SCOPE OF PRACTICE

AMERICAN CHIROPRACTIC ASSOCIATION ANDREW LWLOR STJ LL

OSTEOPATHY

INNATE INTELLIGENCE

SOMATIC DYSFUNCTION

INTERNATIONAL

STRAIGHT

ANTON MESl\o\ER

CH IROP RACTORS

ASSOCIATION OF

ASSOCIATION

SUBLUXATION Tr-lOMSONlk"liSM

CHIROPRACTIC COLLEGES

INTERVENTIONS

TONE

PARADIGM

). F ALAN

TREATMENT

HOWARD

B.J. PALMER

LESION

VITALISM

BIOPSYCHOSOCIAL

MAGNETIC HEALING

WORLD CHIROPRACTIC

CAN,WIAN CHIROPRACTIC

MANIPULATION

ASSOCIATION CO:"GRESS OF CHIROPRACTIC STATE ASSOCIATIONS

ALLIANCE WORLD FEDERATION OF

MASSAGE MIXER

CHIROPRACTIC

ONE CAUSE-0NE CURE

T

manually applied skills, in one form or another, have been found in an cultures on all continents. What was it that made Palmer's contribution sufficiently noteworthy to form the basis of a profession that, a century later, spans the globe? Similar to his contemporary, Andrew Taylor Still, the founder of osteopatJly, Palmer did not view the spine, or even the full skeleton, as an isolated body part to be tended solely at the site where symptoms arose. Rather, each person articulated a paradigm of human health in which the spine played a centra] role. A.T. Still related the integrity of the spine and skeleton to the proper functioning of the circulatory system and theorized a broad impact on health and well being as a consequence of alterations of that relationship. Palmer, on the other hand, empha­ sized the relationship between the skeleton (especially the spine) and the nervous system and theorized a system-wide interdependence,

he chiropractic profession traces its roots to the American Midwest at end of the nineteenth century. Daniel David Palmer. a man in many ways characteristic of his times, wove together the threads of his era's metaphysical and scientific thought to create a philosophy, science, and art of healing tbat has now entered its second century. Palmer's varied health­ related interesI.;; ranged from what was known in his day as magnetism and 1nngnetic healing to his signature contribution-identifying a funda­ mental relationship between functional skeletal abnormality and the potential for adverse effects on the nervous system. Attention to the human slieleton did not begin with Palmer. As described in Chapter 1, "Forerunners of the Chiropractic Adjustment," throughout history countless people have been acknowledged for their talent in caring for vari­ ous components of the skeletal system. Such

15

16

PART ONE

HISTORY, PHILOSOPHY, AND SOCIOLOGY

in which a person's state of health depends on proper integration between skeletal structures and tlIe function of the nervous system. Perhaps Palmer's greatest contribution was not the deJivery of a spinal adjustment but rather his concentrated focus on the effects of spinal dynamics on nerve function, as well as the development of a body of knowledge and clinical skills to address the clinical manifestations of these effects. Palmer was not the first to discover that the human body is capable of self-regulation and healing, nor was he the first healer to use manual techniques. Palmer was, however, the originator of an approach to healing that incor­ porated specific manual techniques into a para­ digm that accorded supremacy to tlle role of the nervous system (rather than the circulatory sys­ tem) in physiologic regulation and healing.

HEALTH CARE AND PHILOSOPHIC LANDSCAPE IN D.D. PALMER'S ERA To understand how Palmer arrived at his unique synthesis, it is essential to understand the state of late nineteenth century health care in the United States. Allopathic doctors of the time did not yet enjoy the status they now possess and did not have to meet the same rigorous educa­ tional and licensing standards as today. 1Iuch of medical practice emphasized using so-called heroic therapies, such as leeching, cupping, and bleeding. Because the public often perceived these methods as worse than the ailments they sought to cure, Americans were hungry for alter­ native approaches to their health problems. 1 Several more natural healing systems, less invasive than allopathic medicine, gained popu­ larity during the nineteenth century. Among these systems were 2 : 1. Homeopathy, founded by the German physician Samuel Hahnemann, which used as its medicines highly diluted qualltities of various substances, primarily from plant and mineral sources 2. Thomsonianism, a system of healing founded by the American herbalist Samuel Thomson, in which overexposure to cold was considered a central cause of disease

J. Hydrotherapy, which emphasized the internal and external therapeutic uses of water 4. Nature Cure, which used a vegetarian diet, along with light and air 5. Hygienic System, which amalgamated the hydrotherapy and Nature Cure movements 6. Osteopathy, founded by Andrew Taylor Still, which used manual therapy for correcting osseous lesions (referred to as the osteopathic lesion) proposed to exert a negative effect on circulation and thereby on overall health These approaches to healing shared a prefer­ ence for conservative, minimally invasive inter­ ventions that were believed to allow the body to heal itself. (See Appendix II regarding the rel­ ative invasiveness of various health interven­ tions.) Health care practitioners in this era ranged from those trained in formal university settings to villagers who apprenticed under local doctors and at some point were themselves recognized as doctors. Health education and practice­ related legislation were minimal. Many systems of health and healing were freely espoused throughout the United States, each proclaiming its own superiority and the failings of its com­ petitors. Numerous health fads gained adherents and then lost them, only to be supplanted by newer approaches. Gevitz, a historian of osteopathy, outlined a life cycle for these developments, noting that "move­ ments such as osteopathy, homeopatlIy, and eclecticism, generally have a natural life cycle. They are conceived by a crisis in medical care; their youth is marked by a broadening of their ideas; and their decline occurs whenever what­ ever distinctive notions they have as to patient management are allowed to witlIer. At this point, no longer having a compelling reason for exis­ . tence, they die."3 To survive for many genera­ tions, a healing art must provide a unique and valuable service, as allopathic medicine, den­ tistry, chiropractic, and other professions have done. Similarly, its practitioners must not lose sight of its basic purpose: to restore patients when ill and to aid them in their daily quest for health.

CHAPTER 2 The Cltiropractic Paradigm

17

PAL.\tIER'S MAGNETIC HEALING AKD METAPHYSICAL INTERESTS

portive milieu for the pioneers of new healing methods.o

Palmer's interests extended beyond the purely physical aspects of health and healing as he explored the energetics of the body, as well as paranormal phenomena. During the nineteenth century, the American religious landscape included various forms of spiritualist and meta­ physical speculation, and Palmer's curiosity was piqued by these influences. Anton Mesmer's concept of animal magnetism was used by many individual practitioners such as Palmer and adapted by Mary Baker Eddy for use in her Christian Science, although Benjamrn Franklin had dealt the concept a nearly fatal blow in a famous experiment in the royal court of France early in the nineteenth century. In this earty example of a blinded clinical trial, Franklin demonstrated that healing effects occurred when patients believed they were being mesmerized, although no healing effects were noted if pAtients were ignorant of Mesmer's magnetic passes. 'I Mesmer used magnetic healing methods to treat a wide range of disorders, including hysteri­ cal blindness, paralysis, headaches, and joint pains. IIJa,gnetic healing primarily involved "laying on of hands" to transmit healing energy and may also have included vigorous mbbing, manipula­ tion, or both. (See Chapter 1 for greater detail.) In his work with magnetic healing, D.O. Palmer believed that he was able to attain a higher degree of specificity than other magnetics. s During this same era, spiritualism, the belief that consciollsness survives beyond death and that it is possible to contact the spirits of those who have died, also gained in popularity. Mediums purporting to facilitate this contact traveled the country, and seances were held in the parlors of many well-respected members of society. D.O. Palmer was part of the metaphysi­ cal movement of his day, attending spiritualist meetings then common in the Midwest. Other major philosophic influences in that era were the transcendentalist philosophers Henry David Thoreau and Ralph Waldo Emerson, whose love of nature and fierce independence of thought and action resonated with the individualistic spirit of many Americans and prOVided a sup­

D.D. PALMER'S CORE CHIROPRACTIC CONCEPTS Though the individual components of Palmer's chiropractic philosophy did not originate with him, he was able to blend recognized spiritual and metaphysical concepts together with the then-current scientific principles to create a unique ethos for the chiropractic healing art. The relationship between the structure and function of the body formed the essence of chiro­ practic's approach to health care. Chiropractors sought to influence the body's capacity to heal itself through tbe nervous system by applying specific forces to the spine. According to Palmer, function of the nervous system can be altered by a subtle change in position of a vertebral seg­ ment. Once function of the nervous system was altered, the entire organism can become pre­ disposed to incoordination (dis-ease) and, ulti­ mately, disease. Stated in a current conceptual framework, "a structural problem within the spine contributes to diminished neurologic ability to cope with the environment, and the abUity of the body to heal itself is decreased. Palmer believed the cause of most disease is displaced vertebrae; the disease is an effect of that displacement."7 Although few contemporary chiropractors would llOW endorse a one cuuse-ane cure expla­ nation of human health and illness (With sublux­ ation being the cause and adjustment being the cure), the interdependence of structure of the spine and function of the nervous system remains a cornerstone of the philosophy and practice of chiropractic today. D.O. Palmer conceived of nerve function in the context of vibration and tone, common explanations for his time. Disease, he claimed, resulted from fluctuations in nerve tone, "nerves too tense or too slack."s Palmer asserted that either "too much or not enough energy is dis­ ease."8 and that disease, rather than being some­ thing external that invades the body, is instead the result of internal imbalances involving hyperfunction or hypofunction of organs and

18

PART ONE

HISTORY, PHILOSOPHY. AND SOCIOLOGY

systems. From this perspective, the resistance of the host is more significant than the power of the pathogen. Chiropractors are not now, nor were they in Palmer's time, the only health care practitioners to place primary emphasis on strengthening the internal resistive forces of the body. The uniqueness of chiropractic lies in its assertion that the spine prOVides a key to affect­ ing the nervous system, the controlling and coordinating system of the body. Thus according to Palmer, the mechanical process of spinaJ adjustment was employed for vitalistic purposes. Vitalism is an explanatory model that suggests the body requires something greater than physi­ cal and chemical processes to function. In its more extreme forms, this something greater is given theologic significance. 9 Chiropractors have generally looked at the physiologic processes of the body as expressive of intelligence, or a wis­ dom of the body. Some early chiropractors phi­ losophized about the source of that intelligence; however, many chiropractors have been content to acknowledge that the functions of the body are not wholly explicable by mere physical and chemical laws and that the nervous system seems to function largely to express the body's integrative capability. Palmer noted that the physical structure of the body is challenged through the activities of daily liVing and theorized that these challenges, or stressors, take three primary forms, the three Ts-trauma, toxins, and thoughts. Current dis­ cussions of the philosophy of chiropractic con­ tinue to include these three challenges (often expressed as physical, chemical, and emotional) and their adverse intluence on tone or function of the nervous system, as well as in the causation of subluxation and illness.

REINTERPRETING PALMER'S ORIGINAL CONCEPTS Palmer may have crystallized an idea and defined a philosophic context within which to employ it, but he was unable to constrain others, including his son, from modifying and reinter­ preting chiropractic and its clinical application.

Similar to many sons, Bartlett Joshua, or B.J., followed in the footsteps of his father; and simi­ lar to many sons, he did not see eye to eye with his father. A nearly legendary level of disagree­ ment, rivalry, and antagonism arose between the two. These disagreements did not end at the family dinner table but reverberated throughout the chiropractic profession. D.D. envisioned chiropractic as a way to treat the full skeleton and also saw it integrated with matters of thought, trauma, and toxicity. D.D. theorized that the three Ts lead to skeletal man­ ifestations, which continue to compromise the body's capacity for well being. B.J. focused much more specifically on the mechanics of the spine, with correction of vertebral malposition and attendant neural compromise, together known as subluxation, assuming a primary role in help­ ing sick people get well. Although many chiropractors, then and now, have maintained that spinal or vertebral sublux­ ations have more profound effects on health than subluxations of the extremities, B.J. Palmer went further. He simply stopped correct­ ing subluxations beyond the spine, as a matter of both practice and philosophy, declaring such nonspinal subluxations to be of little significance to the chiropractor. Eventually, B.J. asserted that the only area of the spine capable of true subluxation was the upper cervical spine, the occipito-atlanto-axial region. For decades, between the early to mid-1930s and mid-1950s, the Palmer School's technique department taught only upper cervical methods (H.r..t Himes, unpublished notes, 1956). The split between the Palmers was one among many in Ule early years of the profession. In the first decade of the twentieth century, many com­ peting school., of chiropractic were founded, such as the National School of Chiropractic (later National College of Chiropractic and now National University of HeaJth Sciences), founded in 1906 by Palmer graduate J.F. Alan Howard. Many of these new schools were not simply new institutions, but also new schools of thought based on alternate interpretations of the most appropriate and efficient application of the ideas first expressed by D.D. Palmer a few years earlier.

CHAPTER 2

The Chiropractic Paradigm

AREAS OF CONTROVERSY From this environment of creativity and contro­ versy emerged various factions and viewpoints within the chiropractic commwlity that still exist today. The key elements of division ceoter on the following: • Procedures that should appropriately be included and applied in the scope of chiropractic practice • Range of effects of chiropractic care for the patient • Clinical value of subluxation correction • Appropriate terminology with which to describe chiropractic methods and their effects • Questions that are related to isolation from. or integration with other health care practitioners and professions, especially allopathic practitioners

SCOPE AND APPLICATION OF CHIROPRACTIC SERVICES Differences of opinion as to the range of services that doctors of chiropractic should provide led early in the profession's history to the develop­ ment of the labels straight and mixer. Most straight chiropractors focused almost exclu­ sively on the vertebral subluxation and its m.an­ ual adjustment. In contrast, many mixer practitioners used additional clinical approaches as adjuncts to adjusting the spine. Depending on state law and individual preference, such adjunctive therapies have included, but are not limited to, physiotherapy, dietary counseling and nutritional supplementation, acupuncture, midWifery, herbology, and massage. An examination of their approaches to diag­ nosis provides further distinction between straight and mixer chiropractors. Before dis­ cussing these distinctions, it is important to note that all North American doctors of chiropractic, regardless of philosophic allegiances, are quali­ fied as portal-of-entry proViders and have the responsibility to determine whether a patient will likely benefit from chiropractic care and whether a patient should be referred for other

19

care for a nonchiropractic health condition. In some cases, co-management with another prac­ titioner is the appropriate choice. Grouping chiropractors into straight and mixer categories is an oversimplification. Chiropractors' attitudes regarding diagnosis and methods of inter­ vention vary substantially even within the straight and mixer categories. The follOWing examples iUustrate some of these combinations. The order of these examples is not Intended to indicate the authors' preferences; 1. Chiropractors who primarily perform a musculoskeletal diagnostic workup and use adjustment as their sole intervention 2. Those who primarily perform a musculoskeletal diagnostic workup and use adjustments along with exercise, dietary recommendations, rehabilitation, other adjunctive procedures, or any combination 3. Those who perform no diagnosis beyond the analysis of spinal subluxations and use adjustments as their sole intervention 4. Those who perform a broad diagnostic workup, including the musculoskeletal and other systems, and practice as musculosl{eletal specialists, using adjustments and various adjunctive procedures primarily for treating musculoskeletal disorders 5. Those who perform a broad diagnostic workup, including the musculoskeletal and other systems, and practice as complementary care generalists, using adjustments and adjunctive procedures with a strong emphasis on nutritional therapy, including supplements for treating disease 6. Those who limit their practice to diagnosis, specifically diagnostic imaging (chiropractic radiologists), and who serve as consulting specialists A common denominator in examples 1 through 5 is the use of spinal adjustments to improve and maintain musculoskeletal function and to support the body's homeostatic mechanisms through the adjustment's effects on the nervous system, thus helping the body heal itself.

20

PART ONE

HISTORY, PHILOSOPHY, AND SOCIOLOGY

VALUE OF THE ADJUSTMENT, RANGE OF ITS CLINICAL EFFECTS Many people who were trained in the early Palmer tradition viewed chiropractic care as a panacea or near-panacea for all iUs of the human body. Correcting the vertebral subluxation was understood to be all that patients needed, and once this was accomplished, little else remained to consider or to do, other than to ensure that no new subluxations developed. Other practitioners viewed the adjustment as one among many nat­ ural approaches to bring aid and comfort to patients. Currently, doctors of chiropractic, as well as some outside the profession, continue to debate the full clinical value of the chiropractic adjustment! manipulation and correcting subluxation or joint dysfunction. To pose the central question: Is the chiropractic adjustment the key to all the ills of humankind, or is its influence limited to musculoskeletal complaints? Although the vast majority of chiropractors hold positions in the broad middle ground between these extremes, the question of how to resolve conflicts among scientific evidence, anecdotal observation, belief, and tradition remains unanswered. At this time, despite advances in chiropractic research, many issues cannot be resolved based on firm evidence. Nevertheless, the way the profession ultimately addresses the inevitable conflicts between newly emerging evidence and traditional beliefs will undoubtedly shape its future.

LANGUAGE FOR DESCRIBING CHIROPRACTIC Words have power, and the words used to describe the principles and practices of chiropractic con­ tinue to stir controversy. To some chiropractors, the issue is purely semantic; to others, it is a mat­ ter of principle in which tlle choice of terminology is a strong indicator of one's stance on major issues confronting the profession. Should the chiropractor's primary manual intervention be called adjustment or manipula­ tion? Is chiropractic care a fonn of treatment or

does this term iudicate something strictly allo­ pathic? Similarly, is the chiropractic adjust­ ment/manipulation a therapy, with therapeutic 4{ects, or is it better termed an 'inte1'Vention or a procedure? Is the entity addressed by adjust­ ment/manipulation a subluxation, segmental dysfunction, or somatic joint dysfunction? Is the practitioner of chiropractic to be known as a chi­ ropractor or chiropractic physician? Doctors of chiropractic have argued OVl;:r these and related matters for almost the entire history of the pro­ fession. This text cannot resolve such questions, but it can frame the issues in a nonadversarial cootext so that entry-level students and other readers can understand both points of view. Notably, many uniquely chiropractic terms were first introduced so as to avoid criminal con­ viction for the illegal practice of medicine. On the advice of attorney Tom Morris in the 1907 Morikubo'V. Wisconsin case,lO the chiropractor argued that chiropractors analyze rather than diagnose, adjust rather than treat, that chiro­ practic is not therapeutic, and that chiropractors do not treat disease but instead adjust to remove subluxation, the cause of disease. Thus accord­ ing to this reasoning, if medicine is defined as the diagnosis and treatment of disease, chiro­ practors were not guilty of practicing medicine. To a great extent, controversy regarding choice of language in chiropractic springs from a concern on the part of straight chiropractors that adopting the language that the medical and osteopathic professions use (Le., manipulation, treatment or therapy, and lesion or somatic dys­ function rather than adjustment, intervention, and sublw::ation) represents an unacceptable comprom ise for the sake of acceptance within the mainstream health care system. A parallel concern on the part of mixer chiropractors is that failing to adopt the terminology in wide­ spread use throughout the health professions will contribute to the continued marginalization of chiropractic.

INTERPROFESSIONAL RELATIONS Historically, relations between doctors of chiro­ practic and medical physicians have often been

CHAPTER 2

The ChiroprActic Paradigm

difficult, although this has begun to diminish in recent years. Having been disparaged by most medical physicians and attacl<ed by political medicine since the profession'8 inception, many chiropractors have been understandably cautious in seeking alliances with medical physicians or integration into the mainstream medical delivery system. Although some chiro­ practors have always wanted to ally and inte­ grate with the medical profession, others have staunchly opposed such moves. Ironically, the decision to integrate did not belong to the chi­ ropractors; thus chiropractors remained out­ side of mainstream health care. This is finally changing. As a profession matures, its relations with other professions must mature as well. Healthy interproiessionaJ relations must be based on mutual respect and understanding. A key question for chiropractic's future is: How can chiropractic be integrated into the main­ stream health care delivery system so that chi­ ropractic services are readily available to all who can benefit from them? Moreover, of equal significance: How can such integration be achieved without diluting the unique iden­ tity of chiropractic to the point at which it is unrecognizable? Probably, no single answer to these questions eXists. The future shape of the profession will likely be worked out, step by step, in numerous pilot projects in a wide range of settings-in pri­ vate chiropractic and medical practices in which interprot"essional referral in both directions becomes the norm; in interdisciplinary (includ­ ing joint chiropractic-medical) practices in which practitioners work out the best ways to cooperate for the benefit of their patients; and in larger-scale enterprises such as the health care systems serving veterans and the active duty military, in which chiropractic inclusion is now in its early stages. In each of these situations, it is important not to mistake uncertain beginnings for failures. Inevitably, as new relationships are developed and tested, both successes and diffi­ culties will occur. Creating positive, sustainable interprot'essional relations depends on a willing­ ness by all involved parties to build on their successes and learn from their mistakes.

21

CONTEMPORARY EXPRESSIONS OF THE CHIROPRACTIC PARADIGM Example One: Traditional Paradigm Traditionally, the core chiropractic paradigm has included the follOWing: 1. The body is a self-regulating and self­

healing organism.

2. The nervous system is the master system that regulates and controls all other organs and tissues and relates the individual to his or her environment. 3. Spinal biomecbanical dysfunction in the fonn of vertebral sublm:ation complex may adversely affect the nervous system's ability to regulate function. 4. The central focus of the doctor of chiropractic is to optimize patient heaJth by correcting, managing, or minimizing vertebral subluxation through the chiropractic spinal adjustment. These four points constitute the foundation of traditional ch iropractic. Moreover, they convey this essence without metaphysical terminology. Chiropractors comfortable with the term innate intelligence will recognize this concept in the first component. Similarly, those chiropractors who prefer to think of self-regulation and healing in terms of homeostasis and normal physiologic function are accommodated. Notably, the rela­ tionship between structure and function as mediated by the nervous system is given promi­ nence here. This principle is the essence, the distinctive feature, of chiropractic thought and practice.

Example 1\vo: Biopsychosocial Paradigm Other recent expressions of chiropractic's essence build on these core concepts, explicitly incorpo­ rating a contemporary biopsychosocial model of health. One such description ll expresses the chiropractic paradigm as follows: 1. Health is the natural state of indiViduals,

and any departure from this state

represents a failure of the individual to

22

PART ONE

HISTORY, PHILOSOPHY. A."ND SOCIOLOGY

adapt to the internal and external environment or is the result of adverse adaptation. The innate tendency of the body is to restore and maintain health by (compensating) homeostatic mechanisms, reparative processes, and adaptive responses to genetic and acquired limitations. 2. Health is an expression of biologic,

psychologic, social, and spiritual factors,

and disease and illness is multicausal.

This view is a holistic philosophy of

health.

3. Optimal health is unique for any individual. Health involves enabling individuals to fulfill their biologic, human, and social potentials realistically. This Viewpoint also implies individual responsibility for health. The chiropractor is simply the facilitator and, through cooperation with the patient, patient education, and adherence, they together achieve health for the patient. Health also implies a belief in healthy liVing (good nutrition, constructive exercise, stress management, and good posture). 4. The structure and functioning of the neuromusculoskeletal system is central to maintaining good health and combating disease. The functioning of the musculoskeletal system is integrated with neurologic function and is expressed by the various regulatory systems of the body. Although they express the chiropractic para­ digm in different terms, these two models have much in conunon and no overt areas of dis­ agreement. The second model includes all the basic chiropractic premises of the first, with additional emphasis on the social and spiritual dimensions of health, the cooperative nature of the chiropractor-patient relationship, and the value of health-promoting self-care activities such as diet and exercise. As Ian Coulter, a pro­ fessor at schools of dentistry and chiropractic who has written extensively on chiropractic and its role in the health care system, aptly notes in his book, Chimpractic: A Philosophy for Alternative Health Care, 9 when it comes to chi­ ropractic intraprofessionaI philosophic disagree­ ments, "to an outside observer, the differences in

terms of philosophy are less than the similari­ ties," 'adding that "{tlhose external to the profes­ sion have had great difficulty in understanding the nature and importance of these philosophi­ cal issues."

Example Three: Association of Chiropractic Colleges Paradigm 12 The preeminent contemporary expression of the eh iropractic paradigm was written in 1996 by the presidents of all North American chiroprac­ tic colleges under the auspices of the Association of Chiropractic Colleges (ACe). These institu­ tions, many of which were founded by early chi­ ropractic leaders, represent the full spectfilm of mainstream chiropractic thought. In a landmark of professional unity, every North American chi­ ropractic college preSident agreed to a common paradigm (Fig. 2-1) that defines the purpose, principle, and practice of chiropractic. In the years follOWing development of this ACC COI\­ sensus document, other chiropractic organiza­ tions (including the American Chiropractic Association. International Chiropractors Associa­ tion, Canadian Chiropractic Association, World Federation of Chiropractic, Congress of Chiro­ practic State Associations, and World Chiroprnctic Alliance) have endorsed it as a description of the paradigm under which chiropractors from all points on the spectrum practice (see Appendix IH).

ASSOCIATION OF CHIROPRACTIC COLLEGES CONSENSUS DEFINITIONS On cbiropractic: Chiropraclic is a health-care discipline which empha­ sizes the inherent recuperative powers of the body to heal itself without the use of dmgs or surgery. The practice of chiropractic focuses on the rela­ tionship between structure (primarily of the spine) and function (as coordinated by the nervous system) and how that relationship affects the preservation and restoration of health. Doctors of Chiropractic recognize the value and responsibility of working in cooperation with other health care practitioners when in the best interest of the pa.tient.

CHAPTER 2

The Chiropractic Paradigm

23

THE ACC CHIROPRACTIC PARADIGM

PATIENT HEALTH through quality care

PRACTICE

• Establish a diagnosis

• Facilitate neurological and biomechanical integrity through

appropriate chiropractic case management

• Promote health

PRINCIPLE The body's innate recuperative power is affected by and integrated through the nervous system

EDUCATION

RESEARCH

RELATIONSHIPS WITH OTHER HEALTH CARE PROVIDERS

Fig. 2-1 The ACC Chiropractic Paradigm, 1996. (.Association of Chiropractic Colleges, with permission.) The ACC continues to foster a unique, distinct chi­ ropractic profession that serves as a health care discipline for all. The ACC advocates a profession that generates, develops, and utilizes the highest level of evidence possible in the provision of effective, prudent and cost-conscious patient evaluation and care.

On subllL'i:ation: A subluxation is a complex of functional, structural,

andlor pathological articular changes that compro­ mise neural integrity and may influence organ system function and general health. A subluxation is evaluated, diagnosed and managed through the use of chiropractic procedures based 011 the best 11vfulable rational and empirical evidence. The preservation and restoration of health is enhanced through the correction of the subluxation.

Examilling several components of this paradigm in greater depth is instructive. First, the ACC paradigm emphasizes that the fundamental pur­ pose of chiropractic is "to optimize health" and that "the body's innate recuperative power is

affected by and integrated through. the nervous system." Across all differences in style, the sub­ stance of chiropractic rests on this foundation­ that the body is self-regulating and self-healing and that the nervous system is the primary receptor, integrator, effector, and coordinator. The practice of chiropractic is described to include appropriate diagnosis, facilitating neuro­ logic and biomechanical integrity through chiro­ practic methods and promoting health. The attention given to the diagnostic responsibility of the doctor of chiropractic in this paradigm is noteworthy. Throughout the course of chiro­ practic history, chiropractors have debated the appropriateness of not only the term diagno­ sis, but also of the process that it entails. Some chiropractors have maintained that diagnosis is purely the purview of the allopathic practitioner and that because chiropractors do not focus on treating disease, an emphasis on the diagnosis of disease is contradictory. Current accreditation and licensing standards give to all doctors of

24

PART ONE

HISTORY. PHILOSOPHY. MTD SOCIOLOGY

chiropractic the responsibility of a porL11 of entry provider. This paradigm simply reflects the cur­ rent state of chiropractic practice when it notes that part of the chiropractor's job is to establish a diagnosis. III outlining this component, among others, of chiropractic practice, the ACC para­ digm does not mandate a particular therapeutic or management approach. Subluxation is a chiro­ practic diagnosis. Chiropractic adjustment facili­ tates neurologic and biomechanical integrity, and health promotion can be practiced through a vari­ ety of means, including education and referral. Significantly, the ACC paradigm defines chi­ ropractic as a discipline that emphasizes the body's ability to restore health without the use of dmgs and surgery. Some chiropractors have expressed concern that efforts to obtain the right to prescribe drugs might ultimately prevail, resulting in a major redefinition of the histori­ cally conservative, natural orientation of chiro­ practic thought. The broad support for the ACC paradigm should help lay that concern to rest. Addressing discord within the profession sur­ rounding the meaningfulness of the ternl subluxa­ tion, the ACC paradigm stands behind continued use of this term, describing it as capable of com­ promising neural integrity and potentially influ­ encing organ system function and general health.

The consensus achieved by the chiropractic college presidents included the visual descrip­ tion of the chiropractic scope of practice is pro­ vided in Fig. 2-2. The ACC paradigm asserts that chiropractic care is appropriate for general health promotion and early deviation from health. Chiropractors, of course, can also pro­ vide care when dysfunction progresses to tbe symptomatic level and even at the advanced stages of disease, as long as no contraindications exist and, when indicated, co-management is pursued. The ACC paradigm encourages collaborative care, consistent with the way Americans use chi­ ropractic. Surveys have documented that the population does not generally select only one type of practitioner for their health care. In fact, most people who consult chiropractors for cer­ tain types of care (musculoskeletal conditions in 90% of cases) also see a medical physician for other needs. lJ Implicit in the ACC diagram is the responsibility of the chiropractor to recognize when co-management and referral are appropri­ ate. If the patient has a vertebral subluxation, the doctor of chiropractic is the most appropriate practitioner to manage that condition; however, the patient may have a concomitant problem that requires concurrent care by another health care

THE ACC CHIROPRACTIC SCOPE AND PRACTICE

D Chiropractic Care Medical Care DIAGNOSIS Disease .....- - - - - - - - - - - - - - - - - - - - . Health

Chiropractle care

Palliative care

Advanced Signs! Dysfunction SUbluxation Deviation disease symptoms

General health promotion

MANAGEMENT

Fig. 2-2 ACC Chiropractic Scope and Practice. (Association of Chiropmctic Colleges, with permission.)

CHAPTER 2 Tbe Chiropractic Paradigm

practitioner. In some cases (e.g., an apparent malignancy on x-ray films), referring the patient out for immediate medical care before initiating chiropractic care is necessary. Chiropractors have long used the Biologic Spectrum H or Health Continuum (Fig. 2-3) to educate patients abollt the processes of good health and the significance of preventive self­ care activities. These visual tools in combination with the ACe Scope and Practice diagram help demon­ strate that health is not a state but rather a process. Further, they emphasize that disease is generally the result of long-standing alterations in the lxxIy's regulatory functions (pathophysiology) that may produce no symptoms and are thus unde­ tected. In many cases, health care does not hegin wItH symptoms are present. However, by the time symptoms are exhibited, the patient bas often tmly been "sick" for a very long time (Fig. 2-4). Chiropractors, along with other nonallo­ pathic practitioners, emphasize the value of care at the presymptomatic stage, when the patient is experiencing stress to the body-mind system. Intervention at this point seeks to prevent

presymptomatic abnormalities from developing into disease. At this stage, the chiropractor acts largely as a health coach, advising the patient about conservative self-care strategies such as diet, exercise, and stress-management tech­ niques. Similarly, the chiropractor checks the patient's spine for subluxations and proVides adjustments to address spinal biomechanics to foster optimaJ functioning of the nervous system and thus to maintain health. As the patient's condition progresses toward the rigbt of the spectmm, the chiropractor or other doctor will be required to playa greater role in care. Self-care is still important; however, intervention to reduce symptoms and prevent progression is the focus. [0 some cases, thiS intervention may need to come from practition­ ers of various other disciplines and specialties.

ROLE OF PHILOSOPHY IN CHIROPRACTIC The philosophy of chiropractic is alive and well in the profession. GroWing numbers of chiroprac­ dc educators, practitioners, and researchers are

-~-----~------o------~-------¢------~-~ Full 3 Ts Subluxation Dis-ease Disease Death potential (peE) (no (symptoms) symptoms) ~'ig.

2-3 Health continuum. Three Ts-Trauma, Thoughts, and Toxicity. peE, Physical, chemical, emotional.

Opportunity to intervene with risk factors modification

Earliest opportunity to intervene with screening

--~--_!_--~-------_t
Fig. 2-4 Pathogenesis. 15

25

Pathogenetic Detectable Symptoms risk factors pathophysiological abnormality

Death

26

PART ONE

HISTORY, PHILOSOPHY. AND SOCIOLOGY

engaging in spirited philosophic inquiry and dis­ course in professional publications and presenta­ tions. At a World Federation of Chiropractic (WFC) conference in November 2000, educators from chiropractic colleges around the world met to consider the role of philosophy in chiropractic education. That conference produced a series of consensus statements, including the following l6 : 1. A shared approach to health and healing, based upon a shared philosophy of chiropractic, is important for the identity and future of the chiropractic profession. 2. Chiropractic is a unique discipline, but it exists as part of a broader entity-the health care system. Accordingly, the discussion of philosophy as a discipline and the philosophy of health care, as well as specifically the philosophy of chiropractic, should be important components in every chiropractic curriculum. 3. The philosophy of chiropractic should be taught and developed in a manner that is intellectually defensible in the discipline of philosophy. Significantly, chiropractic educators and represen­ tatives of chiropractic professional associations from all points on the philosophic spectrum agreed that a shared philosophy of chiropractic is important not only for the identity of the profes­ sion, but also for its very future. Further, these educators and associations affirmed that the chi­ ropractic curriculum should include education in the philosophy of chiropractic, applied with a vig­ orous spirit of intellectual inquiry. Recent publications by chiropractors and oth­ ers have suggested that a robust philosophy of chiropractic does not require abandoning tradi­ tional chiropractic principles. These authors 9 ,17 have suggested that chiropractors share important philosophic underpinnings, including Vitalism, holism, naturalism, therapeutic conservatism, humanism, and critical rationalism, witl1 other healing disciplines, such as aCUpwlCture, natur­ opathy, classical osteopathy, and others, and therefore they hold forth the promise of inter­ disciplinary cooperation in the interest of better serving patients.

DEALING WITH DUALISM Chiropractic thought grew out of a seeming dual­ ism of matter and intelligence that piqued D.D. Palmer's curiosity. Perhaps it should come as no surprise, then, that the profession that Palmer founded still struggles with this dualism, with thinkers and practitioners striving to understand science and philosophy, matter and intelligence, and structure and function. Seeing things in terms of either-or rather than both-and appears to be a genera] human tendency, and chiroprac­ tic is no stranger to this tendency. Various his­ toric figures aligned themselves more closely with either vitalism or science. However, infer­ ring that those who embraced the vitalistic phi­ losophy were unable to understand science or were uninterested in its findings would be a mis­ take. Similarly mistaken is the notion that those chiropractors who strongly supported scientific exploration are not "principled" chiropractors. A need exists for both science and philosophy in the profession; there is room for both not only in the profession as a whole, but also within indi­ vidual chiropractors.

IB~yiew Question..~ 1. What was the fundamental distinction between D,D. Palmer's chiropractic concepts and A.T. Still's osteopathy? 2. What is vitalism? 3. What are the threaTs? 4. How did B.J. Palmer's approach to chiropractic differ from that of D.D. Palmer? 5. What are some of the differences between the straight and mixer approaches to chiropractic? What are the areas of common ground between these approaches? 6. What is the basis of the controversy regarding the use of the terms adjustment versus manipulation, treatment versus intervention, and subluxation versus

somatic dysfunction? 7. What are the four points in the traditional chiropractic paradigm? 8. How does the biopsychosociaf model differ from the traditional model?

CHAPTER 2

The Chiropractic Parndigro

9. What are the main points of the ACe paradigm? What is unique about the development of this model? 10. What are the ACe definitions for chiropractic and subluxation?

,Concept Questions 1. Is vitalism a necessary component of chiropractic? In what ways is the concept of vitalism consistent or inconsistent with contemporary health science? 2. What is philosophy? What is the philosophy of chiropractic? What is the appropriate role of philosophy in contemporary chiropractic?

REFERENCES 1. Moore JS: Chiropractic in America: the history oj a meclical alternative, Baltimore, 1993, Johns I-Jopllin~ University Press. 2, Pizzorl1o JE: Naturopathic medicine. In Micozzi MS, editor: Pundamentals ofcomplementary and alt.errul.­ ti~!e medicine, New York, 1996, ChurchiU Livingstone. J. Gevilz N: The DOs: osteopathic medicine in America, Baltimore, 1982, Johns Hopkins University Press. 4. KaplChuk TJ: History of vitalism. In Micozzi MS, edi­ tor: FlIlIdamelltals of complementary and alter­ nati~'e medicine, ed 2, New York, 2001, Churchill Lil'ingstone.

r

27

5. Gielow V: Old dad chiro; a biography oj D.D. Palmer, founder of chiropractic, Davenport, Iowa, 1981, Bawden Bros. 6. Miller A: Transcendentalism's inspiration to chiro­ practic philosophy and practice,Todays Chirapmctif::

29:2,2000, 7. Waagen G, Strang V: Origi n and development of tra­ ditional chiropractic philosophy. In Haldeman S, edi­ tor: Principles and practice of chiropractic, ed 2, San Mateo, Calif, 1992, Appleton & Lange. 8. Palmer DO: The chiropractor's adjuS(Qr, Portland, Ore, 1910, POrtlAnd Printing House. 9. Coulter 10: Chiropractic: a phiwsophy.for alternati'l,.'(' health care, Oxford, 1999, Buttenvorth-Heinemann. 10, Rehm WS: Legally defensible: chiropractic in the courtroom, 1907 and after, Chiropr [-list 6:50, 1986. 11. Phillips RB et al: A contemporary philosophy of chi­ ropractic for the Los Angeles College of Chiropractic, J Chiropr Human 4:20,1994. 12. Association of Chiropractic Colleges, Minutes, Chicago, July 1, 1996. 13. Eisenberg OM et al: Perceptions about complemen­ tary therapies relative to conventional therapies among adults who use both: results from a national survey, Ann Int Med 135:344, 2001. 14. Strang V: Essential principles oj chiropractic, Davenport, Iowa, 1984, Palmer College of Chiropractic. 15. Woolf SH, Jonas S, Lawrence RS, editors: Health pro­ motion and disease prevention in clinical practice, Baltimore, 1996, Williams & Wilkins. 16. Chapman-Smith 0, editor: New international consen­ SliS on philosophy, Chiropractic Report 15:1, 2001. 17. Gatterman 111: A patient-centered paradigm: a model for chiropractic education llnd research, J Altern

Complement Med 1:37J, 1995,

Major Themes in Chiropractic History Glenda Wiese, MA Key

Tenns.

A~IERICA.'Il CHIROPRACTIC

ASSOCIATION ASSOCIATION OF CHIROPRACTIC COLLEGES B."SIC SCIENCE LAWS

_ MANAGED CARE

N EU ROCALOI\! ETER

ORGi\..NIZATION

PHYSIOLOGICAL rn-IERAPEUTICS

MEDICAID MEDICARE

SUBL\.J)(.\TIQN

NATIONAL BOARD

UNIVERSAL CHIROPRACTORS

COMMI1TEE 01\ QUACKERY

OF CHIROPRACTIC

COU:-ICIL ON CHIROPRACTIC

EXMIINERS

EDUCATIO:,>/ INTERl'ATlONAL CHIROPRACTORS ASSOCISf(ON

ASSOCIATION \VILK V. AMERICAN MEDICAL

NATIONAL CHIROPRACTIC ASSOCIATION

ASSOCIATJON WORLD FEDERATION OF

NATIONAL INSTITUTES OF

CHIROPRACTIC

HEALTH

~! ithin

5 years, chiropractic celebrated its centennial, chiropractic education cele­ ted 100 years, and a third millennium was red in. These times are appropriate to stop consider the major themes in chiropractic ry. The major themes of chiropractic are nufied in this chapter and, when possible, are ologically discussed. Although selection of list of major events in chiropractic is, of , a subjective process, this text relies . y on the works of Walter \Vardwell, RusseH ns, William Rehm, Herbert Year, Vern ow, Pierre Louis Gaucher-PesUlCrbc, and ph Keating, Jr. in developing the selections expounding on the themes that are disd. The author of this text is indebted to ese scholars of chiropractic history.

Daniel David (D.D.) Palmer, Canadian by birth, performed the first adjustment on an .African­ American man, Harvey Lillard, on September 18, 1895, in Davenport, Iowa (Fig. .3-1). Palmer, who was 50 years old at the time, tells the story:

rl'

He had been so deaf for seventeen years that he could not hear the racket of a wagon or the ticking of a watch. I made inquiry as to the cause of his deafness, and was told that when he was exerting himself in a cramped, stooping position, he felt something give way in his back and immediately became deaf. An examination showed a vertebra racked from its normal position. I rerJsoned that if the vertebra was replaced, the man's hearing could be restored. [ racked it into position by using the spinous process as a lever, and soon the man could hear as before. There was nothing "accidental" about this as it was accomplished with an objective in view, and the result expected was obtained. 1

ANIEL DAVID PALMER AND THE

Palmer had been studying and practicing mag­ netic healing'" since 1886, and his evolution

RMULATION OF THE HIROPRACTIC THEORY

~Magnetic healing was a form of energy healing involVing the laying on of hands. It may also have included vigor­ ous rubbing and manipulation of various kinds.

occasion of the first chiropractic adjustment of course, the first major event in chiropractic.

29

30

PART

O~E

HISTORY, PHILOSOPHY, AND SOCIOLOGY

from magnetic heali..ng to chiropractic was grad­ ual. He was weU read in the fields of anatomy, physiology, neurology, and pathologi find used his extensive Imowledge to develop a theory to explain his clinical successes. When Palmer applied his newly developed technique to other patients, he observed that other disorders responded to the thrusts he used to reposition vertebrae. One of his patients had a heart condi­ tion that had failed to respond to the usual med­ ical care. Palmer examined the patient's spine and found a displaced fourth dorsal vertebra that he theorized was pressing against the nerves that segmentally innervate the heart. After he adjusted this segment of the spine, the patient experienced relief. Of this second attempt, Palmer said, "Then I began to reason, jf two diseases, so dissimilar as deafness and heart trouble, came from impinge­ ment, a pressure on the nerves, were not other diseases due to a similar cause?") D.D. Palmer accepted his first student in 1897, and soon students were graduating from his Palmer School and Infirmary (later renamed Palmer School of Chiropractic (PSC)) to both practice and teach chiropractic. In 1903, D.D. Palmer and his son Bartlett Joshua (B.J.) fonned an equal partnership, which was to continue until 1906. In that year, D.O. Palmer was tried and found guilty in Scott County, Iowa, of prac-

Fig. 3-1 Artist John Dyeuss' rendering of the first adjustment, performed by D.O. Palmer on Harvey Lillard, September 1895. (Courteb'Y Chiropractic Centennial Foundation, Davenport, Iowa.)

ticing medicine without a license, after which he sold his share of the PSC to his son and moved west, where he opened schools in Oklahoma, Oregon, and California. Ntcr leaving Davenport, D.D. Palmer assem­ bled a collection of his writings in his 1000-page magnum opus, The Chiropractor's Adjuster: A Textbook of the Science, Art, and Philosophy of Chiropractic for Students and Practitioners (1910). Undoubtedly, D.O. Palmer's formulation of the theory of chiropractic and its elucidation through his writings are the seminal and most important event in the history of chiropractic.

B.J. PALMER AND THE DEVELOPMENT OF CHIROPRACTIC B.J. Palmer was the second major influence on the development of chiropractic (Fig. 3-2). Always careful to describe his father as the

Fig. 3-2 B.J. Prllmer, D.O. Palmer's son, president of the Palmer School of Chiropractic (PSG) from 1906 until his death in 1961 and a leading force in the development of chiropractic. (CoU11esy LiLJ1'WY Special Collections, Palmer College of Chiropractic, Davenport, Iowa.)

CHAPTER J

Major Themes in Chiropractic History

"founder" of chiropractic, B.J. Palmer consid­ ered himself the "developer" of chiropractic, and proceeded to do so in style. On purchasing his father's lull I' of PSC, B.J. began developing it into one of the largest health practitioner schools in the country, with the school's population grow­ ing from 400 in 1911 to 3000 by 1923. 4 Botb Gibbons" and \Vardwcll 6 attribute the survival of the fledgling chiropractic profession to B.J. Palmer's flamboyant marl{eting and his dogged insistence that chiropractic remain "pure and unadulterated." According to Wardwell, "Without BJ. chiropractic might not have survived. A col­ orful multimedia salesman for chiropractic, he used lectures, pamphlets, 27 books, and his own radio station to spread the word about chiro­ practic to students, patients, and the public."7 BJ. was a charismatic and energetic speaker who traveled around the country, boosting chi­ ropractic and testifying on behalf of chiro­ practors before courts and state legislatures. Although B.,J. was a controversial figure, his pro­ nouncements against raising educational stan­ dards (he declared that they were "veneer and polish..., which [would] weaken the profession and cause a large reduction in the number of chiropractors,") were used in the courtroom 8g&inst chiropractic; however, not a man or woman who knew him questioned his undying yally to chiropractic.

EFENSE OF CHIROPRACTIC

. COURT

third major event or series of events in the his­ ry of chiropractic was the struggle to defend 'ropractors in court against the charge of prac­ cing medicine without a license. Although D.D. er was not the first to be accused of prac­ ng medicine or osteopathy without a license e was tried and found guilty of the offense in 9(6), the trial of Shegataro rl'lorikubo (PSG duate, 1903) in La Crosse, Wisconsin, in 7 was a watershed event that helped deter­ ine the strategy that chiropractors would opt to defend themselves against future s of unlicensed medical practice. The jury acquitted Morikubo. The defense mey, Tom Morris, convinced the jury that

31

chiropractic was not osteopathy or medicine; rather, it was a new form of treatment. B.J. Palmer retained Tom Morris as counsel for the Universal Chiropractors Association (DCA), and they proceeded to use the argument that chiro­ practic was a separate and distinct science from medicine. The central purpose of the DCA, with B.J. Palmer serving as its secretary for 20 years, was to raise funds to pay bail and fines for arrested chiropractors who adhered to the "straight" chiropractic philosophy. In addition, its purpose was to defend chiropractors in court and to lobby for state licensure of chiropractors, separate and distinct from medical practice acts. By 1927 the DCA had defended chiropractors in 3300 court cases. s

OTHER PIONEERS Although B..J. Palmer casts a giant shadow on the landscape of chiropractic history, several other intluential pioneers deserve mention. Solon Langworthy, the founder of the first school to provide serious competition to D.D. Palmer's PSG, was very influential in early chiro­ practic history (Fig. 3-3). With Oakley Smith and Minora Paxson, Solon Langworthy pub­ lished the first textbook on chiropractic in 1906, A Textbook of Modernized Chiropmctic. He also published an early journal, The Backbone, which D.D. and B.J. used as a model for their jour­ nal, Tlte Chiropractor. Langworthy also organ­ ized the first chiropractic association in 1905, the American Chiropractic Association (ACA) (not related to the current ACA). Although Langworthy's school, journal, ~llld association did not last long, his impact was far reaching on the early profession. Willard Carver had been a friend and some­ times legal counsel for D.D. Palmer, but he grad­ uated from the Charles Ray Parker School of Chiropractic in Ottumwa, Iowa, in 1906, rather than from PSC. Garver referred to himself' as the "constructor" of chiropractic, as opposed to B.J. Palmer being called the "developer," and he referred to his college in Oklahoma City as the "Science Head," in contrast to B.J. Palmer's "Fountainhead." Carver went on to preside over four separate institutions in Oklahoma City,

32

PART 01\'E

HISTORY, PHILOSOPHY, AND SOCIOLOGY

HERE ARE SOME OF THE KEYS ON WHICH I PLAY IN REMOVING PRESSURE FROM PINCHED NERVES. THER!'BY ALLOWING NATURE TO CURE DISEASE,

CHIROPRACTIC (Kl" 1'10- PRAK'-TIK)

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We n.bo l)llhU,.h .. l~(:kb(Hle, .. a: lllorilhl)' hook dC"'Qt~d lc> body ~nd brain 'buUding. be a. copy.::iOc 3. year J three Ul(lnthiittiallOc;..

Fig. 3-3 Solon Langworthy, president of the American Sohool of Chiropractic in Cedar Rapids, Iowa, co-author of the first chiropractic textbook, editor of the early journal The Backbone, and the first serious competitor (0 the PSC. (Courtesy Library Special Collections, Palmer College of Chiropra<::tic, Dus)enpoTt, Iowa.)

Washington, D.C., New York, and Denver, which eventually merged with other schools. When the new Oklahoma legislature convened in 1907, Carver introduced the first bill to legalize chiro­ practic in that state (Fig. 3-4). It did not pass. For years, his training as a lawyer would be used when called on to testify for chiropractic in leg­ islative hearings. Carver authored 18 books and exerted a great intluence on the new profession. John Howard, a 1905 graduate of the PSC, resigned from the PSC faculty in 1906 and started a competing school in the same building in which D.D. Palmer first practiced and fonnu­ lated his theory of chiropractic. Howard moved his National School of Chiropractic (NSC) to Chicago in 1908, where it was able to take advan-

Fig. 3-4 Willard Carver fighting for chiropractic legislation in OkJahoma. (Painted by Robert Lawso1l, Courtesy Chiropractic Centennial Foundation, Davenport, Iowa.)

tage of its prOXimity to Cook County Hospital to offer observation of surgeries. By 1912 the school was offering physiological therapeutics and had several medical physicians on its faculty. In 1914, Howard sold the NSC to one of its faculty, WiUiam Schultz, M.D. Under Schultz's leadership, NBC became the major broad scope chiropractic influence. It was eclectic in its approach, and it offered physiologic therapeutics, naturopathy, and various other adjunctive procedures, in strong contrast to B.J. Palmer's straight, hands­ only approach to chiropractic. Tullius Ratledge, another early chiropractic educator, heavily influenced the development of the profession in California. He moved his school from Kansas to California in 1911 and continued as President of the Ratledge College of Chiropractic until he sold it in 1951 to Carl Cleveland, 'Sr. Ratledge served 75 days in jail in California in 1916 rather than pay his fine. In one year alone, 450 chiropractors were jailed in California for practicing medicine without a license. 9 Ratledge was active in the 1922 California referendum, which won licensure for chiropractors. California Governor

CHAPTER 3

Major Themes in Cbiropmctlc History

Friend Richardson pardoned all chiropractors in jail at the time of the referendum's passage, declaring they had been unjustly accused. Sylva Ashworth, the last pioneer in tllis atten­ uated list, graduated from the PSC in 1910 and became aotive in Nebraska state politics, serving on the first chiropractic board of examiners for that state. Her daughter, Ruth, and son-in-law, Carl Cleveland (1917 PSC graduates), started the Central College of Chiropractic in Kansas

33

City in 1922, renaming it the Cleveland Chiro­ practic College in 1924. In 1951, Carl Cleveland took leadership of the Ratledge College of Chiropractic, renaming ·it the Cleveland Chiro­ practic College of Los Angeles in 1955. Sylva's great-great grand-daughter, Ashley, became the world's first fifth-generation chiropractor, and she currently serves as an administrator and faculty member at Cleveland Chiropractic College-Kansas City (Fig. .3-5, A-G).

34

PART ONE

HJSTORY. PHILOSOPHY. Ai\lO SOCIOLOGY

STRUGGLE FOR LICENSING LEGISLATION The fifth major event-actually, a series of events-that chronicle chiropractic's stntggle for state licensure, was an effort that would require diligence for over 60 years. Politics, both that of organized medicine against chiropractic and that of "mixer" and "straight" chiropractors against each other, q extended the process in the United States from before 1913 when the first state, Kansas, licensed chiropractors, until 1974, when legislation for chiropractic was passed in Louisiana. J() The years between are filled with hundreds of stories of tragedy and triumph. Chiropractors in California proVided a strik­ ing example of success after years of stntggle. As previously noted, more than 450 California chiropractors went to jail rather than pay a fine. Often, they would set up their portable adjusting tables and proceed to treat their patients in jail (Fig. 3-6, A). Texan Charles Lemley (1892-1970) was arrested 66 times. A parade was held for fellow Texan Paul Meyers, complete with patients and a brass band, when he was released from jail. Herbert Reaver held the record for the "most jailed," haVing paid eight fines and been incar­ cerated four times in Ohio (Fig. 3-6, B). Even when licensing was granted, the question of who sat on the examining board could deter­ mine the ease of obtaining licensure for a would­ be practitioner. States dominated by straight chiropractors tended to have boards dominated by chiropractors, whereas states dominated by mLxers had medically oriented boards in many O"Mixers" have been historically referred to as chiro­ practors who use ancillary methods to treat their patients in addition to the chiropntctic adjustment. These meth­ ods may include electrotherapy, hydrotherapy, acupunc­ ture, acupressure, and vitamin therapy. The disagreement over whether these ancillary procedures are within the purview of the chiropractor has fomled the basis for debate between the "straights" and "mixers." In real­ ity, however, this bimodal separation of chiropractors has never existed. In a statistical sense, there Is a "nor­ mal" distribution, with most chiropractors falling some­ where in the middle (see Chapter 2 for further discussion).

A

B Fig. 3-6 A. Fred Courtney, one of the many chiropractors prosecuted in California for practicing medicine without a license, is shown adjusting from his jail cell in Los Angeles, circa 1921. B. Herbert Reaver, the most jailed chiropractor. (A from Fountainhead News 19(26), 1921. B courtesy Librwy Special Collections, Palmer College Qf'

Chiropractic, Davenport, Iowa.)

cases, although there are many exceptions to this ntle. Another alternative, which was used to limit the number of chiropractic practitioners, was to examine all practitioners-medical, osteopathic, and chiropractic-by the same "basic-science board."

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Major 'Themes i~ Chiropraet~c History

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~EUROCALOMETER

In August 1924 in a speech entitled, "The Hour Has Struck," B.J. Palmer introduced the neu­ rocaIometer to the profession. It was a hand­ held, heat-sensing instrument, which he insisted was necessary for the chiropractor to detect sub­ luxations. It could be leased for a fee that would include lessons in how to use it and periodic checks and repairs. Many RJ. supporters believed the cost of leasing the instrument was exorbitant and that B.J.'s insistcnce on its LIse downplayed the efficacy of palpation in detecting subluxations. The neurocalometer controversy, the sixth event in the history of chiropractic selected in this text, coincided with B.J. Palmer's dramatic transition from using full-spine adjust­ ing techniques to using the upper cervical-only Hole-in-One (HIO) technique, and it marked the beginning of the decline of B.J. Palmer's influ­ ence in the field. Although he would continue to exert a powerl'ul influence on the profession, he would no longer be its undisputed leader.

DEVELOPMENT OF T'VO STRONG NATIONAL

ASSOCIATIONS The development of two strong national associa­ tions was the seventh influence to shape chiro­ practic. Partially as a result of tlle erosion of support for R.I. Palmer and partially as a result of tougher basic science laws* and a renewed medical assault, by 1929, PSC's enrollment had dropped by 90%.11 By 1930 the importance and lntluence of the UCA declined, with a 50% drop ·Basic scient'€ laws established examinations that certi­ fied candidates from all major healing arts in the basic sciences of anatomy, p~lthology, physiology, chemistry, and public health. These laws were enacted with the pur­ pose of excluding chiropractors and other practitioners with supposedly inadequate training. The basic science laWll elevated educational standards in those professions In which students had difficulty passing the examina­ tions. By 1969, chiropractic education had improved to the point that four state basic science boards recognized the chiropractic board examinations as being eqUivalent. By 1980, all states had repealed their basic science laws.

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35

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. in -membership. B.J. Palmer resigned as secretary-treasurer, and the DCA merged with the original AC1\ to form the fledgling National Chiropractic Association (NCA). B.J. Palmer continued to exert his influence through the Chiropractic Health Bureau, renamed the International Chiropractors Association (ICA) in 1941. A campaign to merge the two national associations in 1963 resulted in a new ACA, with a resulting smaller membership in the lOA. ]n 1987 a renewed effort to merge the two national associations led to their first joint con­ vention in Las Vegas, Nevada. Promerger forces led by lCA president Michael Pedigo and vice­ president Virgil Strang secured a majority vote of ICA members in favor of the merger, but they failed to achjeve the constitutionally required two-thirds vote. Antimerger forces were led by Sid Williams, who became president of a smaller leA after some in the promerger camp (includ­ ing Pedigo and J.F. !\'fcAndrews) left to join ACA. Pedigo later became the first and only chiro­ practor to have served as president of both ICA and ACA; l\fcAndrews, a former ICA executive director and fonner president of Palmer College, became ACA's Vice-President for ProfeSSional Affairs. The two organizations continue to remain separate, and the strajght-mixer, nar­ rowscope-broadscope split that began over 100 years ago continues to this day.

CAMPAIGN BY THE AMERICAN MEDICAL ASSOCIATION TO "CONTAIN AND ELIMINATE" CHIROPRACTIC The eighth event, the American Medical ASSOCiation's (MiA's) campaign to eliminate chi­ ropractic, first started in the 1920s and accel­ erated in 1963 when the AJ.vlA founded its Committee on Quackery (originally called the Committee on Chiropractic). When chiropractic sought inclusion in Medicare, the Secretary of Health, Education, and Welfare's report recom­ mended that chiropractic not be included, because it was "not based upon the body of basic knowledge ... that has been Widely accepted by tbe scientific community," and that "tbe scope

36

PART Om:

HlSTORY. PHlLOSOPHY. AND SOCIOLOGY

and quality of chiropractic education do not pre­ pare the practitioner to make an adequate diag­ nosis and provide appropriate treatment." 12 It was later revealed in internal AMA documents in the landmark Wilk v. AMA et al. antitrust case that the MIA heavily intluenced the results of Secretary Cohen's report and that these results had been determined in advance. Next, the M'fA launched an aggressive cam­ paign against chiropractic in popular journals such as Reader's Digest, Consumer Reports, and Good Housekeeping. In response to the vitriolio campaign against chiropractors, the ICA and ACA worked together to publish Chiropractic's White Paper on Health, Education, and Welfare Secretary's Report (1969), contesting the data and its conclusions. Since then, the ICA and ACA have held a joint legislative oonference in Washington, D.C. (1983) and have frequently joined foroes to respond to legislative threats.

Fig. 3-7 John Nugent, PSC 1922, spearheaded early reforms in chiropractic education. (From The National Chimpractic Journa.l, NO'Vember 1941.)

COUNCIL ON CHIROPRACTIC EDUCATION (ACCREDITATION) The ninth event to influence chiropractic his­ tory was the recognition of a national chiroprac­ tic accrediting agency. Enrly chiropractic education lacked consistent standards; signifi­ cant variations in the duration and quality of educational curricula existed. John Nugent, often referred to as the "Abraham Flexner" of chiropractic, was appointed chair of the NCA's committee on educational standards in 1935 (Fig. 3-7). For the next 30 years he cajoled and threatened the heads of the chiropractic schools, mostly for-profit educational enterprises, to adopt stricter, more stringent standards. He believed that chiropractic eduoation must be raised to a level that the academic community and the federal and professional accrediting agencies would recognize. The numbers tell the story. In 1930, 42 chiropractic institutions existed, most with courses of 18 months or less. When Nugent retired in 1963. 15 chiropractic educational institutions were operating in the United States with all but 3 haVing made the transition to professionally owned, not-for­ profit educational institutions with independent boards of directors. IJ

The NCA Committee on Educational Standard~ became the Council on Chiropractic Education (CCE) in 1947. In 1953 the CGE made the 4-year curriculum standard, and by 1968 it had adopted the 2-year preprofessional requirement. In 1974 the U.S. Office of Education recognized the CCE as the official accrediting agency for all chiroprac­ tic colleges. Currently, 16 U.S. and 2 Canadian chiroprac­ tic colleges are operating in North America; all are nonprofit and reqUire a minimum of 3 years prechiropractic collegiate studies, and they all offer a 4- to 5-academic-year chiropractic pro­ gram. With the advent of Bachelor programs in biology and Master programs in anatomy, nutri· tion, and sports chiropractic, most colleges have achieved regional accreditation, as well as CCE recogni tion. As the sale educational accrediting agency for chiropractic colleges, CCE was the first entity to bridge the gap among the various fac­ tions in chiropractic education effectively, bring­ ing all of the key stall.eholders to the same table. This fact is as important as CCE's role in stan­ dardiZing chiropractic education and elevating its standards.

CHAPTER J

Major Themes in Chiropractic History

CHIROPRACTIC COVERAGE BY MEDICARE AKD OTHER INSURAKCE PLANS The inclusion of chiropractic in insurance plans is the tenth key event in chiropractic his­ tory, According to Ward\vell 14 chiropractors competed on a level playing field, economically peaking, until third parties began paying for health care. As Medicare, Medicaid, and employee group health insurance plans paid for more health care services in the United States &her World War II, chiropractors faced a crisis. Patients would only pay chiropractors out-of­ pocket, forgoing their insurance, if they were wealthy, dedicated, or desperate, Chiropractors used political action to pass "insurance equality laws." Despite the AMA's strongest opposition, Congress voted to include chiropractors under Medicare in 1972. Currently, more than one half of all federal, state, and private health plans Include chiropractic coverage, although there are often restrictions on the number of patient visits or the modalities used.

37

In the years foUowing the National Institute for Neurological and Communicative Diseases and Stroke (NINCDS) Conference, other interdiscipli­ nary conferences on the spine took place; in 1982 the American Back Society was founded to promote interdisciplinary conferences of chiro­ practors, osteopaths, physical therapisl<;, and medical physicians. The 19908 witnessed the beginning of significant interdisciplinary research and substantial NIH grants to chiropractic col­ leges to study chiropractic scientific principles and the clinical benefits of chiropracHc care.

\VILK ANTITRUST SUIT In 1976, Chester Wilk and four other chiroprac­ tors, Patricia Arthur, James Bryden, Steven Lumsden, and Michael Pedigo, launched the twelfth event-an antitrust suit against the AMA and 10 other medical organizations (Fig. 3-8).

THE NATIONAL INSTITUTE FOR :EUROLOGICAL AND COM~lU~ICATIVE DISEASES AND STROKE CONFERENCE The eleventh event was a conference held in 1975 at the Bethesda, Maryland, campus of ~8tionaJ Institutes of Health (NIH), sponsored by the U.S. Congress as an "independent, unbi­ ased study of the fundamentals of the chiroprac­ tic profession." Medical physicians, osteopaths, and chiropractors assembled to discuss spinal manipulative therapy. In the resulting document, The Research Status oj Spinal ManiplLlative Therap)) edited by osteopathic physician Niurray Goldstein, most of the participants concluded that spinal manipulation: Pro\'ides relief fwm pain, particularly back pain, and sometimes cures, and may be dangerous, particularly If used by non-physicians; !there was I a difference of opinion (ocusing on the issues of indications, con­ traindications, and the precise sCientifio basis for the results obtained. IS

Fig. J-8 ArUst Kirk Miller's rendering of the Wilk and colleagues courtroom victory. In October 1976, five chiropractors filed suit against the American Medical Association (A:vlA) and 10 other health care associations to stop the boycott against chiropractic. Depicted in the foreground (left to right) are Michael Pedigo, Patricia Arthur, and Chester Wilko In Ute background is attorney for Ule plaintiffs, George McAndrews. Seated behind Ute bench is Judge Susan Getzendanner. (Courtesy Chiropractic Centennial Foundation.)

38

PART ONE

HISTORY, PHILOSOPHY, AND SOCIOLOGY

They charged that the AMA and others had engaged in a conspiracy to monopolize health care and restrain competition by maldng volun­ tary professional associations between doctors of medicine and doctors of chiropract.ic unethical. Further, they contended that the AJ\lA had been working with medical physician-dominated insurance companies to strangle the chiroprac­ tic profession economically. After two 8-week court trials and two appeals to the United States Court of Appeals for the Seventh Circuit (and one petition to the United States Supreme Court by the defendant medical societies, which was denied), United States District Judge Susan Getzendanner found the AMA guilty in late 1987 of an illegal effort to destroy the profession of chiropractic through boycott. She entered an injunction, national in scope (which is still in force today), prohibiting the AMA and all who act in concert with the NvLA from acting in any private manner to interfere with interprofes­ sional relations between medical physicians and doctors of chiropractic and their institutions. She also reqUired the A!'rlA to publish her deci­ sion in The Journal of the American Medical Association. Although interprofessional relations have improved in the last 15 years, the economic real­ ity is that medical physicians and their organi­ zations continue to lise their influence on insurance companies, hospitals, and media to influence doctors of chiropractic and their patients adversely.

ASSOCIATION OF CHIROPRACTIC COLLEGES PARADIGM The thirteenth event is a series of consensus statements. In July 1996 the Association of Chiropractic Colleges (ACC), represented by the presidents of all seventeen CCE accredited schools, presented a series of consensus state­ ments,J6 which sought "to clarify professional common ground" and to define chiropractic's role within the health care system. For the first time in 100 years of chiropractic education, all U.S. chiropractic coJlege presidents reached a unani­ mous consensus on definitions fundamental to

chiropractic. The ACC position on chiropractic follows: • Chiropractic is a health care discipline that emphasizes the inherent recuperative power of the body to heal itself without the use of drugs or surgery. • The practice of chiropractic focuses on the relationship between structure (primarily the spine) and function (as coordinated by the nervous system) and how that relationship affects the preservation and restoration of health. In addition, doctors of chiropractic recognize the value and responSibility of working in cooperation with other health care practitioners when it is in the best interest of the patient to do so. • The ACC continues to foster a unique, distinct chiropractic profession that serves as a health care discipline for all. The ACe advocates a profession that generates, develops, and uses the highest level of evidence possible in the provision of effective, prudent, and cost-conscious patient evaluation and care.]? The ACC's position on subluxation is: • Chiropractic is concerned with the preservation and restoration of health and focuses particular attention on subluxation. • Subluxation is a complex of functional or structu ral (or both) and/or pathologic articular changes that compromise neural integrity and may influence organ system function and general health. • A subluxation is evaluated, diagnosed, and managed through the use of chiropractic procedures based on the best available rational and empirical evidence. 18 See Chapter 2 for further discussion of the ACC paradigm. In 'November 2000 the World Federation of Chiropractic (WFC), in association with the ACe and the National Board of Chiropractic Examiners, met in Fort Lauderdale, Florida, to discuss philosophy in chiropractic education. From that meeting came the following consensus statements: • A shared approach to health and healing, based upon a shared philosophy of

CHAPTER 3

Major Themes in Chiropractic History

chiropractic, is important for the identity and future of the chiropractic profession. • Chiropractic is a unique discipline, but it exists as part of a broader entity-the health carc system. Accordingly, the discussion of philosophy as a discipline and the philosophy of health care, as well as the philosophy of chiropractic specifically, should be important components in every chiropractic curriculum. • The philosophy of chiropractic should be taught and developed in a manner that is intellectually defensible in the discipline of philosophy. 19

CHIROPRACTIC IN THE MILITARY

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In January 2002, President Bush signed the Department of Veterans Affairs Health Care Programs Enhancement Act of 2001. The bill included a mandate to establish a permanent chiropractic benefit within the Department of Veterans Affairs (OVA) health care system. The passage oj this bill represented a victory in a 8t~e that began in 1944 when Representative J.H. Tolan of California first introduced similar legislation. The bill was sponsored by House Veterans Committee Chairman Christopher Smith (R-New Jersey) and personally champi­ oned in the Senate by Majority Leader Tom Daschle (0-80uth Dakota). This legislation authorized the hiring of chiro­ practors in the OVA health system; it set a broad lIOOpe of chiropractic practice and allowed the chiropractic profession to participate in the Implementation of the new benefits through an IlMsory committee partially composed of chiro­ practors. Key provisions of the DVA law include (1) immediate phase-in of the program, (2) des­ tion of at least one OVA medical center in h geographic service area of the Veterans th Administration to prOVide chiropractic 'ces, and (3) a scope of chiropractic services t proVides a variety of chiropractic care with rices for neuromusculoskeletal conditions, . ~ the subluxation complex.

39

for years, the chiropractic profession bad also lobbied, with little success, the Department of Defense (DoD) to open its health care facilities to chiropractors. In 1995 the DoD agreed to a S-year Chiropractic Health Care Demonstration Program with test sites at 13 different military installations. The Oversight Advisory Committee evaluating this project reported that 81.5% of the chiropractic patients described the improve­ ment in their condition as "excellent," and that incorporating chiropractic could save the mili­ tary $28 million in lost work days as a result of back pain and other musculoskeletal conditions. In response to the overwhelmingly positive results of the demonstration project, President Clinton Signed P.L. 106-398 into law in October 2000, mandating that chiropractic care be made available to all active-duty personnel. These two events, the passage of the DVA and Veterans Affairs bills, coming as they did within 15 months of each other, are the fourteenth major event in the history of chiropractic. Another area of the military in which the chiro­ practic profession continues to seek recognition is tbe awarding of commissions similar to those received by podiatrists, optometrists, and psy­ chologists.

CHIROPRACTORS IN HOSPITAL AND INTEGRATED SETTINGS Early in the history of chiropractic, some chiro­ practors could admit patients to hospitals and treat them there. With the MtA's antichiroprac­ tic campaign in the 1960s and its insistence on a strict adherence to the Code of Medical Ethics (which prohibited association with a chiroprac­ tor), hospitals were unable to admit chiroprac­ tors on their staffs if they wished to gain or keep accreditation. After the chiropractic victory in the antitrust SUit, hospitals began to open their doors slowly to chiropractors, which represents the fifteenth major event in chiropractic history. The first hospital to accept chiropractors on its staff was Lindell Hospital in St. Louis in 1984. 20 By J 990, at least 60 hospitaJs and ambulatory surgical centers had chiropractors on staft'21; by 1997, that number had grown to approximately 200. 22 Although the number of hospitals granting

40

Pil,.RT DIVE

HISTORY, PHILOSOPHY, AND SOCIOLOGY

privileges to chiropractors continues to grow, they remain a minority. Another consequence ot the MfA's removal of the ban on medical physicians cooperating with chiropractors has been the increase in the for­ mation of multidisciplinary clinics and prac­ tices. Most opportunities for chiropractors to practice in integrated settings involve family practice or pain management groups. Other opportunities lie with acupuncturists, natur­ opaths, massage therapists, psychologists, and other complementary practitioners. The com­ plexities ot starting such a practice are many, but the potential for improved patient care is great. "If managed by caring, competent, and compassionate people, the multidisciplinary practice holds forth the possibility of a more integrated, patien t-ceo tered model. "2)

RESEARCH RESULTING IN RECOGNITION BY THE UNITED STATES, GREAT BRITAIN, AND CANADA During the 1990s, several research reportS were favorable toward chiropractic. These reports represent the sixteenth major event in chiro­ practic history. The RAND study (1992V~ towId that spinal manipulation benefits some patients with acute low back pain, and it is appropriate for mallY patients with acute low back pain and for some patients with subacute low back pain. In a. study published in the British Medical Journal, Meade and colleagues (1995) found a "29% greater improvement in patients with back pain treated with chiropractic compared to those treated with hospital outpatient manage­ ment."24 In Canada, two studies commissioned by the prOVincial government of Ontario, authored by health economist Pran Manga in 1993 25 and 1998,26 recommended that the gov­ ernment increase coverage of chiropractjc, expand chiropractic priVileges, and facilitate more cooperation between chiropractic and medical professionals. In 1994 the U.S. Agency for Health Care Policy and Research released its Clinical Guideline Number 14: Acute Low Back Problems in Adults,27 which concluded that

spinal manipulation is one of the most effective and safest treatments for low back pain.

IMPACT OF MANAGED CARE Because managed care orgmlizatiolls (MCOs) currently playa dominant role in the American health care marketplace, their policies to\'..·ard chiropractic are critical to the future of chiro­ practic and represent tbe seventeenth event influencing chiropractic. MCOs have been slow to accept chiropractic, and when they accept chiropractic services, the range of covered serv­ ices is often narrowly defined. In addition, MCOs seldom grant chiropractors status as primary care providers, which means that in some cases, referral from a medical physician is required to receive reimbursement. A key stntggle for chiro­ practic in the new century will be itS full partic­ ipation in managed care plans. Although 41 states mandate insurance reimbursements for cbiropractic services,28 most managed care providers claimed that state-mandated insur­ ance coverage was not an important factor in determining chiropractic coverage. All six of the new MCOs in 2000 who responded to a survey listed market demand and consumer interest as IJrimary motivators for offering coverage for complementary and alternative services. Of the six MCOs responding to the survey, all but one included some degree of chiropractic care. (For a more detailed discussion on managed care, see Chapter 29.)

CONCLUSION The Palmers and the other pioneers that fol· lowed were of a different time, yet their concepts have weatbered an entire century. Chiropractic has responded to forces similar to those that challenged nineteenth century medical seolari­ ans-and it has survived. The political climate. educational reforms, and legislative trends, as well as the rise of a strong medical community and the increased research in chiropractic effi­ cacy, are factors that are enormously int1uential in the marketplace of health care. Chiropractic has survived and flourished in a century that witnessed the demise or assimilation of several

CJ-1\PTER 3

Major Themes in Cbiroprllctic History

other healing disciplines. Understanding our his­ tory, Santayana suggests, may help us avoid the mistakes or pitfall' of the past.

1. How did D.O. Palmer found chiropractic? 2. What was the neurocalometer? Why was it controversial when introduced? 3. What was the first national chiropractic association?Who organized it? 4. What were the first and last states in the United States to license chiropractors? In what years were these licenses granted? 5. Historically, what issues divided straight

and mixer chiropractors?

6. In the Morikubo case, what was the basis for the chiropractor's defense against charges of practicing medicine without a license? 7. Which chiropractor was arrested 66 times

on charges of practicing medicine without

a license?

8. When did the U.S. Office of Education recognize the CCE as the official accrediting agency for all chiropractic colleges? 9. What was the final verdict in the Wilk

v, AMAcase?

10. What is the current status of chiropractic in military and veterans health care in the United States?

t

Questions

1. What are the advantages (if any) and disadvantages (if any) of having two major national chiropractic associations rather than one? 2. What unifying beliefs and objectives are common to all groups in the chiropractic profession? How might these be used to support the advancement of chiropractic? 3. What might be some of the major events in chiropractic in the next 50 years?

1. Palmer DO: The science, all and philosophy of chiro­ practic. Portland, Ore, 1910, Portland Printing House. 2. Gaucher PL, Donahue J, Wiese GC: Daniel David Palmer's medical library: the founder was "Into the Bterature," Chiropr Hist 15(2):63, 1995.

41

3. Palmer DO: The science, art and philosophy of chi­ ropractic, Portland, Ore, J910, Portland Printing House. 4. Wjese GC, Peterson DR; An overview of chiropractic educational institutions, 1896 to the present, J Chi1'Opr Ed 4(4):104,1991. S. Gibbons RW: The rise of the chiropractic educational eSL1blishment: 1897-1980. In DzamalJ FL, editor: Who's 'who in chiropractic, Littleton, Colo, 1980, Who's Who In Chiropraccic International Publishing. 6. Wardwell \'v1: Chiropractic: history and e'Colution oj a 'new prq!'ession, St Louis, 1992, Mosby. 7. Wardwell WI: Sixteen major evenls in chiropractic history, Chiropr Hist 16(1):66,1996. 8. Turner C: The rise of chiropractic, Los Angeles, 1931, Powelll'ublishing. 9. Reed L: The healing cults, Chicago, 1932, University of Chic;lgO Press. 10. \Vardwdl Wl: Chiropractic: history and evolution of a new professwn, SI Louis, 1992, Mosby. 11. Wiese GC, Peterson DR: An overview of chiropractic educational institutions, 1896 to the present, J Ch.iropr Ed 4(4):104,1991. 12. Cohen WJ: Independenl practitioners under Medicare: a repon to COtl~ress, Washington, DC, 1968, US Department of Health, Bducatlon, find Welfare. 13. Gibbons RW: Chiropractic history: turbulence and triumph-the survival of a profession. In Ozaman FL, editor: Who's who in. chiropract·w international 1976-78, LittJeton, Colo, 1978, \Vho's Who in Chiropractic Jnternationlll Publiahing. 14. Wardwell WI: Chiropractic: hislO'ry and evolution of a ne-w profeSSion, St LouiS, 1992, Mosby. 15. Goldstein 111: The research Ma·rus of spicnal manip­ ulative the-rapy. A Workshop held at the NIH, Feb. 2-4,1975, Betbesda, Md. DHEW pub. No. (NlH 76-998), NINcns. 16. Cleveland CS JII: Vertebml subluxation. In Redwood D, editor: COnlemporaT)' clJiropraccic, New York, 1997, Churchill Livingstone. 17. Association of Chiropractic Colleges: The chiroprac­ tic paradigm: ACC position on chiropractic. Retrieved I?ehruary 4, 2002, htlp://ww\o\,.chlrocol­ leges.com. 18. Association of Chiropractic Colleges: The chiroprac­ tic paradigm: the subluxation. Retrieved February 4, 2002, htlp://www.chirocolleges.com. 19. World Federation of Chiropractic: Proceeding from a

conference 011 philosophy in chiropractic education, Fort Lauderdale, Fla, 2000, WFC. 20. KingJ: Hospital privileges: yesterday's dream, todl1.Y's reality.lCA Review 40(2):41, 1984. 21. Wardwell WI: Chiropractic: history mul evolution of a new profeSSion, St Louis, 1992, Mosby. 22. francis RS, Buriak J, Ladenheim CJ: Chiropractic in hospitals and integrated settings. In Redwood D, edi­ tor: Contempora.ry chiropractic, New York, 1997, Churchill Livingstone.

42

PART ONE

HISTORY. PHILOSOPHY, AND SOCIOLOGY

23. ShekdIe PG et al: Spina) manipulation for low-back pain, Ann Intern Med 117(7): 590, 1992. 24. Meade TW et al: R.."lndomized comparison of chiro­ practic and hospital outpatient management for low back pain; results from e~tended follow up, 8MJ 311(5 August):349, 1995. 25..Manga P et al: The effectiveness and cost-"l!ectiveness of chiropractic management of low-back pain, Ottawa, Ontario, 1993, the author. 26. Manga P, Angus D: Enhal1ced chiropnu:tic coverage muler OHIP w; a means of "educing health care costs, attaining better health outcomes and achiC'O­ ing eqUitable access to health seroices. lonline).

Ontario Chiropractic Association. Available from Internet: http://www.chiropractic.on.calexecsum­ mary.html. 27. Bigos SJ et al: Acute low back problems in adull.S: clinical practice guidetine No. 14. Rockville, Md, 1994, Agency for Health Care Policy and Research, Public Health Service, U.S. Department of Health and Human Services. 28. Pelletier KR, Astin JA: Integration and reimburse­ ment of complementary and alternative medicine by managed care and insurance providers: 2000 update and cohort analysis, Altern Ther Health lolled 8(1):38, 42,2002.

PART TWO

ANATOM~

BKOMECHANliCS ND PHYSiOLOGY 9

CHAPTER

Spinal Anatomy

Patrick Coughlin, PhD

Key Tenns,

_

AFFERENT

FORAMEN MAGNUM

PEDICLES

ALAR LIGAME/I;TS

FORAMEN Th\NSVERSARIUM

PELVIC GIRDLE PIA MATER

ANASTOMOSES

FUNCTION;\L SPINAL UNIT

AN:-.lUlXS FIBROSUS

GLIA

PIAL ARTERIAL PLEXUS

ANTERIOR LONGITUort-:/'L

GOLGl TEN~O1\; ORGANS

POSTERIOR LONGITlJ01NAL

LIGAMENT AI\TIGENIC

GRAY MA'fTeR HERNIATE

LIGAMENT PROPRIOCEPTIVE

APICAL LIGAMENT

HUNCHBACK

RM"lI

ApOPHYSEAL JOINTS

lLIOLl;MBAR LIGA.>vIENTS

SACROSPINOUS LIGAMENT

AR.~C(-JNOlD ~,'lATER

INFARCTION

SACROTUBEROUS LIGAMENT

ARTICCLAR PROCESSES

INION

SAGITTAL

ASSOCI.~TION NEURONS

INSERTION

SCHMORL'S NODES

ATL.~

IN-rERCRISTAL LINE

SCLEROTOME

AXIS

INTERNEURONS

SINlJVERTEBRAL NERVES

CAUDA EQUINA

INTERSPINOUS LIGAMENTS

SOFT TISSlJF;

COLLATERAL CIRCULATJON

INTERTRANSVERSE

CONDYLES

LIGAMENTS

SOMITES SPl "AL ARTERIES

oes

CONCS MEDULLARIS

INTERVERTEBRAL DISK

SPJ.

CORONAL

INTERVERTEBRAL FORAMEN

SUBARACHNOID SPACE

DENTIClJL....T E LIGAMENT

ISCHEMIA

SUPRASPINOUS LIGAMENT

DERMATOME

KYPHOSIS

SWAYBACK

DISK HERNIATION

LAMINAE

SYNOVIAL

PROCESSES

DORSAL HORN

LATERAL FLEXION

TENDONS

DORSAL ROOT GANGLION

LIGAMENTS

TENSeCRITY

DliRA MATER

LIGAMENTUM FLAVUM

TENTORIUM CEREBELLI

ECTODERM

LIGAMENTUM NUCHAE

TRACTS

EFFERENT

LINEA TERMINALIS

TRANSVERSE PROCESSES

ENDODERM

LORDOSIS

TROPISM

EPINELRIU\I

LYMPHATIC

TRUE PELVIS

EQllILiBRIAL TRIAD

Mi\..\1 MII>LAR Y PROCESS

VALSALVA MANEUVERS

EXTENSIO~

MENINGES

VENOl1S PLEXliSES VENTRAL HORN

P.~CET JOl~TS

MESODERM

F.-\LSE PELVIS

MUSeLf. SPINDLES

VERTEBRAL FORAMEN

FALX CEREBELLI

MYOTOMES

VESTIBULAR SYSTEM

FALX CEREBRI

NW.RAL ARCH

VISCERA

FASCIA

NEURAL CRESTS

WHlTE MATTER

F..\SCICULI

NEUROVASCULAR BUNDLE

WOLFF'S LAW

FILUM TERMINALE

NUCLEUS PULPOSUS

ZYGAPOPHYSEAL JOINTS

FtExlON

ORIGIN

4.S

46

If 11

PART TWO

ANATOMY. mOMECHANICS. ANO PHYSIOLOGY

n the study of the anatomy of the axial skele­ ton and its related soft tissues, several foun­ dational concepts must be understood. First is that of bilateral symmetry. In theory (although tllis is almost never the case), the left side of the body should be an identical mirror image of tlle right side. AJthough this symmetry is ideally tme of tlle musculoskeletal system, it is not tme of the visceral organs. The ability to adapt to changing conditions is another trait of living organisms. In humans, tllis ability takes the form of maintaining, balance while negotiating cbanging or uneven terrain (or sometimes even while standing or sitting still) or while responding to various external stimuli (e.g.) antigens, emotional stresses, the occasional life-tb reatelli ng event). Postural adaptations are accomplished tllrough a system tllat can be referred to as the equilibrial triad. This system is composed of three elements: (1) the proprioceptive system, found throughout the body in the Golgi tendon organs (GTOs), the muscle spindles, and the nerves tlIat innervate these receptors; (2) the vestibldar system, fOWld in tlle inner ear, which signals the nervous system regarding the position of the head; and (3) the visual system. Adaptations to antigenic challenges are pri­ marily mediated thorough the immune system. However, as more evidence accumulates, tlle immune system is clearly interrelated with and is heavily intluenccd by both the endocrine and nervous systems. Responses to other forms of stress are processed through the autonomic nervous sys­ tem, which is discussed jn some detail later in this chapter. Understanding this system, how it innervates the viscera, and its interplay with tlle somatic nervous system (that which inner­ vates tlle muscles, joints, fascia, and sltin) is absolutely crucial to the informed practice of the adjustive/manipulative arts. Familiarity with the principles of tensegrity will provide a more thorough understanding of the operation of the musculoskeletal system and the proper maintenance of posture and balance. Tensegrity is a concept originated by tlle artist Kenneth Snelson and the architect Bucluninster Fuller, which posits a balance of compressional

and tensional forces through a body that exists in a gravitational field. Simplistically speaking, the bones and disks of the vertebral column are built to withstand compressional forces, and the muscles and ligaments are tlle tensional ele­ ments of the a...xial skeleton. [11 addition, the ten­ sional elements are p1"eloaded (Le., muscle tone and connective tissue tension are at rest), which adds to the stabiJity of the :-;ystem. When com­ pression and tension are in balance, an upright posture can be maintained with a minimum of work. Within this framework, tlle words origin and insertion will not be used to describe the attachments of the muscles. These common terms have been used over the years based on certain assumptions of the kinetics of tlle body. Specifically, the word origin has been used to describe a more prOXimal or stable attachment, and insertion is ascribed to the distal or mobile attachment of a muscle. However, especially rei· ative to the muscles that influence the spine, an important point to realize is that either muscle attachment can produce movement, sometimes simultaneously, and thus it is believed that these two terms are too limiting. The embryologic development of the human organism establishes a time line for the early period of life. A basic knowledge of this early his­ tory aJlows for a more tllorough understanding of the ultimate arrangement of the human body, as well as the existence of anatomic variations and, in some cases, birth defects. Wolffs law is a concept with which all stu" dents of 8llatomy should be familiar. \Volft"s law simply states that when stress is placed on a bone, it undergoes a tissue reaction whereby its form may change to fit its function. An impor­ tant point to remember is that bone is living lis­ sue, and as such, it will react to stress and its local environment. An example of this phenom­ enon is the difference in size and shape of the vertebrae of a large, physically active man, com· pared with a small, inactive woman. The vertc· bra of the man would bear more weight and be subjected to greater stresses. Therefore the ver· tebral body would be larger, and the processes would be longer and perhaps broader and thicker, given that the muscles attached to these parts of the vertebra would be pulling harder to

CHAPTER 4

Spinnl Anatomy

47

perform more work. This concept, although not specifically stated, can also be extended to soft tissues, such as ligaments, tendons, and other connective tissues, which also respond to the forces placed on them. The various rhythms and oscillations of the body are also important for the clinician to appreciate. Most notable are cardiorespiratory rhythms and the (hopefully unimpeded) move­ ment of tlle diaphragms of the body. These rhythms can be exploited in manual procedures to the advantage of both the clinician and the patient.

"e

e

rl­

Ilt

of jn

lle

Dn

VERTEBRAL COLUMN AS A WHOLE

on

:iy. to

nt, lile reI­

an ,ole nes Icse nan arly his­ ~g of f as ~nd, stu­ law

orn­ erte­

d be ver­ esses

and these er to

Anatomically, the human body is arranged len~thwise as a series of building blocks or seg­ ments. This arrangement can be observed most directly by looking at the individual vertebrae that make up the spinal column, which extends from the base of the skull to the "tail bone," or theeoocyx. Just above the coccyx is the sacrum, which is a single bone resulting from the fusion of five vertebrae. This fusion is significant because the sacrum articulates with the pelVic bones that, in turn, articulate with the femurs. This relationship produces an arch, which has the sacmm as its keystone. The spine, or vertebral column, is usually com­ posed of 33 individual vertebrae. Proceeding from superior to inferior, these vertebrae are 7 cerVical, 12 thoracic,S lumbar, 5 fused vertebrae forming the sacrum, and 4 rudimentary vertebrae, usually fused, forming the coccyx (Fig. 4-1). Each region of the spine is curved in the sagit­ tal (fronl to back) plane of the body. The cervi­ cal and lumbar regions are curved with a posterior concavity, referred to as lordosis, or a lordotic curvature. The thoracic and sacral regions possess an anteriorly concave curvature, referred to as kyphosis, or a kyphotic curvature. Both of these curvatures exist within a normal range. However, curvatures outside the nor­ mal range will be seen. For example, excessive thoracic kn>hosis (hyperkyphosis) is commonly referred to as buncbback (especially when com­ bined with scoliOSis, as described later), and

Fig. 4-1 Posterior and lateral views of the spine.

excessive lumbar lordosis is commonly referred to as swayback Under ideal conditions, the spine is vertical in the frontal (side-to-side) plane of the body. Lateral cun'atures are referred to as scoliosis and can exist separately or in combination with hyperkyphosis (hunchback) or hyperlordotic curves. The curvatures of the spine are sometimes referreu to as primary and secondary. Early in embryonic development, the spine is C-sbaped (Fig. 4-2), that is, a single l,yphotic curve (pri­ mary). As time passes, the spine gradually straightens, until at birth, two secondary Jor­ dotic curves begin to appear in the cervical and lumbar regions (secondary). As the infant learns to raise and hold his or her head erect with the supporting muscles of the neck, the cervical lor­ dotic curve is enlarged. Later, as the infant

48

PA.RT TWO

ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

Fig. 4-2 Development of the curvatures of the spine; A, fetus; n, infant; C. adult. learns to stand and walk, the lumbar lordosis is enhanced as a result of the activity of the poste­ rior spinal musculature.

FUNCTIONAL SPINAL UNIT The functional spinal unit (FSU) includes two adjacent vertebrae and the joints that linI, them, as well as the skeletal muscles that move the joints. The FSU is closely related to the body seg­ ment (see the Embryonic Segmental Development section in this chapter), which also includes the spinal nerves, blood and lymphatic vessels, and fascia. Other bones, muscles, and associated fascia ee.g., ribs, intercostal muscles in the thoracic region), as well as visceral structures within the body cavities that receive innervation from the autonomic portion of the spinal nerves, should also be considered elements of individual seg­ ments.

VERTEBRAL CHARACTERISTICS Although the vertebrae vary considerably in size and shape from region to region and within spe­ cific regions, certain characteristics are common to all (Fig. 4-3). Each structure has an anterior body and a posterior vertebral arch, or neural arch. The arch consists of four elements: the pedlcles, the transverse processes, the laminae,

and the spinous processes. The pedicles, which are short and stout, attach to the vertebral body posterolaterally. The pedicles form part of the boundaries of the intervertebral foramina through which pass the spinal nerves and other structures (see later discussion). The transverse processes, which extend laterally from the ends of the pedicles, are of varying length. The lami· nae. which are generally broad and flat, project posteromedially from the transverse processe or pedicles. The spinous processes, which extend posteriorly from the midline junction of the laminae, are of varying length, shape, and angulation and can, in many cases, be easily pal. pated. The posterior aspect of the vertebral body and vertebral arch forms the vertebral foramen. The collective group of vertebral foramina creates the vertebral or spinal canal, which contains the spinal cord and related structures. Projecting in both superior and inferior direc­ tions from the laminae are the superior and inie· rior articular processes, which form part of the synovial joints with the vertebrae above and below. The angle of the joint plane is of great sig­ nificance because it will direct the motion of the FSU. The vertebrae develop from the embryonic sclerotome (see later discussion), which con· tains several specific elements that are common

CHAPTER 4

Spinal Anatomy

•• •

49

: '

.

E A. Body B. Transverse process C. Pedicle D. Lamina E. Articular process F. Spinous process * Vertebral foramen Pi~. 4-.'

E

The parts of the vertebrae.

ich ,dy he

o

Centrum Neural arch _Transverse element Costal (rib) element * Costo-transverse foramen

Ina

lcr

o

ds ect ses 'ch of nd a1­

. ..

nd he les he

ec­

111&.4-4 Developmental origins of the vertebrae.

to all venebrae. The vertebral body corresponds to the centrum (or central element, Fig. 4-4).

The pedicles, base of the transverse processes,

n

laminae, and spinous processes correspond to the neural arch element. The transverse ele­ ments form the transverse processes. 111 addi­ lion, costal elements may be found, which in the thoracic region become the ribs but which also

persist in other regions and will be described later. The costal element is often overlooked, especially in the cervical and lumbar regions. The costal element makes up the anterior por­ tion, including the anterior tubercle of the cervi­ cal vertebra, and forms the majority of the transverse processes of the lumbar vertebra, as well as the anterior portion of the ala of the

50

PART TWO

ANATOMY, B10IvlECHANICS. AND PHYSIOLOGY

sacrum. The costotransverse foramen exists solely in the cervical and thoracic regions. The significance of the costotransverse foramen in the cervical vertebrae is the formation of the foramen transversarium for the passage (and presumably for the protection) of the vertebral artery. Failure of midline fusion of the posterior arch results in spina bifida, a potentially serious condition.

SUPPORTING STRUCTURES Anterior Longitudinal Ligament The anterior longitudinal ligament (Fig. 4-5) is broad and thick. Extending from the basilar por­ tion of the atlas to the sacrum, the ligament attaches to the anterior surfaces of the vertebral bodies and intervertebral disks. Superiorly, the anterior longitudinal ligament extends from the anterior arch of the atlas to the occiput as the anterior atlanta-occipital membrane and inferi­ orly as the anterior sacrococcygeal ligament. The anterior longitudinal ligament limits ante­ rior protrusion of the intervertebral disks and hyperextension of the spine. This ligament is prone to damage in whiplash-type injuries in which the spine is hyperextended as a result of rapid acceleration (or a blow from bebind).

Posterior 10000gitUdlnaIligament .-;:::::~==:::::-::::--

Vertebral

body---

Intervertebral disk-_

Posterior Longitudinal Ligament This ligament is found on the posterior surfaces of the vertebral bodies and intervertebral disks. Within the vertebral canal, the posterior longi­ tudinal ligament (Fig. 4-6) is Illuch narrower than the anterior longitudinal ligament. Extending from the axis to the sacrum, this ligament is con­ tinuous superiorly with the tectorial membrane and inferiorly with the deep dorsal sacrococcygeal ligament. Lateral extensions of the posterior longi­ tudinal1igament exist at the level of the interver­ tebral disks. The posterior longitudinal ligament prevents posterior protrusion of the intervertebral disk and spinal hyperflexion.

Ligamentum Flavum These ligaments (Fig. 4-7) are found extend­ ing from the articular process to the spinous process and connect adjacent vertebral laminae and attach to the anterior surface of the lamina above and the posterior surface of the lam­ ina below. The word flavum (L. for yellow) is used to describe these ligaments because of their yellow coloration resulting from the predomi­ nance of elastic tissue. These ligaments are the most important of the posterior ligaments in lim­ iting flexion of the spine.

Antel'ior longitudinal ligament

Vertebral body - - - - ­ Pedicle - - - -

Posterior longltudinalligament Antel'lor Iongltudinailigament .....4-l-_.

::'~

"-_

Intervertebral disk ---~k

Fig. 4-5 The anterior longitudilla\ligament.

Fig. 4-6 The posterior longitudinal ligament.

CHAPTER 4

SpinaL Anatomy

pulposlIS (a remnant of the embryonic noto­ chord) and a peripheral, fibrocartilaginous 3unulus fibrosus. The annulus fibrosus is arranged in concen­ tric rings. The collagen fibers in each ring run obliquely from one vertebra to thc next, and in each succeeding ring, the fibers run in the oppo­ site direction; that is, one set of fibers runs clocl<­ wise, the next counterclockwise, and so forth. This arrangement limits the amount of torsion allowed on the disk and the amount of rotation of

Intervertebral Disk s s. .r

e

The anterior fibrous joints (symphyses) between the vertebral bodies arc formed by the interver­ tebral disks (Fig. 4-8). Thc disks are found between the vertebral hodies froUl the C2-C3 to the lumbosacral junction. A small, rudimentary disk also exists between the sacrum and coccyx and possibly between caudal coccygeal seg­ ment . The intervertebral disk consists of two basic components: a central, gelatinous nucleus

Spinous process - - _

Transverse process -

(1­ lamina ----....;>",,:=----+~+--

fit 4-7

The ligamenta tlava.

Annulus fibrosus . .----l;,;;-'-t--

Nucleus pulposus

AP

- - Nucleus pulposus Annular lamellae

F'~

4-S The intervertebral disk

51

52

PART TWO

ANATOMY, BIOMECHANICS, i\.ND PHYSIOLOGY

A

c

46

48

50

49

Fig. 4-9 Deformation of the intervertebral disk. (From J(apandji lA: Physiology of the joints, New York, 1990, Churchill Li'Vingsc.one.)

the vertebrae relative to one another. In addi­ tion, the fibers are under tension, creating a pre­ loading effect, which increases the stability of the joint when it is not under stress, and increas­ ing the ability of the disk to adapt to the stress placed on it, similar to the cables in a suspension bridge. The outer portion of the annulus fibrosus has a blood supply and is innervated by the sinuver­ tebraJ nerves, which may be the cause of much idiopathic bacl, pain. The inner portion has nei­ ther innervation nor blood supply and is nour­ ished by diffusion, as is the nucleus pulposus. The nucleus pulposus is composed mainly of water, which is bound to a gelatinous matrix by high concentrations of hyaluronic acid. As men­ tioned, the nucleus is nourished by diffusion, primarily from the periphery of the disk. Dynamic

weight bearing has a demonstrable effect on the shape of the disk (Fig. 4-9). During movements of the spine, the nucleus, because of its relative incompressibility, acts as a swivel or pivot around which one vertebra in the FSU can move relative to the other vertebra (Fig. 4-10). Additionally, as the spine moves, the shape of the disk changes because of the elasticity of the aIUlUlus fibrosus. This cluUlge causes the nucleus to move in vari· ous directions, depending on the action of the moment. The pressure of the incompressible nucleus, in turn, causes the annulus to bulge slightly. The bulge is typically held in check by the integrity of its own fibers, as well as by the anterior and posterior longitudinal ligaments. However, under severe loading, these fibers can mpture, creating an injury referred to as a her­ niated nucleus pulposus (HNP) or "slipped"

CHAPTER 4

28

29

Spinal Anatomy

53

between the transverse processes (iutcrtrans­ verse ligament...) and spinous processes (inter­ spinollS ligaments). A long, thiel, ligament is also found extending between and over the tips of the spinolls processes, tlle SUpnlSpinous ligament, which extends from the axis to the sacrum. In the cervical region, dus ligament forms an attach­ ment point for the ligamentum nuchae. The inter­ spinous and supraspinous ligaments in the cervical region are quite strong and, in decelera­ tion-hyperflexion injuries, can actually avulse the spinous process of the vertebra.

Zygapophyseal Joints

rig.4.10 Intervertebral disl, acting as a swivel in Ka.pa.n(~ii fA: Physiology of tbe joints, New York, 1990, ChurchilllAvingstone.)

vertebral motion. (From

disk. During the aging process, the water content of the annulus gradually decreases, and coUa­ gen cross-linking increases, which causes the annulus to become less elastic and more brittle. Consequently, the probability of incurring an Jrol during certai n lifting maneuvers is increased yet can be prevented by proper posture during this activity ("Lift \vith the legs, not the back. "). The arrangement of the anterior and posterior longitudinlll ligaments holding the annulus in check predisposes herniation in a posterolateral direction, which unfortunately is in the direc­ tion of the intervertebral foramen. Often, nerve impingement and severe pain accompany disk herniation. Occasionally, the nucleus can herni­ ate in a superior or inferior direction, creating a defect in the vertebral bodies, known as hmorl's nodes, which can be visualized radi­ ographically.

The additional intervertebral ligaments are descrihed as being part of the fibrous interverte­ bral joints hut can also be thought of as check ligaments. These additional ligaments are found

The zygapophyseal joints (also called apophy­ seal joints or facet joints) occur between the superior and inferior articular processes of the vertebrae. Zygapophyseal joints are synOVial joints with a thin, loose, somewhat elastic fibrous capsule and are of the gliding type. The joint facets are covered with hyaline cartilage and are oriented at oblique angles, which are region specific (Fig. 4-11). These joints signifi­ cantly affect tlle movements of the vertebrae. OWing to their oblique orientation, motions in the transverse plane (rotation) and frontal plane (lateral flexion or sidebending) are said to be coupled. Although a very small amount of pure rotation or lateral l1exion is allowed because of the intervening joint space, the facets engage quickly, and the direction of motion changes to conform to the facet plane. Although the plane of the facets is region specific, a gradual change in orientation tal{es place so that abrupt changes do not occur (e.g., between the cervical and tho­ racic regions). However, vertebrae do exist that exhibit characteristics of one region in the supe­ rior articular processes and of the caudal region with the inferior articular processes. Such verte­ brae are described as transitional (Fig. 4-12).

BLOOD SUPPLY AND INNERVATION OF THE VERTEBRAE AND JOINTS The blood supply to the spine and related tissues differs from region to region. In the cervical region, the vertebral artery and its branches

54

PART TWO

ANATOMY, BIOMECHA.i'liICS. AND PHYSIOLOGY

Fig. 4-11 Orient.ation of the zygapophyseal joints.

\('

~ .-/'

(

,

. -",

I SEVENTH CERVICAl,. I

I TWEI.FTH THORAClC I

I FIRST THORACIC I

Fig. 4 -12 Tra nsl tional vertebrae.

provide the primary blood supply to t.he verte­ brae. In the thoracic and lumbar regions, typical segmental arteries supply the vertebrae. In the sacral region, the blood supply is derived from the lateral sacral branches of the internal jliac arteries (Fig. 4-13).

Segmental Artery The typical segmental artery is similar in distri­ bution to that of the spinal nerve (Fig. 4-14). Many of the segmental arteries are branches of

the aorta, The descending aorta lies slightly to the left of the midline; therefore the right seg­ mental branch must cross the midline (Le., the vertebral body) to reach the right side of the body. As the artery crosses the vertebral body, it sends off small branches to supply it, the anterior longi· tudinal ligament, and the anterolateral portion of the intervertebral disk. The primary segmental artery sends its first (major) branch back tOward the midline struc­ tures and is thus sometimes referred to as the recurrent or spinal artery. The spinal artery has

CfL\PTER 4

Spinal Anatomy

55

Basilar a. ---+-::'L Anterior spinal a. -~mt'~

--'Iaraa. ~-I'€1f"'~"-~. Vertebral a ­ Ant..........

Posterior spinal aa.

Aorta---f, I

Anterior spinal artery

••

Al1ery of adamklewlcz

•• •

•

• I POSTERIOR I Fi,I!.4-13 Arterial supply of the a.xial skeleton.

Perforating branch Anterior intercostal a.

Lateral cutaneous branch

I Dorsal ramus

Fig. 4-14 The segment..'ll artery and its main branches.

several important branches (Fig. 4-15). Radicular branches course along the spinal nerve and sup­ ply its proximal portion, including the dorsal root ganglion. The radicular arteries terminate in anastomoses with the anterior and posterior spinal arteries (of the spinal cord). Branches from both sides anastomose as the anterior spinal artery, an important coUateraUzation for the

spinal cord. The spinal arteries continue into the vertebral canal and send off dural and vertebral branches, which slIpply the meninges, the verte­ bral body and posterior arch, the ligaments within the vertebral canal, and the posterior por­ tion of the intervertebral disk. The next branch point of the segmental artery follows the pattern of a spinal nerve, that is, the

56

PART TWO

ANATOMY, BIOMECHANICS. AND PHYSIOLOGY

segmental

artery

Fig. 4-15 Branches of the spinal artery. dorsal and ventral rami (L. for branches). The dorsal ramus penetrates the paraxial fascia and muscles, supplying them, and reaches the super­ ficial fascia, where it supplies it and the overly­ ing skin. The ventral ramus proceeds laterally and enters what is referred to as the neurovas­ cular plane, between (in the thoracic region) the innermost intercostal muscle and the internal intercostal muscle. In this fascial plane, the seg­ mental nerve and its cOrresponding vein accom­ pany the artery. At approximately the midaxillary line, a lateral branch is given off, which penetrates the muscles and comes to lie in the superficial fas­ cia. At this point, the lateral branch sends off anterior and posterior branches, which supply the fascia and skin. The ventral ramus continues anteriorly to just lateral to the midline, where it penetrates the body wall to reach the superficial fascia (the anterior cutaneous branches) and skin. In the tboracic region, the anterior intercostal artery anastomoses with the internal thoracic artery. A vein of the same name accompanies each branch of the artery.

Vertebral Artery The vertebral artery branches directly from the subclavian artery (Fig. 4-16). The vertebral artery runs deep to the anterior scalene Illuscle

and enters the foramen transversariulll of the sixth cervical vertebra (06). Although an inter­ vertebral foramen is found at the seventh cervi· cal vertebra (07) for the vertebral vein, the vertebral artery does not enter it. The artery fol­ lows this course until it traverses the foramen of the atlas (Fig. 4-17). The artery then courses posteriorly and medially in a groove on the pos­ terior arch of the atlas, pierces the posterior atlanto-occipital membrane, and enters the cra­ nial cavity via the posterolateral aspect of ule foramen magnum of the occiput. From this pOint, each vertebral artery courses forward to the anterior aspect of the brainstem, and the two vessels come together at the level of the pons to form the basilar artery. A high degree of elastic­ ity of this artery is necessary in the upper cervi­ cal region to withstand the torque generated by nonnal range of motion of the atlanto-axial joint (90 degrees). Because the artery is held stable in the foramina intertransversarii of both the atlas and a.xis, significant stretching of thiS artery occurs during normal rotational excursion of the head. Range-oJ-motion testing and impulse· oriented manual techniques in this area can put this artery at risk, especially in older patients with atherosclerosis. Patients may also exhibit rotational dysfunctions resulting from develop­ ing or congenital insufficiency of this artery.

CHAPTER 4

Spinal Anatomy

57

Vertebral artery

Atlas

e f s

Vertebral artery

;­

r I­

e

s o o o

Y t

n

ut

s it p-

Atlas (posterior arch) -+--~~~::::-~-""~>o<:'\ Ligamentum f1avum

---;.---~.

Axis---

Vertebral artery

fig. 4·17 The vertebral artery, upper section. 1\vo views of this critical part of the pathway of the vertebral mery are shown here. In the superior view, the posterior turn that the artery takes can he seen when it passes Ihrough the foramen transversariulU of the atlas, as well as t.he medial t.urn as it crosses the posterior arch of the atlas (in the groove) to reach the foramen magnum of the occiput. The reader should be aware of the elastic DIIUre of this artery and realize that it.s structural int.egrity can be severely compromised by atherosclerosis.

VENOUS DRAINAGE OF THE SPINE Rather than a single arterial supply of various IllUclures, the venous return of the spine is a

series of plexuses, which ultimately drain into the caval system (Fig. 4-18). Within the spinal canal, two epidural ple.x:uses may be found, one anterior and the other posterior. These veins drain the spinal cord and meninges, as well as

58

PART TWO

ANATOMY. BIOMECHANICS. Al'ID PHYSIOLOGY

Basivertebral velns'lf'------

Posterior internal

.3."::~";;;;;II-venous plexus

Anterior external venous plexus Spinous process

Anterior internal

venous plexus

Fig. 4-18 The spinal venous plexus. This cutaway section of the lumbar vertebrae shows the venous plexuses and their communications with one another. The reader should note the basivertebral veins draining the vertebral body and the communications of the internal venous plexuses and the external venous plexuses. as well as the existence of the spina! (intervcrtebml) vein, corresponding to the spinal artery.

Anterior external venous plexus

Anterior internal venous plexus Intervertebral (segmental) vein ~--

Radicular veins

Posterior extemal venous plexus

Fig. 4-19 Venous drainage of the lumbar vertebra.

the vertebrae via the basivertebral veins. The plexuses will communicate with the spinal veins through the intervertebral foramina and with the anterior and posterior external venous plexuses adjacent to the vertebral bodies and spinous processes, respectively (Fig. 4-19). These plexuses, in turn, communicate with other veins

in their respective regions, including the pell' cavity. Of clinical significance is the fact these veins cont<Jin no valves, thus blood How in either direction within them. This ch acteristic becomes problematic in men wi malignancies of the prostate in which metastl cells can tmvel through these veins to the ve

CHAPTER 4

bral column and seed there, or they can travel aU the way to the brain. IN~ERVATION A~D

OF THE SPINE RELATED STRUCTURES

Recurrent branches of rhe primary dorsal rami of the spinalllerves innervate the vertebrae, joints, dura, and intervertebral disks. These recur­ rent nerves are also referred to as sinuvertebral nert>es, which are distributed with the spinal arteries extemal to the vertebrae and reenter the spinal canal through intervertebral foramina. The sinuvertebral nerves contain nociceptive (pain) fibers, as well as proprioceptive fibers, which innervate the zygapophyseal joints. Autonomic fibers are also present, which innervate the ves­ sels in the area. Because of the intersegmental nature of the vertebrae, sinuvertebraI nerves from the Ilerve above and below will innervate each vertebra and its associated zygapophyseal joints.

REGIONAL SPECIALIZATIONS

Occiput, Atlas, Axis Theoccirut is one of the bones that make up the base of the skull (Fig. 4-20). This structure artic­

Spinal Anatomy

ulates with the two temporal and parietal bones through uneven, fibrous joints known as sutures. The exterior surface of the occiput has two lines, the superior and inferior nuchal lines, for muscle attachments, and a palpable, midline external occipital protuberance (inion). The inion serves as an attachment site for the ligamentum nuchae. The foramen magnum, located at the base of the occiput, serves as the bony land­ marl" indicating the transition point of the cen­ tral nervous system from brainstem to spinal cord. The occiput has two convex articular processes, the occipital condyles. which articu­ late with the atlas. In addition, the occiput con­ tains the hypoglossal canals through which the twelfth cranial nerves (hypoglossal) pass on their way from the brainstem to the muscles of the tongue. The interior surface of the occiput displays features related to the structures that attach to it, pass through it, or articulate with it (Fig. 4-21). Anteriorly, the occiput has a postlike, basilar terminal, which articulates with the body of the sphenoid bone. In addition, a small tuber­ cle forms part of the jugular foramen, the origin of the internal jugular vein. On the interior sur­ face, several ridges and grooves are visible. The ridges are the attachment sites of the dura as it reflects off the occiput to contribute to the

_--::------"""--_~-External occipital protuberance (Inion) .~-..::--"~"""-

Superior nuchal line Inferior nuchal line - Extemal occipital crest

JugUlar process

lay har­ with .atic ~rte-

PIg.4.20 External view of the base of the occiput.

59

60

PART TWO

ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

",,~r§1.~~~~

'gtal-....-~ .

.,

Groove for superior sagittal sinus • Intemal occipital protuberance

Groove for transverse sinus Intemal occipital cres! -

Jugular process

Foramen magnum

Fig. 4-21 Intemal surfaces of the occiput.

Anterior tubercle Facet for articulation with dens Superior articular facet Transversa foramen

, Y'".... --l._ _

Groove lor Posterior vertebral artery tubercle

.....

Inferior articular process

Anterior tubercle

Fig. 4-22 The atlas.

formation of the dural venous sinuses, which drain most of the blood from the brain. Grooves in the occiput represent spaces where the arter­ ies that supply the meningeal tissue course. Centrally located is the foramen magnum, which serves as the egress point of the brainstem from the cranial caVity as it establishes continuity with the spinal cord. The atlas eCl), as its name implies, holds up the globe of the skull, through its articulation

with tlle occiput (Fig. 4-22). The atlas is an
Spinal Anatomy

CJL\PTgR 4

61

Dens Superior articular facet for atlas

- Transverse process Inferior articular process Dens Spinous process

Superior Brticular facet for atlas

EIIi-a;t-m.=-.

Facet for articulation "~-1wlth altas

Transverse process

Pedicle

Inferior articular facet for CS

-

.-

Fig. 4-23 The axis.

an atyp­ ; body is s during m as the iculation the spin­ the pos­ :lesses of ~ontal

in

,r sigtlifi-

cant flexion-extension of the occipito-atlantal joint, as in nodding the head. The "cupping" of the facets allows only small amounts of sidcbending or rotation, these motions being accomplished by the combined actions at the other intercervical joints. However, the convex­ concave relationship of the occipital condyles with the superior articular processes of the atlas creates a modified ball-and-socl<et joint in which movements in all three planes of space are pos­ sible. Bilateral grooves in the laminae adjacent to the superior articular processes form a sup­ pon structure for the vertebral arteries as they travel from the foramina intertransversaria of the atlas to the foramen magnum of the occiput. The axis is an atypical cervical vertebra for several reasons (Fig. 4-23). The vertebral body differs significantly from other cervical vertebrae in that it contains a superior extension, known as the dens (L. for tooth). The dens actually rep­ resents the embryonic vertebral body of the atlas, which undergoes dissociation from the atlas and absorption into the body of the axis during development. This process results in a large degree of rotation between the atlas and axis (approximately 90 degrees under normal circumstances). The dens also has a facet for articulation with the anterior arch of the atlas. The superior articular processes are positioned

more allteriorty in relation to the transverse processes, actually associating with the pedicle, as opposed to the inferior articular processes, which are more typically associated with the lamina. The angle of tlle superior facet is more horizontally (axially) arranged than the more coronally (or paracoronally) arranged inferior facet. The spinous process is bifid but is consid­ erably longer posteriorly tllan both the posterior arch of the atlas and the spinous process of the third cervical vertebra. Consequently, t11is is the first cervical spinous process that can be pal­ pated. The (elationship of the foramen inter­ transversarium is important. The foramen is directly inferior to the superior articular facet. In the anatomic position, this foramen is also inferior to the foramen transversaJium of the atlas. However, the degree of rotation available at this joint, can endanger tbe vertebral artery, especially in the presence of pathologic condi­ tions such as atherosclerosis and vertebrobasilar insufficiency. \\Then grouped together, the occiput, atlas, and axis display complex yet interesting rela­ tionships, which follow the function of the joints that connect them (Fig. 4-24). The superior and inferior articular facets of the atlas are angled in opposite directions. That is, the superior articular facets wedge inward (medially), and the inferior

62

PART TWO

ANATOMY. BIOMECHANICS, AND PHYSIOLOGY

Fig. 4-24 Cl-C2 relationships.

Fig. 4-25 Anterior-posterior open mouth x-ray of the atlas and axis.

articular facets wedge Olltward (laterally) (Fig. 4-25). When a severe blow to the top of the head is incurred, the atlas can fracture, and given this arrangement, each lateral mass will be forced laterally, which can be seen on x-ray examination (Fig. 4-26). The planes of the facets directly affect the type of motion allowed in thjs joint. The atlas and axis articulate so that apprOXimately 90 degrees totaJ or 45 degrees in each direction is allowed to rotate of the bead. The center of the

dens actS as the axis of rotation of the joint. An important point to remember is that the den begins during development as the body of the atlas but subsequently separates from it to fu with the body of the axis. The facet (zygapoph~' seal) joints, which are between these two bon are almost in a transverse (horizontal) plan again to allow free rotation. As mentioned pre\' ously, the course of the vertebral artery as passes between these two bones is importan Because of the degree of movement allowed he

CHAPTER 4

Spinal Anatomy

63

Fig. 4-26 Jefferson fracture of the atlas.

AtIanto«cipItaI

joint capsule Anterior

- - atlantO«Cipltat membrane

Fig. 4-27 Supporting structures of the occipito-atlanto-axial complex (anterior view).

An dens f the fuse Iphy­

t.

Dnes,

,lane, >revi­ as it tanto here,

the artery has developed a significant amount of

slack (as well as elastic fibers in its wall), which takes the foml of a kink at this location.

Occipito-Atlanto-Axial Ligaments The occipito-atlanto-axial (OM) region contains supporting soft tissues that are unique to this area. Anteriorly, three groupings of ligamentous struc­ tures exist, two of which are typical of the verte­ bral column (Fig. 4-27). The joint capsules of the

occipito-atlantal (OA) joint and the atlanto-axial (AA) joint make up one group, and the anterjor longitudinal ligament make up the second group. Additional atypical supporting elementS are also present: the anterior atlanto-occipital membrane and a medial extension of the atlanto-axial joint capsule. The laxity and elasticity of these liga­ ments allow the anatomic range of motion at these jointS. However, the supporting role of these jointS is of extreme importance because dislocations jn this area can be life threatening.

64

PART TWO

AA'ATOMY. BIOMECHANICS, AND PHYSIOLOGY

The AA joint is complex because of its pri­ mary function of allowing significant rotation in the transverse plane. The ligaments, which serve to hold the dens of the axis close to the anterior arch of the atlas, are of the greatest significance, because dislocation in this area can be fawl. A deep layer of the posterior longitudinal liga­ ment is present, known as the tectorial mem­ brane (Fig. 4-28). The layer connects the occiput

to the axis by spanning the distance between dIe dens and foramen magnum. Deep to the tector­ ial membrane are several additional ligaments (Fig. 4-29). The transverse ligament of the dens extends from two tubercles on t11e anterior arch of the atlas tubercles and slips posterior to tbe dens. This ligament has superior and inferior extensions (fasciculi), which together with tbe transverse portion are known as the cruciform

Posterior longitudinal ligament

OccIput

Atlas --e.rTecborialnMHnbrane (deep part of posterior longitudinal ligament)

Axis - - - - 7 " " : " -

Posterior longitudinal ligament

Fig. 4-28 OCCipita-atlanta-axial laminectomy and supporting structures.

Alar ligament

OCciput

Atlas ---f'--""-="--

AxIs - - - - - j " " ' ! ' - -

Deep (accessory) part of posterior longitudinal ligament

Fig. 4-29 Occipito-atianto-axiallaminectoJl1Y and SuppoT{ing structures.

CHAPTER 4 Spinal Anatomy

(L. for similar to a cross) ligament. In addition,

the alar ligaments extend upward and outward from the apex of the dens toward the occiput. The apical ligament of the dens extends from the tip of the dens and attaches to the occiput. The median Ai\. joint has two components consisting of 3n anterior synovial cavity and a posterior bursal sac (Fig. 4-30). The alar ligaments sepa­ rate the joint into two separate compartments. The transverse ligament ql the dens supports the posterior compartment posteriorly. This lig­ ament holds the dens snugly against the poste­ rior arch and prevents posterior displacement, which can seriously jeopardize the spinal cord. The existence of these two synovial cavities is of geat importance because of the lubricating properties of the synovial fluid. The amount of friction that would result if these bones were approximated without lubrication would be sub­ stantial, especially considering the number of limes the head is turned in a single day. In median section, the continuity of the posterior atlanto-occipital membrane with the ligamen­ tum fla\'um can be visualized (Fig. 4-31).

Typical cervical vertebrae are specialized in sev­ eral ways (Fig. 4-32). The bodies are smaller

than the vertebrae below, which bear more wei,ght. The vertebrae also have anterolateral lips, the uncinate processes. Associated with the uncinate processes are additional synovial joints Imown as the uncovertebraLJoints (of Luschka), which are unique to the cervical vertebrae. The space between the vertebral bodies, occupied by the intervertebral disks, is larger in the cervical region than the space in the thoracic region because of the relative height (or thickness) of the disks. ThiS difference is one factor that predisposes these disks to herniation. The trans­ verse process contains a foramen transversar­ ium, the conduit for the vertebral artery. The anterior portion of the t.ransverse process, con­ tabling the anterior tubercle (an attachment site for the anterior intertransversarii muscle group), represents the costal element of the cervical ver­ tebrae. The tip of the transverse process, termed the posterior tubercle, represents part of the true transverse process and is an attachment site for the posterior intertransversarii muscle group. The articular processes are thickerled to form what are commonly referred to as articular pillars. The designation pillars stems from the fact that the interarticular (zygapophyseal or facet) joints in this region are arranged in the transverse plane, thus the articular processes sit atop one another, similar to blocks of a column

ransverse ligament

TRANSVERSE SECTION THROUGH DENS

LC---->rl Synovial cavities Dens Transverse ligament

4-30 Supporting ligaments of the dens.

65

66

PART TWO

ANATOJVCY, BIOMECHANICS, AND PHYSIOLOGY

Ant amlantOoOCClpltal memb. Ant. longitudinal ligament Apioalligament of dens ~~~~-I Upper cruciform ligament ~~~-~-

Tectorial membrane

~~=I=-- Synovial cavities

- "Fransverse ligament r-n---1- Lower cruciform ligament Post. Iongltudinaillgament Post. atlanto«cipltal mamb. "-J.!--'t--

Ugamenlum f1avum

"1!&ii'~~~--Ir--Nuchalligamenl

Fig. 4-31 Supporting structures of the Occipita-atlanta-axial complex.

Groove for spinal nerve InferiGr articular facet Uncinate process

Lamina

TransveJSe process '6---Body

Spinous process _-liiioolll-

IIlilmalnferior artfcular facet

Fig. 4-32 The typical cervical vertebra,

(Fig. 4-33). The tnmd as one proceeds in an infe­ rior direction is for the angles of the facet joints to change from a transverse orientation to a coronal orientation. Cervical vertebrae have a spinous process that is bifid, accounting for the pairing of the interspinales muscle group in this region. The arrangement of the articular facets of the cervi­ cal vertebra represents an adaptation to the need for a high degree of rotation for the head and neck (for visual scanning: approximately 7

to 8 degrees each, totaling about 45 degrees [0 each side) (Fig. 4-34). However, the angle of th facet joints is such that rotation is coupled wi sidebending (lateral fleXion) to the same side Conversely, sidebending in this region is allowed, which is coupled with rotation to th same side. The degree of flexion allowed in ea of these joints will permit herniation of nucleus pulposus in a posterior and lateral rur tion, impinging on the exiting nerve. Herniatio does not usually occur directly posterior.

CHAPTER 4 Spinal Anatomy

Uncinate process

67

, Superior articular process - - - - - Lateral mass Transverse process Inferior articular facet

Body

Inferior articular facet

Fig.4·33 Relationships of the cervical articular joints.

NTEROLATERAL

••• Fig. 4-34 The plane of the cervical zygapophyseal joints. to ~. the ~s

~ith side. also I the each the irec­ ltion iorly

because of the presence of tlie posterior longitu­ dinal ligament. The intervertebral foramen is located just between the articular process and the vertebral body. The cervical nerve, exiting the foramen, passes just posr.erior to the verte­ bral artery (which is traveling through tlie fora­ men transversarium) and is "guided" to the periphery by a groove in tlie transverse process. The uncovertebral joint is just anterior to the

intervertebral foramen. Degenerative disease of this joint can also cause nerve impingement. The supporting ligaments and joint capsules of tlie cervical vertebrae and their respective intervertebral joints are flexible enough to allow tlie range of motion necessary for appropriate functional movement of tlie head. However, these supports will also limit motion such that disloca­ tion does not occur, or any action that might be

68

PAHT TWO

ANATOMY, BIOMECHANICS. AND PHYSIOLOGY

damaging to the spinal cord (via shear, torque), which would be disastrous. (See Chapter 6 for descriptions of shear, torque, and other biome­ chanica! concepts.) The posterior longitudinal ligament and the ligamentum flavum both limit flexioo of the neck. The ligamenta tlava also limit rotation to a lesser degree. The ligamentum nuchae, which also functions as a major muscle attachment in the cervical region, virtually sur­ rounds the tips of the spinous processes in the sagittal plane.

bles that of a lumbar vertebra. This process again illustrates the gradual transition in vertebral structure, which adds considerable stability to the spine. The singular specialization is the presence of articular facets for Ule ribs. Typical thoracic ver­ tebrae have two rib clemijacets. The superior facet is located at the point at which the verte­ bra articulates with the rib, which shares its number (1'6). The inferior facet is located at the point at which the vertebra articulates with the rib from the segment below. The first and twelfth ribs, though, articulate with a single thoracic vertebra and thus only possess a single rib facet. In the mid-thoracic region the zygapophyseal joints are coronally (or paracoronally) arranged (Fig. 4-36). This arrangement allows a significant amount of flexion (forward bending). Extension would also be allowed if not for the angle of dec­ lination of the transverse process. Significant rotation would also be allowed, were it not for the presence of the rib cage. From superior to inferior, the plane of the thoracic facets changes from a horizontal-oblique plane (similar to the cervical vertebrae) to a vertical-oblique or para­ coronal plane in the mid-thoracic region, then to a more sagittal (or parasagittal) plane, complet­ ing another transition to Ule usual arrangement of the lumbar vertebral facets.

Thoracic The thoracic vertebra is traditionally known as the "typical" vertebra, primarily because of the presence of all the basic vertebral elements and the lack of special features (Fig. 4-35). The tho­ racic vertebra is composed of an anterior body and posterior arch, which consists of paired pedicles, transverse processes, laminae, and a single spinous process. The spinous process is angled down ward in the thoracic vertebrae. In the upper thoracic vertebra, the spinous process is only slightly declined, resembling that of a cer­ vical vertebra. In the mid-thoracic region, the angle of declination reaches a peak, which then decreases as the lumbar region is approached. The spinous process of the lower thoracics resem-

.. Body

..

Superior articular process Transverse process

... Transverse process Spinous proC$$$

.. Fig. 4-35 The thoracic vertebra.

Inferior vertebral notch

s again rtebral ility to ~ncc

of ver­ llperior ~ verte­ Ires its 1 at the lith the twelfth horacic b facet. physeal rranged nificant tension . of dec­ nificant not for erior to changes r to the or para­ , then to :omplet­ ~ic

CHAPTER 4

Spinal Anatomy

The anterior longitudinal ligament in the tho­ racic region is typically broad alld limits exten­ sion (along with the oblique angle of the spinous processes). The interspinous ligaments, supra­ spinaliS ligaments, and the posterior longitudinal ligament conversely limit tlexioll. The ligamenta fla\'8, which also limit ilexion, form the poste­ rior borders of the intervertebral foramina. The intervertebral disli:s arc relatively thin compared with those ill the cervical and lumbar regions

69

(Fig. 4-37). This differential in thickness accounts for the relative rarity of disk herniation in this region,

Lumbar The lumbar vertebra has a body that reneets the amount of weight it bears (Fig. 4-38). The pedi­ des and laminae are thick and broad, and they surround a spinal canal, whieh is generally oval

SUPEROANTEROLATERAL

,.,.

(

~ement

Fi~,

4-36 The plane of the thoracic zygapophyseal joints. Transverse costal ---'facet

.Intertransverse - - - ­ ligament Superior

costotransverse ligament Lateral RadIate Ilgament

Inferior costal demlfacet

Fig, 4-37 Ligaments of the costovertebral joints.

costotransverse ligament

Rib tubercle

70

PART TWO

ANATOrvfY. BIOMECHANICS. AND PHYSIOLOGY

..

..

Body

Inferior articular Spinous prooess process Superior articular

Transverse process

process

Pedicle

Spinous _ _+-..,. process Body

Inferior articular process

Fig, 4-38 The typical lumbar vertebra.

POSTEROSUPEROLATERAL

-......

_­

ANTEROSUPERIOR

Fig. 4-39 Orientation of the lumbar zygapophyseal joints. or heart shaped. The transverse processes are considerably longer than those in the thoracic region. This difference is caused by the fact that developmentally the tmnsverse process is a costal element. At the base of each transverse process is a tubercle known as the accessory process. The spinous process is much broader than that of the thoracic vertebra. Even though it is considerably shorter overall, the spinaliS

process projects further posteriorly and can be palpated with relative ease (with the possible exception of LS). Associated with the laminae are the articular processes, which in the lumbar region are typically oriented in the sagittal plane (Fig. 4-39). This arrangement allows for consid· erable flexion and extension (to be limited by lig. aments and joint capsules), a moderate amount of lateral flexion, but little rotation (about 1.5

CHAPTER 4

SpiuaJ Anatomy

71

Superior artiCular process ofLS

Inferior articular process ofL3 _ --

Superior articular process ofL4

Mammillary process

Spinous process

.440 The articular joints of the lumbar vertebrae.

. 441 Three-dimensional computed tomographic image of L2-L3 zygapophyseal joints.

ees to each side per segment). The superior d inierior articular processes are arranged so t the upper lumbar vertebra fits inside of the e below it, similar to a telescope (Figs. 4-40 d 4-41). The superior articular process of the wer vertebra !lares out to allow the inferior 'cular process of the upper vertebra to slip \\11 inside it. The superior process has a ridge

lateral to it known as the mammillary process, which serves as an attachment site for the. mul­ tifidus muscle. The oblique orientation of the facet joints also gUides rotation (along the longi­ tudinal axis) so that when rotation takes place, lateral flexion (sidebending) is coupled to it. The lordotiC curve in the lumbar region and the height differential of the anterior and posterior

72

PART TWO

ANATOMY. BlOJ\IECH.N\ICS, AND PHYSIOLOGY

borders of the vertebral bodies cause a varying amount of deformation of the intervertebral disks (Fig. 4-42). The dishs in this area are sig­ nificantly thicker than those in the thoracic region, allowing for greater cushioning but also increasing the probability of herniation. In the normal lordotic curve, the forces of gravity and weight bearing tend to push the nucleus pulpo­ sus in an anterior direction, accounting for the slight bulge in the disl{. As aging progresses, how­ ever, the height of individual disl{S decreases, which decreases the longitudinal dimension (height) of the intervertebral foramina, thereby increasing the risk of nerve impingement. The ligamenta flava form part of the posterior border of the intervertebral foramina. Injuries to these ligaments, which cause local edema, can result in nerve impingement at the foramen and radi­ ating pain (radicutopathy). In the case of the nerves below LI, this pain can radiate down the lower Hmo. In tbe case of a disk bulge or hernia­ tion into the lumbar spinal canal, more than one nerve root can be impinged because of the pres­ ence of the cauda equina (the collection of spinal roots that occupy the vertebral canal below the inferior end of the spinal cord), result­ ing in additional symptoms. Clinicians should check aJJ local dermatomes and myotomes (strength testing and reflexes) to determine the

Fig. 4-42 Lateral view of the lUOlbM spine.

exact location and extent of any pathologic con· dition, bearing in mind the possibility of multi· pie bulges. Typically, the lumbar facet joint is oriented close to the sagittal plane (see Fig. 4-39), which allows considerable nexion and extension, some lateral flexion, but very little rotation. The lower lumbar facets may turn toward the coronal plane, similar to the thoracics. This situation allows a greater degree of rotation at these levels but can also contribute to the development of instability in the area.

Sacrum The sacrum is a wedge-shaped bone represent· ing the fusion of five spinal segments (thus five pairs of sacral nerves are associated with it). The base of the sacmm faces superiorly, articulating with LS, and the apex poims inferiorly, prOViding an articulation with the coccyx (Figs. 4-43 and 4· 44). 1\\'0 alae (L. for Wings) can be seen to extend laterally from the sacral base to articulate with the ilia at the sacroiliac joints. Four anterior and posterior foramina are present, which trans· mit the primary ventral and dorsal divisions of the sacral nerves. The fiftll sacral nerve does not usually exit via a foramen but slips under the notch just medial to the inferior lateral angle.

CHAPTER 4

~ con­ multi­

.ented

which some

lower Jronal

.Iation

levels ent of

Spinal Anatomy

tation and contributing somewhat to rotational instability in the area. Asymmetry in these joints (facet tropism) can result in the predisposition to significant musculoskeletal problems, result­ ing principally from the amount of force brought to bear in this area. Rather t.han the smooth surface of tbe ante­ rior sacrum, three longitudinal bony protuber­ ances may be found on its posterior aspect. The median sacral crest displays the remnants of

Hcveral articular surfaces are present: the two auricular surfaces for articulation with the iliac bones of the pelvis, the superior articular processes for articulation with the inferior artic­ ular processes of LS, and the articular surfaces for joining the sacrum to the coccyx. The facets of the superior processes can be aligned in the sagittal plane, similar to the typical lumbar facet alignment, or more toward the coronal plane, representing a departure from the lumbar orien­

Superior articular process

-Promontory

esent­ 18 five

Ala

:). The

tlating ,viding and 4­ ~en to

- - Transverse ridge

culate

It.erior trans­ OilS of les not er the

gle.

Coccyx

Fig. 4·43 Anterior view of the sacrum and coccyx.

Sacral canal .,.....

~~~-,.....--Superior

articular ptOC&$s

Auricular surface

1-";':;'-i-1l.--H:it-- Medi8n sacral crest

-lJ-J.I----lntermediate sacral crest Lateral.sacral crest ~1J"""'7"/'-- _ _

Posterlor'sacral foramen

Sacral biatus

Coccygeal ,transverse

pr.oeess

...

Fig.4-44 Posterior view of the sacrum llJld co<:cyx.

73

74

PART TWO

A.l'lATOJ>IY, BIOMECHAi'llCS, AND PHYSIOLOGY

the spinous processes of the original unfused sacral segments and serves as an attachment site for the erector spinae and multifidus muscles. The intermediate sacral crest, 'which lies just lateral to the posterior sacral foramina, repre­ sents fused articular processes, also serving as a muscular attachment site. The lateral sacral crest lies just medial to the auricular surface and is the site of attachment of the posterior sacroil­ iac ligalllents and joint capsule. Medial to the articular processes is the sacral canal, which transmits the nerve roots from the lumbar spinal canal to the anterior and posterior sacral foramina (for the passage of the ventral and dorsal rami, respectively). Also contained in the triangular sacral canal are the meninges and the filum te rmin ale, the caudal extension of the pia mater (Fig. 4-45). Although the dural sao usually terminates at the level of the second sacral vertebra (S2), the dural sleeves continue \vith the nerve roots to the individual foramina. The distal end of the sacral canal opens to form the sacral hiatus, with two protuberances, the sacral cornua (which articulate with the coc­ cyx), on either side. ThiS opening can be used in certaio clinical situations to gain access to the dural sac or subarachnoid space. The last sacral nerve (65), the coccygeal nerve, and the filum

Superior artlcular process

tcnninaJe exit the saQral hiatus. The 85 leaves the hiatus, with its ventral ramus proceeding in an anterior direction just adjacent to the inferior lateral angle of the sacrum. The dorsal ramus of the coccygeal nerve (mixed with fibers of 85) provides cutaneous sensory innervation of the area around the coccyx. Tbe filum terminale attaches to the dorsal aspect of the coccyx to give longitudinal support to the spinal cord.

Coccyx The coccyx, though resembling the tail of a rat· tlesnake, is actually the remains of the vestigial tail of the human. The coccyx is usually com· posed of four fused segments, with the first per­ haps being separate. The first coccygeal segment bas remnants of the articular processes and pedi· cles, called cornua, which articulate with the apex of the sacmm; it also has mdimentary transverse processes. The coccygeus muscle attaches to the lateral aspect of the coccyx. From the tip of the sacrum extend the pubococcygeus muscle (pan of dIe levator ani muscle group) and the anOCOC­ cygealligament, which help to support the pehic diaphragm. A single coccygeal nerve is associated the coccyx, which has only a sensory function and is distributed to the skin of the natal cleft.

-f-_

Promontory

Posterior sacral ----+--+fJl foramen Median

sacral crest

';---Ala

Vj..........,I,,k----Remnant of

Sacral hiatus ----...;~,\.,

Sacraloomu Coccygeal cornu

Fig. 4-45 Median section of the sacrum and coccyx.

intervertebral disk

CHAPTER 4

r

t !(

e e e

n

Pelvic Bone (Innominate Bone, Hip Bone) The peh'ic bone represents the fusion of the Uium. ischium, and pu.bis (Fig. 4-46). The 'point of fusion, close to the center of the acetabular fossa, is the point at which the head of the femur resides to make up the hip joint. Fusion gener­ ally takes place between the ages of 20 and 2S years. Following this terminology, the various fea­ lUres of each bone are named thus (e.g., iliac crest, ischial tuberosity). Above the acetabulum is thickening of the iliulll Imown as the iliopectineal or iIiopubic eminence. This eminence increases the weight-bearing capacity of the pelVis. Many of the protuberances of the pelVic bones can be palpated on the body surface, prOViding • valuable diagnostic tool for the trained pro­

f! ional (Figs. 4-47 and 4-48). The iliac crest,

posterior superior iliac spine (PSIS, as indi­

cated by the dimpling on the skin), anterior

superior iliac spine (ASIS), ischial tuberosity,

and pubic tubercle are aU normally palpable on

the patient. The i.schial spine (Site of attach­

IIleIIt of the sacrospinous ligament) and anterior

Inferior iliac spine CAlIS) are generally not pal­

pable. Posteriorly, between the PSIS and ischial hJberosity, is the sciatic notch, which has Important relations with the sciatic nerve and

Spinal Anatomy

7S

piriformis muscle and forms the anterior bor­ der of the greater sciaticforamen. The outer sur­ face of the ilium is the point of the attachment of tbe gluteal musculature hence the term gLuteal surface. Below the gluteal surface of the ilium is the socketlilte acetabulum, the site of articula­ tion with the femur. The acetabulum presents an incomplete outer rim and an inner fossa. In the fossa is a cartilage-covered lunate surface, which is the actual site of femoral articulation (and weight bearing). The arc of the coxal bone from the PSIS to the ischial spine forms a notch. This notch is known as the greater sciatic or ischiadic notch and is very significant in that both the pirJfonnis mus­ cle ancl the sciatic (also called ischiadic) nerve pass by to reach the lower limb from the pelVic cavity. In the lateral view, the relations of the iliosacral articulation are more apparent. The reader should note that a line drawn from the 1\81S to the anterior margin of the pubic bone is vertical. In addition, the angle formed by a line drawn from the top of the pubic bone to the sacral promontory is approximately 60 degrees from the horizontal. The pubic bone presents superior and infe­ rior rami that fuse with the ilium and ischium, respectively. The fusion results in a deficient area in the bone, the obturator foramen. In Hfe, this

76

PART TWO

ANATOMY,

BIOMECHA-~iCS,

Posterior superior iliac spine (PSIS)

AND PHYSIOLOGY

Anterior superior iliac spine (ASIS) Anterior inferior

Superior pubic ramus Inferior pubic ramus Ischial

Obturator

tuberosity

foramen

Fig. 4-47 Lateral view of the pelVic bone. lIIaccresl iliac fossa Posterior superior

AnteriGr superior Iliac spine (AStS)

Iliac spine (PSIS)

Anterior inferior

iliac spine (AilS)

Areualellne

Iliopectineal eminence

Pectineal Une --~"

Superior pubic

ramus

Inferior pubic ramus

Ischial spine

~ Lesser sciatic nolch Ischial tuberosity

Obturator foramen Fig. 4-48 Medial view of the pelvic bone.

foramen is covered by the connective tissue of the obturator membrane. The obturator artery and nerve pass through this membrane and it, along with the pubic rami, serves as an attach­ ment site for Ule obturator internus and exter­ nus muscles. The ischial spinae and tuberosity are the two major landmarks of the ischium. The ischial spine is the attachment site for the coc­ cygeus muscle, as well as for the sacrospinous ligament. 'fhe ischial tuberosity, which is tbe

attachment site for the hamstring muscles, is also the bone on which a person sits. The inner surface of the iliac portion oi the pelVic bone possesses the concave iliac fossa, prOViding an attachment site for tbe iliacus mus­ cle (the fossa also forms part of the false pelvis' which houses a portion of the abdominal lis­ cera) (see Fig. 4-48). The auricular surface is the point at which the ilium articulates with tbe sacrum. Projecti ng forward from the auricular

CHAPTER 4 Spinal Anatomy

77

Supmspinous ligament Posterior sacroiliac

"gament Greater sciatic foramen Sacrospinous ligament

Tr~6verse

acetabular

ligament

Posterior lateral

sacrococcygeal ligaments Lesser sciatic foramen sacrotuberous ligament Obturator membrane

Fig. 4-49 Lateral view of the pelvic girdle.

, is the

sa, rlUS­

vis. vis­ the the ular

surface and continuous with the pectineal line is the arcuate line, which forms the posterior COI11­ ponent of the linea terminalis (the pelvic brim, or dividing line between the true pelvis and the false pelVis). The anterior portion of the pubic bone articulates with the pubic bone from the opposite side via the fibrocartilaginous pubic 8)"/1lphysis. The two inferior pubic rami form an angle, which varies from men to women. In \\'omen, the angle is considerably more obtuse, which, in effect, increases the distance between the ischial tuberosities for easier passage of a baby through the birth canal. Two important ligaments extend from the sacrum to the pelVic bone (Fig. 4-49). The sacro­ tuberous and sacrospinous ligaments form two separate foramina of the pelVis. The sacrotuber­ ous ligament extends from the inferolateral aspect of the sacrum to the ischial tuberosity (the part of the pelvis on which a person sits). The 8llcrospinolls ligament extends from the sacrum, just anterior to the sa.crotuberot1s liga­ ment. to the spine of the ischium. In their rela­ tionship to the sciatic notch of the pelvis and to each other, the two ligaments form the ,greater scialicjommen, whereas the sacrotuberous lig­ ament in association with the sacrospinous ligament forms the lesser sciatic f01-amen. A sig­ Dificant number of structures pass through these

foramina from the pelvic oavity to the lower limb and perineum. In addition, a set of iliolumbar Iigament.'l may be found, which add support to the lumbar spine by spanning the distance between the transverse processes of L4 and L5 and the iliac crest.

Pelvic Girdle and Sacroiliac Joint The articulation of the two coxal bones, the sacrum, and coccyx is what is referred to as the pelvic girdle (Fig. 4-50). The angles of the acetabula afe angled downward and slightly for­ ward, which is important for proper weight bear­ ing by the lower limb. The pelVic girdle forms a closed biomechani­ cal system for weight bearing. The center of maSs of the body is located within the pelVic cav­ ity, approXimately at the level of second sacral vertebra (82). The two femurs, as they articulate with the pelvis, form two buttresses that support the pelVic girdle. The sacmm actually forms the keystone of an arch, which is made up of the head and necl{ of each femur, the acetabulum, ilium, and sacrum. When considering the weight of the torso, upper limbs, and the bead being borne from above, as well as tl1e articulation between the lumbar spine and pelvic girdle, it is easy to rationalize the existence of strong supporting

78

PART TWO

Ai"IATOMY, BIOMECHANICS. AND PHYSIOLOGY

Iliolumbar Ilpment Anterior sacroiliac ligament

Ant8flOr Iongltudll18l Ilgament

Greater SCIatic fora"*,,

Fig. 4·50 Anterior view of the pelvic girdle. structures to assist in this task. [t is also easy to understand the preponderance of low back pain given the amount of force that must be tolerated by these structures over time. A line drawn across the top of the iliac crests is referred to as the intercristal line. which usu­ ally passes through the inferior end of L4 (or in many cases through the L4-L5 disk). If a struc­ tural variant places the intercristal line abnor­ mally low, the result is abnormally long (and possibly unstable) iliolumbar ligaments, predis­ posing the individual to lumbar sprain and strain. The sacroiliac joint is somewhat complex. The sacroiliac joint is a synovial joint that, over time, develops a varying amount of fibrocartilagi­ nous attachments, referred to as interosseous lig· aments. The unusual arrangement of the articular surface of the sacroiliac joint is described by vari­ ous authors as "L" shaped, "hockey stick" shaped, or "golf club" shaped (see Fig. 4-49). Because the sacroiliac joint is subjected to tremendous force during weight bearing, very strong ligaments must support it. In addition to the interosseous liga­ ments, two sets anterior and posterior sacroil­ iac ligaments may be found (Fig. 4-51; see also Fig. 4-50) The anterior sacroiliac ligaments are an extension of the joint capsule and are thickest at the level of the third sacral vertebra (83). The posterior sacroiliac ligaments extend from the

spinous processes of the sacrum laterally to the PSIS and beyond and inferiorly to the sacrotuber· ous ligament.

CONTENTS OF THE VERTEBRAL

CANAL Meninges The meninges are connective tissue coverin,gs arranged in three distinct layers that cover and protect the spinal cord from exoessive mOI'e· ment and damage (Fig. 4-52). These layers con· sist of the dura mater (L. for tough mother), arachnoid (L. for weblike) mater, and pia (L. for loving mother) mater. Between the arachnoidaud pia is a space, the subaraclmoid space. which contains the cerebrospinal fluid (Fig. 4-53). The cerebrospinal thud, which bathes the brain and spinal cord, both protects and nourishes these vital structures. The most external layer of the meninges, tM dura mater, is a thick, tough connective tissue layer (Fig. 4-54). The dura mater is continuous from the cranial cavity to the sacrum (82) andis composed of two distinct layers: the periosteal dura (attached to the intemal surfaces of the skuJI aDd spinal crnlal) and the meningeal dura. These two layers split at strategic locations. In

CHAPTER 4

79

Spinal Anatomy

Iliolumbar Itmunent ~+---::-'-'-~

SupraspInous ligament

PosterIor sacroiliac ligament

Greater sciatic foramen sacrotuberous ligament .... 8acrospInous ligament

Lesser sciatic foramen Obturator foramen Posterior sacrocoecygeal ligaments

Fig. 4-51 Posterior view of the pelvic girdle.

the ber­

Spinal cord ~--l~~""

Pia mat$r

--+O~oif- Subarachnoid

space (OSF)

.L

~-~"4-ArachnGid

J..--+-.... Subdural space ings Denticulate· ligament

and

(PIA)

Dve­

con­ -1---..... Dura mater

~er),

. for and hich The and ese

the

/;.;........-+ Epidural space F'~. 4-52

The spinal meninges.

the cranial cavity, both layers become lined with endothelium, creating tbe dural venous sinuses, which drain the large portion of blood from the brain and also serve as a major reabsorption point for the cerebrospinal tluid. The meningeal dura also reflects from the inner surface of the cranial cavity to form the falx cerebri and falx cerebeUi that separate the cerebral and cerebellar hemi­ spheres and the tentorium cerebelli, which sepa­ rates the cerebnun from the cerebellum.

Fig. 4-53 Cross-section of the meninges.

The dura is firmly attached to the internal surface of the skull and to the vertebral foramina of the atlas and a.."{is. The layer then separates from the vertebral surface, creating an epidural space, which contains the blood vessels that supply the vertebrae and contents of the verte­ bral canal. This space continues to the level of vertebra 82, at which point the dura then finnly

80

PART TWO

ANATOMY. BIOMECl-L\NlCS, AND PHYSIOLOGY

Conus _ _ff­ medullarls

PedIcIes

~:J.­ _ _~.-Dura~---­

Cauda

equlna -----"::JH+.

Dural sleeve opened

A

B

Fig. 4-54 Laminectomy of the lumbar spine and sacnln1, showing the dural sac (A) and the sac opened (8).

- -Afact1no1d mater (cut)

Fi~.

4-55 Opened dural space showing the nerve rootlets and denticulate ligament.

reattaches to the interior of the sacral canal The dura covers tbe individual nerve roots and nerves as they exit tbe spinal canal, fusing to the pedicles at the intervertebral foramina. The arHchnoid mater is a more delicate, avas­ cular membrane, which is attached to the inner surface of the dura. Thin, weblike projections extend from the arachnOid to the pia, which are responsible for its name. The arachnoid extends along the nerve roots, as does the subarachnoid

space, and both terminate approximately lit intervertebral foramen. The pia mater is a single-cell connective ' sue layer that adheres directly to the surface the neural tissue, including the individual c nial and spinal nerve rootlets. The pia has t specializations (Fig. 4-55; see also Fig. 4-54): t filum terminate, which extends from the end the spinal cord to the sacrum and cocco thereby tethering it longitudinally, and the

CHAPTER 4

ticulate ligament, which supports the cord later­

ally. The denticulate ligament is a series of pial projections, located primarily in the thoracic region, which project from the lateral surface of the spinal cord, penetrate the arachnoid, and anchor to the dura. In the lumbosacral region, the dural sac extends to the level of 82, beyond which the indi­ vidual dural sleeves pass out toward the sacral foramina (see Fig. 4-55). When the dural sac is opened, the end of the spinal cord is seen at 1..,2. Inferior to this level is the cauda equina, consist­ ing of the dorsal and ventral roots of the remain­ ing lumbar and sacral nerves. Also present in this area is an inferior extension of the pia mater, known as the filum terminale. This connective tissue element extends from the tip of the spinal cord (conus meduJlaris), through the sacral hia­ tus, to attach to the external-posterior aspect of the apex of the sacrum and coccyx. This tissue anchors the spinal cord longitudinally and pre­ vents excessive movement within the canal.

Spinal Cord and Spinal Nerves Passing through the intervertebral foramina between the vertebrae and proceeding from the spinal cord to the periphery are 31 pairs of spinal nerves (one for each Side, wit h the excep-

Sympathetic ganglion

Raml

communicantes

tthe

e tis­ ee of era­ two : the ·nd of eyx, . den­

Dols8l root

gangUon

Spinal Anatomy

81

tion of the coccygeal nerve, which is fused at the midline). Each of these spinal nerves contains sensory and motor nerve fibers that are distrib­ uted to the periphery. In many cases, the nerves are accompanied by arteries, which supply blood to the same region supplied by the Iipinal nerve (Fig. 4-56). In addition, the neurovascular bun­ dle contains veins and lymphatic vessels, which serve to drain away waste products from tbe same territory. Each segment may appear to function as a separate entity, but this is not the case. Because of significant overlap both inside and outside the central nervous system, in a sense each segment is aware of activity that transpires in the segments adjacent to it. Individual nerve rootlets course inferiorly and are surrounded by the dura and arachnoid as they coalesce to form the spinal nerve (see Fig. 4-56). The sleeves of dura follow the nerves to the inter­ vertebral foramina and also surround a swelling, which represents the location of the dorsal root ganglion, the point at which the cell bodies of sensory (afferent) neurons reside. This fascial layer is continuous with the connective tissue covering of the peripheral nerve, also known on the histologic level as the epineurium. The indi­ vidual nerve roots are suspended in the cere­ brospinal fluid present in the subarachnoid space, thus affording additional protection from trauma.

82

PART TWO

A.!'olATOMi: BIOMECHAl\ICS. AND PHYSIOLOGY

SPINAL CORD SEGMENTS

C1-----·...,....~~

C2-­

- - - C2 (AxIs)

C3-------~~__;~~:'lr-·----C3 C4 ---'--.....L

cs--_ _

-C4 -t----C5

C6­_ _~~~~~ r-.-~-C6

C7-·--.......::::::.

:3~~~~r-----07

T1

Fig. 4-57 The cervical nerves. The points of exit of the spinal nerves in the cervical region are deserving of special note (Fig. 4-57). Convention describes the Cl nerve as exiting between the occiput and atlas (Le., supe­ rior to Cl vertebra), C2 between the atlas and axis (superior to C2 vertebra), C3 nerve between C2 and C3 vertebrae, and so on until nerve C8, which exits inferior to vertebra C7. Thus eight cervical nerves may be found, and only seven cer­ vical vertebrae are present. This problem is sim­ plified by realizing that the base of the OCCiput, in spite of being a bone of the skull, is actually embryologically part of the vertebral column and is sometimes referred to by authors as CO. In the thoracic, lumbar, and sacnl1 regions, the total number of vertebrae corresponds exactly to the number of nerves. The exit patb of the nerves changes from superior to Inferior. The first two nerves exit posterior to the articular pillars, whereas all the rest exit anterior to the pillars. Nerves C3 through C7 exit in a more typical fashion (for cervical nerves), traveling in a small groove in the transverse process and just posterior to the course of the vertebral artery. As the spinaillerves proceed from the cervical region caudally, the declination of the path of the roots from spinal cord to their respective intervertebral foramina significantly increases

(Fig. 4-58). This increase is caused by the difier· ential growth rate and size of the spinal cord reI· ative to the vertebral column. ThiS difference results in the tip of the spinal cord (conus medullaris) residing approximately at the L2 vertebral level. Knowing the location of the ver· tebral segment relative to the spinal cord seg­ ment is important when dealing with vertebral injuries that affect the spinal cord and predicting the symptoms that result. A mle of thumb that can be followed is that in the upper thoracic spine, the spinal nerves decline approximately two vertebral levels before eXiting the canal. [n the lower thoracic spine, the nerves pass three vertebral levels before exiting the foramina Given that the upper lumbar spine represents the beginning of the COllUS medullaris of the cord, injuries to these vertebrae usually affect only the sacral spinal cord segments (which is not to minimize the injury, because these seg. ments control bowel and bladder function, as well as sexuaJ responses).

Spinal Cord The spinal cord extends from the end of the medulla of the brain stem, approximately at the level of the foramen magnum of the occiput, bl the first or second lumbar vertebrae. At this point, the spinal cord tapers to a point, known as

CHAPTER 4

Spinal Anatomy

83

SPINAL CORD SEGMENTS CI

Cervical segments (8)

Occipital bone (occiput)

CI Cervical vertebrae (7)

Thoracic segments (12) CI Thoracic vertebrae

(12)

Lumbar segrneht8 (5)

Sacral segments (5) Coccygeal segment (1) CI

Lumbar vertebrae (5)

I!!i!'I Sacrum (S1-S5)

• Coccyx (C01-o04)

Fig. 4·58 Relationships between the spinal cord segments and vertebral segments.

ffer­ Irel-

Dorsal rootlets __

~nce

)nus ~ L2 ver­ seg­ ~bral

Ventral

'ting that

root

rec llina. !ents . the Heet Dh is seg­

,as

t

the the t, to

this nas

Fig. 4-59 The spinal cord and spinal nerve roots and branches.

lbe conus medullaris. The cord is made up of neurons and supporting cells known as glia, of which there are several types. In cross section (Fig. 4-59), the spinal cord has gray matter and white matter. The designations gray and white are the result of the appearance of the tissue before fixation, histologic staining, or both. The wbite matter, which surrounds the gray, is made up primarily of myelinated neuronal processes,

which are mIming longitudinally along the cord. Collections of functionally related fihers are organized into tracts, which have similar origins and destinations inside or outside the central nervous system. The gray matter consists of neuronal oeD bod­ ies and supporting tissue, along with a substantial number of small blood vessels and capillaries. The gray matter typically has a shape that is described

84

PART TWO

ANATOMY, BIOMECHANICS.

as being as a butterfly. Dorsal and ventral horns (or columns if viewed three-dimensionally) are present. The dorsal part of the gray matter is populated by neurons, which are principally involved in sensory functions, ~lIld the ventral wing contains neurons whose primary function is motor. Interspersed throughout the gray mat­ ter all along the cord are association neurons or intemeurons, which interconnect sensory neu­ rons to each other, and to motor neurons. In the thoraciC region, a lateral extension of the gray matter eXists, known as the intermediolateral cell column, which is the site of preganglionic sympathetic nerve cell bodies.

Spinal Nerves Afferent and efferent fibers enter and leave the cord respectively as rootlets that then coaJesce peripherally into dorsal (afferent) and ventral (efferent) roots. These roots then merge to form the spinal nerve, which exits the spinal canal at the intervertebral foramen (see Fig. 4-56). After leaving the spinal canal, the spinal nerve begins to breal{ up into branches (rami), which proceed to their respective targets of innervation. An analogy can be made to a tree that has its roots in the spinal canal, its trunk at the intervertebral foramen, and its branches out in the periphery. The dorsal roots contain a swelling, which rep-

A1~n

PHYSIOLOGY

resents the dorsal Toot ganglion, the location of cell bodies of the afferent nerve fibers. These cells are derived from the neural crests. The con­ nection between the segmental nerve and the sympathetic chain (Via gray and white rami communicantes) occurs immediately olltside the spinal canal (Fig. 4-60).

BLOOD SUPPLY OF THE SPINAL CORD The blood supply of the spinal cord is deriv primarily from anterior and posterior spi arteries, which are branches of the vertebr arteries within the cranial cavity (see Fig. 4-15) These arteries run the length of tJle spinal co and are supplemented at intervals by anast moses with branches of the segmental arterie Below tbe arch of the aorta, tJle segmental arter ies are branches of the descending aorta. AboI' the aortic arch, the segmental arteries a branches either of the ascending vertebral arter ies or of the ascending cervical branch of t thyrocervical trunk The importance of collateral circulation' this area cannot be overstated. However, areas present an increased risk as a result lower perfusion pressure. These areas are t transition zones between the cervical and th

Dorsal root

SpinaJ cord ~---t+ Ventral root --..",...-++--1\

Sympathetic chain

--..,.l........A-t-#-ll

SympathEftlc ganglia

Fig. 4-60 Relationships of the spinal cord, spinal nerves, and sympathetic chain.

CHAPTER 4

of ~se

)n­

:he ,mi ide

ved

lnat

Jral 15). ~ord

sto­ ·jes. ter­ love are 'ter­ the

in two It of the tho­

rl

racic cord segments and between the thoracic and lumbar cord. Occlusions in these "watershed" areas can lead to significant ischemic lesions of the spinal (lord. In the mid-thoracic region, an artery isgtlnerally somewhat larger in caliber than other arteries in the region. This type of artery is known asthearteryojAdamkiewicz (see Fig. 4-13). The segmental arteries send spinal branches into the intervertebral foramen. Radicular branches stem from these arteries, which follow the spinal nen'es back toward the spinal cord. As these nerves break up into the dorsal and ventral roolS, the radiculars send off anterior and poste­ rior hranches, which follow the roots to the cord. These arteries, in turn, give off smaller arteries that directly supply the tissues of the central nervous system. This arterial system is referred to as the pial arterial plexus. These small arter­ ies course on the surface of the cord, sending penetrating branches into the deeper layers. The vessels of the ventrolateral plexus represent an anastomosis of the posterior and anterior spinal aneries; the posterior plexus is anastomosis of the two posterior spinal arteries. The sulcal OTle1)', which TUns deep within the anterior sul­ cus of the spinal cord, supplies through its pene­ trating bnlllches the central area of the spinal cord. Although some overlap of distribution occurs, this by no means implies full collateral­ lzalion. Occlusion of any of these arteries results In tissue ischemia or infarction. leading to major neurologic defiCits. The venous drainage of the spinal cord and \'eltebrae is extensive (see Fig. 4-18). Extending the length of the spine are four continuous plexuses of veins, designated internal and exter­ nal, anterior and posterior. The reader should JIO(e that the internal venous plexuses lie in the epidural space, embedded in the epidural fat. The veins draining the neural tissue are similar in c:ourse to the arteries, with the exception that only one main posterior spinal vein exists. These veins contain no valves, thus blood may flow in either direction. In addition, the veins form a sig­ nificant route for the spread of infection, as well as for the metastasis of tumors. As noted earlier, In men, prostate tumor cells can use this route to seed into the individual vertebrae and all the way to the brain. The valveless nature of these veins

Spinal Anatomy

85

also provides a conduit for the release of venous pressure during Valsalva maneuvers (forcible exhalation effort against a closed glottis), sneez­ ing, and coughing. Unfortunately, paroxysmal increases in intravenous pressure can occasion­ ally cause disk herniation.

EMBRYONIC SEGMENTAL DEVELOPMENT During the third and fourth weel<s of develop­ ment, the embryo consists of three layers of tis­ sue: the dorsal ectodenll, the ventral endodenn. and an intermediate tissue layer, the mesoderm. Subsequently, tlle trilaminar germ disk under­ goes folding along a longitudinal axis, resulting in the development of the neural tube (Fig. 4-61). While neural tube fusion is tal
86

PART TWO

ANATO.MY, BIOME.CHANICS, AND PHYSJOLOGY

Fig. 4-61 Neural tube formation and development of the somite.

c=J Sclerotome

Myotome c=J Dermatome c::J Neural tube

•

Notochord

Fig. 4·62 Development of the somite: dermatome, myotome, and sclerotome.

growth, thei( position shifts, gradually moving around the neural tube and notochord to fuse with their counterparts from the opposite side. This tissue ultimately fonus the vertebrae and intervertebral disks. At this point, the peripheral process of the segntental dorsal root (cell bodies derived from the neural crest) has grown into the somite, and as it splits into its respective parts (dermatome, myotome, sclerotome), these nerve processes also split and follow the tis­ sues to wherever they migrate in the embryo.

The centra] process of the segmental do root grows into the developing spinal cord makes connecUons with the appropriate neu within the appropriate segment of the devel ing central nervous system. The cell bodies co tinue to reside adjacent to the vertebrae and I become the neuronal cell bodies of the do root gangli'on. By the fourth week of development, the scI tomes corresponding to the somites are separat by loosely arranged intersegmental mesench,

CHAPTER 4

87

Spinal Anatomy

_ Myotome . . Cranial sclerotome r::::J Caudal sclerotome c:::J Vertebral body c:::J Intervertebral disc Intersegmental artery 0 Intersegmental nerve

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rl£.4-63 Development of (he venehrae and intervertebral disks.

dorsal 'ord and neurons

evelop­ ies con­ and will e dorsal

(rt 4-63). ,A,s time passes, the cells at caudal end of each sclerotome proliferate aod con­ dense, fusing with the cephalic end of the scle­ rotome below. This portion of the sclerotome forms the vertebral body, which, because of this fusion, is intersegmental. tvreanwhile, the sclero­ tomal tissue between the cephalic and caudal ends iails to proliferate, thereby leaving an area ofIess dense tissue between the vertebral bodies above and below. This tissue contributes to the formation of the annulus fibrosus of the jnter­ venebral disk. The remaining notochordal tissue persists as the nucleus pulposus. This tissue is the only remnant of the notochord in the new­ born and adult, the remainder being obliterated by the formation of the vertebral bodies. At this stage, because of the intersegmental nature of the vertebrae, the myotomes are in a position correspondin,g to the intervertebral disks. The peripheral process of the corresponding segmen­ tal nerve has already grown into the myotome (as well as the dermatome and sclerotome) to Innervate it. Given the nomenclature of the ver­ tebra, each nerve is said to exit the spinal canal below (or above as in the cases of Cl through C7) Its corresponding numbered vertebra. As the lII}'olome migrates to its final destination in the embryo, the nen'e that innervates it will follow. As the myotome begins to migrate in a ventro­ lateral direction, it splits into two parts: a dorsal

epimere and a ventral bypomere (Fig. 4-64). AB the myotome splits, so does the nerve that inner­ vates it, forming a dorsal ramus (epimeric) and a ventral ramus (hypomeric). The epimere ulti­ mately becomes the intrinsic muscles of the back (erector spinae, transversospina I group), which are innervated by dorsal rami. The hypomere eventually develops into the extrinsic muscles of the back (as wetl as contributing to the development of tbe muscles of the limb), which are innervated by ventral rami of the spinal nerves. The reader shouJd also note that the hypo mere splits additionaJly into tbree lay­ ers and that the innervating nerve comes to lie between the deepest and next deepest layers. ThiS fascial plane becomes known as the neu­ rovascular plane. The three layers of the body wall are consistent throughout the trunk, form­ ing part of the thoracic and abdominal walls. In the adult, these muscles have been given differ­ ent names (e.g., intercostal muscles viz. abdom­ inal obliques), relative to their locations, but their derivation i!:' the same, the.principal differ­ ence being the presence of a fully developed rib cage in thl' thoraCic region. The organization of myotomes in the embryo roughly resembles that of the dermatomes. This relationship diverges somewhat as muscles migrate to their ultimate destinations, especially in the limbs. Certain myotomes at either end of

R8

P,'\RT TWO

ANATOMY. BIOMECHAJ."'HCS, AND PHYSIOLOGY

Intrinsic back muscles

Muscles of; the body walls

Fig. 4-64

Develop~nent of

the myotomes-spinal nerves.

the embryo are reabsorbed (e.g., most of the occipital and coccygeal myotomes). Insofar as seg­ mentation and innervation are considered, the relationship established earlier in development between the dermatome, myotome, and sclero­ tome is maintained. Understanding of segmenta­ tion is clinically important in differential diagnosis between peripheral nerve and nerve root lesions, as well as in recognizing reflex patterns, segmen­ tal dysfunctions, and the relationship between superficial structures and underlying viscera. Changes occur in the relationship between the vertebral column and the spinal cord during development as a result of differential growth (see Fig. 4-59). At approximately;) months in utero, the spinal cord reaches to the end of the vertebral column. As the fetus increases in length, growth of the spinal gradually slows, effectively resulting in a cephalad movement of the end of the cord and the creation of the lumbar cistern, cauda equina, and filum terminale. At birth, the cord resides approximately at the level of the third lumbar vertebra. Continued growth in the new­ born chaJlges the relationship further until the cord attains its final position between verte­ brae Ll and L2. Notably, in spite of this differen­ tial grO\vth and movement, the spinal cord is still tethered longitudinally by the filwn tenninale. Being aware of variation in this positioning is important, especially if lumbar puncture to obtain cerebrospinal fluid is indicated. Fluid must

be obtained without endangering the cord, neces· sitating the lumbar approach. Lumbar puncture perfonned below L2 or lower will generally avoid risk.

Review Questions 1. What are the three elements of the equilibrial triad through which postural adaptation is accomplished? 2. Explain the concept of tensegrity as II applies to the musculoskeletal system. 3. What are the components of the FSU? 4. What are the primary functions of the

anterior and posterior longitudinal

ligaments?

5. What is involved in disk herniation? 6. In what ways are the atlas and axis

vertebrae atypical?

7. Which ligaments are unique to the upper cervical area? 8. Why is facet tropism a complicating factor in case management? 9. Describe the structure and function oflhe meninges. 10. What are the primary functions of the dorsal and ventral horns of the spinal cor

Concept Questions 1. How do the intrinsic muscles of Ihe bact maintain the spine as a tensegrity struC!U

CHAPTER 4

2. What motions are allowed or restricted by the zygapophyseal joints in each region of the spine, and how does this relate to coupled motion? 3. How does the proprioceptive system of the vertebral column function to maintain erect posture within the conceptual framework of compensation?

SUGGESTED READINGS Coughlin P, editor: Principles and practice of manual dleTapeucics, New York, 2002, Churchill-Livingstone.

d., neces­ Juncture

.Uy avoid

t tural

it tern.

IS

SU7 the

17

s !

upper

19 factor

n of the the ina! cord?

e back structure?

Spinal Anatomy

89

Kapandji IA: The physiology of che joints, 'Volume three: che tnl'!lk. and 'Vertebral column, cd 2, 8dlnburgh, 1974, Churchlll-LiviJlgstone. Larsen W.J: Anatomy: development, fu.'T/ccion, clinical correlations, Philadelphia, 2002, WB Saunders. Sadler TW: Langman's medical embryology, ed 8, Baltimore, 2000, Williams and Wilkins. White AA, Panjabi !vIM: Clin-ical biomechanicS of the spine, ed 2, Philadelphia, 1990, Lippincott. Williams PL, editor: Grays anatomy, cd 38, New York, 1996, Churchill·Livlngstone.

Spinal Neurology

Patrick Coughlin, PhD

Key Terms

_

ACETYLCHOLINE

GAMMA MOTOR NEURONS

REFLEXES

ACTION POTENTIAL

GANGLION

RETICULAR FORMATION

ADRENERGIC

GUARDll"G

SENSITIZATION

AfFERENT INHIBITION

HYPERALGESIA

SENSORY

A FIBERS

INTEROC EPTO RS

SENSORY FIELD

ALLODYNIA

MECHANORECEPTORS

SO\l!\

tvIOTO'R

Sm,IATOSOMATIC REFLEX

ALLOSTATIC RESPONSE ALPHA \fo'roR

N n;RONS

MYELINATED

SOMATOVISCERAL REFLEX

ANAPHYLAXIS

NEURAXIS

SPLINTING

AUTONOMIC NERVOUS

N EUROTRANSM ITTERS

STI MULUS- INOt/CED

SYSTEM AxO:" CENTRAL NERVOUS SYSTEM

N EUROTRANS MITT!::R SPILLOVER

ANALGESIA SUBSTANCE

OLiGODENDRocrTES

C FIBERS

PARASYMP.A.TH ETIC

CnOLlNERGIC

PARAVERTEBRAL

P

SUPERIOR CERVIC...L

GANGLION SYl\"PATHETJC

COLLATERALIZE

SVM PATH ETI C CHAIN

COWERGENCE

PERIAQUEOUCTJ\L GRAY

'THERMORECEPTORS

DENDRITE

PERINEURIUM

TONIC RECEPTORS

DIVERGENCE

PERIPHEI~AL NERVOUS

DORSAL ROOT GANGLION

SYSTEM

SYMPATHETIC GANGLION

VASA NERVORl1M VISCERA

ENDOGE~OlJS OPIATES

P}fASIC RECEPTORS

VISCERO-SOMATIC REFLEX

ENDONEURIUM

POSTGANGLIONIC NEURON

VISCERO-VISCERAL REFLEX WrTHDRN.VAL REFLEX

EPINElJRIGM

PREGANGLlONI(; NEL'RON

EXTEROCEJYrORS

PROPRIOCEPTORS

F.~CILn!\TION

RAMI COMMUNICANTES

thorough wldersmnding of the spinal nerve and its implications in diagnosis and case ment necessitates a review of its developIt in the embryo, as discussed in Chapter 4. this light, the basic architecture of the nerve its components (Le., the tree analogy) mes clear. This chapter offers a more func01 approach, with emphasis on informat-ion 'ssing in the peripheral nervous system and relationship to certain activities in the central us system. The information presented here by no means comprehensive, but it serves as a

springboard for further study (see Suggested Reading). Neurons convey information in the form of impulses or action potentials, which typically travel in a specific direction. The peripheral nervous system (PNS) , which consists of the spinal nerve roots, spinal nerves, and peripheral nerves, is responsible for bringing infonnation about the external and internal enviromnents to the central nen'ous system (eNS), Which consists of the brain and spinal cord. This type of input information is referred to as sensory or afferent.

91

')2

P,\RT TWO

,\N,\TO\IY. B10\IECIL\NICS..\ND I'IIYSIOLO(;Y

The P.:'-lf) also transmits responses to sensory stimuli. bringin,g motor or <-:ttcrellt output infor­ mation from the CNS to t:lrgct tissues in the periphery.

BASIC STRlTCTl'RE OF THE

:\'EI TRO~ The neuron is made up of three b:lsie P:lrts. The soma. or eel/I)()dy. is the point :It which the cell nucleus resides along with other cellular or,ganelles (Fig. :)-1). Extending from the soma arc two types of processes. The dendrite. which receives signaling information from the local en\·ironmCllt. contains. or is associated with. receptors that are designed to sense specific stimuli or react to specific chemical transmit­ ters. ]\eurons mav hm'e hundreds or even thou­ sands of dendritcs. dcpending on thc sizc and complexity of their rcccptive ficlds. Thc second

type of cellular process is the ax01l. alol1~ which a si,gnal travcls as an action potential. .\ction potentials arc typically ,gencrated in an :Ixon ria the summation of signals received from thc den· drites. which C:ln be either stimulatory or inhibitory. When the action potcntial reaches the end of the axon. it causes the rch.:ase of one or more neurotransmitters. which signal either othcr neurons or specific target tissues ..\xom can branch cxtcnsi\'(:l~·. allowin.g a sin~le neuron to communic:lte \\'ith and send signals to many other neurons. Th is phenomenon is knOlm as divergence :lnd is signifie:ltlt when the spreaa of information is desir:lhlc for the organism (Fi!. :)-2). In this e:lse. the sign:l] is s:lid ttl he umpli· fied. COI1\"ersely. \\'hen si,gn:lls from multiple neuronal sources termin:lte on a singh.: neuron, eon\'ergenee is s:lid to exist (Fig. :)-.1). \\llen convergence exists. some si,gnals may he excita· tory; others tlt:ly be inhihitory. ,\s with all neo·

Synapse

J 0

~-

Axon

Fig. ;';-1 Sehematie \'iew 01':1 typieal neuron. indicating synaptic inputs to its dendrites (althou,gh other sites are possible) and informntion tlow down its axon. reaehing synaptie endin,gs on other neurons. Information tlowis unidireetional because of mo\eeular speeializations of various parts of neurons. The sc!.\ments em'ering the axon represent the myelin sheath that eoats many axons. and the ,gap in the axon represents :1 missing extent that mi,ght be as [on.!.\ as 1 meter in length. (From Nolte.l: The human brain: ;111 introdudion to its funetional anat()(ll~', ed S, ."it LOllis, 2002, }vlos{iY.)

<:1 L\PTER S

rons, the SIIIIII\1:Itl'l\1 'It' si,~nals Illay (or may 1lot) reach the tllll'shoid ;'1' the stilllulated neuron to gener
FACTOI{S I\FU'E:\Cf:\'G CONDPCTIO\ rELOCfTY Neurons of the 1'\,'\ :11'(' associated with SC/z'U'UlIIl eells (myelill). TllL'~l' LTII,s arl' rL'sponsihk for sup­ portin,~ :lml illsul:l[illl; :L\OIlS, allowin,g for nwre efficient proP:I,~:ltioll of :Ietion potentials. ~eurons

A III

A

Spillal :\'cmolol2.Y

arc said to hc myelinated or 1lI1mydilwtcd. dependin~ on the numher of times a Sehwann cell wraps around a ,~iven axon (often rderred to as a tiher) (Fi~. ."-.f). ,\ction potelltials arc propa~ated :don~ axons with \'ar~'ing speeds. The speed of an aetioll potcntial depends prim;lrily on two factors: the di:lll1ctcr of the axoll and the ckgree of myelina­ tion. Larger diameter and heavily myelinated axons (A fihers) COI1\T~' impulses eOIlsiderahly taster than smaller diamcter unmyelinated axons (C fihcrs). The differcnee in propagatioll speeds hccomes important when discussing the transmission of pain (see later discussion).

B

L Axon

DIVergence in same tract

Divergence in multiple tracts

Fig. 5·2 llil'L'I),\L'l1ee ill neuronal

pathwa~'s:

Schwann cell cytoplasm

A, jivcr~eI1l'e with ill 'I pathway to cause amplifkat\oll of Ihe sll2.nal: II. di\'l'n~ence into multiple traets til tr:ll1slnit the sit:nal to sep,lrate areas. (From (;/Iyt()11 .1(;: l/ull .I: Texthook of medical phvsiolol2.~', l'l! ltI, !'hi!w!clphiu, :.!()()] , WI)

Schwann cell nucleus Node of Ranvier

Saunders. ) Source

A Source #1

.....~,!/ (;2::=:::-:::::::=-- Unmyelinated axons

B

1 so~;ce_---«7)>---- so~~ce Convergence from si~gle source

Convergence from multiple sources

Fig, '\·3 Convergence of multiple input fihers onto a neuron: ,\, I1lnltiple input fihers from a single source; Il, input fihers fwm multiple sourecs. (From GlIywnAC: Jlull.!: Texthl}('\; of llIedieal physiolol2.Y. ed 10, I'hiladell'hi:l, lOll/. II'll ,....' uU/ulers.) sin~e

B Fig. S-~ Function of the Sehwann cell to insulate nerve fihers; A. the wrapping oj a Schwann cell memhrane around a large axon to form the myeliu sheath of the myeliu;lted nerve fiher. (:v[od(tled/rolll Leeso/l rs. Leeso/l 1\: llistology. Pili/wld/Jhia: ]'J7'). IV7J Sal/Hders.) B. Partial wrapping of the nwmhrane and cytoplasm of a Schwann cell aronnd Illultiple unmyelinated nerve fibers (shown in cross scction). (From Uuylllll "\(;: Hall J: Textbook of medical physiology, ed HI. j'hi/wldplliu, 20() 1. wn Sal/Ilders.)

I'"\HT TWO

.\1\XfOl\IY. KIOl\IECI L\NICS..\1\1) I'IIYSIOL()(;Y

BASIC STRUCTURE OF THE SPIX"\L CORD ~pil1al eOI'd rL'\L':d~ t\\l) matter and \\'hite matter (Fig, ::\-::\), The J.-:my II/utter i~ a hutterfl~'-~h;lped column of nCITe cdl hodie~. ;t:\on~. alld den­ drite~, Ikcau~e of the metaho!k Ileed~ of the neurunal edl hodie~. a ruhu~t hlood ~upply i~ contained in the~ray matter, prodding its ehar­ aeteristk :lppearaneL', The l!/lttc/:t7y i~ suhdidded into a pair of dorsal (or posterior) horns, or eolumns (when seen three dimensionally), and a pair of Yentral (or anterior) horns, or eolllmn~. The dorsal horn~ are responsihle for proeessin,g sensory information. whieh enters the cord where the dorsal root of the spinal nerve joins it, "\xons from the dorsal root will pem:trate the dor­ sal horn to \'arying depths hdore terminating and synapsing with other neurons, or they will leave the ,gray matter to form a traet. The 'c'-"lite muttcr. in contrast. consists prima­ rily of myelinated axons formin~ asccnding and dcsccndin,g tracts that cOIl\'CY information to

"\

ero~~

,'L'etion of the

h,l~ie eomponent~: ,~ra\'

Posterior intermediate sulcus Posterolateral sulcus

Anterior white commissure

\

othcr areas of the C='JS. Specialized edb ~allea oligodcndrocytcs arc responsihle for (melina· tion in the C\'S. The white matter i~ ~uhdi\idea into eolllmn~ or funiculi, whose nal1l~s are derived (rum their relationship with the gral' matter: anterior. posterior, and lateral. Th~ latty myelin sheaths are responsible for the coloration of the white matteL

SEXSOHY NEliHO\'S The sensory neurons contained in the spinal nen'es arc of the pselldounipolar varierv IFig, ::\-()) , The cell bodies of these sensorv neuron! arc located in the dorsal root gan,glioIl (DRG),

Dorsal root Sympathethlc chain

Lissauer's tract

Anterior median fissure

Fi.~. :;-:; General L'ross seetion;tl alwtolllY of the spinal eOI'd. reprL'sented in this ease hy thL' ei.l(hth eervieal sq~lllent. 1'j.~ Posterior funieulus; ~ IF anterior funieulus; U·: lateral funieulus: I'll. posterior hort1; 1111. anterior horn; 1(;. interllledi
Fi,~. 5-(, Scheme ~ho\\'il1g the eonstitutiOl1 of a typieal spinal neITL', In the Ilppcr pure of the dia~ram. the spillal eOI'd nen'e roots shO\\' the somatie eomponents, III the /o'u:cr Jlun pf the diagram. the spinal roots show the \'iseer;t! eomponents. somatic efferent and prel(an,l(lionic svmpathetie fihers. somatic afferel1t alld visceral afferent fihers. and postg:IIl,l(lionic sympathetic fibers, (From lI'illillllls I't. editor: (;ra\,\ :IIJ:1tOITIY, cd .18. tondon. I')!)S. Cllllrcllill-Li',:ings{(JIlc.)

<:JL\I'TI':E

are ~r~ty

'Itty rion

I':neh 1l1(, II· 'Iroll cOlltains a pl'riphLTal process, lI'liil'\: ' ,:t'lll!S til thc pl'ripher\' aJon~ the pntli Llkcll !" till' SpilLl 1 Illnl' and its hrllJ1ches, :llId ,t " Iii I;d I\rocc 'c.. "~I, 'l'il l'xtL'llds inlo the (:\S)I' iill dOl'sld 1',,,>1 "I thc spinal nerve. EvclI ill('!I~i! \lk pcriphlLd prol'ess of the Ill((; IlCllI'''' " [l'Chnic'lllll :1 i1l'ndrite, it is more ottell ,.. :i1kd illl ;1\OIl hCL';lllSC an :Iction potelltinl Irllll'i., ;!iOIIe; If !o\\llrd till' spin:d conI. Thm'nrl' 11l;J1I\'l'iIISSl'S of 1)1(; IlL'urons. hut the most COllll1lOI1 Ilc'urons tlJ:lt trllllSlllit pain are

'ina!

hg. rons ( ;).

.Thie

~

A ganglion is a collection of functionally related nerve cell bodies outside the central nervous system. Nerves whose cell bodies reside in ganglia can be sensory (somatic or visceral), or motor (visceral). All ganglion cells are derived from the embryonic neural crest.

Spillal :'-:euro!ogy

the "\ fihcrs (fllst-l'ondul'tin~) and C fihl'rs ( s low-eo n d uet i Il~). Thl'sl' IIlTIl'S CIIIl\'l'\' a wide ran,~l' of Sl'nsa­ t ious. 1'::lclis!)l'L'ific: c.L'lIs:ltion is referred to as a /lwill/lit\, S'lIl1l' L'\:llllp!cS are li~ht touch. proprio­ c..epti\'L'SL'll.SII( ions I~i\'i 11~:1 sense of position to thc hOlh·l. :Illd I)ain Thesc and other ll1od:llitil's are diseusscd !:Itcr in this ehllptcr. Spedfil' reeeptors exist for c:lch modality (Fig. :"-7). Sensor\' rel'l'p­ tors are dh'idl'd il1to thrce hasil' t\,pes: extero­ eeptOl·s. whieh earn' information that ori~inates outside or on the surfael' of thc hody. interoeep­ tors. \Vh il'h eOll\'ey illformation originatin,g from inside the hOlk. and proprioeeptors. whil'h pro­ \'idl' information on hody position lind mo\'el11cnt. Suhelassl's of the cxteroeeptors ineludc: • ~lcehanorl'eepti\'c (toueh. hearing) • Therl11orl'ecpth'e (temperature) • :\oeiel'pti\'e (pllin) • Chemoreel'pth'e (smell, taste) • Elel'trol11agnetil' (\'ision)

lorsal amus

entral 1m us

:nuni­ ·!s

he

Fi~, 5-7 SOIiIC of tliL' Sl'11S0r\' elldings fOUlld ill ,~l:lhrous (sillooth :llld h:lre) skill. ,lv1, \lcissller l'orpuscle; Me, Merkl'll'l'lL /'(;, !';Ieilliall L'orpusl'lc; R ]{uft'illi l'llding. (From X(Jltl'.I: TIll' hUlllall hr:lill: :Ill illtroduetioll to its funetil!lIal :IIl:lrolll~', ['iT S, ,"'t LOll is, :!()():!, ,\los/).\'.)

I',\RT TWO

,\:'\i,\TO.\IY. BIOYIECHA.'\ICS.

Sube!
,\:,\1)

I'IIYSIOU)(;Y

The special senses (smell, \'ISlon. hearing. and taste) arc eOll\'eyed Iw the cranial nen'es. ,\n important point to rememher is that each neuron has :1 specific receptor or set of receptors on it~ peripheral end that arc consistent with the tyPC of information that the neuron eOIl\'evs (i.e .. neu­ rons are modality specific). j\lso wortll\' of note is that some DR(; neurons arc quite long. For example, a single neuron carryin.~ pain inform;!· tion from the foot mi~ht he ,) to -l- feet or lon~er depending on the height of the indi\'idual. The peripheral distribution of the sensory neu· ron conforms to its distribution in the embryo ana fctus (sec Chapter -l-). In addition, these neurons can branch or eollateralize quite extensiye]yon their peripheral ends. This branchin,~ can re~l1lt in an extensive sensOl"y field for a single neuron Thus the sensor~' component (alon~ \dth the motor component) of the spinal nerve is distrib· uted to the dermatome (for touch. temperaturc, and pain), the myotome. and the sclerotollle (tor proprioception and pain). The derma tomes of the spinal nen'Cs follow a specific pattern, \\'hieh is routinely exploited by clinicians (Fig. :'i-H). For example. if a spinalncrve is dama,~ed, the p:ltienr may experience numhness or tinglin~ :d()n~ (he nerve's dermatome. By contrast, if :1 spin:llnerre is impinged by another structure such as an intervertebral disk, the patient may experience radiating pain along the entire length of the der­ matome, in spite of the site of impingement bein~ quite small and proximal. The central process of the \)RC neuron proj­ ects through the dorsal root of the spinalnem into thc dorsal horn of the spinal cord, ,\s the~e nerves collateralize (branch) peripherally, ther can also collateralize centrally, resulting in 3 specific field of distribution for the incoming sig­ nal. This property means that a sin,gle [me; neu­ ron can communicate with many nenrons in the spinal cord. producin,~ a variety of effects. From the dorsal horn of the spinal conI, modalitr­ specific neurons relav to or directly enter the nerve tracts that eOI1\'ey specific types of inform;l' tion upward to the brainstelll and cerehral cortex (discussed Inter). This specifici ty in eonl'eying a specific type of information from the periphe~' to a specific tract and subsequentl~' to a speciiic area of the CNS is known as a [aheled line,

CIL\I'TEIt:)

;, and

~lotor

)\,'curolls

Sommie motor neurons come in two varieties: alpht\ ;Iml ,~aIl111l:1 (.\et. and .\y) motur neurons, .\Ipha llloWr neurons are responsible for inner­ \'atin~ and activating sheletal musclc lihers throu,~h the myoneural junction, These neurons fall into the cat<:gorv of lar,ge diameter, last­ eonduetin,g ncrve fibers, Acetylcholine is secl-cted into the l11\'oneural junctioll, which, in turn, stim­ ulates the muscle to contract. Galllma moto," neurons are responsible for innervating n1l1scle spindles, which establish a set point for muscle tone (Fig. ;;-9). These neurons arc somewhat smrillcr in diameter than alpha motor ncurons and thus conduct impulses at a somewhat slower \'doc'it\" I-.lotor neurons, similar to sensory neu­ rons, can have exceedingly lon,~ axons, projeet­ in,~ from the spinal cord all the way to tbe trtr,get muscle.

l~uron

its c type .. nell­ ,I note ~. For t'ornul­ ionger, ll!1

'Y

III proj­ tI nerve ,'- these 1\, they l~ in a III,£, sig­ ~( ; nell­ " in the , From "tality­ t cr the \forma­ I cortex Lving a riphery ,pecific

()7

Nellrolo~y

Somatic

'". An

nell­ \'() and L'urons cl~' on result I c'uron. th the listrib­ rature, '11e (for " of the Ilieh is 'l), For l'tl ticnt >ll~ the ! nerve tiS an ,'rio-mee he oer­ It heing

Spillal

STRUCTURE OF THE SPINAL NERVE

Fi~, ~"S Ihlll:tI()llles.

(Jloditledfn!l/l Uri/IkeI' 1?H.,

.)lIhs,l/'; \ellr()I(j~\·. ,<"'flrill[i,fiehl, Ill, [')<Jr" C/wr[cs C Tltollllls; cud ill (J1l.\'[()1l ,\e: Ill/If .f: Texthook "fmedical ph\'si()I()~\', cd 10, /'hi/(/(/dphiu, 200l, WI! Sill/wiers.)

The spinal nen'e derives its nomenclature from the early anatomists whosc descriptions com­ pared it with a tree, with roots, a trunk, and branehcs (Fi,~, 5-10). Because of its position in the body, the nervc is said to have a dorsal (or posterior) root, a ventral (or anterior) root, eaeh of which penetrates thc spinal cord (ns roots penetrating the ,~r()und). The roots unite to form the spinal nerve (the tree trunk). Hlwrtly therc­

Motor nerve

~'c--- Muscle

spindle

Fi~, S·,) !;cllrollal eireuit of the stretch rdlex. (Fmm (illyroll "\C: /lull .I: Texthook of medical physiology, cd 10, Philauelphia, ]()(Jl, IFIi SUl/wlers,)

1'.\RT TWO

,\:\XIO~I\. BIO~IECII.\:\ICS.. \:\/l

1'IlYS]OL()(;Y

-

Fi l\

a in IiI

Se

(a:

inl co tio

a

tUl

Fig. :i-l0 (;ontinllity of spin:t1meninges :lIld the she:lths of peripheral llern.'s, The eol1tillllit\' het\\'ccn spill:!1 suhar:lellllOid spaee and e.\traeelllll:lr spaee within llelTe fascieles is indicated ll\' the :IITO\\ clllerging from boill the eut end of thc nerve and thc \'icinit~' of " dorsal rootg:lIlglion, Uli., I)ors:i1 root; S(;. s~'llIpathetic ,gangliotl; \'l~, ycntral root. The pi:1 lllater is retlcetl'd from thc l';\it zone of thl' Yl'ntral rootll'ts for clarit\', (Frolil/irsrit' J?\~' (;l'ncral histolo,g~' of thcmalllnw!.lJcrli/l./9... S.SI)ri/l~cr-\lTI(l~.)

after. the nerVe divides into dorsal and ventral primary rami (L. for hranehes). Before the hranehing of the spinal nerVe, some of the \'is­ eeral aiferents and dferents hraneh from the nerVe to connect with the paravertehral chain of

sympathetic ganglia, forlllin,g the rami COlIIlllU' nicantes (Vi,g. S-Il), The dorsal rami proceed ill a posterior direction to innen'ate the skin :lml intrinsic muscles of the hack, The \'l~lJtr:d ral1ll conti n Ue ina \'en trola teral eli reetiolJ i1lJdgiw lIil

illl tht em (th pal ees Be<

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r\cl1r()I()~y

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Dorsal nerve root

Fig. S,II

S~lJclllc

sItO\\·in.t: the relatiol1s of a cCITil'al nCITe and its gan.glion to

:1

cCrI'ical \·crtcbra.

(Fmlll

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a

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Illllllhcr of additional branchcs to skill and muscles of the trunk and

inn~mlte the

I,>pinal rOlll hoth !11~\ion;

/{ rscic

i ~()mmu­ lroceed in sldn and 11tral rami 1111 give off

limbs. The or.~anization of the spinal nern: may ~~ell1 etlilfusing at first, hut with some reasonill~ (alill repetitioll), the concept should bceome mtuitive. If the spinal cord is compared with a eomputer, thell it e:1Jl he vicwed as an informa­ tion proeessor. Sellsory information can be con­ sidered input dat:1 (similar to that obtained from a mouse or ke\'hoard). ~Iotor information, in turn. ean he considered output (similnr to an image on a Il\onitor or sound from a speal\erl. "\s the struetures that carry information (in this e:l~e the ner\'e roots) approach the processor (the spin:d coni), they separate and enter the rart of the computer that is responsihle for pro­ eessing the t\'pe of information 11l~ing conveyed. Because the dors:i1 horn of the cord is responsi­ hie lor proeessing sensory information, thc dor­ sal root eOIl\'eys sellsory information to it. Similarl\'. the \'entral root transports motor (eir~rellt or output) information from the ventral horn of the spinal cord, which processes motor information, to the target or.~an (in this case the ~keletalll1usele).

Once the roots of the spinal nerve JOll1, the information they' carry hecomes mixed (sensorv plus motor). When the spinal nerve begins to hraneh distally (i.e., the rami), hoth sensory and motor information arc carried to the tar.~et area. Thus in the case of the dorsal ramus, sensory information is heing .~athered from the skin of the hack, and the motor component is prodding innervation (stimul:ltion) to the intrinsic mus­ cles of the hack (e.0,., the ereetor spinae).

CONXECTIVE

TI~~UE

CO?\IPOXENT~

The conduit of a spinal nerve and its branches is made up of eonneetive tissue, which together with myelin sheaths supports and protects the impulse-eonductin.~ axons. Three distinct divi­ sions of this connective tissue have heen deserihed: • Epin~uriuIl1, whieh surrounds an cntire nerve and its major branches • Pel;lleuriullI, which surrounds smaller bundles of nen'e fihers • Endoneurium, which surrounds indi\'idual nerve fibers (Fi0,. 5-12)

lOO

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Fasciculi

.\!\.\TO~IY.

BIOl\1 EC I L\!\ICS..\!\D PI lYSIOLO(;Y

Fat cells Myelinated nerve fibres

Endoneurium

I

Perineurium Epineurium

Fig. :;-12 Cross-section of
(Fmlll

This eonnedin~ tissue heeomes apparent :IS the spinal l1elTeS exit the intervertehral foramina. If the relative di:ul1etCJ' of the nerve roots inside the vertehral canal is compared with the diame­ ter of the nerves in the periphery. it heeomes clear that a si,gnifieant amount of connective tis­ sue has heen added to the nenT for its protec­ tion and support. For example. the nerve roots that comprise the sciatic ncr\'(: mi,ght eo llee­ th'ely approximate the diameter of a small pen­ cil. yet the sciatic nern~ is typically the diameter of the human thumh~ In addition to the eonneetive tissue cells and matrix elements. the tissue of the nerve has a vascular component. Smal1 arteries (vasa nervo­ nnn) supply the nerves and small local veins, and lymphatics drain them. AlTTONO~IIC

Williul/ls I'L, editor: (;r
LOW/Oil,

1995.

)

NERVOUS SYSTEM

The autonomic nervous system (l\NS) controls or il1t1uenees many of the involuntary (visceral)

functions of the hod~. The i\NS differs from the somatic part of the peripheral nervous sYst~m in the types of sensory information it conducts. the way the information is processed ill tht' C~S, and the degree to which it reaehes conscious· ness (usually nor). In addition. the X\S diifen from the somatic system in the way motor infor· mation is conveyed. I{ather than having a single neuron sending a signal all the way from th~C~S to a t:lrget musele. the ;\}\'S relavs this informa· tion to its target tissues via a two-neuron hooku~ (Fig. S-lJ). The first neuron in thescriesi, referred to as the presyHaptic or preganglionic neuron, the second hein,g named the po"rs\'· Hilptic or postganglionic neuron ..\s can De inferred hy these names, the two neurons in the series communicate with eaeh other ria a synapse, which takes place within an int~rven· ing sympathetic ganglion. Sympathetic ganglia are located in the paravertehral s~'II1pathetic' chain, which extends from the upper cervical' spine to the coccyx, and in preaortie (pr~mte·'

(;J L\I'TEI{;;

Spillal :\curology

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Preganglionic sympathetic neuron ,. Acetylcholine

~,!~­

Norepinephrine

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)r~~ganglioniC '~~~~Sympathetlc neuron

Fig. s·n Schellle o! till' !\\'O-lleUrllll hookup betweell the eelltralnernllls system and the tar,g<.:t organ, (Froll! Kolle.l: The IHlIllal1 hrain: an illtroduction to its functional anatol1l~', cd 5, ,",'1 IA)l/is, lOll.!, Jlos!Jy) bral) ganglia, 10l':ltcd on the anterior surtaec of the ahdol1lin:i1 :wrt:1 The ,\I'\S is rcsj1IJ11sihk for innerv:ltin,g four types of tissues ill [he hody: • Smooth nlllsclc (found in all blood vessels excl'pt l':ipill:iries, the gut tuhe, the hrOlwhial trec, thc hladder, and in many other stratc,~ic locations) • Cardiac l11usde (the heart) • GlanJulnr l'pithdiul1J (org:inized into discretc structurcs, sueh as s:llivar~' and sweat glands, l'Xoerine glands of the pancrcas, and :IS sheets of tissue lining the body cavities) • Lymphoid tiss\le \c.,~., the splecn, lymph nodcs, thYlllllS, tonsils) TheANS ha, two div'isiol1s or suhsystellls. which are antagonistic to Olle :Illother and, under nor­ mal circumstances, exist in homeostatic halallce with one another (the ~'in-Y:lJ1g principle). These subsystems arl' referred to as the sympathetic and parasympathetic divisions Synonyms for these divisions, whieh are perhaps more descrip­ tive, are th<.: e!w/"(wo!llIl1!)(lr and cnmiosucra! divisions or svstclllS (1\0., :;-1-0. The ratiollale forthese terms is simple: they descrihe the loca­

tions in thc eNS of the ccll hodies of thc presy­ naptic motor neurolls of each division, Thus the cell hodies ut' thc presywlptie neurons of the snnpathetic division are 1()L'ated in the thoracie and lumhar sq~l11enrs of the spinal cord, llsually from Tl to L2. wlwrc:ls those of the par:ls~'lIJpa­ thctie division :Ire located within the hrainstem (those associa ted wi th era n ial nen'es ,1 loculo­ motorl. 7 [facial!. () [glossopharyngeal!, and 10 I \':l,gus I). and sacr:iJ sc,gments of the spinal cord (S2 to S-+). From a functional standpoint. the sympathetie division of thc ANN is designed to stimulate the hody to react to a threat, thcf(~!It or }1i,!J,!zt response, aud its motor portion is dis­ trihuted to the entire hody. Conversc!y, the parasympathetic division is designed for meta­ holie fUllctions. the rest anel di,!J,l!st system. and its distrihution is restricted to organs within hody cavities, and in the head with structures primarily associ:lted with the visceral tube. These (WO divisions are also sometimes refcrred to as adrenergic and cholincrgic. respeetiYcly. hecause the principal neurotransmitter of the postsynaptic s~'mpathetie neurons is epineph­ rinc (adrenaline) :Ind that of the posts~'naptic parasympal!Jeties is aeetvlcholine.

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Fig. :;·1-1- Origin and distrihution of svmpathetie (left) and parasympathetic (ri~lzt) eflcrents. l'ostgan,~li()lljc neuro]]s that 1i,'C in sympathetic chain ganglia and projeet to the hod~' wall and upper extrelllit~· an: Ol11iltcd from the di:l.gram to a"oid exeessi"e complexity. Their axons travel in spinalnern:s in a way analogous to th:n indicated for the lower-extremity supplv. ,\Ithough the cranial nerves have distinct and separate parasympathetic contents, suhstantial ""er!ap exists in the contents of ,uHral roots ~~ to ~--I. CU, CiliaI"

gan.glion; C\:(;, ee]iaegallglion; n, pupillary dilator; IA/G, inlcrior mesenteric ganglion; LU. laerinl;ll~lal1d:OG. oticg:lIlglioll; j'uU, parotid gland; I'U, pter~'gop:ilatine ganglion; S, pupillary sphineter; SuU, suhm:lIldihul:lr :II1J

suhlingual s:di",lrvglands; S( ,'(;, superior cervical ,g:lJlglion; ,')'U, suhmandihu!:lr .g:lJlglion; SAIU, superior mesenteric .g:m.gIiOll. (J/odit'ied,tl'o/ll ,\fettler 1':\: i\'CllnJWW[(JII1Y, cd], St LOllis, ]')48, MosllY: citcd ill So/rd' The human hrain: an introduetioll to its fUlletional anatom~', cd S, St LOllis, ]UU], Mosl}y.)

c< n

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h gl

tc

tf

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CIL\I'TER:;

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important tunetion ot the

;\~S is to !T~lll::rl' ! ,j""d I1mv to difterent areas ot th~ hod\', SlIjlpliill;': :k' l1lost hlood to the or,gans allli tbsliCS rh:ll [lel'cI it most in :l11vgi\'en situa­ tionle.~" shulllill~ h!t,wi ;I\va~' tmln gut OI)~anS and into SkL'IL'f;d liiuselc riming the t'ight-or-t'light r~sponse ).

DISTRIBl'TI()\ () F SY~I p"\ TIl ETIC ~I()TOR

:\I,:t']{ONS

B~eause

the sVlllpathetie dterents ori,gillate ill the t1loraeo!umbar spinal cord and v~t are ultim;ltelv found throu,ghout the hody, tour p~ripheral distributioll strategies arc employed. Th~se p:llhll':II's erlll Ill' categorized as follows, I()~at~d (jnl\'

Schema I: Illtrasc~1l1cnta] (TI throu~h L~) In this pathw;!v. the presvnaptie neuron exits th~ eord ill the I'entral mot ..joins the spinal n~r\'e,

and passes through the intervertebral loramen. The Ill'urOIl then leaves the spinal n~r\'e and ell tel'S the sympathetic chain gan­ ~Iioll throll,~h the white ramus communicans (so nam~J heeause the pregan,glionie neurons are myelinated), where it terminates in a synapse with the postsvll;lptie neuron. The postsynaptie n~uron sends its aXOIl haek to the (same) spinal ner\'~ throu~h the grit\" ramus eommunicans (so named bee;llIse the aXons are unmyelinated) to h~ distrihuted to the tar,get tissues within that

Spinal

\'el1rolo~y

10.1

and to the chain ,g;l11,glia helow Lo? Once the pre­ ,ganglionic neuron termin;ltes in a ehain~anglion ;md SYIl:lpses. the post~angliollk a"OIl reenters the spin;t1 IlU'\'L' tlrnlllglr the ,graY ramus eOIll­ nluniL'aIlS. TlJis prl J,-'L'~S i~ how sympathetks are distrihuted to the uppl'r ;md lower extremities. IlL-cause till' ~pinal nen'es arc not distrihuted to the head (other than the posterior scalp). the sympatheties use anotlJer pathway to reach these targets. "\t this point, the prq~an~lionie axons termilwte in the slIpc!'ior cervical gan­ glion (thc most superior limit ot the s\'lllpathetk eh;tin) (Fig. :i-]:i). Once the si,gnal is transmitted throu,gh the SVlwpse, the postsynaptic axons project to a plexus contained within the walls of the enrotid ;Irteries (intern;r! and external), which suppl~' thc lwad. I'\ot only do these nen'es innelTate these arteries, Inn they also follow them to other target tissucs ill the hcad.

Sehema .1: To the Organs of the Thoraeic Cavity (Tl through T4) In this p;lthwa~', prcgan~lionie axons (trom scg­ ments '1'1 thmu,gh T-l) reach the s~'J1]pathetie chain as deserihed earlicr and terminate in the chain ,ganglia. Postsynaptic fihers then pmJect trolll the chain direetl~' to the or,gans of the tho­ racic eavity as the cllnliuc IllTVeS, which travel throu,~h the cunlilJ]JlIlnwllury plexus (which ineludes pnrasympathetk contribution trolll the \'a,gus nerve) located Oil the aorta and hase of the heart alld the mots of the lungs.

s~gment.

Schema 2: Intersegmental

ml

At this point, the pre,g;lIlglionie neuron exits the cord Ihrou~h the ventral ramus, joins the spinal nerve, and le;lves the llen'e to enter the sympa­ thetie ehain through the white raIllUS eommuni­ cans. Rather than terminatin,g in a sYnapse, however, the axon continues through the ,gan­ ~lion and aseellds or dcseends through the chain to another Se,~lIlellt. This pathway allows tor dis­ trihution of the pre,ganglionie sympathetic neu­ rons not onlv within the '1'1 through Lo? cord segments, but also up to the head and neck (throll~b the eenieal extension of the chain)

Schema 4: To the Organs of the Abdomen. Pelvis. and Perineum (T5 throu,gh L2) i\t this point, the presynaptic axons pass from the spinal cord to the s~'mpatlwtic chain as pre­ viously deserihed. Once in the chain, however, this population ofaxons docs not terminate, hut rather hypasses the chain without synapse. These axons then coalesce with other se,~mental groups to form the splanehnk nerves, which arc di\'ided into tour sets. The ,greater splanchnic nerves receive contributions from segments T:i throu,gh T() (which ultimately innervate the or,gans of the fore,gut), the lesser splanchnic

IO-!

1'.\1('1' TWO

.\;,\.\'TO.\\Y. B\():\IECIL\;\;\CS. X\D I'IIYS]OU)(;Y

Anterior cerebral artery \

Internal carotid artery

Middle cerebral ortery Posterior communicating artery

Maxillary artery ./Auditory tube

Posterior cerebral artery Basilar artery _" Ascending pharyngeal artery Transverse process of atlas Internal carotid

artery

Obliquus inferior - _.. _~.~,,~ Superior cervical

sympathetic ganglion

Occipital artery Carotid SinUS

palatine artery Styloglossus

Vertebral artery

Deep cervical artery

-fie.. ..

Inferior ---r:-'­

thyroid artery

. Facial artery 'Lingual artery Superior thyroid artery Ansa subclavia

Descending scapular artery Phrenic nerve Fi.~.

5-15 Dissedioll slwI\'in!.\ the mnjor nrteries of the neck allLl the S~'1Il 1';1 thetic eh:lill, (Frolll II 'illiwlls j'L, (iLlY's ;In;ltolllY, ed 38. LO/lr/o/l, /<j')S, (;!tllrdlill-Li·vin!.!s/(illC.)

editor:

nefn~s

feceh-c contributions from T10 and Tll (which innefvatc the of,~ans of the midgut and the~onadsl. the least splanchnic nerves from '1'12 (which inncrvarcs the kidncys), and thl: lumbar splanehnics frolll L I and 1.2 (which in Ilc'rvate thl: of,~a ns of the hi ndgllt, pl: h'is, and pl:rincum) . .\11 hut the lumbar splanchnies cross the diaphragm to the abdol11in:1! cavity, at which point thl:y synapsl: with postganglionic sympa­ th<:til: nl:urons whosl: ecll hodies arl: 10l:atL'd in

thl: lariol1s preaorticganglia. The post~al1glion­ ies thl:n follow thl: brilnehl:s of the aorta to the t:lrget org:lns and tissues in thl: ahdomcn, pelris, and perineum, In thl: ease of the pell-ic :lI1d per­ ine:t! structures, the nl'ITl:S travel in a large group of nellrons c:dlcd t Ill' ltYI)(),~{(,stric plcxw "\n important point to remember is th:ltsignil~ kant divl'1'genee ()el'urs in the sympathctic gar· glia. That is. :1 sin,g]c presynaptic symparhetir neuro!l IIJ:1~' collateralize and stil1Ju!:If(; IlIultiple

CIL\I'TEl{ 5

Spinal

rostsVII:IIHic !Wli'''IIS, This aetion is one way that thc :!rous:1! re:,I" ·"'c' is amplified to ,~uarantee an adcqw!tc rc'''I''JiJ'c from thc' hOlh, ()f eourse, occasiollalh, I!I!.' r,-,'p,)JjSl' is ilJ;ipproprimelY strollg or 1)l!lj'J!I~,.d. rlsl!ltiJl~ in dYsfunetion.

D!STRIIWTI( ).\ OF PAR,\SY\\ P,\TII ET I C MOTOR :\El'I{();\S As mCllti(Jlll'l1 prL'\i()lIsly, tile parasympathetie divisioll of the .\:';S is also known as the cnlll­ iosllcml di\'isi()I1, Ilecause the pres~'n:lptie neu­ rona! cel! !Jodies :Ire loeated in the brain stem and sacral spinal e()rd ..\s the axons of these nelTes cxit the l1euraxis (fro!1l the brain, spinal coni, or both), thc\' :Ire ass()eiated with four of the erani:J! IIcrvcs (C;-';s.\, 7, (), and 10), as well as with saer;J! ncrves ~ . .\. aud -l (S:? throll~h S-l). The presy­ naptic IJaras\'lI1pathetic neurons assoeiated with cranial nerves .1 (()eulo!1lotor), 7 (facial). and ()

ADRENAL \IEIJ( 1.1 \

The adrenal medulla consists of secretory cells that are actually neurons, specifically postsynaptic sympathetics. The function of these neurons is to secrete epinephrine (and norepinephrine) directly into the bloodstream, which, in turn, carries this arousal neurotrans­ miller to all the tissues and organs of the body. The adrenal medulla receives preganglionic fibers primarily from the greater splanchnic nerves, but also from the lesser, and least splanchnic nerves (i.e., T5 through T12).

PARASYMI'XIllETIC ,"\ER\T

:\cllrolo~y

(glossophar~'ngeal)

relay with postsynaptie neu­ rons whose eellll
VISCERAL AFFERENTS Sensory information from l'iseeral struetures is eOI1\'eyed to the C:-;S, mostlv throu,~h small­ diameter, slow-eondueting neurons (C fibers), The ecll hodies of these neurons are loeated in dorsal root ganglia and in ganglia assoeiated with speeifie eranial ner\"es, most notahly, the \'agus (::'-110, hut also assoeiated with other era­ nial nen'es and saeral ner\"es 2 throu,gh ~). The parasymp:lthetie afferent neurons primaril~' con­ vey the sensation of streteh from the hollow ur,~ans (gut tuhe, bladder). The sympathetie affer­ ents arc associated with the eardiae and splaneh­ nil' ncr\"L'S and almost exclusively eonvcy pain. Theretorc pain sensations from the or,~ans of the thoraeic and abdominopelvic eavities enter the spinal cord at segments '1'1 through L2. This arrangement is one reason why Yiseeral pain is rderred to somatic structures within these spinal cord sq~ments (see latcr discussion). For example, pain from the heart is rderred to the dCrInatomes, myotomcs, and selerotomes of seg­ ments '1'1 through 'I' -l. These structures include

Sl 1'1'1.\ TO TilE IIEAD

In­

Lhe

Cranial Nerve

Relay Center

Function

.-is, cr­

Oculomotor (3) Facial (7)

Ciliary ganglion Pterygopalatine ganglion

Accommodation of the eye (for close vision) Lacrimation, innervation of glands and vessels of the nasal and oral cavity Submandibular and sublingual salivary glands, innervation of glands of the tongue Parotid (salivary) gland

r~e

is.

Submandibular ganglion

I if-

In­ ,tic pie

Glossopharyngeal (9)

Otic ganglion

105

I'.\HT T\\'O

.\;\STO\IY. mO\IECII.\;\ICS, .\:\1> I'IIYSIOLO(;Y

the ldt chest wall and medial left arm, spine and rihs. :lIld muscles inllclTated h\' thcsc scgmcnts.

REFLEXES Rdlexes :lrl' simplc nl'urollill loops ill \\hil'!J ;1 stimulus alld responsc occur as the result of a direct scnsorimotor hookup. In neurol<\gie terms. a stimulus aeti\'atcs a scnsory ncuron, which. in turn, directly adi\'atcs:1 motor ncuron (monosynaptic), produein,g a response (see Fi,g. :'>-<)). "\ rdlcx may also oeeur through an inter­ \'enin,g neuron (disvnaptie) or multiple neurons (pol~'synaptie), !\eurons that mediate these sig­ nals within the spinal cord are rderred to as ill{CnlCllr()/IS. Somc of thcse interneurons are exeitator~': others nre inhibitory. By l'ombinin,g the modulatory effeets of these neurons, rdlexes (as well as other activities mediated through the spinal cord) are mrelv. if ever. all or nOlle in terms of the response to a stimulus. l 'nder normal eireull1stmll'es, most rdlexes can he deserihed as either soma tie or viseera!. in \vhieh both parts, or limhs (sensory and motor), of the rd1ex are in\'()lve the same distrihution (e,g .. similar to a stretch rd1ex of a partieular muscle or withdraw:tl rdlex from a painful stim­ ulus Isomatie I or the stretch-void reflex of the bladder and reetum Iviseeral] ). 1I0wever, rdlexes ean also be descrihed hy the type of innerva­ tion that is present in the afferellt Iimh of the reflex, followed hy the efferent Jimh. Therdore these same types of reflexes ean e:lrry the terms sOlllatosolllatie. as the strdeh reflex. or viseero­ visceral. as the voidin,1~ reflex. .\s mi,ght he imagined, retlexes ean and do oeeur without the inclusion of the eerehral cortex, neither with the sensory component (conscious­ ness) nor the motor eomponent (intention). Thus reflexes arc aeti\'e and funetiona!. even in the e\'ent of a spinal eOI'd injury (with the execption. of course. of the injured se,gment). "\s mentioned previouslY, sensory neurons collateralize and interaet with more than one neuron in thc spinal eOI'd, as wcll as eommuni­ eate with interneurons, whieh can also braneh. One result of this eollateralization and inter­ communieation is that somatosensory nenrons can interact directly or ill<.lireetl~' with viseero­

motor neurons (i.e .. those that \yill illnenate the four typcs of tissues discussed earlier), The same l'an he said for viseeral sensory neurons interaetin,g \vith soma tie motor ncurons. This interplay hetween the somatie and \'isecraJ mm· ponents of the spinalncn'es creates two :Idditional suhelasses of reflexes, namely somatoYisl'tral and Yisecro-somatie. Beeause of the distribution 01 the motor neurons of the sympathetie di\'bion of the autonomic nervous s~'stem, this t~'pe 01 interaetivity is generally restrieted to spinal cord segments T 1 through L~ (within the limits ot anatomie variation), The implieations of this phenomellon are sig· nifieant to the praetitionc'r of adjustive/manipula· tivc proeedurcs. Not onl~' docs this intcraetilitv mean that viseeral disease c;m cxhihit. in part, as palpahle, somatic In'pcrtonieity. hilt also that eorreetion of the dysfunetional somatic compo· nent lllay positi\'d~' intlucllee the ahilit\· 01 the body to eomhat and perhaps to rcetify the prob· lem. Conversely. allowing a ehronie suhluxation or segmental dysfunction (diseussed later) to go uneorreetcd 111:1\'. ne'iati\'eh' ,..... . intlucllec the func· tion of the visceral struetures associated with that segment and perhaps neighhoring segmcn~ (Fig. :'-1(»).

PAIN (NOCICEPTIOX) Pain is a proteeti\'C function of the hod\'. People who are una hie to sense painful stimuli hal'e a greatly inereased risk of injury :lIld tissue dam· age. Pain is sensed hy free nerve endin,gs that are funetionally nonadaptive, This faetor is impor· tant given that this feature of pain receptors allows the sensation of pain as long as the painful stimulus is active, gi\'ing the body accurate, up­ to- th e-m om en t inform a tion.

Nociccptors Nociceptors (pain reeeptors) rcspond to three types of stillluli: meehanicaL thermal. and ehemical. l\' on nocieepti ve meeh:ulOreeeptors normally respond to speeifie stimuli that are not painful. llowcver, whcn thl' intensit~' of a mechanical stimulus hegins to eallse tissue dam· age, loeal nocieeptors heeome aeti\·ated. The

ClL\l'TI~I{;)

nate

The

Spinal

:\eltrolo~y

_ _ _- -

~\\runs

107

Somatic afferents (sensory) from joint capsule golgi. receptors, etc.

~;=~c--:=:;;;;;;~~~~~= Motor , - - - - - SympatheTic efferents

This .1\ eom­ ditional 'fal and ,tion of ,!i\'ision t\'pe of il:tl cord llllits of

Posterior primary diVision 1"0

~:)pi;1()rnalanllc

trunk

~

Monosyllaptlc gamma efterent ---,," Can neetar_ neurones Sympathetic preganglionics Motor neurones

White ramus

___+_-___+_

-~,-

-.---+----==----.:...-,,.­

sig­ "Ill ipula­ r:tctivity I p:lrt, as tl"o that eompo­ I'. of the i he proh­ I>luxation <.'1') to go Iile fune­ Ilell with "u!,111ents :11T

Anterior primary division

Sensory

Sympathetic:

vasomotor

pilomotor

sudomotor

Fi~.

Iv. People ,IIi have a "..,tle dam­ ~.., that are is impor­ receptors lite painful 'unIte, up-

d to three rmal, and , )reeeptors Ii that are c:l1sity of a tissue dam­ \:\ted. The

S·H, SeIl0)11:1 ot the spillal lIen'e slwwing sen'r:1l possihle patlJ\\,ays ot transmissioll. (Courtesy (!i ihl'vid V \. \! ))

IItili~. Ii( J.

\at11~

is trlle 01 tissue dama,ge caused hy ill 1L:1l1perature. The numher of L'ltem­ ieals that will stimul:lte !1oeiceptors, tlwrelw eallsillg p:till, is 1:lirh' 1:lr,ge. These stlhst:lIlces indlilk-, hilt are Ilot limitcd to, hrad~'ldnin and histamille (Illedi:ltors of inflammation), sero­ tlJnillla llL:lIrtltrallsmitter), potassiul11 ions, and h\'llr()g~1l iOlls (acids: this hecollles important II'h~1l thll1king ahout the pain of muscle lati,guc resllitillg lrolll :1 huildup 01 laL'tic acid :ll1d how Ihis Ilhe1lOIllL:1l01l eontrihutes to maintainin!!, and ~xa~L:rh:ltil1,g segmcntal dysfunction). Local tissue isdll'lIliu (lack of proper oxy,gclJ satura­ tion) ~nl1 also aetis'
extr~ll1es

Pathways of Pain Conduction Pain is conduetcd periphcrall~' and ccntrally hy two distinct pathwa~'s, onc last and the othcr slm\'. Each of thesc pathways rcaehes differl'lJt areas 01 the hrain and is consequentlY pereei\'ed diffcrcntly.

Fast P/lin The fast pain pathwa\', which responds to mechanical and thermal stimuli, is rcsponsi­ hie for sharp, lancing, wclI-loc:t1izcd pain and he,gins with conduction throu,gh an .\ fiber, a

P.\WI' TWO

lOS

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I'IIYS!OLO(;Y

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, _ / Fast-sharp , - ;. pain fibers

nerve

(,,-..or

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Fj~. 5-17 Transmission of both fast-sharp and slow-<:hroni<: pain si~nals into and through th<: spinal cord on their way to th<: brain. (Fmm UuyWll .IC: Ilall.!: Textbook of m<:dieal ph~'siology, nl }il. l'hi/wldphiu, 211111. WH 8(//mrllTs.)

Cortex

.·71

Fi.~. :;-lS ;\ntl'rior and lateral divisions of the anterolall'ral pathway. (Fmm (Juyttl1/ ,Ie': Ilull.!: Textbook of medical physiology, ('(I IO, ]'hillllidphia. ..!()() I,

liB Sllll1ldcrs.)

thin, poorly n1\'elinated neuron, which condllcts impulses from 10 to JO meters per second. The central processes of these neurons enter the dor· sal horn of the spinal cord, where they smapse with a numher of neurons (Fi.g. :>-17). One setDI these seeondan' neurons transmits signals up the spinal cord to the thalamus. These IWUrons cross the midline and ascend to the thalamus in a Wltl called the spinothalamic tract or anter()later~1 s~'stem (AtS). The information is then rel:I\'ed in the thalamus and projected to the eerebral cor· tex, specifically the posteentr:il gyrus of the pari· etal lohe (Fig. :>-1.')). This pan of the eortex is somatotopieally arnmged so that specific hod\' parts are represented ill various loe:ltions of (he gyrus (Fi.g. S-}\)). This configuration allows the cortex to localize the pain to a \'en' hign degree (i.e., the individual can tell exactly where the pain is located). The ,\LS is a good example of the labeled line prineipk, in whieh llIultiple neurons form a pathway destined for a specilic location in the C:'oJS (Figs. :;-20 and :;-21). Thc llRC ncurons of the fast pain pathway will also svnapsc on other neurons that gener· ate an appropriatc response to the stimulus. One of thcsc responscs is thc withdrawal retlex, in which alpha motor ncurons are .';[illlulated.·. resulting in almost immediatc muscle eontrac· tion, thus allowin.g the or,ganism to avoid (he continued painful stimulus. The primary neuro· transmitter for tlwsc ncurons appears to beglu· tamale, which is rclativcl~' shorr acting (Le.. quickly extinguishcs).

(:1 L\PTEI{;)

Spinal

~eurolo~\'

8/0-w

,,
20()],

I, e( lIlducts ,,'ond. The ! l'r the dor­ I,.'\' synapse ( )ne set of ~> l:t\s up the \lrons cross liS in a tract II] lerolateral 11 relayed in ','rehral eor­ " ()f the pari­ he cortex is j)L'cific hody :Ilions of the Ition allows :1 \'ery high ,'..aetly where ,,)( It.! example '1ieh multiple 1', Ir a specific

Fi~, ~-I') Ikpresentatioll of ril", different are:ls of the hlith ill SOI11:lrosenson' ;lrea I of rhe eortex. (From 1','!(ldd \\'. JiIlSIIIIISSCH T: Cerehral eOl'rex of man, a dllJic:t1 Stlltl\' Ilr loealizatioll of fUl1etiol1, XC'i.C lli/'h,

Pain

Slow pain is the more long-lasting, poorl~' local­ ized. deep. humin!!. type of pain, Slow pain is L'olldueted from the periphery hy sl1lallunmyeli­ nated C fihcrs. which conduct impulses at a rate as slo\\ as 0.::; meters per second, ThesL' fillers arc n:sponsihle for :I more delayed perception and response to pain. Simil:lr to the fast p:lin fillers, these neurons enter the cord through the dorsal horn and terminate on secondary Ileu­ rons, wIJieh conduct the impulse up the spinal cord in the l\LS. IIowe\,er, the \':lst majority of these seeondary neurons, rather than projecting to the thalamus, terminate in the hrainstem reticular formation, an extremely old part of the CNS. The reticular formation lies Jeep within the hrainstem and is m:lde up of neurons with relati\'ely short axons. Extending the entire length of the hrainstem and spinal cord, the reticular formation is responsihle for a ,'ariety of fUlletions. One function is to stimulate the or,gan­ ism to a state of increased alertness (the reticular­ :letivating system), whieh cert:linly occurs during

I'HJ8, //(/(11['1:)

Premotor area

Primary motor area (precentral gyrus)

Primary sensory area (postcentral gyrus)

::;-:~ 1 ).

pathway ,s that gener­ ..,timulus. One \\a\ reflex, in L' stimulated, lSc1c contrac­ to :1\'oid the rimary neuro­ ears to he glu­ t acting (Le., ):lin

Fi~, ~-20

L:llcr:t! ,'jew of the hrain shOWing the primary motor (preeentraIgyrus), prel11otor, and prill1ar~' (po,teclltral gvrus) arens of thc cerebral cortex. (From C'I'III/Icr UJ), /Jurl),v S.:\.· Basic and elinicnl :ltJ:lllIlm'lIf tlie spine, spinal eord, and .\NS, Sf LOllis, ]')l)S, ;\:!osl)y.)

SCIMfl'

109

110

1'.\!n'TWO

.\:\.\TO:\IY. BIO:\IECII.\:\ICS.. \:\1> I'IIYSIOLO(;Y

Paracentral lobule

Cerebellum Fi~.

:)-21 ;"Iedial

Medulla oblongata

Medial Irontal gyrus

Superior colliculus 01 the midbrain

Pons

of the hrain. The par:leentr:d lohuk. \\'hieh is the cflntillll:lrilJll of the pril1l:Ir\' l1lotor area and prinwn' scnsor\' arcas (posteentral ,~~TUSJ of the ccrehr:d cortex. is indicated. The medial frontal .~HUS (postcrior rc~ion) is the !oeation of the supplel11elltan' l1Iotor arc:!. (From CrW/llT (;J). j)((rhy SA nasie and dinie:d anatol1lY of the spine. spin:d cord. and .\:\S. ,"'r LOllis. ](j()S. J/os/).\'.) \'ie\\,

(preeentral~\Tus)

the expericnee of pain. This increased vi,~ilanee is crucial to the futnre a\'oidanee of pain. The reticular formation, in turn, projects to the lim­ bic systl'm. which ,~O\'LTns emotional responses, as well as to the hypothalal1lus, which si,~nifi­ eantly influences the activity of the Al\'S. In ;Iddi­ tion, the reticular formation eOl1ll1llmieates with the periaqueduetal gray of the midbrain, which projects back to the spinal cord to inhibit pain sensation (sec Inter discussion). The primary neurotransmitter for slow lxlin is the peptide substance P. the effects of which arc considerably more long lasting than ,~lutal1latl' and is partially responsible for the chronicity of slow pain. l\'ot onl~' is substance P secreted at the cen­ tral tl'rminal of a C fiber, but it is also secreted :It the peripheral end. Substance I' has been shown to act as a eyto!i.ine in the intlal1lmatory responSL'. ,\nother transmitter implicated in the pain path­ way is calcitonin gene related peptide (;( ;1{1').

Visceral Pain Pain from the thoracic and abdominopcl\'ic "is· eeral or~ans is exelusi\-cly transmitted hy sub· stance P-producil1~ (: fibers. By comparison lI'itn the somatic nociceptive s~'stem, the numher 01 p:lin tibers in the bod v cavities is rel:iti\'cIY ie\\'. These nerVeS, as mentioned pre\·iousl\,. are pri· l1larily associated with the sYmpnrhetics ana enter the spinal coni trom T 1 to L2 .. \s sub· stance l'-produeillL: l\eurOl\S, thesc neurons il\teraet with the slO\\ pain path\\,;I\, secondary l\eurons, which project up\\'ard throu,L:h the .ILS (Fi,~. ;';-.2.2). :-'Iost ot these l\eurons tced into the reticular tormation, but some reach the thala· mus. From the thalamus, third-order tihel"sproj· eet to either the parietal cortex, or the insular cortex, which has no somatotopic arrangement (Fi,~. ;';-.2J). The insular cortex apparcnt]\, deals ill part with the relative sense of lI'ell heing. As

(:1 L\I'TEIZ:;

I II

Spinal :"euroloL:Y

Hypotllalam us

Somatic afferents

~

~

/~~

..-'c:

Reflex connections

:Irea ,llcdial S. \:

\ iI: vis­ 1\' sub­

'Il with libel' of h' few. 'In' pri­ L'S and \s sub­ ll.:urons '()ndary lhe ALS into the c' thala­ 'rs proj­ insular

I~ement

[Iv deals

>cing. As

I I

----~--[

Lower motor neuron Skeletal muscle

Smooth muscle, cardiac muscle. glands

Autonomic motor neuron

Reflex connections

Fi~, ~·22 !':Ir:dlcls flL'tII'eell somatie :ll1d autonomie parts of thc l1el'l'ous S\'stcm, Both parts il1l'oh'e speei:t!ized allerents :lIld dferellts. rdlcx eOl1l1ec,tions. :lIld aseendinL: :ll1d dcseellllin,L: patlll\'a\'s to and tr0l11 Ili.L:her ICI'cls of Iheeelltr:d lIervous ,,'stem, 111 the ease of the sympathetic :llld parasymp:lthctiL' sYstems. hO\\'cI'cr. thc hl'p"th:d:lIllIlS rllthel' th:111 the thalanlus reeeil'es 1111leh of thc aseellllill,L: illforlllatioll. and the hYpothalallHls ratherth:11I the eerehr:d eortex is a major souree of deseelldil1L: p:lth\\,:I\'S, 111 :Idditioll. sYmpathetie :lIld paras\'mp:nlll'tie tl':Il1Smissiol1 t" the periphery il1\'oh'es and illterllledi:lte synapse ill all autollomie ,L:allL:lioll. (1'1'II1tIA',,!rl'.!. The hUIlI:1I1 hraill: :111 illtr<>duetion to its fUlletioll:t! :111:ltoll1~'. cd 5. St Lo//is. ]lili.:!. ,\!os!i,\',)

su~h. \'is~~r:11 jJ:lill primarily eodes to eonscious­ ness as a s~llse of l10t fl'elin,t\ well. without a great d~al of speeifieit\' (e)~,. a stomaehaehe J, The relatil'd\' small Ilumber of fibers, eoupled with till' ~l'lltr;d distrilllLtion of c: fibers (i.e,. not man\' fihl'rs reaeh the th:J!:lI1ltls and thus the cortex) :1l'l'IJlLllts for the poor loealization of this tyre of paill, lIoweYer, the nonadaptabilit\, of th~se n~ur()IlS ;dol1~ \\ith the aetivity of suh­ stance I' is rl'spol1siiJle for the rel:ttive sel'erit~' and lon~ lastil1~ Il:Ltlll'e of \'iseeral pain,

Inhihition of Pai Il The pain jJatll\\'a\' eall IlL' interrupted by all inhi1Jitorl' SI'Stl'Lll within the eNS, This path"ay

ori,~inates

in the lIlidhr;Jin and is known as thl' These neurons proj­ eet (send axons) to another area of the hrain­ stem known as the raplle nuelei. where the~' rela\', The raphe nllelei neurons, ill turn, projeet to the dorsal horn of the spin:il eOI'll. seeretin.~ elldo~enous opiates ;IS tlteir primar\' neuro­ transmitter (the enl,ephalins and endorphins), This aetion cffecti\'e1~' shuts off the transmission of pain information from the primary nocieep­ tors to tlte seeol1dar~', aseendin~ neurons of the ,\LS. The inhibition of pain is presumahly a sur­ \'il,:t! meehanism that allows the indiYidu:t! to funetion in spite of experiencin,~ pain, The 1'.\(; eells reeeive input from the eerebral eorlex, whieh explains the remarkable eolltro! some pcriaqueduetal~ray(1',\(;),

112

P.\IrJ'TWO

.\:".\TO\IY. BIO\IECIL\!'\ICS, ,'u"![) I'IIYSI< l\.()(;Y

Fi.~, 5-2.1 Llter:i1 surl:ll:e of tlie leit eerehntl hemisphere showil1~ the insular cortex. Parts of the telll(lontL parietal, and the front:i1 lobes h:I\'(; heell relllO\'ed. (Fro/ll "'il/iu illS I'L, editor: (;ray's :In:ltmnv, ed 38, Low/otl, JI)I).'), Churchill·

IJL'i 1l,~,WOIlC. )

individuals demonstrate in tolerating otherwise extremely painful stimuli. The pain pathway can :dso be interrupted by certain aetivities or hehaviors, as well as by eleetrieal stimulation, Stimulus-induced analgesia. or afferent inhi­ hitioll. is an adaptin: heha\'ior th:tt is used to distmet the nCITOUS system from the pereeption of pain, Examples include ruhhing an elbow that has just been bumped, scratching an itch, shak­ ing off a traumatizcd joint, :ll1d others, These bclwviors :!fC dcsi,gncd to hombard thc CNt) with additional stron.g stimuli so as to turn the atten­ tion of the s~'stem toward that stimulus and away from the pain. In the proeess, thc individ­ ual hecomcs more ;l\vare of the behavior than the pain, Other behaviors are desi,gncd to avoid p:tin: Patiellt: "It hurts 'Ichell I do thaL" C[illic:iall: "Thell dOIl't do thut. " • ,\s the person lies in bed asleep for extended periods. the pressure from the mattress can produee loeal tissue isehemia, which stimulates noeieeptors. The response is to 1I10VC awav from the stimulus hy tllrnin,g over. • As :t weight-hearing joint hegins to deteriorate from arthritis, the person develops a eharaeteristie anra]gie (pain­ avoiding) gait to walk around or awav from the painful joint surface (a limp),

• As the muscles of the low hacl, respond to ~ minor tissue injury I1\' eontraetill~ OI'lT lime, they heeome f:lti,gued, resulting in an increase in local tissue pi 1. This stimulus :lcti\;ltcs nocieeptors, eansin,g more pain in the llluscles, leading to additionalguardill~ The patient comes to the otfiee and states that his or her haek "went out.·' The patiellt exhibits a characteristic posture. which h:ls dCleioped to reduce the amount of pereeil'ed p;lin hUl which is usually mechanically inettieiL'nt. eausin,g additional muscle tatigue alld I!lore pain. Other responses to pain: • Uuardin,g or splintin,g Splinting rakes place; whcn an injury to ;1 joint occurs. The local tissue damage e:!use~ swelling and pain, which, in turn, aetilalCS nociceptors. These noeieeptors interact with alpha and ,gamma motor neurons, eremill.!\ hypertonicity of the muscles that !l10\'l, the joint. This hypertonicit~· (alon,g with the tissue tension rcsulting from the swelling) has thc effect of decreasing the range of !l1otion 01 the joint, thus preventing further injury. Guarding takes plaee whcn an injllr:' to or intlammation of the ahdominal ,'isccra occurs, Guarding is an example of a dscero-solllatie retlcx are, In this case, the pain frp!l1 thc viseenl is transmitted to the spinal cord \ia C fibcrs, which enter the cord in the I()\n~r thoracie segments, Thesc ncurons stimulme nJpha and ,gaml1l:l motor neurons tll:!t innervate the muscles of the abdominal 1\~IL which beeolllc hypertonic, The eOlltraetion 01 these muscles not onl~' helps pr(Tent :1 repetition of the trauma, hut :l1so helps hold the organs in place, whieh also prC\'eIlts turther injury. • Referred pain (Fig. ;)-2ef) This condition also oeeurs as thc result of visecra I or,0,;111 involvcl1lcn t. 'l\vo phenomcna arc operative in this situation. The t'irst is cOl1'ver~elLcc, in which n visceral ;tt'fL'rent eonver,ges on a secondary llellrOn or the .\LS and activatcs it. This action sends a si~ual to the cortex, which interprets the inforIna[ion as pain eO!Jling from a somatic strllctllrc. Because the visceral atfercnts cnter the cord

CI L\PTEl{ 5

:1

the his ,hits I'Jped

,d

at spillid COi d segments T 1 throu,gh 1,2, the IJilrielli \Iill jll'l'l'ei\'e pain within that somatic segml'llt (i ,t" dermatome, l11\'otOl11e, selen,tol1ll'I, The second phenomenon is neurotransmitter spillover. ,\s mentioned Ilrl'l'ioll,iI', !lOciceptors are nonadapti\'e: that iS,;ls thl' I'ail1 persists. they will continue to fire, SUhsllllll'l' 1'. characterized as a long-acting

11\! t

!

Ire

I c'~

\Iith 11~

lile , (issue (he "t the

Visceral nerve fibers

Skin nerve fibers

Fi~, ~·2-l

\!l'ch:lIliSIll of rct"erred pain and rct"erred ,\C: Hilll.l: Textbook of lIIedical physiolog\', cil W, Phi/wldphiil, 200], WB h\'pcral~csi;l, (FrOlIi (;lIywn

,eeurs, marie Ill: \ \'ia C i

,I'

lulate

SlIIlIIrlcrs, )

Spinal Neurology

neurotransmitter, is therefore continuously secreted into the dorsal horn, ~uhsequently, more and more secondary ,\1,~ neurons (iIH:luding those ot the tast pathway) become im'ol\'ed in transmittil1,~ the pain. For example. the heart. which reeei\'es motor inner\'ation trom T I throu,~h T..J., will transmit pain back to those same cord segments, The patient will become aware of a ,'ague tightness in the chest resulting the \'agueness of the pain coded trom the visceral affcrents. Ilowever. as the pain persists and more substance I' is secreted into the dorsal horn of the spinal cord. secondary ,\L~ neurons become activated, The patient now complains of frank chest pain and pain running down the left arm (along the dermatomes of '1'1 through T..J.). ~peeitie referred pain patterns exist for most organs, which is an important reason to carefully stud~' the sqi,mentation of the ,\N~ (Fig, 5-25). The intlux of substance l' and the intersegmental eollateralization of C fibers in the dorsal horn can also cause the spread of pain to adjacent segments. accounting for some patients' complaints of neck pain durin,g a heart attack. • The al10statie response (allostasis) This reaction is an adaptive response. which can result from prolonged stress on the s~'stem

Esophagus Stomach

d \Yall, ction at

Liver and gallbladder

I

~

Il.l

hold

Pylorus Umbilicus

ot , lInena ~( is 'ent he ,\1,8

::::=---~~r-~-i----

Appendix and small intestine

-:t:::T-t---1r--~t---- Right kidney Left kidney

,i~nal to

'mation lire. he cord

Fi~. ~-2~ Surfllcc areas of rct"erred pain from differellt viseeral or,galls. (From medical phYsiolo~\', cd lO, Philadelphia, 200 J, WB Swmrlers.)

(iuyt01!

AC: /lull .I: Textbook of

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Hypothalamus

Excites

Stress

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elan~b'" \

(

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eminence

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vessel Portal (CRF)

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Relieves

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Inhibits \

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Adrenal

1

1 Gluconeogenesis 2 Protein mobilization 3 Fat mobilization 4 Stabilizes Iysosomes

-;0..

;' Cortisol

/

Fig. ~-2() :\It:ehanisill for regulation ofgllleoeortic()id seeretion., \L'T" . . \dretlocortieotropiL' hOrJlWtle; L'I{f<~ eortil'otrophitl-reil'asin~faetor. (Fmlll (;U\'t()1/ .\C': l/ull.!: Tcxthook of llledie:i1l'h\'siolog\'. L'r! Iii, I'!liludd!J!liu. I~ \. Wli SUI/wiers. ]Ii()]).

(Fig. :"i-2h). One sueh stressor. of L'ourse. is pain. linfortunately. multiple inputs to this feedhaek loop (i.e .. multiple stressors) m:lY he present. whieh ean exaeerlwte the eondition. Ilo\\'e\Tr. the allostatie rl'sponse underscores the holistie n:lture of the interaetivity and mohilization of se\'eral. it not :II\. hody systems. Startin,g from the souree of p:lin. the impulse tr:l\·els to the spin:lleonl and :lseends throu,gh the "\LS \'ia seeond:lry neurons . .\I:lny of these neurolls projeet to the rcticular fOrJ1l:llion. \yhieh ascends through the hr:lin­ stem to the hYpoth:llamus. Stressful input to the hypoth:l]amus causes thc secretion of eorticotropin-relc:lsi ng hormone (: RI [L wh ieh m(gr:ltes through thc h~'pophyseal port:ll system (the yaseul:lr systcln) to the :Interior pituitary, CR!] stimulates the synthesis :lnd sceretion of adrenocortieotroph ie hormolle (,\CTlIl into the hloodstream. which ultimately makes its way to the adren:i1 eortex, "\t this point. the synthesis and secretion of hormonl's is stimulated, Cortisol. whieh h:ls :I wide r:lngc of systemic effects. ineludin,g suppression of the immune system.

is one of these hormunl's, Immunc suppression is import:lnt in preYentil1~ anaphylaxis (:I sc\'ere rcaction to al1ti~el1s o[ the :dlergic response l, .\ldosterone. which regulatcs kidne\' function. is :lI1othcr hormone prmluccd hy the adrcnal eortex. ,\ third hormone is alllirostcncdione. a reproductiYe hormone. <: 1\1 I

StrL'ss

~

'I ( :ortisol-epinephrinL'

f­

.\<:'1'1 [

Therefure strcss elearl\' h:ls :1 ,glohal outreach in thc hody hcc:luse of the intereonneeti\'it\, of the ner\'()l\s. endoerinc. :lnd immul1e SYstems, The som:ltic componcnt oj dise:\se is easil~' extrapol:ltcd ,gi\'en its intluenee Oil the nel"\'ous system. Unfortunately. ,\CTII also cxerts a stimulator~' effect on thL' :ldrenal medul!:L whieh. as mL'ntioned earlier. s\'nthesizL's ;\I1t! seeretes epinephrine, InerL':lsed le\,c!s of Sl'rum epinephrine inerease the st:m: of alertness hut also perpL'tll:lte the strcss reaetion-ad,lj1ti\'e response caused hy direct input to the reticular formation. the closure point of the loop. • Faeilitation and sensitization "\s pre\'jously IlIclltioned. noeieepturs ;Irc L'onsidered nonadapting, ()Il the cOlltrary.nor onl~' do lhe~' not adapt. hut they also h:m':! un ique property known as sensitization, Sensitization. s\'\!onymous with facilitation, oecurs when :1 painful stimulus is applied orer time. Rather than dcere:lsin,g its r:lle of tiring, the noeieL'ptor aetuall\' illcn:uscs its impulse rate, In addition. the excitation threshold 01 the nociecptor mCllIllrane hceomes si,gnifieantly lower, resulting in inerL':lsed tiring rates from suhthreshold stilllldi. This eh:lraeteristk mcans th:lt onee a noeiecptori~ faeilitated. a less than painful stimulus heeomes p:!inful. :I condition li.llO\\'n :Is hyperalgesia. I,'acilitation ean also extend til the seeondary neurons in the pain p:ltIl\y:!r. ]owerin,g their threshold for firin,g, This dcerease e:llIses allodynia. in whieh \'arious normal stimuli heeome p:linflii. \ell\'(m;i1 beha\'ior of this kind in the trigeminal system

115

,~~l'Jl~

O[

i I iell

Ii' 'rJl1one lid

(jlh.:rive

1] j

II 1\

I(;\~) Il"j!onsihle for the se\'erity and L!ur:llilll: '>lll1i~r;linl' helldaehes, Because of J1~riJ1iJl'lli: ,.\ ,rl:lp "f reCL'P1 i\'e fields, as \n:]] :i' ~l'lllr;t1 !)\'l'\'LIj! ot tiL·ld~ o( di~trihutiol1, ~tlllr~ 'plll:d L'ord se,~mclJ(s eal1 heconJe IlIl,i111:llcd, !l'lIding to se,~mel1tal d~'sfunctiol1, TIi" 1,lllllilllll'llOll \YIIS first elucidated by the J11i\"I,jIl~I'i In'in hOlT, l'h.I). .\'/JIL' Iii II/( 1'('(11/('1': .1!rhowJ,Iz lIlI (!t' thc lJrc''-'i­ III/,sly l/il'/llI"III'Ii ,,;c('lIllrios Ilrc rClI[ ulld potCII­ rilll, Ilil'l' IIl'l' pl'l'SL'lI/c,tI u,>; thc "'worst ClISe. " Thc nlll'nll'ril' loops rllllt l'xist ill thc I)()dy cllull[C it

reach in

(II

i t\'

"rll/ll'l'S. \\'IIL'II

I/lIli/llllillllll/IIL'Ostusis ulltlcr Ilormu[ circllm­

lIisrlllJtiolls occur. (hc [)()dy is U/le! scU~corrcc( (1Irr'II~/11I /lIllIllnT 1/ hculill,iJ, /lnK'csscS.

11/,111

111...-'

: I~l-':ISC is

"11 the

11/,/1' to

CO/llPC/lSU(L'

SI~(;\IE\'T.\L i I din,

:/,~~

and

DYSFl1.'JCTION

11ll' information presented thus far, for the existence of segmental dvs­ rllll~lilll1 is rclatileh' simple. Distillation of the

I;il'l'tl 1111

1ll:lkil1~:1 C:I,C

coneept to its most fundamental components \\'ould include initi;1! perturbation (disturbanee) of the segmelltal svstem. an attempt to self-cor­ rect. a de~t:lhilizatiolJ of the system, and il1LTl'ased risl, for further perturbation, Ilo\\'e\'er, the more OIJL' is II\\'are of ull the implications of the !Jmh' segmen t, (the anatomy, physiology, pathology), the more one is equipped to diag­ nose and treat. III {(([ditioll, wu[erstwzdill,iJ, (!t'tlle -visceru[ cmll])(!Ile/l{ us it relutes to the sq~lIIellw­ timz wu[ distrilwtiml (!t' (he ,\J\'8 is (!t' /JurlmwllIzt im!Jor(wzce. ,\s defined in Chapter -1, the segment ineludes the spinal nelTe and lIlI the tissues it inlJen':ltes, both somatic and \'iseera!. Segmental dysfunction can have a variet~- of eauses and expressions, By definition, the exis­ tence of the somatic component in disl'ase is the ddinin,~ factor, the llnderstandin,~ of \\'hich predisposes the ehiropractor to a sin,~uJarly useful set of manual tools for diagnosis and treatment. .\lso bearing in mind the nature of the muscu­ loskeletal s~'stem as a tensegrity structure,

,II e of '1'1111 )11\\\\\ \IW SI'IR.\L

dircct ,,1, ,,,ure

Somatic pain

I.glutamate, substance P, etc.)

:IIT I ra r~', not , !Iavc a ion,

!itation, !,]icd over ,)f fi rin,~, 1111 pulse ,,!Jold of Ised firing .'iceptor is \IS :IS \tend to ':Ith\\'ay,

Acute inflammation (swelling, etc.)

atrophy, fascitis)

Somatosomatic reflexes

--.

Somatovisceral reflexes (77)

(guarding or splinting response,

muscle spasm, segmental dysfunction)

Increased sympathetic output (local vasoconstriction)

Ilis

\':Irious r' J! wi I:d system

Chronic inflammation (fibrosis, immobility,

Ischemia

P,\H.T TWO

116

Al\L\TO:\IY. mO:VlEClIANICS. AND PHYS\OLOCY

coupled with the prime directive of the equilibr­ ial triad (consisting of the visual, proprioceptive. and \'estibular systems as described in Chapter -t J. maintaining an upright posture for \'isual acuity underscores the importance of holism in clinical practice, Briet1~· stated. the relative halance of the hody in space is routinely suhjected to challenges to which the individual usually adapts and self­ corrects. Indeed, some disruptions of thc mus­ culoskeletal system go untreated for years without any complaint from the individual. IIowever, over time, the hody gradually loses its capacity to withstand these challenges and hegins to decompensate, which is usually when an individual becomes a patient.

Review Questions _ .. - _ . - _... - . - - -

----

-

-

--

-­

1. Describe the basic structure of the neuron. 2, What is the relationship between the diameter of a nerve and the speed at which impulses are conducted by that nerve? 3. Explain the role of the dorsal root ganglion. 4. What are the primary types of

exteroceptors and interoceptors?

5. How is knowledge of dermatomes useful in diagnosis? 6. How does the role of alpha motor neurons differ from that of gamma motor neurons?

7. Why is the diameter of the sciatic nerve substantially larger than the combined size of the nerve roots that comprise it? 8. What are the four types of tissue

innervated by the AI\JS?

9. Describe the roles of the sympathetic and parasympathetic divisions of the ANS, 10. If the spinal cord's function is seen as information processing in a computer, what are the inputs and outputs?

1. How can muscle hypertonicity or spasm contribute to maintaining the inflammatory state? 2. How can segmental dysfunction contribute to visceral disease? 3. How can visceral disease contribute to segmental dysfunction?

SUGGESTED RK,U)JNGS Cramer G\), Darhv S,\: Basic mul clinical UllIIWIII.\' IJldll spille, spinal cord, alld ANi), St LOllis, 1')()~. ~losny Guyton ,\(:, llall .IE: '[exc!Joo!? (it' medical },hysiollJ(\: d 10, Philadelphia. ~OOl, \VB Saullders. Larsen W.I: Anatomy: lle·velopmenc. .!1metioll. clillitlii correlations, Philadelphia, ~O(j~, \VB Saunders. \villiams PL, editor: Crely:' wwtollly. cd Js. London 1 ()'J5, Chun:hill-Livingstolle. Zigmond M.I et al, editors: Fundamental nl'lIm,ICICIlCf, San J)ie~o, 1'J9(), ,\cadcmic Press.

Basic Biomechanics

Joseph Morley, DC, PhD

Key Tenns ACCELERATION

HOOKE'S LAW

STRAIN

ANISOTROPIC

HYSTERESIS

STRESS

CHONDROCYTE

IMPULSE

TENSILE LOADING

COMPRESSION

INERTIA

TORSION

CREEP

KINEMATICS

TRANSLATION

DISPLACEMENT

LATERAL FLEXION

VELOCITY

DISTRACTION

NEWTON'S THREE LAWS OF

ELASTICITY

T

_

IvlOTION

EXTENSIO

PENNATE

\VOLFF'S LAW

FLEXION

PLASTICITY

WORK

GROUND REACTION FORCES

SHEARING

he human body is continually subjected to external and internal mechanical forces that tend to produce structural deformation of ue. These forces, which include gravity, muscle activity, and ground reaction forces I.e., the result of foot and ground interaction ring locomotion) are resisted in the body by ne, muscle, and ligament, as well as other ft tissues. Loads, or external forces, can be dividual or a combination of compression, rsion, translation (i.e., shearing), and tensile ding. Understanding these forces and the ys they affect the hard and soft tissues of e musculoskeletal system is essential for hiropractors, who are directly concerned 'th the restoration of balance and mobility to e spinal column and other musculoskeletal ctures. This chapter introduces the key terms and ncepts of biomechanics that chiropractors I with throughout their careers. It comple­ nts Chapter 4 (Spinal Anatomy), adding tail on the qualities and functions of the vari­ tissues that make up the musculoskeletal tern.

VISCOELASTICITY VISCOSITY

TYPES OF LOADING, STRESSES, AND STRAINS Translation and Shearing Translation occurs when all particles in a body move in parallel at a given time. When one body undergoes translation with respect to another adjacent body, shearing forces result. An exam­ ple would be two adjacent vertebrae. If a load is applied to a structure and no rotation occurs, then shearing can result (Fig. 6-1). For example, if the left hand is tightly wrapped around T12 and the right hand around LIon a plastic model of the spinal column and an attempt is made to pull T12 while not allow­ ing Ll to move, then a shearing force at the T12­ Ll disk will occur. It is the sagittal orientation of the T12-Ll facets that permits this type of move­ ment (Fig. 6-2). Shearing, which usually occurs in combination with other forces, can cause a fracture-dislocation. The orientation of the mid­ cervical facets (Fig. 6-3) favors fracture-dislocation in car accidents involVing violent forward flexion of the head. Fortunately, soft tissues such as the annulus fibers of the intervertebral disk contribute

118

PART T\VO

ANATOMY, BIOMECHANICS. Al'\ffi PHYSIOLOGY

Position 2

A Position 1

B Fig. 6-1 A. Translation. When a body (boat) moves such that a line PIQl jn it moves parallel to itself, the body is said to translate. Lines joining the same point on the body in two different positions (e.g., line Pl2and~ are called the translation vectors. The translation vectors of all points on the body are always equal and p to each other, indicating translation of the body. n. Rotation. A body is said to rotate when a line in it does move parallel to itself. In the boat, the line P2~ is not parallel to P). Q]. (From Panjabi MM, 'White AA: Biomechanics in the musculoskeletal system, New York, 2001, Churchill Li'tlingstone.)

Thoracolumbar junction T12-DLl apophyseal joint

Lumbosacral junction L5-DSl apophyseal joint

Fig. 6-2 Posterior view of the thoracolumbar and lumbosacral junctions. The transition in the orientation ci facet surfaces within the zygapophyseaJ joints between the two junctions is visualized. Compare sagittal orientation of T12-Ll. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for ph . rehabilitation, Be Louis, 2002, 1\10 ·by.)

CHAPTER 6

119

Basic Biomeclultlics

resistance to shearing forces and thus to the c1ini­ cnl stability of the spine.

Compression, Tensile Loading, and Distraction

dy 1<2z)

allel not

6-J Lateral view of the cervical spine. The ation of the iaccts at the zygapophyseaL joints is ized, (From, Herzog W: Clinical biomechanics spinal manipulation, Philadelphia, 2000, rchill Li;;-ingstonc.)

Flexion is accompanied by compression of ante­ rior structures and tensile loading (Le., elonga­ tion or loading in the vertical axis) of posterior structures (Fig. 6-4). Compression in the spine resulting from tlexion is possible and largely due to intervertebral disks that extend tJ1e height between the vertebrae. The spine is susceptible to compressive loads, either in single episodes involving high forces or by constant low-force compression. If flexion is violent, as in a car aCCident, then anterior compression injuries and posterior tearing of the restraining soft tissue is possible. Significant compression (loads greater than 600 pounds per square inch [psi]) of verte­ bral end plates and bodies can result in compres­ sion fractures or herniation of discnl material through the vertebral end plate. Distraction and tensile loading are not common but can occur in an automobile accident when the seat belt restrains the trunk (Figs. 6-5 and 6-6).

Cervical flexion

Anterior longitudinal ligament Compressed annulus fibrosus -----...." 2H~,...-I-Jl- Capsule of apophyseal joint

6-4 Flexion of the cervical spine. Flexion slackens the anterior longitudinal ligament and increases the between the adjacent laminae and spinolls processes. Eiongttted and taut tissues (thin black arrml.ls) and ened tissue (wavy black arrow) are indicated. (From Neumann DA: Kinesiology of the musculoskeletal m: fOllndations for physical rehabilitation, St Louis, 2002, Mosby.)

120

PART TWO

A

ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

B

o

E

F

Fig. 6-5 Effects of dJfferent types of forces acting on a saUd object. A, No forces acting; B. compressive force F6 C. tensile force Fr; D shear force Fs; E,

bending moment B; F, torsional moment, or torque T. (From Adams MA et ai: The biomechanics of back pain, Edinburgh, 2002, Churchill L.ivingstone.)

Extension and Lateral Flexion Loading Extension is accompanied by compression of posterior structures and tensile loading of ante­ rior structures. If Violent, it can result in injuries opposite to those observed in flexion. Inter­ vertebral discs are largely responsible for per­ mitting compression and the resultant extension (Fig. 6-7). If forced, lateral flexion loading can cause injuries similar in pattern to those observed in forced flexion-compressive injuries on the side toward lateral flexion and tensile loading or dis­ traction injuries on the side opposite lateral bending. As occurs in flexion and extension, the disks contribute to the degree of lateral bending that ;s pennitted.

Rotation or Torsional Loading Rotation or torsionalloadi~occurs when all par­ ticles in a body move in concentric Qircles or arcs. The vertebral motion segment is far more resist-

Fig. 6-6 Component forces acting on the lumbar spine. C, Compression; S, shear; BM, bending moment in the sagittal plane; AT, a:
ant to compression, distraction, and bending it is to rotation. Rotation or torsion is poten damaging because it results in shearing, te and compressive forces combined within material or body undergOing rotation. 'lb is resisted by the ribs in the dorsal spine by the more sagittal-oriented facet joints the upper lumbar spine. At the L5-S1 jo the iliolumbar ligaments provide resistance torsion.

Stress Stress is the force per unit area and inv internal forces within a body that arise result of external loads applied to the Internal resistance to an externally applied is inherent in any tissue. The degree to loading is resisted depends on the material, size, and the load applied. Low levels of . stress maintained over a long period or high els of stress applied over a short period can

CHAPTER 6

Basic Biomechanics

121

Cervical extension

6-; Extension of the cervical spine. The extension stretches the anterior longitudinal ligament decreases the space between the adjacent laminae and spinous processes. (From Neumann DA: Kinesiology the musculoskeletal system: foundations for physical rehabilitation, St Louis, 2002, Mosby.)

MA

tissue damage. Stress can result in defonna­ of a body or strain. Deformation of a body be temporary or permanent (Fig. 6-8). Biologic materials are anisotropic; in other , their response to loading varies with the tion of loading (Fig. 6-9). For example, bone Is compression differently than it resists loading or shear loading; ligaments resist 'Ie loading diJferently than shear loading. ke's law states that deformation increases in rtion to the load that is applied; that is, n increases in proportion to the body's mal stress that is resisting the applied load.

IOMECHANICAL HARACTERISTICS OF TISSUE

JIves asa

lOdy. load

'hleh 1, its

issu

llev­ esul

'city is the tendency of tissue under load to m to its original size and shape after ~al of the load. Rubber bands and ligaments examples. Strain is instant. No energy is lost defonnation, and the tissue returns to its shape. Plasticity is the property of a material that tly deforms when a load is applied and not return to its original shape when the is removed. When the applied load is

beyond the material's elastic limit, deformation results. Bone can alter its shape pennanently, according to loads that are placed on it. Viscosity is the property of a material that does not deform instantly when a load is applied. Stress develops but strain is delayed; conse­ quently, deformation is related to time. Failure to return to the original shape when the load is removed is a property of pure viscosity. Energy is absorbed within the material. ViscoelaSticity, a combination of viscosity and elasticity, is the property of a material to deform slowly and nonlinearly when a load is applied and to return to its original size and shape slowly and nonlinearly when the load is removed. Articular cartilage and intervertebral disks exhibit viscoelastici ty. Creep is an increase in strain of a material that occurs dUring constant stress from loading. It is a defonnation of a viscoelastic tissue to a constant, steadily applied load. In the body, the structure undergoing creep mayor may not return to Its original length or shape, depending on the load and whether the structure is dam­ aged. A damaged intervertebral disk can deform when u.nder a load in a shorter time than that of a normal disk.

122

PART

n\'o

ANATOMY. BIOMECHAN1CS. AND PHYSIOLOGY

Principal

compressive group XX-Cross section

A

Secondary .--­ compressive group

B

SecondaJy tensile group

c

Fig. 6-8 Stresses on a long hone. When subjected to bending (A). the normal tensile stresses (+) are on the convex side, whereas the nomlal compressive stresses (-) are on the concave side of the bent bone. Torsion (torque) on a long bone (8) produces different types of stresses-tensile, compressive, and shear-at a poin~ depending on the direction chosen. C. Normal trabecular pattern of the proximal portion of the femur is sho Four of the anatomic groups of trabeculae are indicated in this schematic drawing. Ward's triangle lies within the neutral axis, where compressive and tensile forces balance one another. (A and B from Panjabi MM, ll'hilt AA: Biomechanics in the musculoskeletal system, New York, 2001, Churchill Lit,>ingstone. Cfrom Tay/or JAY, Resnick D: Skeletal imaging: atlas of the spine and extremities, Philadelphia, 2000, WB Saunders.)

Hysteresis is an effect of repeated loading and unloading of a tissue. Although a tissue may resist one or more loads, the constant repetition of loading may cause the elastic limit to be exceeded. In the human body, hysteresis can be thought of as overuse. The material may not return to its original shape after many repeti­ tions over a long period. Thus the loading and unloading characteristics are not the same. If a tissue is subject to fatigue or has a weakness in its internal architecture, repeated loading and unloading may result in damage. In the interver­ tebral disk and surrounding tissues, repetitive lifting in a forward-leaning position may result in repetitive axial loading with no opportunity for recovery, which may damage the annular fibers, ligaments, and muscles. If an articular joint has poor ligamentous support or if the muscles mov­ ing the joint are weak, then the articular carti­ lage may be damaged from repeated loading. Overuse combined with poor soft tissue support and protection can lead to damage.

QUALITIES OF MUSCULOSKELETAL TISSUES Muscle Muscle fibers aligned parallel to a tendon able to transmit all their force to the te Muscle fibers aligned in a pennate fashion to tendon transmit less than. 100% force to the don. A pemlute arrangement occurs when muscle fibers are at an angle to the direction pull. A good example of this arrangement is gastrocnemius muscle (Fig. 6-10).

Fascia Muscle tissue is surrounded by connective ti .in the form of fascia. Thus muscular activity dependent to a cert<'1in extent on the conn ' tissue sheath that surrounds it. Fascia res favorably to tensile loading by impro\ing mobility; it also responds to inactivity by ening.

CHAPT~R 6

&1sic Biomecbllujcs

123

Bone strength Plantaris

Gastrocnemius (medial head)

Gastrocnemius (lateral head)

ry

c he

t\ 6-9 Anisotropy of bone. The strength of bone

on

Merial in the mid-diaphysis of a long bone varies in diiferent directions. Generally, the axial strength is die greatest. (From Panjabi }vl111, White AA: Biomechanics in the musculoskeletal system, New bR, 2001, Churchill Livingstone.)

int, shown. thin White

Medial malleolus

Calcaneal tuberosity

JAM,

s

Connective tissues are composed of collagen, ellstin, ground substance, water, and minerals. These components vary with the type and age afconnective tissue. Connective tissue tolerates IelIsile forces well, deforms with load, and recov­ its shape when the load is removed.

Lateral malleolus

Fig. 6-10 The superficial muscles of the posterior comparrment of the right leg are shown, The pennate arrangement of the fibers of the gastrocnemius muscle is visualized. (From Neumann DA: Kinesiology of the musculoskeletal system: foundations for physical rehabilitation, St Lou.is, 2002, Mosby.)

~ve tissu lctivity

nneed rcspon ovi~

by sho

ligaments join bone to bone, stabilize joints, lid prevent abnormal motion in joints. The rs are parallel and directed along the axis of i1e loading. Similar to tendons, ligaments are eomposed of collagen and elastin; however, Iiga­ ts have a higher elastin content tban do ten­ . Ligaments are designed to resist tensile . The greater the cross-sectional area of a ent, the greater the ability to tolerate the Exercise can result in hypertrophy of a Iig­ enlln effect, the cross-sectional area can be d within limits, thus offering increased ce to failure or rupture. Conversely, dis­ or immobilization results in a decrease in a nt's mechanical properties.

The mechanical properties of ligaments change with age, as do other body tissues. As expected, the ability to withstand tensile load decreases with age. The mechanism of ligament failure also changes as the body grows older, with avulsion (i.e., tearing away) of bone at the ligament site becoming more common than actual ligament mpture (Fig. 6-11).

Tendons Tendons are joined to muscles and lie parallel to them; as a result, they bear the same load as the muscles. Tendons support muscle forces and defonn minimally. They can store some potential

124

PART TWO ANATOMY, BIOMECHANrCS, AND PHYSIOLOGY

c

c.1. 500N i.l. 150N

S.1.

SOON a.1.1. 700N

p.1.1. 1.1. 1DON 350N

Fig. 6-)1 Relative strength (in Newtons) of lumbar intervertebral ligaments (9.81 N: 1 kg). a.l.l., Anterior longitudinal ligament; If, ligamentum Oavwn; c.l., capsular ligaments of the zygapophyseal joints; i.f., interspinous ligament; s.l., supraspinous ligament. (From Adams MA et al: The biomechanics of back pain, Edinb-urgh, 2002, Churchill Livingstone.)

energy in the form of elastic strain energy, which is evident in the kangaroo. The storage of energy also occurs in the quadriceps and gastrocnemius and soleus muscles in running humans. Immediately after heel strike, the quadriceps and gastrocnemius muscles act as brakes and contract while elongating. Tllis contraction is eccentric, and this elongation of muscle under load is similar to the stretching of a rubber band. Energy is stored in the stretched muscle or mb­ ber band. When the knee starts to flex and the ankle starts to plantar flex during the propulsive phase of stance, stored energy is returned, which makes running or walking more energy efficient. Tendons must support large muscle forces with minimal deformation; as a result elastin content is less than it is in ligaments. The colla­ gen fibers are arranged in pa(allel and run longi­ tudinally. Tendons, similar to ligaments, are designed to resist tensile loads. As with other body tissues, tendon function decreases with age and disuse. Exercise results in a greater cross­ sectional area as a result of hypertrophy. This gives the tendon the capacity to resist more of a

load Without injury. Histologically, transitio areas are the weakest link in any tissue. TbII the area within which tendon and muscle merj or where bone and tendon merge is often the . of injury. Patellar and Achill.es tendon injuriesil runners are common and good examples d injuries in transitional areas,

Bone The bones of the skeleton are changing theirbjlJo chemical content and mechanical propertiu continuously throughout an individual's liie,3l the slteleton is remodeled slowly but continually AB would be expected, the mineral content and a bjJj ty to resist compression declines with advancing age, a phenomenon that is more prlf flounced in women than in men. The strength~ bone per unlt area is similar in men and women, but because of hormonal changes, women hal'e. greater tendency to lose bone with age; COO* quently, less unit area exists to resist loads and forces. Other factors that can contribute to ~ loss are immobilization of a body part or a gtn­ eral lack of physical activity. According I WoIirs law, bone is shaped by the forces pia on it or the lack of force as in immobilization. As noted earlier, bone is anisotropic, whKt means that its strength depends on the OIienlao tion of bone matrix with respect to the direclioo of the load. Bone is made up of 35% collagen and other proteins, 20% water, and 45% minerals, roll! notably calcium. The collagen imparts a degrceec viscoelasticity, and the minerals impart strengQ and stiffness, The order of load resistance is least for shearing and greatest for compression, ~idl tensile load resistance in between. Diet, disease, and hormonal levels can aft'a1 osteoblastic and osteoclastiC actiVity levels am thus the biochemical composition of bone. The change in biochemical content of bone alters ill mechanical properties. This change is w demonstrated in osteoporosis, where a 105S i calcium results in a decrease in the trabecWr pattern and cortical diameter of bone, makiRgt easier to fracture. Deficiency of vitamin D results in uncalcified osteoid that makes subject to mechanical deformities, which II observed in rickets.

CHAPTER 6 Basic Biomechanics

IS

c

0­

C·

as

ly. Ild th

'0­

of

:0,

~a

"e­

nd

one ~n­

to ;ed

. e is a solid matrix of collagen em bedded 8 proteogIycan gel. Water is attracted by the yean gel. .A.s water enters the gel, the gel lis. This swelling stretches the collagen fibers their tensile stress balances the swelling . This phenomenon occurs in the unloaded . A compressive load applied to articular e is immediately resisted and results in ation of the cartilage. This deformation es pressure within the cartilage. A creep nse follows this increase in pressure if the is maintained. During the creep response, in the cartilage exits to an area of lower . This fluid can aid in joint lubrication. is time-delayed, depending on the viscos­ oi the 11uid and is a viscoelastic property. C8JI be likened to the action of a shock rbcr in a car.

The swelling of articular cartilage helps

surface defect.s and minimizes friction. tionally, tluid exiting cartilage under load reduce contact between surfaces. ThiS ion of contact helps prevent or delay wear tear. Articular cartilage is best designed resist compressive loads and to distribute in even manner t.he force caused by loading. ouglt damaged cartilage goes through a ling response that originates in the cbon­ .rtes, cartilage has a small capacity to I and repair itself. The effects of trauma, and tear, and degeneration on body struc­ depend 011 various factors, including the nicaJ properties of the structures. A norSow of 11uid in and out of articular cartilage lesnutrients and removes waste, which can be accomplished with physical activity. billzation can lead to the degeneration of ar cartilage.

discipline of kinematics deals with motion body but not with the forces involved in motion. Rather, it deals with the following les: TIme refers to the duration of an activity. example, in gait analysis, how long is the in contact with the ground during a jog or

125

during a sprint? The short contact time for the sprint means a high-loading rate for muscles and joints involved in sprinting and a higher chance of overuse injury. Position. The position of a body or body part during an activity can give clues as to the nature of an injury. For example, a football player who is standing still and looking down field sustains an illjury when another player hits the lateral aspect of his knee at a perpendicular angle. Displacement. Displacement is tbe change in position of a body or body part. Instinctively, displacement is thought of in linear terms­ pushing a book across a desk, walking down the street, moving an object from a high shelf to a lower one. Angular displacement also exists. A car speeding around a circular racetrack, an ice skater finishing off a routine with a series of rapid spinning moves, or a basketball player making a hool{ shot over a tall defender are all exanlples of angular displacements. Linear displacement is easy to measure, but angular displacement requires a bit more thought. For example, eight runners, one in each lane, are lined up at the starting line on an eight-lane track that is perfectly circular. Obviously, the runner in the iuside lane will cover less distance in a single lap than each of the other runners. The important factor is not the number of laps that are run but the radius from the center of the fjeld to the specific lane. In circular terms, the runner in the outside lane subtends a greater arc of motion than the nll1ner in the inside lane. Velocity. Velocity is the change in position with respect to time. It has botb magnitude and direction, whereas speed has only magnitude. Acceleration. Acceleration is the change in velocity with respect to time. It is conventional to describe acceleration as meters per second squared (m/s 2). Acceleration can be constant, or it can grow at an increasing or a decreasing rate, or it can decline at an increasing or a decreasing rate. It can be described as positive when going in one direction (e.g., a ball thrown upward) or negative if going in the opposite direction (e.g., a ball falling toward the ground). Negative

126

PART TWO

ANATOIVIY. BIOMECHANICS. A.!\ffi PHYSIOLOGY

acceleration is called deceleration. As with velocity, accelenltion can be linear or angular. Acceleration is a major factor in sports injuries and automobile accidents. Rapid acceleration or deceleration of the head, shoulder, or any body part can result in tearing, fracture, or rupture of tissue. If a stationary football player is hit perpendicularly at the lateral aspect of his lmee by a force of 4 g, then his lmee will experience a force accelerating the tmee at four titnes the acceleration caused by the force of graVity. In injuries caused by a car hitting a brick wallar another large object, acceleration is negative.

KINETICS

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Kinetics is the study of forces producing motion

lrregul

and their effects. To understand kinetics, famil­ iarity with certain force-related concepts is essential. Mass. Mass is the quantity of matter within an object. Inertia. Inertia is the property of a body to remain at rest or in uniform motion in a straight line unless acted on by an extemal force. This concept is called Newton's first law, or the law of inertia. Bodies tend to resist changes in motion. The mass of the body determines the magnitude of this resistance (Fig. 6-12). Mass moment of inertia. Mass moment of inertia applies to rotating bodies that move at a constant angular velocity or bodies at rest that have a fixed axis. Such bodies tend to remain in motion or at rest unless acted on by an external force. This resistance to change is determined by the mass of the body and where the body lies on the axis of rotation (i.e., the radius squared). Force. Force is a push or pull exerted on a body that tends to produce acceleration. Force gives rise to Newton's second law, which is that a force acting on a body causes an acceleration in the direction of the force. Momentum. Momentum is an amollnt of motion. Momentum equals mass times velocity. Increasing either the mass of a body or its velocity will increase the momentum.

body, ( if the t examp diver II mass " somew 1 . TI interet the pol force 0

omenl

c

Fig. 6-12 Newton's three laws of motion. A, First law. A body remains at rest or in uniform motion until it is acted on by an external force. A book will remain on the table forever if it is not dislUr~d B. Second law. Force equals Illass time acceleration. Therefore the acceleration (a) of the car is inl'e~~ proportional to its mass (m) and directly proportional to the applied force (F). C. Third Jaw. Reaction equals action. The thntst created by the engines of tbe shuttle pushes exhausted gases downward, which, as a reaction, pushes the rocket· plane upward. (From Panjabi 111M, White JlA: Biomechanics in the musculoskeletal system. Ne'o£ York, 2001, Churchill Li.'Vingsrone.)

If a truck with a mass of 7000 kilograms (kg)

(15,432 pounds) and a car with a mass of

400 kg (882 pounds) are traveling toward

other at a constant velocity of 20 kilometer;

fore acts. I

CHAPTER 6

\eaction ~ction

In. A. First

III motion . A book lot disturbed acceleration. u is inversel

-Iv

~: Third law. ated by the d gases ~s the rocke

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AA:

system, New

lograms (kg mass of 19 toward ) kilomete

it

per hour (km/hr) (12.4 miles per hour (m/Iu]), the force that they exert on each other when they collidc head on will be the same, but the momcntum of each approaching the collision and the effect of the crash will be quite different. This is due to the different masses. Center Qfmass and center of gravity. In physiclI or hiomechanics, reducing the mass of a body to a single point and concluding that the body's ma.'lS is concentrated in this point is often a convenient presumption. The center of mass can bc considered as the point about which the entire mass of the body is equally distributed. The center of mass of a 11at plate is easy to ftnd-it is at the origin. The plate would be able to balance if it were placed on a rod at its center of mass. The center of mass of Irregularly shaped bodies, such as the human body, can be more difficult to locate, especiaJly Uthe body is in an unusual position. For example, during a dive in which an Olympic diver is performing a forward flip, the center of mass will actually lie outside of the body, lIOII1ell'here between the outstretched arms and legs. The center of gravity is often used interchangeably with center of mass; however, the point in a body through which the resultant force of gravity acts is the center of mass. MomCfIt. Moment of force is the product of force and distance through which the force acts. [t tends to cause a twisting around the axis of rotation. A wrench or a long lever used to tum a wheel is an example of moments being ~enerated. Work. Work is force acting over a distance or force times displacement. Pwer. Power is the rate of doing work. 1IpuIse. An impulsive force is the force that two ooIIiding bodies exert on one another. This bee usually acts over a very short period, such IS dUring in an automobile collision.

APPLYING BIOMECHANICAL CONCEPTS whiplash injuries, acceleration or decelera­ lion or both that involve substantial rotation and

Basic Biomechanics

127

KINETlC CHAINS

In an open kinetic chain, the most distal seg­ ment ends without attachment to any other structure. The head resting on the cervical spine is a good example, as is the hand. In a closed kinetic chain, the end segment is joined to another structure. In a closed kinetic chain, motion of one segment is related to the other segments in the chain. The pelvis is a good example, as is the leg when the foot is in contact with the ground. (For further dis­ cussion of kinetic chains, see Chapter 19.)

translation of various body parts can occur over very short periods. Croft l discusses the four dif­ ferent phases of the whiplash automobHe injury. Automobile collisions are nooelalltic, as opposed to elastic collisions such as billiard balls or a squash ball hitting a wall and rebounoing. In nonelastic collisions, the vehicles involved strike each other and then assume the same velocity. For this to happen, the accident must result in a great deal of permanent deformity of the vehi­ cles involved-a good example of plasticity. As an example, a crash in which a car is struck from the rear is considered. In phase I the torso of the driver in the front vehicle is forced backward against the restraining seat. The head and neck remain stationary, and the vehicle accelerates forward, which creates high-tensile forces on the neclL In phase II the head is accel­ erated rapidly posteriorly, as a result of the events in phase 1. This phase creates high-tensile loading on anterior neck structures and high­ compressive loading on posterior neck struc­ tures. In phase III the head and torso are reaching their maximum posterior acceleration while the acceleration of the vehicle is decreas­ ing. In phase IV the vehicle is not accelerating, and the head, neck, and torso rebound or decel­ erate forward. The seatbelt restrains forward deceleration of the torso; consequently, the head and neck bear the brunt. The weight of the head and the long lever arm of the cervical spine contribute to this whiplashing effect and associ­ ated soft tissue damage. Croft reports that the acceleration of the bead can be 2.0 to 2.5 times the acceleration of the vehicle. In an automobile

128

PART TWO

A!\,\TOMY, BIOMECHANICS, AND PHYSIOLOGY

collision, each cervical motion segment con­ tributes its acceleration to the segment above. Because the cervical spine has multiple motion segments, this acceleration effect at the distal or open end of the cervicocranial kinetic elwin is considerable.

Throwing a" BaH A good example of the effects of one motion seg­ ment on acceleration and subsequent velocity is observed when comparing the velocity of a ball thrown by an elite fastball pitcher with the velocity of a ball thrown by an elite fast bowler in cricket. A cricket ball and basebaJl vary in mass by apprOXimately 14 grams (g) (1/2 ounce), which is negligible. Both the elite fast-ball pitcher and the cricl{et fast bowler throw their respective balls at 150+ km/hr (t)~ mlhr). The baseball pitcher throws from a relatively station­ ary position on the mound. The cric!,et fast bowler takes a run up to 20+ meters (22 yards). The difference is that the cricket fast bowler must keep his elbow extended. Cricket regula­ tions do not permit elbow Ilexion when launch­ ing the ball. The elimination of this one motion segment, the elbow, means that the cricket fast bowler must run 20 meters (22 yards) or more at a high speed to throw his ball with the same velocity of the relatively stationary baseball pitcher.

,Review Questions 1. What structures in the body resist structural deformation of tissue? 2. In an automobile accident involving a violent flexion injury, tissues in which part of the vertebral motor unit are likely to undergo compression?Tissues in which part are most likely to tear? 3. What two types of structural damage can result from the application of compressive

loads of over 600 psi to the vertebral end plates and bodies? 4. Which structures in the dorsal and lumbar spine are best equipped to resist torsion? 5. How is the pennate form of muscle biomechanically advantageous? Give one example of such a muscle. 6. Describe the anisotropic property of bone 7. How does the mechanism of ligament failure change with advancing age? 8. What are three factors that affect osteoblastic and osteoclastic activity leve~ and thus the biochemical composition of bone? 9. How does immobilization contribute to the degeneration of articular cartilage? 10. In biomechanics I terms, what is the difference between stress and strain?

Concept Questions 1. Which biomechanical forces are involved~

the various types of chiropractic adjustments?

BIBLIOGRAPHY Adams /o.'!A et al: The biomechanics of back

pa1i

Edinburgh, 2002, Churcltill Livingstone. Herzog W: Clinical biomechanics of spilJal11lalli~ lion, Philadelphia, 2000, Churcbill Livingstone. Neumann DA: Kinesiology of the mllsculoskclelal,~ tem: foundations for physica.l rehabilitation, Sl J.ouif. 2002, Mosby. Panjllbi /-"IM, White i\A: Biomechanics in the musculos. wi S)'st.em,]\ew York, 2001, Churchill Livingstone. Taylor J1"\II'I, Resnick D: Sheletal imaging: atlas ojtlle.ytlIt and extremities, Philadelphia, 2000, \VB Saunde~.

REFERENCE 1. Croft AC: Biomechanics. In Croft AC, foremanSl editors: Whiplash injuries: tile cervical accderg.

tionldccelerati(J1l syndrome, ed 3, Philadelpbil, 2002, LippillcoU-Williilms &. Wilkins.

i:I

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ertebral subluxation is at the core of chiro­ practic theory, and its deteCtion, manage­ andcorrection is at the hcart of chiropractic . .This central defining principle is simulta­ : asource of debate within the profession. l chiropractic's first century, subluxation was predominately in structural terms 2./ and t\'OJ\'ed from a simplistic static concept, inter­ as a malpositioned spi.nal segment (bone Uplace), to a contemporary model presented dynamic and complex biomechanical entity of components. The components of the . model include abnormal joint motion, r and connective tissue changes, and vas­ inIlammatory, and biochemical changes. In . a most significant component of this t the associated neurologic manifestations, result in symptoms either 10caUy or at seg­ • innervated anatomic levels (i.e., der­ myotomes) far distant from the point of dysfunction. The orthopedist Jackson that mechanical derangement or inflamma­ tbesespinaljoints may cause pain, sensory mor disturbances, or both anywhere along tal distribution of the nerves. s The

ORGANIZATION

neurologic component of the vertebral subluxation complex (VSC) provides chiropractors the poten­ tial to move beyond symptomatic treatment of low back pain and other musculoskeletal ailments and to contribute to patient health, welilless, and enhanced function and quality of life. The term subluxation comes from the Latin sub, meaning under or less than, and luxation, which means dislocation. Stedman.'s Medical Dictionary defines the term as "an incomplete lux­ ation or dislocation; though a relationship is altered, contact between joint surfaces remains."9 Contemporary interpretation embraces the con­ cept of sublu..". ation as a motion segment in which alignment, movement integrity, physiologic fimc­ tion, or any combination is altered, although con­ tact between joint surfaces remains intact. IO Application of this term is fundamental to communication between chiropractors and their patients. For explaining the subhe
129

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130

PART TWO

ANATOMY, BIOMECHANlCS, AND PHYSIOLOGY

theoretical model of vertebral, motion segment dysfunction that incorporates the complex inter­ actions of pathologic changes in nerve, muscle, ligamentous, vascular, and connective tissue. 12 This latter model serves as a basis for commu­ nicating chiropractic concepts to the scientific community. Classical and contemporary medical practition­ ers, osteopaths, and chiropractors have referred to the concept of subluxation extensively.lJ However, these professions differ on defining the term and interpreting its clinical significance. In the scien-

tmc literature, the terminology describing the functional or structural disorders of'synovial.ioint structures has varied in name and description, ranging from the orthopedic context as a partial or incomplete dislocation to the chiropractic per. spective that includes minor misaligmncnt d articulations, hypomobUe spinal segments, 01 both. 13 Box 7-1, from Peterson and BergmaD,u provides an overview of contemporary tenninol­ ogy describing synovial joint dysfunction. Rome, IS in an extensive literature review, Jus identified over 296 synonyms (41 used to descri~

Bc»c 7 o

Box 7-1

TERMS DESCRIBING FUNCTIONAL OR STRUCTURAL DISORDERS OF THE SYNOVIAL JOINTS

ORTHOPEDIC SUBLUXATION This term is used to describe a partial or incomplete dislocation. CHIROPRACTIC SUBLUXATION This term is used to describe the alteration of the normal dynamic, anatomic, or physiologic relation­ ships of contiguous articular structures; a motion segment in which alignment, movement integrity, or physiologic function is altered, although the contact between the joint surfaces remains intact an aberrant relationship between two adjacent articular structures that may have functional or patho­ logic sequelae, causing an alteration in the biomechanical or neurophysiologic reflections of these articular structures or body systems that may be directly or indirectly affected by them. SUBLUXATION SYNDROME This term is used to describe an aggregate of signs and symptoms that relates to the pathophysiology or dysfunction of spinal and pelvic motion segments or to the peripheral joints. SUBLUXATION COMPLEX This term is used to desoribe a theoretrc model of motion segment dysfunction (subluxation) that incorporates the complex interaction of pathologic changes in nerve, muscle, ligamentous, vascular. and connective tissues. JOINT DYSFUNCTION This term is used to describe joint mechanics that show area disturbances of function without struo­ tural change-subtle joint dysfunctions that affect quality and range-of-joint motion. DefinitiOll embodies disturbances in function that can be represented by decreased motion, increased motion,. or aberrant motion. Joint hypomobility: Decreased angular or linear joint movement Joint hypermobility: Increased angular or linear joint movement; aberrant joint movements aretyp­ ically not present Clinical joint instability: Increased linear and aberrant joint movement; the instantaneous axes rotation (centroids) and patterns of movement that are disturbed SOMATIC DYSFUNCTION

This term is used to describe impaired or altered function of related components of the somatic (

framework) system; skeletal, arthrodial, and myofascial structures; and related vascular, lymphatic, and neural elements.

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CHAPTER 7

Vertebral Subluxation

131

7·1 TERI\IS DESCRIBING FUNCTIONAL OR STRUCTURAL DiSORDERS OF THE OVIAL ]OINTS-CONT'O EOPATHIC LESION

is term is used to describe a disturbance in musculoskeletal structure or function, as well as accom­ 'og disturbances of other biologic mechanisms, This term is also used to describe local stress or rna and subsequent effects on other biologic systems (e.g., effects mediated through reflex nerve ys, including autonomic supply of segmentally related organs),

IS term is used to describe the state whereby an articulation has become temporarily immobilized

s Ie

a position that it may normally occupy during any phase of physiologic movement; the immobi­ ion of an articulation in a position of movement when the joint is at rest or in a position of rest nthe joint is in movement. Peterson D, Bergman T: Chiropractic technique: principles and procedures, ed 2, St Louis, 2002, Mosby.

It

r,

roiliac subluxation) and terms for the biome­ 'cal condition lUlown to chiropractors as uxation. Such synonyms include manipula­ spinal lesion, functional spinal leslon, dys­ cHonal segmental unit, somatic joint ction, articular dyskinesia, joint blockage, mobile vertebral segment, and vertebral fLx­ , . As an example, Seaman 16,17 proposes the joint complex dysfunction to embrace ologie and functional changes in a jOint, luding negative effects of hypomobility­ obility, functional imbalances of muscle tening or shortening, and myofascial trigger 18. Lack of uniform terminology, however, created confusion and impeded interprofes­ discussion. e way to review the basic principles of adjustment-manipulation is to look at the cal characteristics of the entity to which adjustment or manipulation is applied. Despite various theoretical explanations for the mech­ of action of spinal adjustment/manipula­ (see Chapter 8 for greater detail), subst.1I1tial ent exists on certain fundamental clini­ characteristics of the manipulable lesion or subluxation. IS This chapter explores vari­ aspects of the theoretical models of vertebral tion.

earliest concepts of subluxation predate chi­ 'cby more than 200 years. Haldeman cites

the earliest English definition of subluxation from Randle Holme in 1688,19 who described it as, "dis­ l.ocation or putting out of joynt." Haldeman 13 and others 20-22 cite the foUowing 1746 description from J oannes Herricus Hieronymus,2J who wrote, "subluxation of joints is recognized by lessened motion of the joints, by slight change in position of the articulating bones and pain." Terrett24 cites an 1821 description by Edward Harrison: When any of the vertebrae become displaced or too prominent, the patient experiences inconveClience from a local derangemem in the nerves or the part. He, In consequence is tormented with a train of nerv­ ous symptoms, which are obscure in their origin as they are stubborn in their nature. Harrison pursued the subject further, writing in 1824 that motion, as well as alignment, played a defining role in subhucation: The articulating extremetles are only partially sepa­ rated, not Imperfectly disjoined ... and ... tJw artic­ ular motions are imperfectly perfonned, because the su.rfaces of the bones do not fully correspond. Thomas Brown, \\'filing in the Glasgow Medical Journal in 1828, coined the term spinal irrita­ tion. 25 Four years later, The American Jourrwl of Medical Sciences began citing reports from European physicians about tenderness of verte­ brae corresponding to diseased organs, with such observations taken as confinning a diagno­ sis of spinal irritation. 25

132

PART TWO

Al'l"ATOMY, BIOMECHANICS.

Donald Tower 26 quotes physician J. E. Riadore's 1843 Irritation of the Spinal Nerves as follows: "[If) any organ is deficiently sup­ plied with nervous energy or of blood, its func­ tions immediately, and sooner or later its structure, becomes deranged." Riadore con­ cluded that irritation of nerve roots resulted in disease and advocated treatment by manipula­ tion. These conclusions regarding nerve irri­ tation were published 2 years before the birth of D.O. Palmer. 2J By 1874, Andrew Taylor Still, a medical physician who founded osteopathy 21 years before Palmer's discovery of chiropractic, devel­ oped bis own concept and terminology. Still described the osteopathic lesion in terms of pressure applied by muscles to blood vessels coursing through and around these muscles, thereby shutting off the life force of the involved tissue. 27

CHIROPRACTIC SUBLUXATION­ EARLY CONCEPTS Although the founder of chiropractic, D.O. Palmer, continued to modify his early concepts and explanations of chiropractic even until his death ill 1913,28 the sustaining, central Palmer hypoth­ esis described subluxation as a "partial or incom­ plete separation, one in which the articulating surfaces remain in pa rtial cantac t. "2'> His hypothesis further proposed that sucb subluxa­ tions might impinge on spinal nerve roots as they exit through the intervertebral foramina. This action was postulated to ohstruct flow of vital nerve impulses between the central nerv­ ous system and the periphery and to induce lowered tissue resistance and disease in the seg­ mentally innervated tissues. 2,3,30 The founder later postulated that the primary cause of dis­ ease was interruption of normal tone resulting from subluxat.ion, in which nerves became too taut (resulting in excess nerve energy) or too slaclt (producing too little nerve energy).28-30 In the December 1904 Palmer School of Chiropractic periodical, The Chiropractor, pre­ sented as "A monthly journal devoted to the int.erests of chiropractic-'KI-RO-PRAK-TIK, "3J D.O. Palmer states:

Ai~D

PHYSIOLOGY

Ni nety·five percent of all deranged nerves are made sub-luxatiolls of vertebrae which pinch nerv~ some one of the 51 joint articulations of the spinw Uillilo Therefore to relieve the pressure upon nerves means to restore normal action-hence, mal functions, perfect health.

This statement lil{ely represents the ear" published mention of subluxation in the c . practic literature. Significantly, the senior Pal saw at least limited value (5%) in the adjus of nonspinal articulations, stating that ne related to nonvertebral joints may be impi rather than pinched. According to Gibbons,32 lvlodemized Chi practic,33 by SmitJl, Langworthy, and Pax published in 1906, was the first chirop textbook to use the teml subluxation and to re it to the intervertebml foramen. This work also tbe first to assert the supremacy of the ne in relation to health and dise~lse, in contrast to osteopathic concept of supremacy of the blood. cbiropractic's early years, this citation ' served as legal defense in arguing the distin . between tlle practice of chiropractic and that osteopathy and medicine. In addition, chiro tic's focus 011 the importance of the nervous . tem and its emphasis on the correction of vert subluxation became key factors in defending ropractors and in early attempts by the prot to gain separate licensure. Langworthy and colleagues also were the to characterize subluxation as a fixation and describe the field of motion of a vertebra. view of subluxation as a dysfunctional state of tebral motion gradually fell into disuse until 19 when the dynamic concept of subluxation reintroduced with the motion palpation re of the Belgian chiropractors Gillet and Lichell.

FOUNDER'S DEFINITION In 1910, D.O. Palmer discussed subhL.xation in text, Science, Art and Philosophy q/ Chiropro as foUows: A vertebra Is said [Q be displaced or a luxation Vi the joint surfaces are entirely separated. Sub·) is a partial or incomplete separation; one in which articulation surfaoes remain in partial contact. This

CHAPTE:R 7

>by to

colese or-

icst iro­ mer lcnt rYes

ged

Vertebral Subluxation

lion is so often referred to and k.nown by chiro­ as sub-luxation. The relationship existing 'eCll bOlws and nerves are so nicely adjusted that , one oi the 200 bones, more especially those of the ebral column, ctmnot be displaced ever so little with­ impinging upon adjacent nerves. Pressure on nerves tes, agitates, creates an excess of molecular vibra­ , \\'h(~~ effects, when local are knovm as inflamma­ , when general, as fever. A subluxation does not . or liberate vital energy. Vital energy is expressed iunctional activity. A subluxation may impinge against es, the tnmsmitting channel may increase or tile momentum of impulses, not energy. OI'S

'ctie

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}ften ctlon at of prac­ sys­ tebral

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c first md to . Thi

Dfver1938,

n

was

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CoJlege taught no adjusting methods except upper cervical specific technique. Not until 1956 dJd the school reintroduce instruction in adjusting t.ech­ niques for the full spine (I-limes HM, Policy Talk, unpublished letter, January 4, 1956).

STEPHENSON'S DEFINITION According to Lantz,.1.' the definition of subluxa­ tion most. widely quot.ed by early chiropraQtors was from R.W. Stephenson's 1927 Chiropractic Text Book,4 which states: A subluxation is a condition of a vertebra that has lost

liro­

son,

'e1ate . was erves o the

133

. the early 19308, B.J. Palmer had developed a t of subluxation distinct from that of his r. The younger Palmer represented subllL'{a­ lIB restricted to a displaced upper cervical ver­ that created nelVe impingement, resulting in erence with the transmJssion of vital nerve ',J In his 1934 textbook, The Sublu,,"~ation Thei\djustment Specif~, B.J. maJntained the only suhllLxation of sigl1itlc~UJce was that of atlas venebra in relation to occiput or axis:

reaffirm that no amount of "adjusting" upon uny. y or all vertebrae below occiput, atlas, or aXis, or would directly ADJUST THE SPECIFIC ·dircction torqued subluxation causing any, yor all sickness in tl body. Any vertebra below or axis MAY BE misaligned but CANNOT BE LUXATED:1 [Emphasis in original text.)

. Palmer's delineation between simple mis­

ment and true subluxation is significant. . ment of a vert bra was described as no than compensation to the major subluxation. Thus in a span of 30 years, the Palmer School cept of subluxation and adjustment evolved the founder's 1904 description of an entity ing any of the 200 joints of the body, but rily the joints of the spinal column, to the ger Palmer's insistence on exclusive adjust­ tofthe full spinal column only and then later his idea that subluxation was an entity limited to the atlas vertebra in relation to the put and axis. This later concept, !mown as Hole in One Technique (HIO), was developed the early 19308. For two decades, Palmer

its proper juxtaposition with the one above or the olle bl:l1ow, or both; to an extem less that a luxation; which impinges nerves and interferes with the transmission of mental impulses.

Stephenson, a 1921 Palmer School graduate, insisted that nerve interl'erence must exist t.o qual­ ify the condition as a subluxation. Stephenson's definition served for decades as the preeminent expression of the static model (bone out of proper position or alignment) of vertebral subluxation.

DYNAMIC MODEL Beginning with the writings of Gillet,J4 IIIi,')6 and Mennell,Ji and continuing through the works of Sandoz,38 Dishman,J'f and Faye,41) the dynamic characteristics of joint subluxation moved t.o the forefront, with subluxation and joint integrity now described not solely in struQtural terms, but in functional terms as wetl with emphasis on altered joint motion. In this context., joint mal­ position became a potential sign of altered joint function, but not absolute cont'irmation. 11

CONTEMPORARY DEFINITIONS Contemporary definitions describe t.he subluxa­ tion as central to the principles of chiropractic science. Examples of policy statements regard­ ing subluxation are the following:

State Statutes The concept of subluxation is specifically identi­ fied in many U.S. srate statut.es defining t.he

134

PART TWO

ANATOMY, BIOMECHANICS, A1'\j'D PHYSIOLOGY

practice of chiropractic. Nter extensive review, Hendrickson'll concluded that many state chiro­ practic statutes either directly or Implicitly iden­ tify chiropractic with subluxation or the elements of subluxation complex and specify the doctor of chiropractic's responsibility for adjusting the spine and adjacent tissues for the purpose of eliminating nerve interference. An analysis by Hendrickson follows. Examples of state statutes that expressly iden­ tify the detection of and caring for subluxations as the core of chiropractic practice include: Arizona: A doctor of chiropractic is a portal Ql entry health care provider who engages in the practice of health care that includes: the diaglWsis and correction of subluxations, junctional vertebral or articular dysarthrosis or neuromuscular skeletal disorders for the restoration and maintenance of health. Treatment by adjustment of the spine or bodily articulations and those procedures preparatory and complementary to the adjustment including physiotherapy related to the C01Tection of subluxations. (Arizona Revised Statutes Annotated, Title 32, Chapter 8, Article 2 32-925(a), No.1, 3) Connecticut: The practice of chiropractic means the practice of that branch of the healing arts consisting of the science of adjustment, manipulation and treatment of the human body in which vertebral subluxations and other malpositioned articulations and structures that may interfere with the normal generation, transmission and expression of nerve impulse between the brain, organs and tissue cells of the body, which may be a cause of disease, are adjusted, manipulated or treated. (Connecticut General Statutes Annotated, Title 20, Chapter 372, Section 20-24, (1)) District of Columbia: "Practice of Chiropractic" means the detecting and correcting of subluxations that cause vertebral, neuromuscular, or skeletal disorder, by adjustment of the spine or manipulation of bodily articulations for the restoration and maintenance of health. (District of Columbia Code 1981, Part 1, Title 2, Chapter 33, Subchapter J -2-3301.2(3)(A))

Delaware: The practice of cltirop-mctic includes, but is not limited to, the diagnosing and locating Ql misaligned or displaced vertebral subllL.'\'!ation complex. (Delaware Code Annotated, Title 24, Chapter 7, 701 b,j Florida: "Pracl'ice of chimpTactic" means (/ noncombative principle and pmctice consisting of the science, philosophy, and art of the adjustment, manipulation, an(/ treatment of the human body in which vertebral subluxations and other malpositioned articulations and structures that are interfering with the normal generation, transmission, and expression qf nerve impulse between the brain, organs, and tissue cells of the body, thereby catlsin~ disease, are adjusted, manipulated, or treated, thus restoring the normal flow qf nerve impulse which produces normal function and consequent health by chiropractic physicians using specific chiropractic adjustment or manipulation techniques .... (Florida St'-itutes Annotated, Title Xx.;·m, Chapter 460, Section 460.403 (8) (a)) ldaho: "Adjustment" means the applicatioll0' a precisely controlled force applied by hand or by mechanical device to a specific joced point on the anatomy for the e~1Jress purpose of creating a desired angular movement ill skeletal joint structures in order to e1imina/t or dec..'Tease interference with neural transmission and correct or attempt to correct subluxation complex. (Idaho Code. Title S4 Chapter 7, 54-704 (1) (a)) Maine: Chiropractic. "Chiropractic" means tIte art and science ofidenti/ication a:nd correction of subluxation and the accompanying physiological or mechanical abnormalities. The term subluxation, as utilized within the chiropractic health care system, means a structural or junctional impairment of an intact articular unit. Chiropractic recognizes the inhe1'ent recuperative capability of the human b(}(l~' as it relates to the spinal column, musculo· skeletal and nervous system. (Maine Revised Statutes Annotated, Title 32, Chapter 9, Subchapter 1, Section 451 (1))

cht

Iocati~

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m

maintai

Laws AI Section wYorl chiropr£

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stnwtu,

aubluxa purpose f{fects tJ result OJ oraubl'l.

(Consol!

TItle VII Other stl ubluxat

Nevada, Washingt

Medica

The u.s. and con function

federal S1 inwhic since th reimbu

mum s

only fo ( )(2)(A treatme pine (t authori whioh

1395x (

CHAPTER 7

Vertebral Subluxation

Massachusetts: "Chiropractic," the science oj

rt

Iocatin.4, and removing interference with the rransmission or e.'\"Pression oj nerve force in the human body, by the correction oj misali~nmentsor subluxations of the bony articulation and adjacent structures, more especially those of the verteb'ral column and pelvis, for the purpose ql restoring and maintaining health. (1Iassachusetts General Laws Annotated Part I, Title XVI, Chapter 112, Section 89) New York: The practice of the profession of chiropractic is defined as detecting and

of

and

mof lnd 'al

rpose in inate

de,

tical

s

(Jare

al

OOITeCting by manual or mechanical means sbuctuml imbalance, distortion, or sublu.:wtions in the human body for the purpose Qf removing nerve intelj'erence and the rIects tliereof, where such inteiference is the mult of or 'related to distortion, misalignment (If'subluxation of or in the vertebral column. (Consolidated Laws of New York, Chapter 16, ntle \:lII, Article 132, Section 6551 (1» Other state statutes that define and identify the IUbluxation specifically include Kentucky, Ne\'lIda, New Jersey, Texas, Utah, Vennont, and Washington.

135

Medicare extends these concepts in the statute into the regulations governing the program witl1 an express definition: A chiropractor who is licensed by the State or legally authorized to perform the services of a chiropractor, hut only with respect to treatment by means of man­ ual manipulation of the spine to correct a subluxa­ tion, (42 CFR 482 Subpart B Section 482.12 (7) (c) (1) (v))

Federal st.'1tutes establishing chiropractic par­ ticipation in the Medicaid program employ the same tenninology as tliat in the general Medicare program. Federal employee health benefit pro­ grams recognize chiropractic on tenns negoti­ ated between representative committees of public employees and v~lrious insurance carriers, but the federal workers compensation program identifies and defines chiropractic, onCe again, very specifi.­ caUy to include chiropractors and chiropractic services as follows: The term "physician" includes chiropractors only to the extent that their reimbursable services are limited to treatment consisting of manual manipulation of the spine to correct a subluxation.

Department of Veterans Affairs

edicare and Medicaid Definition U.S. government recognizes the detection correction of subluxation as the primary ion of the doctor of chiropractic. 4J •42 The statutes governing the Medicare program, linch chiropractic services have been included the early 1970s, defines chiropractic and rsable chiropractic services as: ebiropractor who is licensed as such by the State

In aState which does not license chiropractors as

is legally authorized to perform tJle services of

obIropmctor in the jurisdiction in which he per­ such services), and who meets unifo.. . m mini­ standards promulgated by the Secretary, bur lor the purpose of subsections (8)(1) and 2)(A) of this section and only with respect to !ment by means of manual manipulation of the (to correct a subluxation) which he is legally riled to perform by the State or jurisdiction in such treatment is prOVided. (42 USC Sec. x(r) (5)) I

In January 2002, President George W. Bush signed into law new provisions that established chiropractic services as a health care benefit for eligible military veterans in the United States. This law contains a specific passage referencing subluxation, which reads as follows 41 : Program ~or The Provision of Chiropractic Care and Services to VeteraIls. (d) CARE AND SERVICES AVAILABLE. The chiropractic care and services avail­ able under the program shaU include a variety of chi­ ropractic care and services for neuro-musculoskeletal conditions, including subluxation complex. (United States Code, TItle 38, 204 (d))

World Health Organization Classification The World Health Organization (WHO), a mul­ tilateral health care agency of the United Nations, has accepted subluxation as a listing in the International Classification at' Diseases:13

136

PART T\VQ

ANATO\-tY, BIOMECHANICS, AND PHYSIOLOGY

referring to it as "M99.1 Subluxation complex (vertebral)." \'v110 also recognizes the classifica­ tion "M99.0 Segmental and somatic dysfunc­ tion," a subtle variation.

Consortium for Chiropractic Research The 1993 consensus definition of the nominal and Delphi panels of the Consortium t'or Chiropractic Research (CCR)lO refers to sublux­ ation as "... a motion segment in which align­ ment, movement integrity, and/or physiologic function are altered although contact between the joint surfaces remains intact."

American Chiropractic Association The Indexed Synopsis of ACA Policies44 describes subluxation as, "... [aJ motion segment, in which alignment, movement integrity, andlor physio­ logical function are altered although contact between joint surfaces remain intacL" ACA has also adopted the consensus defini­ tions agreed on by the nominal and Delphi pan­ els of the CCRIO,44: Subluxation is an aberrant relationship between two adjacent articular structures that may have functional or pathological sequelae, causing an alteration in the biomechanical and/or neurophysiological retlections of these articular structures, the proximal structures, and/or body systems that may be directly or indirectly affected by them.

The ACA-endorsed CCR definltion~4 for sublu;'{a­ tion complex is: ... [aJ theoretical model of IllOtiOll segment dysfunc­ tion (subluxation) which incorporates the complex interaction of pathological changes in nerve, muscle, ligamentous, vascular and connective tissues.

Intemati onal Chiropractors Association ICA PoHcy Statemcnts45 related to subluxatioo include the following: Of primary concern to chiropractic are abnormalities of stmcture or function of the vertebral column [mown clinically as the vertebral subluxation complex. The

sublu_"'
According to the leA Official Policy Hand­ book 45 : Chiropractic is based on the premises that the relt tionship between structure and function in human body is a significant health factor and tha such relationships between the spinal column alIIl nervous system are the most significant, since the normal transmission and expression of nerve cneJt!" is essential to the restoration and maintenance cl health.

Association of Chiropractic Colleges On July 1, 1996, presidents of all North Amcricaa chiropractic colleges, as members of the Associa­ tion of Chiropractic Colleges (ACe), seeking to clarify professional common ground and deOlll chiropractic's role within the health care dcli~lJ! system, generated a series of consensus positioo statements. 47 This effort represented the fut time in the IOO-year history of chiropractic Clh cation that all college presidents, represcntiol schools with diverse institutional missions, hal reached unanimous consensus on common COlt definitions fu ndamental to the principles of chiJo.

cc n chiI'

CHAPTER 7

f the tigu­ I dis­ ction t1ya

is the aused pres­ spinal

suit of

Vertebral Subluxation

practie. This paradigm is endorsed by the ACA, leA, World Chiropractic Alliance, World Federa­ OOnofChiropractic, the Congress of Chiropractic Ie Associations, and most state chiropractic associations. This consensus therefore represents t common platform from which to communi­ ate the unifying principles of this profession. Chapler 2, "The Chiropractic Paradigm," pro­ Yides the ACC paradigm in its entirety.

eletal

CC Consensus Definitions

Iland-

lC

rela­

in the nd that nn and lee the

Chiropractic is a health-care discipline which empha­ ires the inherent recuperative powers of the bod y to il~1f without the use of dmgs or surgery. The practice of chiropractic focuses on the rela­ lIonship between structure (primarily of the spine) ad iunclioll (as coordimlted by the nervous system) IIld how that relationship affects the preservatloll and ..!oration of health. Doctors of Chiropractic recognize the value and mponsihility of working in cooperation \vith other IIeaIth care practitioners when in the best interest of die patient. The ACe continues to foster a unique, distinct chi­ ropractic profession that serves as a health care disci­ pline for all. The ACC advocates a profession that rates, develops, and utilizes the highest level of nce possible in the provision of effective, pru­ cIeot and cost-conscious patient evaluation and ca re.

cnergy

ance of

:es

Asublu.l3tiotl is a complex of fUlletJonal, structural, or pathologiclll articular changes that compro­ neural integrity and may intluence organ system. nand geneml health. Asubluxation is evaluated, diagnosed and managed the use of chiropractic procedures based on best availahle rational and empirical evidence. The preservation and restoration of health is ceel through the correction of the subluxation.

ONTEMPORARY MODELS FVERTEBRAL SUBLUXATION OMPLEX noted in the ACA and rCA definitions previ­ y cited, the contemporary concept of sub­

137

luxation has been ex.panded beyond a joint phe­ nomenon affecting nerve function to also include the role of muscular, connective, vascular, and biochemical components as part of a complex. This subluxation complex has been defined by Gatterman 20 as "a theoretical model of motion segment dysfunction (subluxation) thllt incorpo­ rates the complex interaction of pathologic change in nerve, muscle, ligamentous, vascular and connective tissues." Although Janse:~8,49 Illi,36 Gillet and Lichens,34 and Homewood so prOVided an early fOWldation, Faye,40 beginning in 1967, popularized the con­ cept of the subluxation complex and organized a five-component model. Dishman 39 characterized the concept as the chiropTactic subluxation com­ ple.'>::, providing additional rationale for Faye's model. Lantz 22,35 modified the original five com­ ponents of the VSC model by postulating three more components; connective tissue pathologic finding, vascular abnormalities, and the inflam­ matory response.

FIVE~COMPONENTMODEL

OF VERTEBRAL SUBLUXATION

COMPLEX (FAYE MODEL)

Building on the work of Gillet and Liekens':u as well us earlier pioneers such as Smith, Lang,­ worthy, and Paxson,33 Faye40 moved beyond the , swtic "bone out of place" or "displaced vertebra" theory of subluxation, placing primary emphasis on dynamic vertebral joint motion. Basic move­ ments of spinal segments include rotation about the longitudinal axis, right or left lateral fleXion, anterior flexion, posterior extension, and long-axi.s distention. Factors inhibiting movement in one or more of these directions may cause abnonnal translation and rotation, contJibuting to biome­ chanic and subsequent physiologic dysfunction and pathologic expressions. Schafer and Faye 51 defined the termfixation as referring to any physical, functional, or psycho­ logic mechanism that produces a loss of segmen­ tal mobility Within its normal physiologic range of motion. }\i; an example, ankylosis of a joint would be considered a 100% fixation. These authors state thtlt clinically most fixations are in the 20%

138

PART TWO

ANATOMY, mOMECHANICS. AI'ID PHYSIOLOGY

to 80% range of normal mobility. According to Schafer and Faye, once the chiropractor has identified the hypomobility, adjustive proce­ dures are used to mobilize the fixation. The ther­ apeutic objective is to deliver a dynamic thrust, employing a specific contact and line of drive with the intention of freeing restricted vertebral joint motion altering specific sympto­ matology. The Faye model of the vertebral subluxation complex (Fig. 7-1) presents sublux.ation as a com­ plex clinical entity comprising one or more of the following components: neuropathophysiology, kinesiopathology, myopathology, histopathology, and a biochemical component. A central element of this concept is that sublux<"1.tion results in pathophysiologic conditions, which can then lead to frank pathologic changes. Moreover, correction of a subluxation is considered to lead to the restoration of nonnal physiologic processes, thus allowing the reversal of reversible pathologic changes.

Specifics of Five-Component Models1 1. Neuropathuphysiulogic component. Biomechanical insult to nerve tissue is proposed to cause neural dysfunction in three forms, individually or in combination, to include: a. lrritation (sustained hyperactivity) of nerve receptors or nerve tissue. This irritation results in facilitating (lowering threshold of excitability) of afferent nerve cells (dysafferen tation) and evoking activity of efferent neurons with nerve cell bodies located in the anterior hom of the spinal cord, which is exhibited as hypertonicity or spasm of muscles. Lateral hom cell irritation, which is exhibited as vasomotor changes, includes hypersympatheticotonic vasoconstriction. Irritation to the cells of the posterior hom is exhibited as sensory changes. b. Compression or mechanical insult (pressure, stretching, angulation, or distortion) to neural elements in or abollt the intervertebral foramina,

within iasciallayers, or tonically contracted muscles. This compression results in degencmtion, which is exhibited as muscular atrophy, anesthesia, and sympathetic atonia,l& including hyposympathicotonic vasodilation and vascular stasis. c. Decreased axoplasmic transport affecting in traa.xonal transport mechanisms for delivery of macromolecules (neurotrophic substances). This delivery is via the axon to end organs innervated by the nerve. Impediments to this microcellular transport mechanism may alter the development, growth, and maintenance of cells or structures that are dependent on this trophic (growth) intluence expressed via the nerve. 2. Kinesiopathologic component. This component is described as hypomobility. diminished or absent joint play, or compensatory segmental kinematic hypennobiIi t:y. Lack of appropriate joint motion is proposed to be associated with a variety of nociceptive and mechanoreceptive reflex functions that include proprioception. In addition, an early manifestation of a chronically fixata! vertebml articulation is shortening of ligaments as an adaptation to limited range of motion. 3. Myupathulogic component. This component may include spasm or hypertonicity of muscles as a result of compensation, facilitation, lIilton's Law, or any combination. (John Hilton, a nineteenth century English surgeon, stated that the nerve supplying a joint also supplies the muscles which move the joinl and the skin covering the articular insertion of those muscles.)9 4. Histopatlwlogic component. This component relates to inflammation, including pain, heat, and swelling, and can result from trauma, hypennobile irritation, or occur as part 01 the repair process. The component also includes osseous tissue changes in the joint

-

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-De

KINESIOI

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CI

3. MYOPA1

_8

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S.BIOCH! _1

--

-I

\

CHAPTER 7

Vertebral Subluxation

139

SUBLUXATION ~ PATHOPHYSIOLOGY ~ PATHOLOGY

AXIOM - Correction of a subluxation restores normal processes and the reversible pathology reverses.

SUBLUXATION - A complex clinical entity oomprislng one or more of the following:

1 NEUROPATHOPHYSIOLOGY ----1.~

Facilitation

-+-+-+-

Anterior horn Lateral horn Posterior horn

-+-

-

Muscles hypertonic Sympathetic vasmotor Sensory

Atrophy

--- Sympathetic atonia

-+- Anthesia

-+-

---... Degeneration .... Decreased axoplasmic flow KINESIOPATHOLOGY

.... Hypomobility ,.... Hypermobility .... Loss of joint play Compensation

- Fixation theory - H. Gillet

-Illi

-J. Mennel

Hypenmobility and hypomobility - Nonmal

Hypomobility and hypermobllity can be in the same motion unit

Change ofax.is of movement

1-

Compensation

--- Facilitation 1 --- Hilton's law

-

Visceromotor reflex.

HISTOPATHOLOGY Cellular flow of inflammatory process

Edema within inteNertebral foramen, impeding flow of circulating fluids

BIOCHEMICAL CHANGES

.... LAS. (Selye) from local tissue damage or further GAS.

.... Histamines

.... Prostaglandins Stress syndrome

.... Kinines :. Proinflammatory

PRACTIC THERAPEUTIC APPROACH

Adjustive procedures • Thrust, reooil, toggle, etc.

Reflex technics Exercise Diel supplementation

Postural advice Modalities Socio-occupational advice Other

I

Produces a specific movement

•

Effects the movement component

of a subluxation oomplex directly

and others indirectly

lor the adjustment

Fi1d the hypomobility; (B) use adjustive procedure to mobilize the fixation; (C) recheck to oonlirm that movement has . approach is then applied to other components of the subluxation oomplex and their causes; therefore, a holistic, interdisciplinary approach lor each patient's health problems. The prognosis depends on the reversibility of the ,the restoration of normal function, and the ability to keep the joints free 01 subluxation-fixations and other causes of - Regular motion palpation examinations to discover early aberrant motion, especially fixations to prevent the . complex from developing. vmh permission, 1986 L. John Faye and The Motion Palpation Institute

'·1 Five-component (Faye) model of subluxation complex. (From Schq/er RC, Faye LJ: Motion palpation chiropractic technic: principles of dynamic chiropractic, Hunlingwn Beach, Calif, 1989, The Motion . Institute, Wilh penni,~sion.)

140

PART TWO

ANATOMY. BIOMECI-L<\NICS, AND PHYSIOLOGY

that may be expressed according to tlle clinical principles of Weigert's law and WoW's law. (Carl Weigert, a nineteenth century Gennan pathologist, stated that loss or destruction of a part or element is likely to result in compensatory replacement and overproduction of tissue during the process of regeneration, repair, or bOtll, as in the fonnation of callus when a fractured bone heals. Weigert's law is also lmown as the over production theory.)9 Julius Wolff, a German anatomist of the same em, stated that every change in the fonn and the function of a bone, or in its function alone, is followed by certain definite changes in its internal architecture and secondary alterations in its external conformation. 9 5. Biochemical component. Hormonal and chemical effects or imbalance related to the preinflammatory stress syndrome and the production of histamine, prostaglandin, and bradykinin. This component is a result of trauma or fixation of the spinal articulation and is proposed to affect nociceptive impulses, resulting in aberrant (deviating from the usual or normaJ) somatic afferent input into the segmental spinal cord. SIn

Primary Clinical Approach The primary therapeutic approach, related to the Faye model of VSC, is a specific dynamic adjus­ tive thrust (e.g., toggle recoil, impulse) to release sites ot' fixation either directly or indirectly. In addition, supportive procedures designed to enhance the healing process, including exercise, rehabilitation, adjunctive procedures, and lifestyle counseling regarding posture, diet, and stress reduction, may be incorporated in clinical man­ agement of the patient.

NINE-COMPONENT MODEL (LANTZ MODELf2 Lantz provides a more structured organi7.:ation for the VSC model (Fig. 7-2) by deSCribing a hierarchy of organization and a pattem of inter­ relatedness of the various components. In addi­

tion to the five components proposed hy Fa~'e, Lantz adds: • Connective tissue pathologic finding • Vascular abnormalities • Jntlam matary response • Pathophysiologic finding Jo ao update to this nine-component model. the term pathoanatomy has been suhstitutedlrt histopathology, and reference to the su[tll patholo!J.v has been changed in favor of mo~ generic terminology. Thus neuro[.ogic rom~ nent is used in place of neuropathology, kill . logic component replaces kinesiopathology. an4 the myology is substituted for myopatholo&!' component. A common denominator between the Fa. and Lantz models is the focus on restricted motion of the manipulable subluxation. Sud! restriction. or immobilization of' the joint cau, some degree of' degenerative change in the mlJSo culoskeletal system and connective tissue tha may adversely affect nerve system function, T~ early introduction of motion via adjustmelll" mrulipuJation, mobilization, traction, and coo­ tinuous passive motion may overcome these hannfuJ effects. S2

Kinesiologic Component The kinesiologic component is represemed at the apex of the Lantz VSC model (see Fig. 7·2, emphasizing the importance of motion and i1l interreJationsh ip with other compollentt Positioned in the diagram beneath the kinesiOo logic component, but interconnected on !he same level, are the neurologic, myologic, vascu­ lar, and connective tissue components. tanl! states: Movem~nt

is affected by muscles (myologic comp>­ nellt); guided, limited and stabilized by conneclil'clis­ sue; and controlled largely by tbe nervous system The vascular system serves the essentialnulririveand cleansing role for alJ tissues and is the conduit for tbe immediate stages of the intlammatory response III least in vascularized tissues). These constitute thetis­ sue-level components of the VSC and each works in coordination with the others to permit lind sustain proper movement. Interference with any single com­ ponent affects all others.

Cl-Lo\PTER 7

Vertebral Subluxation

141

r Connective Tissue

x c I­

I­

d y Anatomic

c ~d

h cs s­ at Ie or n­ 'sc

Physiologic

Biochemic

7·2 Ninc- component (Lantz) model of sublU)(ation COlllplex. (Adapted from LanlZ CA: The vertebral (lOOn. complex. In Gattennan MI, editor: Foundations of chiropractic: subluxation, St LOlLis, 1995, \ willi permi siun.)

neurologic component, a~ de~cribed by , includes the nerve roots, dorsal root gao­ spinal nerve, recurrent meningeal nerve, and articulllr neurology to include mechanorecep­ and nociceptors and related spinal reflex Ivays (see Chapter 8).

nncctive Tissue Component tz' connective tissue component describes Impact of joint immobilization and connec­ tissue changes. This componen[ includes , the intervertebral disks, articular carO­ I interspinous ligaments, and related sup­ ve tissue elements. With connective tissue i1ization, synOVial t1uid undergoes fibro­ •consolidation, progressing t.o more adher­ fibrous tissue and matrix development for deposition of bone salts in the final stages of 'losis."l In the immobilized joint, articular age shrinks resulting from loss of proteogly­ ,54 This shrinkage leads to softcning of car-

tilage, thus rendering the articulation more sllsceptible to daJTla~e by minor trauma,55 In the immobilized joint, adhesions form between adjacent connective tissue structures. 53 This action may occur between the nerve root sleeve and adjacent capsular and osseous stnJC­ tures in the intervertebral foramen, between tendons and ~lfticular capsules, Or between other connective tissue structures. forced motion cre­ ates a physical disruption of the adhesions, breaking intermolecular cross linkages, thereby improving joint mobiHty. Adjustment/manipula­ tion is one means tJlrough which this may be accomplished. 56

Vascular Component The vascular component may also be affected by abnormal spinal biomechmrics. A segmental artery passing through the intervertebral can~11 into the spinal canal supplies each vertebral motion seg­ ment. Through branching, this artery prOVides blood supply to the dorsal and ventral nerve

142

PART TWO

ANATOMY. BIOMECHANICS, AND PHYSIOLOGY

roots. Each canal contains a segmental vein that drains the spinal canal and vertebral col­ umn. These blood vessels are susceptible to the same mechanical insults as nerve roots and may be compressed. Lantz 57 proposes that immo­ bilization may lead to localized venous stasis, creating a negative relat.ive pressure at the area of immobilization and that. lack of proper venous drainage may lead to inflammatory states.

interprofessional cooperation between chiro­ practors and others in co-management and referral of patients.

ndals. 6H differen tornadc in

THREE-COMPONENT MODEL (KENT MODEL)6l

..these val ment ofsy asymmet on.. ··IFu will aU sus tltated an i lead to pro

Inflammatory Component

Dyskinesia

Immobilization of a joint leads to an inflamma­ tory response. 58 The inflammatory process may affect surrounding tissues and affect nerve func­ tion, as implied in the concept of chemical radi­ culitis. 59 This action may represent one example of how degeneration of spinal joints affects the Ileurologic component of VSC. Inflamed nerves are hyperexcitable and exhibit behaVior differ­ ent. from normal nerve function. 6o The dorsal root ganglia (DRG) of normal nerves respond to mechanical stimulation by discharge of action potentials, which stops on cessation of the stim­ ulation. In an int1amed DRG, the action potentia) discharge continues long after the mechanical stimulus has ceased. 59 Although some authors consider the inflam­ matory component part of the vascular compo­ nent of VSC, other authors such as Faye4Q and DishmanJ9 discuss inflammation under the histopathology component of the five-part Faye VSC model. In addition, given the chemical nature of inflammation and tissue repair, inflam­ mation cannot be considered independent of the VSC biochemistry component. The model of the VSC represents the cur­ rent state of the art concept of subluxation and provides a context bridging the basic science and clinical aspects of spinal function, dys­ function, and degeneration. This model offers a framework for discussion of the varied approaches to spinal manipulative therapy, the specific chiropractic vertebral adjustment, and adjunctive or rehabilitative management of the spine. Usi.llg this model in interaction with other health care providers may enhance

Dyskinesia refers to distortions of, difficulty or impairment of voluntary movement. Impair· ment of spinal range of motion may be reliably measured with inclinometry.62 Alterations in set mental or regional ranges of motion arc associ· ated with the kinesiopathologic component ~ subl uxa t.i OIl. 6.1

Kent proposes a three-component modelofver· tebral subluxation to include the components~ dyskinesia, dysponesis, and dysautonomia.

"im

Dysponesis Dysponesis is described as a reversible path()o physiologic state consisting of unnoticed, misdi­ rected neurophysiologic reactions to various agents (environmental events, body sensations, emotions, and thougllts) and the repercussiol1.\ of these reactions throughout the organism. Kent proposes that these errors in ellerg~' expenditure, potentially capable of produci~ functional disorders, consist mainly of covert errors in action potential output from the motor and premotor areas of the cerebral cortex and include the consequences of that output. These neurophysiologic events result in aberrant mus" cle activity that may be evaluated through sur· face electrode techniques. 64

Dysautonomia The portion of the nervous system that conlrob visceral function of the body is the autonomic nervous system. AcqUired dysautonomia may be associated with various functional abnormaUti~ and is proposed as a manifestation of vertebral suhluxation. 65 •67 Dysautonomia may be evaluated through measurement of skin temperature differ·

Kent pro (EMG) re urements nomic ubluxati cific level technique Comm tz. an identified bined co and neuro

POSTUl

UBLU~

MODEL Harrison

~

mental me

iog

a mo<

and biom asymmetr result in d aments, al assert

directly 0 yndrome follows. Alterat tal plane, central m tructurel

that the s

pinal co CNS.S2.90 within th tanding

rio lions, .sions nisrn Ilcrgy ueing ~overt

notor " and

rhe

CI-L~PTER

7

Vertebral Subluxation

'als.(Jb ~ormative values for skin temperature rences have been detennined based on asymp­ tic individuals. Uematsu 69 proposes that: lie values can be used as a standard in assess­ tofsympathetic llerve function, and the degree of metry is a quantifiable indicator of dysfullc­ .... IFurther,1 ... deviations from the normal values all suspicion of neurological pathology to be quan­ led and therefore can improve assessment and to proper clinical management.

I proposes that surface electromyography

G) recording and skin temperature meas­ ments may be llsed to assess altered auto­ mic tone associated with vertebral uxalion and are useful in determining spe­ c le\'els ior application of spinal adjustive nique procedures. Common clinical characteristics of the l"aye, tz, and Kent models of subluxation complex lified in this discussion include the com­ components of kinesiologic dysfunction neurologic dysfunction.

STURAL MODEL OF SPINAL BLUXATION (HARRISON ODEL) . n and colleagues 70-73 depart from the seg­ tal models of vertebral subluxation, propos­ a model related to altered spinal structure biomechanics as observed with abnormal etrical posture. Such postures over time tin degcnerative changes in the muscles, !ig­ nis, and bony stnJctures. 74-78 Further propos­ assert that asymmetric posture may also be y or indirectly responsible for spinal pain romes. 19 An overview of Harrison's concepts IS.

Alterations in posture, especially in the sagit­ plane, have direct and indirect effects on the lral nervous system (CNS) and its associated tures.SO,Bl Evidence supports the hypothesis the stalic and dynamic deformations of the column are directly transmitted to the ,82.90 Understanding the stresses and strains in the eNS may lead to increased under­ ding of altered neural physiology, degenera­

143

tive disorders, and acute or chronic pathologic processes occurring in the nervous system.

Spinal Canal Deformations Caused by Changes in Posture Flexion and Extension The spinal canal changes in length during physiologic movements or alterations in pos­ ture. Flexion and extension in the sagittal plane lead to the largest changes, but scoliosis, lateral bending, and axial rotation also lead to significant det'or013tions of the spinal canal. 7o. n I The axis of motion for single rotations is nor­ mally in the disk or vertebral bodies. 9l Consequently, during tlexion of the spinal col­ umn, structures anterior to this axis of motion will shorten and be exposed primarily to com­ pressive forces, while tissues posterior to the axis will lengthen and be exposed mainly to tensile forces. (See Chapter 6 for descriptions of these biomechanical forces.) The total change in length of the spinal column from extension to flexion was estimated by BreigSO to be 5 to 7 cm, although Louis 92 suggested 5.0 to 9.7 c m. Tb is ch ange in length is greater at the posterior aspect of the canal because of its increased distance from the axis of motion. Thus the strain in the posterior portion of the spinal canal contents will be greater than the strain of the anterior structures. Beginning in maximal extension and moving to maximal fleXion, the anterior portion of the cervical canal increases in length 0% to 24%, and the posterior canal increases by 28% to 61%.81l.S1 Because of the ribcage, the thoracic spinal callal has a decreased sagittal plalle mobility, though an increased kyphosis will increase the length of the canal up to 3 mm. 92 Similar to the cervical spine, the lumbar canal has a relatively large increase in length during flexion. Here, the central axis of the canal increases in length by 20%.80 Holmes and col­ leagues93 measured spinal canal volume in neu­ tral and flexion-extension of the lower cervicaJ spines (C2 to C7) of 10 cadavers. The volume of liqUid displaced increased with flexion and decreased with extension, but the average total

144

PART TWO

ANATOMY, BIOMECl-L\NICS, Ai\lD PHYSIOLOGY

change from extension to flexion amounted to only 1.9 m!. Breig'lO noted that cenrical flexion would affect not only the cervical cord and nerve roots, but also the hindbrain and cranial nerves V through VII. The significance being that cer­ tain cranial nen'e symptoms may be derived from cervical liyphosis or head flexion posture. In addition, Breig noted that several patients with trigeminal neuralgia had axial head rota­ tion postures.

Axial Rotation Axial rotation of the spinal column, sets up a physiologic stress inside the pons-cord tract, although no overall lengthening of the bony canal occurs. 80 ,91 Depending on the segmental level, however, increases and decreases in the canal dimensions do occur. This action is a result of the segmental coupling patterns from axial rotation.

Lateral Bending Lateral bending results in an increase in canal length on one side of the canal and a decrease on the opposite.

Combined Postural Loading With combinations of postures, lateral tlexion of the skull plus an axial rotation of the skull, the canal deformations may be much larger than simply the combination of the two loads, because a shift in the axis of rotation occurs with combined loads. 71

Postural Deformations of the Intervertebral foramina The dimensions of the intervertebral foramina (lVF) will also be affected with change in sagit­ tal plane posture.SO,9J Brieg80 showed that the IVF will decrease in vertical height by 33%, and the cross-sectional area of the space will decrease as a result of the impingement from the zygopophyseal joints on extension. Other authors have observed that the intervertebral space increased by 24% in flexion and decreased by 20% in extension. 91 The dimen­

sions of the IVF change during rotation as II'~[ The ipsilateral side decreases in total am while the contralateral side will illcre:c slightly. Such rotational changes are not asst nificant as those observed with flexion and extension. 7J

ueh as h­ nd muse14 Several lumn-spi onshlp 1>4 on. FujittJ

lumbosacr~

Postural Changes and Neural Dysfunction To what extent do changes in posture or spina! canal length impart enough stretch to the Spr nal cord to increase pressure and decrease blllOl! flow and cord perfusion? Documented evidence suggests that distraction instrumentation, such as those used in surgery or traction devices, pro­ duces significant losses of lumbar and ceniC31 curvatures. 94 Further, it is acknowledged that spinal column distraction results in a redllctiOD of afferent and efferent impulse conductioo, detected by somatosensory-evoked potentials and neurogenic motor-evoked potential.~:· Lew and colleagues96 showed that the spinal cord elongation and displacement caused by traction forces are consistently less than lila produced by cervical flexion. I3reig's case stud­ iesso suggest that prolonged postural defonnities. such as cervical kyphosis, may result in the same neuronal dysfunctions that occur with dis­ traction instrumentation applied to the spine. spinal cord, or those that occur in tethered coni

syndrome. Physiologic changes are known to occur in astronauts exposed to microgravity conditiol1l (space flight).97 Under these conditions, die spillol is decompressed, whic11 results in heightincrea.<.eI of up to 7 em. This increase in spinal colullXl length occurs as a resuJt of straightening of the sagittal plane curves and an increase in dihk height. This change, in turn, results in conSider· able longitudinal stress and strain of the spinl cord and was proposed as a mechanism 10 explain the neurologic dysfunctions found ill astronauts, referred to as microgravity-related physiologic phenomena (MRPP). MRPP COllsi5tJ of nutritional, metaboliC, cardiovascular, neu­ rovestibular, and otolith-spinal retlex changer. sensory, motor, and autonomic dysfunctions

applied to um, dura where trae mentation ve of eft] earehel lng.l04 ThE ohanged e minale in um tern tube and Traction upper eel w also l also Yamad; and anlm Hect of t cord and ogy of tet mechanis a dera Bused 1 o Idative lmpaire on ener tochond rylBtion m tabol prop y fune The dulla and ass will de ure, in increas ural 80

CHAPTER 7

Vertebral Subluxation

as hyperre!1exia, back pain, paresthesia, muscle atrophy were also associated. 71

Several investigators YS- 101 have studied spinal n-spinal cord distraction to clarify the rela­ ip between tension and neuronal dysfuncFujita and Yamamoto 102 studied the effect of sacral traction in SO dogs. Traction was ed to the filum terminale externum, inter­ dural tube, and conus meduUaris. All areas traction was applied showed an initial aug­ ration of spinal-evoked potentials, sugges­ of carly stages of cord impairment. Other chers have shown and verified this find­ 104 The amplitude of spinal-evoked potentials earlier and were larger for the filum ter­ e intcrnum traction than they were for temlinale externum. Traction of the dural and the conus showed similar tendencies. tion 011 these stmcwres influenced the r cervical cord function, and dysfunction also found in the spinal nerve root poten1

Yamada and colleagues l04 ,105 used humans animals in an attempt to understand the t of traction on the filum and lumbosacral and its relationship to the pathophysiol­ oftcthercd cord syndrome. The underlying hanism of this disorder was determined to a derangement of neural tissue metabolism d by longitudinal tensile stress. The tive metabolism of the mitochondria was ired. Neurons and glial cells rely entirely energy derived from conversion of intrami­ ondrial adenosine diphosphate phospholion (ADP) to ATP. Any change in the bolic efficiency of cellular mitochondria roposcd to lead to progressive neuronal ction. 104.l06 e pons-cord tract (mesencephalon, pons, la oblongata, spinal cord, nerve roots, associated cranial nerves V through XII) develop increased intramedullary pres­ ,increased cerebrospinal fluid pressure, and d intrafascicular pressure (inside the cell) resulting from stretch or tensile ,liO,91,lOi-1l0

ch increased pressure in Or around the is known to cause a decrease of afferent and

145

efferent impulse conduction and will increase the risk of damage to the neural and supporting tissues. 111 ­ 113 Harrison and colleagues propose that abnor­ mal postural rotations and translations cause altered stresses in static spinal positions and in dynamic spinal motions. These stress patterns in the spinal cord have been shown to correlate clinically with ahnonnal neurologic signs and symptoms following trauma and nonacute cord injuries. 92 ,114.116 In relation to altered dimensions of the IVF, several experiments have reported on the effects of mechanical compression on the dorsal nerve roots. These effects include disturbance of blood f1ow,1J7,1l8 change in impulse propagation,1l9-12\ inflammation,122-124 increa.<;o in microvascular permeability,125,126 and formation of an intra­ neural fibrotic 8car. 127 ,128 Compression of the dorsal root ganglion has been associated with IVF encroachment. The positions and clinical relevance of the cervical and lumbar dorsal root ganglia have also been examined.\29.lJ3 Given the changes in spinal canal length and volume, and deformations of the NF, at issue is the int1uence of altered posture, spinal align­ ment, and related mechanical forces on the structure and function of the eNS and related neural tissue. Harrison states that prolonged flexion is the most offensive postural loading on spinal struc­ tures. Flexing the upper cervical spine alone results in a significant increase in the intramedullary cord pressure that is in the range, 10 to 20 rom Hg, required to reduce spinal cord blood t10w and cord perfusion. Prolonged stresses of loading of neural tissue may result in impaired oxidative metabolism in the mitochondria. Kyphotic configurations of the cervical and lumbar curves are types of flexed spinal positions, that is, buckling modes. In the context of this postural model of verte­ bral dysfunction, Harrison suggests that, in addi­ tion to symptomatic improvement or resolution, rehabilitative procedures should strive for an anatOmic outcome of improved upright human posture in the anteroposterior and lateral views as a primary focus or goal of care. lJ4 ,lJS

146

PART TWO

ANATOMY, BlOMECHANlCS, AND PHYSIOLOGY

DEFINITIONS RELATED TO SUBLUXATION AND CLINICAL PROCEDURES Other definitions related to subluxation and its management as presented by Gatterman 20 include: Manipulable subluxation: A subluxation in which altered alignment, movement, or

function can be improved by manual thrust

procedures.

Motion segment: A functional unit made up of two adjacent articulating surfaces and the connecting tissues binding to them to each other. Spinal motion segment: 1Wo adjacent vertebrae and the connecting tissues binding them to each other. Manual therapy: Procedures by which the hands directly contact the body to treat the articulations or soft tissues. Mobilization: Movement applied singlllarly or repetitively within or at the physiologic range of joint motion, without imparting a thrust or impulse, with the goal of restoring joint mobi]jty. Manipulation: A manual procedure that involves a directed thrust to move a joint past the physiologic range of motion without exceeding the anatomic limit. Adjustment: Any chiropractic therapeutic procedure that uses controlled force, leverage, direction, amplitude, and velocity directed at specific joints or anatomic regions,

EARLY STUDIES OF EFFECTS OF SPINAL MECHANICAL DERANGEMENT The modern era of research on spinal manipula­ tion began in 1975 as result of the 1974 Senate appropriation for the National Institute of Neurological and Communicable Diseases and Stroke (NINCDS) of the National Institutes of Health (~lH) and with the convening of the his­ toric Workshop on the Research Status of Spinal Manipulative Therapy.1J6 It must be acknowledged, however, that early basic science laboratory investigation into the

relationship between altered spinal struclUN and tissues or organ dysfunction may be (ra back to the first part of dIe twentieth cemul'yil medical and osteopathic literature and as eadr as 1950 for the chiropractic profession.

Louisa Bums: Experimental Osteopathic Lesions in Animals Early investigation of spinal rel1exes bY osteopath Louisa Burns from 1907 1J7 0011' focused on effects of the osteopathic lesioo.l~ Research at the A. T. Still Research Institute iI Chicago conducted by Burns and colleagues11lli 1948 investigated the pathogenesis of \'isoe disease following vertebral lesion, To study cef tain nervous reflexes and lesion-induced distUJo bances in distant visceral tissue, Bums colleagues produced experiment.'l1 lesions in I variety of animals, including rabbits, guinea cats, dogs, and goats. To induce a spinalleskG. the experimente(" would twist and traction spinal segment. Burns 140 describes, "when limit of normal motion is reached, slight suddll additional pressure in the same plane is exe forcing the vertebra just beyond its normal I' of movement and causing a slight strain of tissue." The term lesion is defined as "a mee ical maladjustment of some sort which ope as one of the primary causes of disease." stages of the lesion demonstrated impainnent visceral circulation along with changes smooth muscle function and glandular secret function. Lesioned articular structures dem strated changes in synovial fluid and lat fibrotic changes. Later stages of the les' involved cil;culatory congestion, dencml' related changes, and segmentally organ' somata-autonomic reflex dysfunction, reaul' in disturbed regulation of the viscera.

*

Henry Winsor: Spinal Curvatures and Visceral Disorders [n 1922, medical physician Henry K. Winsor, using cadavers from the University of Pennsyh' ' conducted necropsies to determine whether connection existed between minor curvatures the spine and diseased organs. Fifty bodies w

CHAPTER 7

n

y

y rd 40

Vertebral Subluxation

. ed. The anterior thoracic and abdominal was removed, the organs were removed and . ed, and the anterior surfaces of the verte­ bodies were cleared for ease of examination curvature. Forty nine of the fifty cadavers minor curvatures. Winsor reported, &fly cadavers with diseases in 139 organs, there found curve of the vertebrae, belonging to the 8}mpalhetic segments as the diseased organs times, leaVing an apparent discrepancy of ten, in the \'erlebrae in the curve belonged to an adja­ segmenl to that which should supply the dis­ organs with sympathetic filaments. However, nerve filaments entering the cord or leaVing it or have traveled up or down the cord for a few nts, accounting for all the apparent discrepan­ tion of Winsor's observations (Table 7-1) 'des the following examples: n and pericardium disease was observed 20 cases of the SO cadavers. Minor spinal 'atures were identified in the upper dorsal segments in 18 of the cases. 1\\'0 involved neighboring segment C7 dDl. mach disease was identified in nine cases eight of the nine demonstrating ture in dorsal segments 5 through 9. In case, cun'ature was found in a boring segment. ney disease was observed in 17 cases. ature was observed at dorsal segments through 12 in 14 cases. One case onstrated curvature at neighboring dorsal enls 5 through 9 and "few" at lumbar ent 1 and 2. r took these observations as "evidences of ISSOciation, in the dissected cadavers, of the ral disease with vertebral deformities of the sympathetic segments."

Cleveland, Jr.: Experimental luxation Effects in Rabbits early 1950s, Carl S. Cleveland, Jr. 142 ,143 in study investigated the effects of subluxa­ on the domestic rabbit. Misalignment of tbe rtcbral joint was produced by applying I subluxation splint consisting of three

147

adjustable metal pin clamps supported by a com­ mon suprastructure frame. With minimal surgi­ cal incision, the pin clamps were attached to the base of spinous processes of three contiguous vertebrae. Subluxation was produced by tighten­ ing Allen screws on the splint frame, thereby draWing the middle vertebra to the posterior and then laterally to produce misalignment. This procedure was accomplished under fluoroscopic assistance and verified by radiographs. Physiologic outcomes such as heart rate, blood pressure, and urinalysis were evaluated. Postmortem patho­ logic analysjs was conducted on various organs and tissues. Findings induded two cases of twelfth thoracic subluxation with subsequent kidney abnonnalities. Other experimental sub­ jects demonstrated "heart diseases, valvular leakages, paralysis, arrhythmias, vasomotor paralysis, dropsy, kidney conditions, and the for­ mation of tumors." Vernon J4J cites this study as an innovative first attempt by chiropractic investigators to employ an animal model of spinal subluxation.

A RETROSPECTIVE The forceful dynamic thrust as part of the appli­ cation of spinal manipulation dates from the time of ancient Greece,25,144 as identified by Withington's 1959 English translation of the writ­ ings of Hippocrates, circa 400 Be. Hippocrates recommended that with the patient lying prone on a wooden bed, combined extension and pressure should be exerted on the patient's spine, and ... [thel physician, or an assistant who is strong and not untra.ined~

should put the palm of hand on the hump, and the palm of the other hand on that, to reduce it forcibly, taking into consideration whether the redue-­ tion should naturally be made straight downwards or towards the head or towards the hip. References in this ancient writing to positioning of the hands and whether to direct the force downward or toward the head or the hip are strikingly similar to the fundamental compo­ nents of toggle-type dynamic thrusts and the angle of drive (direction of thrust) found in contemporary chiropractic technique texts.

148

Table 7-1

PART TWO

AJ'lATOMY. BIOMECHANICS, AND PHYSIOLOGY

WINSOR'S CORRELATION OF SPINAL CURVATURES AND DISEASED ORGANS

IN CADAVERS

Vertebral Curvatures

Visceral Disturbances

Sympathetic. Oonnections between Vertebrae and Diseased Organ

Same Sympathetic Segment as Visceral Trouble

Neighboring Segment to Viscera

C7 & Dl D2.3.4

None

0

Inferior cervical ganglia

2

Thymus diseased

2

Pleurae adherent

21

Upper dorsal

19

Lower dorsal

2

Upper dorsal ganglia Lower dorsal ganglia

~9)21

Lung diseases

26

Upper dorsal

26

Lower dorsal

0

Upper dorsal ganglia

26·26

Heart and peri­ cardium cases

20

Upper five dorsal 18

C7 and Dl

2

Upper dorsal ganglia Inferior cervical ganglia

1

Greater splanchnic (dorsal 5-9)

8

Greater splanchnic (dorsal 5-91

12

Stomach diseases

9

Dorsal 5-9

8

13

Dorsal 5-9

12

Cholelithiasis cases

5

Dorsal 5-9

5

0

Greater splanchnic (dorsal 5-91

5 5

Pancreas cases

5

Dorsal 5-9

3

0

Greater splanchnic (dorsal 5-91

3

Splenic affections

11

Dorsal 5-9

10

Inguinal diseases

2

Dorsal 12

2

Liver diseases

Kidney diseases

Prostate and bladder diseases

Uterus and adnexa Visceral diseases

17

8

2 139

139

Dorsal 10, 11,12

Lumber 1, 2, 3

lumbar Lordosis Vertebral cu rve of same sympathetic segment as disease site

Dorsal 10,11,12

Greater splanchnic (dorsal 5-9) Lesser and least Splanchnic

°

Somatic nerve llio-inguinal

14

Dorsal 5-9 Lumbar 1 and 2

7

Dorsal 12

Upper lumbar ganglia

Sacral curve

Last dorsal and sacral few

2

1 few

0 10 Vertebral curve of adja­ cent segment

128

least, lesser, and greater splanchnic Upper lumbar ganglia

Lumbar and sacral ganglia

2 17

1. WI

de'

thi 8

2

Vertebral curve of segments not related to diseased site 1-5

138

2.

sui 3. Ho' 4. Wt1 bet cor D.C 6. Wh nor sub sep

CHAPTER 7 Vertebral Subluxation

The concept of spinal biomechanical dysfunc­

1 6

ilO

10 11

described and treated as the hump some 20 'es earlier by IIippocrates reappeared in medical literature some 300 years ago as the subluxation. 19 Historical literature 2J-25 that spinal biomechanical dysfunction its treatment by manipulation represented an of substantive interest in the early nineteenth­ 'medical conmlUnity. Tills approach later Into disuse in North America as that profession toward the chemically focused allopathic I of patient care. This abandonment of 'pulation by conventional medicine pro­ chiropractors the opportunity to progress little competition from non-DC manual py practitioners and thus to become the skilled practitioners of the spinal adjustt and manipulative procedures. . taining this leadership role in conserva­ management of spinal function will depend the chiropractic profession's ability to ce knowledge through research and clini­ outcome assessment, especially regarding effectiveness of chiropractic procedures in and preserving health. The model of raJ subluxation complex provides a com­ context bridging the basic science and clin­ aspects of spinal function, dysfunction, and lion and may serve to enhance inter­ . nal cooperation between doctors of chi­ ctic and other health care prOViders cipating in co-management and referral of

nls.

l What is the earliest known English definition of subluxation? In what year was this definition proposed? 2. What was D.O. Palmer's view of subluxation? 3. How did B.J. Palmer redefine subluxation? 4. What are the similarities and differences between AndrewTaylor Still's osteopathic concepts and the chiropractic concepts of D.O. Palmer? 5. What role did unique chiropractic nomenclature such as the term subluxation play in the struggle for separate licensure?

149

6. Which early chi ropractors were the first to characterize subluxation as a fixation and to describe the field of motion of a vertebra? 7. Which two Belgian chiropractors developed the concepts of motion palpation? 8. In what ways are contemporary definitions of subluxation similar to, and different from, early definitions of the Palmers, Stephenson, and Langworthy? 9. What are the major characteristics of the

five-component Faye model of vertebral

subluxation complex?

10. What additional concepts are incorporated in the Lantz model?

1. Why did it take until 1996 for the presidents of all North American chiropractic colleges to reach unanimous consensus on common core definitions fundamental to the principles of chiropractic? What intraprofessional divisions kept this consensus from occurring earlier? 2. What role does subluxation play in relation to visceral disease or dysfunction? What evidence supports this answer? 3. In considering various subluxation definitions that have evolved throughout the profession's history, identify examples that may be described as static or positional and those that more closely represent the dynsmic concept or model of subluxation. Are there examples of subluxation definitions that would represent a blend or combination addressing both the concept of altered position, motion, or both? 4. Contrast the differences between the segmental models of subluxation and the postural model of spinal subluxation. Discuss in what ways these two concepts may interrelate.

REFERENCES 1. Nelson CL: The subluxation question, J Chiropr Huma'lI 7(1):46, 1997. 2. Palmer DO: The science, art and philosophy of chi­ ropractic, Portland, 1910, Portland Printing House. 3. Pa.lmer BJ: The sllbllt."Cation specifio--the adjust­ ment specific, Davenport, Iowa, 1934, Palmer School of Chiropractic.

Neurobiologic Relations and Chiropractic Applications Carl S. Cleveland III, DC

Key Temls AFFERENT INHIBITION A.XOPLASMIC FLOW AxoPLAsMlc

TRA~SPORT CIIROi\IC CERVICAL SV:-IDROMF. DI·~.\FFERENTATION

DVS\IENORRHEA DYSPOi\ESIS END ORGAN f\CIUTATION

GATF. CO"lTROL THEORY

_ IMPULSE-BASED NEURAL

PROPRIOCEPTION

REf'LEX ARC

MECHt\J'IISMS INTERPEDICULAR ZONE

SOMATOSOMATIC REFLEX

INTERVERTEBRAL FORJ\;\1INA

SOMATOVISCERAL REFLEX

MORPHOLOGY

TRANS FORA M rNAL

NERVE COMPRESSION

NERVE INTERFERENCE EURODYSTROPHIC

VERTEBRAL SunLUXATION

COMPLEX

VISCERAL DISEASE

HYPOTHESIS NONIMPULSE-BASED NEURAL MECHA,'IISMS

LIGAMENTS

TROPHIC

HYPOTHESIS

SIMULATION

VISCEROSOMATIC REFLEX

and indirect effects on the central nervous system (CNS) and its associated structures. For various reasons, including the increasing body of supportive research eVidence, a rapid expansion of interest has occurred in spinal adjustiveJmanipulative procedures by medical physicians, physical therapists, osteopaths, and health care decision makers. Health providers who manage patients with low back pain and neck pain may find it rare not to have discus­ sion on the topic of spinal manipulation and adjustment because a significant number of their patients are receivi(l.g or considering this form of he~l1tll serVice. An wlderstanding of the various theOries and concepts related to the spinal adjust­ ment, its mechanisms, clinical manifestations, and results is therefore increasingly necessary.6 Various hypotheses have been advanced to explain the association of vertebral subluxation complex (VSC) with neuronal disturbance and related dysfunction and symptoms. 7. 12 Meeker and Haldeman I identify at least five mechanical and neurologic mechanisms (Table 8-1). The common hypotheses related to the neu­ ropathophysiologic manifestations associated

biropractic theory maintains that subluxa­ tion anti adjustment/manipulation have t physiologic effects that include ing range of joint motion, changes in facet kinematics, increased muscle strength, atten­ of alpha-motoneuron activity, enhanced tion, changes in beta-endorphins, and pain tolerance. 1 A common theme in of the various conceptual models of vcrte­ subluxation is the expect:ltion that spinal anical derangement causes some form of dysfunction or nerve interjerence.

'JIg to Vernon 2 :

bs come to be understood as either (1) some of compression of the spinal nerves in the of the intervertebral foramen or (2) ... initi­ ofpain in the spinal joints ... capable of creat­ dary aberrant reflex effects such as increases euron or sympathetic neural activity.

and colleaguesJ -5 propose that prolonged . ns in posture or spinal canal length impart compression, or tensile forces to the cord, especially in the sagittal plane (t1exion ension) and that such postures have direct

155

156

Table 8-1

PART TWO

ANATOMY. BIOMECHANICS, AND PHYSIOLOGY

PROPOSED MECHANISMS OF SPINAL MANIPULATION

Action

Mechanism

Mechanical-anatomic

Alleviation of an entrapped facet joint inclusion or meniscoid that has been shown to be heavily innervated l3!}-140 Repositioning of a fragment of posterior annular material from the intervertebral disk140.141 Alleviation of stiffness induced by fibrotic tissue from previous injury or degenerative changes that may include adaptive shortening of fascial ti ssue142,143 Inhibition of excessive reflex activity in the intrinsic spinal musculature or limbs or facilitation of inhibited muscle activityl44-146 Reduction of compressive or irritative insults to neural tissues 147

Mechanical-anatomic Mechanical-anatomic

Neurologic-mechanical Neu rologic-mechanical

From I-.leeker and Haldeman,l with permission.

Box 8-1 NEUROBIOLOGIC OF S BLUXATION COMPLEX

RELATIONS

CONTEMPORARY HYPOTHESES 1. Nerve compression hypothesis 2. Aberrant spinal reflex hypotheses a. Somatosomatic b. Somatovisceral c. Viscerosomatic 3. Joint dysafferentation 4. Visceral disease simulation 5. Decreased axoplasmic transport a. Neurodystrophic hypothesis

with altered joint mechanics that represent the focus of this chapter appear in Box 8-1.

NERVE COMPRESSION HYPOTHESIS From the beginnings of the chiropractic profession, the theory that nerves can become compressed through impingement from intersegmental spinal biomechanical derangements has been accorded biomechanical, functional, and clinical signifi­ ca11ce 13-21 and has even been proposed as a primary cause of diseaseP-2J Chiropractic authors empha­ size the importance of the intervertebral foramen (IVF) and its anatomic contents-the spinal nerve, nerve roots, recurrent meningeal (sinuverte­ bral) nerves, blood vessels, lymphatics, and con­ nective tissue-and devote much attention to

changes resulting from compression of the ments within the IVF. 13 -18,20-26 Although contemporary research 21-}1 demonstrated that other mechanisms of s ' biomechanical derangement may be responsi for inducing neuronal disturbances, the cl' , significance of nerve compression should not discounted. 21 Cramer and Darb y 22 attributc of the importance of the IVF to the factlh81 provides an osteoligament.ous boundary the eNS and the peripheral nervous systcm, The question is: To what extent are nerves, nerve roots, and dorsal root ganglia neeable to compression or irritation byab biomechan.ics affecting the IVF? The anatolll!' the lumbar and thoracic spine suggests that cient room exists for spinal nerves to pass peded through IVFs in these areas. However, anatomic relationship of the spinal nervc to cervical intervertebral foramen is significantly ferent.

Anatomy of the Cervical Illterverte Foramen Orthopedic surgeons DePalma and Roth describe the cervical spine intervertebral mina as small ovoid canals with vertical d' apprOXimately 10 mm in height, with the posterior diameter about one half the size« vertical diameter. The authors state that the nerve roots and mixed spinal nerves com fill the anteroposterior diameter of the in

CHAPTER 8

or al

e

Neurobiologic R.elations Hud Chiropractic Applications

foramina. The upper one quarter of the is filled with areolar tissue and small • and "small arteries arising from the ver­ ." DePalma ;md Rothman continue, "any taking lesion which pinches the antero­ riOT diameter of the intervertebral foramight be expected to cause some pression of the nervous tissue elements tra­ g this limited space." In contrast, these T8 describe the normal lumber IVF as to six times the diameter of t.he spinal ~,permitting relatively great. freedom from rietion. kson,24 an orthopedist., in describing the 'es of the cervical IVF, states:

I posterior walls of the canals are formed by t.he nt posterior articular processes, but primarily superior articulating process of the distal ver­ The anterior walls are formed by the lateral oi the bodies of the adjacent vertebrae and qns of the intervening interbody articula­ The anterior walls are of great significance • mechanical standpoint, in as much as the roots pass directly over and are in intimate with the margins of the lateral interbody The gliding motion which occurs between joints whenever the head and neck are turned ed in any direction subjects the nerve roots to n if there is any mechanical derangement t.

I to the conclusions of Rothman and a, Jackson concludes: lleJ'Ve rOOls lie 011 the Iloor of the canals and fill anteroposterior diameter completely. The upper th to one-fourth of the foramina, or the iI ruled with areolar and fatty tissues and small Small spinal arteries which are branches from ebral artery pass back through the int.erverte­ ina to enter the vertebral canal. Minute from the nerve trunks which are known as nt meningeal nerve pass back through the bral foramina anterior to the nerve roots. notes that ventral nerve root fibers intimate contact with the margins of interbody joints. The posterior fibers, rior nerve roots, are in intimate contact die posterior-superior articular processes of acent distal vertebrae. Jackson explains:

157

{Because] of their close proximity to the anterior and posterior walls of the intcrvertebral foramina the cer­ vical nerve roots are extremely vulnerable to com­ pression or to irritation from any mechanical derangement or intlammatory condition in or about the foramina. Such irriWtion or compression may cause pain and/or sensory and motor disturbances anywhere along t.he segmental distribution of the nerves. Jackson uses the term cervical syndrome to describe the group of symptoms and clinical findings resulting from irritation or compression of the cervical nerve roots in or about the IVF.24 Lu and Ebraheim,33 in dissections of the dorsal root ganglia of the second cervical nerve, found that the dorsal ganglia are all proximally placed and occupy most of the foramen. The cervical ganglia at this spinal level are confine.d within the foramina between the arch of the atlas and the lamina of the axis. These ganglia occupy 76% of the foramen height. Such anatomic relation­ ships may render the second cervical dorsal gan­ glion vulnerable to entrapment. These authors further state that trauma with extreme rotation and extension, as occurs in whiplash injuries, at the CI-C2 joint has the potential to cmsh the second cervical ganglion between the arch of the atlas and the lamina of the axis and Jllay be implicated in cervicogenic headache. Many patients with headache and or neck trauma have a history of motor vehicle accident typical of whiplash. Cervicogenic headache (see Chapter 24) may result from displacement, abnormal movements, or arthritic changes in the atlas-axiS articulation, compromising the second cervical nerve root and ganglion. In addition, compress­ ing or entrapping the second cervical ganglion involves fibers that contribute to the greater occipit.al nerve. Crelin,34 an anatomist, in a 1973 article fre­ quently quoted by opponents of chiropractic, argued that nerve roots pass through spacious intervertebral foramina and that therefore exer­ tion of pressure on a spinal nerve does not occur. However, a review of the study's methodology coupled with current research demonstrates that Crelin's conclusion is in error concerning the effects of joint subluxation. 35

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Seeking to "prove" that the theory of spinal nerve impingement is "impossible," Crelin J4 obtained vertebral columns from six individuals. Three columns ,,,ere from full-term infants; the others were from adults ages 35, 73, and 76 years. The vertebral column of each was excised within 3 to 6 hours aJter death. The skull was disarticulated from the first cervical vertebra, and the fifth lumbar vertebra was disarticulated from the sacrum. Each spinal nerve was tran­ sected 8 em after emerging from the IVF. Deep paraspinal muscuhuure, ligaments, and joint capsules were left intact. 1\vo metal vises were clamped to a platform supported the vertebral column while it was sub­ jected to compressive forces. Five vertebral seg­ ments of the newborn column and three of the adult columns were suspended between the vises. A Dillon force gauge was used to measure force of compression applied to the vertebra. A range of maximum compression forces, includ­ ing twisting and t1exion, were applied. The osseous boundary of the foramen did not come in contact with the nerve, and Crelin reported that there was never less than 1.S mOl of space completely surrounding the cervical nerves, 3 mm around the thoracic nerves, and 4 mm sur­ rounding the lumbar nerves. Crelin explained that all spinal nerves emerging from their IVFs were exposed before testing and that gentle teas­ ing with small forceps removed the Ilimsy areo­ lar tissue surrounding the nerves to expose ,the border of the "spacious vertebral foramina." However, this very tissue that Crelin removed contains important connective tissue elements that may be compressible36 or, when irritated, may release chemicals haVing an adverse effect on nerve function.J7-4J Some critics of the nenre compression theory have neglected to recognize that spinal biomechanical derangements do not involve "hard bone on soft nerve." Instead, the key issue is the potential for altered interforam­ inal mechanics to affect vascular and connective tissue support structures, as well as the impor­ tant neural components within the IVF.. Contemporary information describes the IVF as an extended interpedicular zone,42 often con­ taining, transforaminal ligaments. 43-47 These anatomic factors, combined with current under­

standing of spinal nerve root sensitivity to p sure 4S-SO and irritation,37-41,SI render Crelin's elusions unsupportable. 52

In terpedicular Zone Giles42 maintains that the IVF should 110 I be conceptualized as a two-dimensional hole, rather as a canal or tunnel through which spinal nerve and other related structures Giles mainL1ins that "neural and associated \' \ar structures within the important inte zone may weU be compromised due (0 \'ert joint sublmmtion. This may result in chronic pression," adding, "The precise significance cally... is yet to be determined." Giles took nine nllldomly chosen sections adult lumbosacral spinal tissue and ex . them histologically for measurement of the 1-,5 and LS-Sl IVF canals. The zone between pedicles of adjacent vertebrae was found to a horizontal length of 8.2 to 12.2 mm. At a imum, the distance between the nerve s tures and the side of the IVF canal was 0.4 to mm for both the L4-LS and LS-Sl segrn Giles concludes that the Crelin stud)' "meaningless as a basis for consideration of possible physiological and/or pathophysiol functions of spinal nerves beyond the int tebral canal as he did not examine the i tant interpedicular zone." that contains spinal nenre root and gangHon. Rather, hee ined only "the relatively insignificant Ia border."

Transforaminal Ligaments-A Key Anatomic Structure As described by Golub and Silverman,4J

foraminal li~aments (TFL) are Iigam bands crossing the IVF at any spinallml 8-1). In dissections ot' 15 lumbar spines senting 150 IVFs, Bachop and Hilgendorf" varying numbers of TFLs. Bakkum4S dete that TFLs, once considered an abnonnali nonnai and greatly reduce the functional partment or space available for the spinal In Bakkum's study, four adult lumbosacral without visible pathology or degenerative

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159

Ventral and dorsal nerve roots within the dural root sleeve

Body of Sl4l8rior vertebra

Intervertebral vein

Artery

Disc

Transforaminal ligaments

Body of inferior vertebra

Recurrent meningeal nerve

Pedicle

Superior articulating

process

8-1 Transforaminalligaments. (Prom Cramer G: Cl-ini~al anatomy of the lumbar region and sacroiliac

In Greenstein a, editor: Clinical assessment of neuromusculoskeletal disorders, St LoUis, 1996, Mosby; permission. Illustration by Dino Juarez, the National College of ChiropTacti~.)

examined, yielding the following results: 3S

the 49lVFs examined (71%) had at least one More than one quarter (27%) had two TFLs, 8% had three or four. Ia the presence of TFLs, the superior-to­ r dimension (height) of the functional rtment containing the ventral ramus of spinal nerve was signij'icantly decreased. 8\'erage height reduction was approxi­ Iyone third (31.5%). In 12%, the reduction at least 50% in the IVF containing a TFL, one case being reduced by over two thirds ~).

rding to Bachop and Janse,46 the higher

TFL is situated in the foramen, the less remains for the spinal vessels. This mical relationship can conceivably lead hernia or venous conge tion. On the hand, the lower the TFL is located, the r the possibility will be of sensory , motor deficits, or both. In a study of ry ligaments of the IVF, Amonoo-Kuoffi colleagues4i conclude that the spinal I se&mental veins and arteries, and the

recurrent meningeal nerve are held in place through the openings between the accessory ligaments within the fVF. In IVFs in which multiple TFLs are present, these nerves and vessels are literally threaded through a lattice created by the TFLs.

Hadley on Subluxation and the Intervertebral Fonnen HadleY,51 a medical radiologist, states that the importance of the IVF lies in the fact that, except for the first and second cervical nerves, each peripheral nerve must pass through one of these openings. The cervical region COn­ tains "a close five-way interrelationship between the foramen, the nerve root which passes through it, the vertebral artery contacting the root in front, the co-vertebral joint anteriorly and the posterior cervical articulation ill back." Hadley also notes that arthrotic and degenera­ tive changes involving these structures may become an important factor resulting in forami­ nal encroachment and that, "bulging disc

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substance, exostoses or subluxation of a poste­ rior joint may produce pressure upon the root." Hadley 51 goes on to state: "Subluxation (par­ tial displacement) of the vertebral bodies ... may present radiographically one or more of the following features: 1. Shift of the corresponding spinous process toward the side of the subluxation with the patient and film exactly centered 2. SHght increase in the size of the corresponding intervertebral foramen 3. Encroachment of the opposite foramen 4. Displacement of the articular surfaces upon each other S. Because of the inclined plane of the posterior articulation, the side of the vertebra is elevated as it is carried forward. For that reason the disc appears thic!<er on the side of the unilateral sub IlL'ca ti on ." Regarding cervical encroachment, HadleySl observes that, in addition to local and referred pain, patients can suffer from bizarre symptoms JOINT RESTRICTJON AND THROAT

I NFLAMMATION Hadley's observation of spontaneous sublux­ ation associated with inflammation of the throat raises interesting questions from a chi­ ropractic perspective. Is this inflammatory process truly a viscerosomatic reflex response, or are these symptoms a result of somatovis­ ceral manifestations leading to lowered tissue resistance in the throat that contribute to the inflammation? In a study of 76 children with chronic tonsil­ litis, Czech physician and manual medicine specialist Lewit53 observed, "The most striking and constant clinical finding was movement restriction at the craniocervical junction, in the great majority between occiput and atlas (70 cases or 92%):' Lewit concluded that Utonsillitis goes hand in hand with move­ ment restriction... mainly between occiput and atlas, with little tendency to spontaneous recovery;' adding, "our experience suggests that blockage (movement restriction) at this level increases the susceptibility to recurrent tonsillitis:'

called chronic cervical syndrome. These sl toms are described as paroxysmal deep or ficial pain in parts of the head, face, ear, t or sinuses; sensory disturbances in the phs!) vertigo; and tinnitus, with diminished he . Vasomotor disturbances include sweating. R ing, lacrimation, and salivation. Hadley "spontaneous subluxation at the Cl·C2 either unilateral or bilateral, is usually a to all inflammatory process of the throat." Commenting on the thoracic region, Ha states, "Since the thoracic roots are relad small, compression of these structures does occur in the foramina of this region." Rega the lumbar region, Hadley affirms that the s nerve occupies approximately one fifth to fourth the diameter of the normal foramen. remainder of the space is taken up by blood lymphatic vessels, areolar, and fatty ti which together constitute a "compressible cushion space which allows the physiol encroachment to occur without nerve co sion." Moreover, "any abnormal constriction the size of a normal rVF if not actually ca nerve root pressure, nevertheless decreases reserve safety cushion space surrounding nerve and may predispose to pressure."

Effects of Degeneration In a study of the kinematics of the lumbar under normal physiologic spinal moll Palljabi and colieagues S4 maintain that in of spinal degeneration, normal physiol motion "may be enough to compromise space around the nerve root to such a d that very little safety margin is leit." authors further state: [With] age and degeneration, the nerve loses its billty and develops adhesions with the IVF

may not easily slip away from the compressing The result may be a chronic threat of com and mechanical irritation leading to inflamma the nerve root. Panjabi, discussing the research of Sunde agrees that "in contrast to the thicker tive tissue covering of the peripheral nen-e, anatomical and mechanical weakness
CHAPTER 8

Neurobiologic Relations and Chiropmctic Applications

nerve root more easily causes interneural is and adhesions to the surrounding IVF

ular Influences on Nerves S!

a physiologist and osteopathic researcher,

res that much of the pathway taken by as they emerge from the cord is through

la1 muscle. The contractile forces of this e along with associated chemical changes profound influences on the metabolism excitability of neurons. In such an environ­ t, neurons are subject to conSiderable 'cal insult (compression and torsion), as 88 chemical influences. Nerve sheaths, which ltensions of the meninges surrounding the cord, extend distally along the spinal roots, providing a root sleeve that allows rves to slide smoothly in and out without during a wide range of vertebral column t. Over tUne, however, slight mechanical may produce adhesions, constrictioos, .Iations. From a chiropractic prospec­ misvulnerability of nerve trunks represents associated with the myologic component VSC and also relates to its inflammatory hemicaJ components.

and Sympathetic Influences r structures pass through the IVF and blood supply to both the bony verte­ lumn and the spinal cord. 56 Ischemia of rve cells within the dorsal root ganglia lead to progressive loss of sensory func­ including proprioception. Edematous re from even slight congestion of venous may affect nerve cooduction. s6 Such nships are associated with the vascular rologic components of VSC. Olmarker lleagues,563 in studying the effects of ental compression on intraneural cap­ and \'enular blood now through tracking traneural transport of tracer-labeled glu­ determined that as low as 10 mm Hg applied to the dorsal roots reduced al transport to the peripheral axons to 30%,

161

Sympathetic ganglia in the highJy mobile neck area and the cervical chain of g.1nglia positioned against the vertebraJ column are subject to stress imposed by motion. This stress may exert profound intluence on the physiology of sympathetic llerve cells. Fl.lrtheonore, the mechanical disturbances or so~uatic insults preViously described by Korr exert slight forces resulting in slight tissue changes witJtin tbe rVF and in paraspinal structures. This condition may adversely affect nerve function. A further proposal asserts that disorders of muscle tension, tissue texture, and visceral and circulatory function are reflected at the body surface as observ­ able diagnostic elements. 49.SO

Neurophysiologic Effects of Nerve Compression Spinal nerve roots, as compared with periph­ eral nerves, have a less abundant protective epineurium, no branching f::lsciculi, and poor lymphatic drainage. 56.5S These facts imply that the nerve root is more susceptible to injury by mechanica] forces. 59 Panjabi and colleagues 54 state that "the nerve root is constrained in the intervertebral foramen and may be easily com­ pressed or mechanically irritated under adverse conditions of degeneration and movement." In consideration of the effects on nerve func­ tion by subluxation or spinal biomechanical impairment, questions arise regarding possible pathophysiologic mechanism associated with com­ pression or mechanical irritation of nerves. Sharpless,GO in a study to determine tlle sus­ ceptibility of spinal nerve coots to compression, concluded: [pressure) of only 10 mm Hg produced a significant conduction bloet" the potential falling to 60% of its initial value in 30 minutes. Mter such a small COUl­ pressive force is removed, nearly complete recovery occurs in 15 to 30 minutes. With higher levels of pres­ sure, we hHve observed incomplete recovery after many hours of recording.

Rydevik 61 determined: Venous blood flow to spinal roots was blocked with 5-10 mm Hg pressure. The resultant retrograde venous stasis due to venous congestion is suggested as a sig­ nificant cause of nerve root compression. lmpainnent

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of nutrient flow to spinal nerves is present with simi­ lar low pressure.

I
Mechanical Tension and the Muscle-Dural Connection Mechanical tension on the pain-sensitive dura mater may contribute to headache. Hack and col­ leagues64 fOtmd that the rectus capitis posterior minor muscle extends from tile occiput to the posterior arch of tIw atIas vertebra and connects via a bridge of connective tissue to the spinal dura. This connection may resist inward folding of the dura, which may compromise cere­ brospinal f1uid flow when the neck is extended. The dura is extremely sensitive, and tension applied during surgery is felt as headache. The muscle-dura connection may transmit forces from the neck muscles to the pain-sensitive area of the dura. This muscle-dura connection may represent an anatomic basis for the effectiveness of manipulation/adjustment, whieh may decrease muscle tension and reduce pain by reducing the forces between Cl and C2 involving the rectus capitis posterior major and oblique capitis infe­ rior muscles (see Fig. 23-5, p. 479).

ABERRANT SPINAL REFLEX HYPOTHESES A basic chiropractic hypothesis holds that abnormal spinal biomechanics and muscle dys­ function have effects, via the nervous system,

throughout the body and that the chirop adjustment is applied not only to restore r of motion and alignment, but also to cause relieve reflex effects in the nervous system. this respect, the chiropractor functions not as an engineer (correcting joint function), aJso as a telecommunications specialist (' eneing spinal reflexes and nerve function).),' Except for skilled movements, body fun are largely reflexive. Examples include h beat, respiratory movements, digestive ac and posturaJ adjustments. Ref1exive respoJl8eS stimuli include muscular contraction and dular secretion. These spinal retlexes, which involuntary responses to stimuli, are pu and exist to regulate physiologic fun . including somatic, autonomic, and end . logic processes. A reflex arc consists of a s Ius-activated receptor, transmission ol'er afferent pathway to an integration center. mission over an efferent pathway to the efi and induction of a reflex response 63 (Fig. 8-2 Retlexes can be divided into four types on the contributions of somatic and nomic nerves to the efferent and afferem ways of the reflexes. These retlexes in (from 8at065 ): 1. Somatosomatic: RetJexes whose aife and efferents are somatic ncrve ii Higher center

Integrative center

Diagram of a reflex

Fig. 8-2 Diagram of a rellex. (From Hctldema3 Principles and practice of chiropractic, ed 2, Norwalk, Conn, 1992, Appleton & Lange; permission.)

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163

2. Visccrovisceral: Ret1exes whose afferents 1. Directly, as a reflex therapy in itself, in and efferents are visceral sensory fibers that the adjustive!manipulative or and autonomic nerve fibers mechanical intervention introduces a stimulus to joint and muscle receptors 3. Somato\'iscernl (also termed somatoautonomic): Retlext:s whose producing a reflex response that modifies afierems are somatic sensory fibers and or inhibits the current facilitated reflex activity, thus reducing pain and causing whose eiferents are autonomic efferent fibers relaxation of paraspinal muscles 4, \'i.'iCerosflmatic (also termed visceromotor 2. indirectly, in that the manual procedure normalizes joint mechanics, thereby reflexes): Reflexes whose afferents are \isceral sensory fibers and whose removing spinal joint and muscle dysfunction that produces abnormal effercnts are somatic m0tor nerve fibers is proposed that joint subluxation or biome­ levels of spinal reflex activity that 'cal impairment can, however, alter these resulted in the facilitated lesion at a es adversely. Korr2i ,28,66-G8 conducted much given spinal segment Akio 8ato,65 a medical physician and'researcher the basic clinical research demonstrating that nged nerve excitability, sustained hyperac­ in the area of spinal ref1ex physiology, states: •oi aiferent receptors, and retlex response Manipulation performed by chiropractors excites associated with movement restriction in somatic afferent fibers in the musculoskeletal struc­ pine. Korr reported evidence of heightened tures of the spine. These afferent excitations may, in 've rcactivity at spinal cord levels associ­ turn, provoke reflex responses affecting skeletal mus­ with palpable osteopathic lesions and cle, autonomic, honnonal, and Immunologic func­ ed reliable increases in galvanic sl\in tions. An understanding of spinal reflex physiology is, nse (GSR) readings at specific cord levels therefore, fundamental to comprehending the effects of manipulation. he termed facilitation, the facilitated seg­ ,or the facilitated lesion. fundamental hypotheses of both osteopa­ VARIETIES OF SPINAL REFLEXES and chiropractic is that locally altered soma­ ral retlexes associated with traumatized Three major types of spinal reflexes-somatoso­ joints evoke a vicious cycle of altered matic, somatovisceral, and viscerosomatio--are referred to extensively in chiropractic, osteopathic, nl and efierem impulse traffiC, therefore to a facilitated or hyperactive spinal seg­ and medical literature. The order in which the l27,2h,t;(,"'9 root words are combined indicates the origin of presented by Dhami and DeBoer,'o this the reflex and the site of its effect, respectively. For example, sorrw,tovisceral denotes that the ini­ clivity is proposed to further alter neu­ activity, both segmentally and centrally, tial stimulus or insult to the nervous system was a somatic receptor as in a spinal joint and that the the cord, resulting in increased local ic tissue changes with altered joint func­ efJerent reflexive manifestation or response is and tissue texture, along with muscle splint­ expressed in a visceral tissue or organ. tenderness, and temperature changes. This tated segment at a specific spinal level Aberrant Somatosomatic Reflex posed to lead to altered sympathetic Hypothesis parasympathetic outflow affecting local larily and ongoing neural and visceral In Greek, soma means "body." In the somatoso­ ty,n matie reflex hypothesis, stimulus at one level of the soma or musculoskeletal system produces al adjustment, manipulation, mobiliza­ and pressure point therapy are proposed by reflex activity in the nervous system, which is to intluence these sustained and facili­ then exhibited elsewhere in the musculoskeletal spinal rel1exes in the following ways: system. The knee-jerk reflex is an example of a

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somatosomatic rellex. A light taQ on the patellar ligament activates stretch receptors located within that ligament and in the tendon of the quadriceps muscle, which i.nserts on the patelIa. Impulses are conducted by sensory (afferent) neurons to the CNS, specifically at the interseg­ mental L3 and L4 levels, where these neurons synapse with motor neurons in the gray matter of the spinal cord. Without conscious involye­ ment of the brain, impulses are then conducted by motor (efferent) neurons back to the quadri­ ceps muscle. The muscle contracts in response to the impulses traveling along its motor nerve. In this example, a stimulus was applied to a receptor in a somatic structure, eliciting a response in another somatic stnlCture. Similarly, stimuli to receptors in spinal structures, whether from abnormal joint or muscle tension or from chiro­ practic adjustment 72 or manipulative treat­ mentJO ,31,73.74 to relieve it, cause various spinal reflex responses in the musculosl<elecal system. The interneurons of the dorsal horn are pro­ posed to be involved in pain inhibition. As an example, strong tactile stimulation, as in skin rubbing, has long been known to diminish sensa­ tions of dull aching or sharp pain originating from an injured area. This decreased sensation is the result of the effect of afferent inhihition or the gate control theory. The mechanical intervention of rubbing activates the large, fast-conducting tactile-or touch-responsive A-alpha fibers (mechanoreceptors), which, in turn, inhibit the synaptic transmission of the pain Signals by blocking the synaptic gates normally used by the smaller C-fibers that convey pain Signals, there­ fore suppressing the Signals of pain. Wyke 30-J2 suggested that spinal manipulation stretches mechanoreceptors in the joint capsule and that this stimulus has an inhibitory effect, mediated through spinal cord intemeurons, on nociceptive actiVity. Increased mechanorecep­ tive input from increased joint motion reduces. or closes, the gate on pain Signal transmission. This proposed mechanism is an adaptation of Wall's gate control theory.75 A subcomponent of the somatosomatic retlex model, referred to as the proprioceptive insult hypothesis 26 .76,77 suggests that receptors in the highly innervated soft tissue in and around joints

may become irritated, leading to retlex m . tions in postural tone and neural integration postural activities. The proprioceptive' hypothesis has been described in chirop \'lritings 78 ,79 as undue irritation and stirn of sensory receptors (including proprioc located in the articular structures and in parasegmental spinal ligaments. This irri may result when structures are under from derangement of the intervertebral units caused by subluxation. Janse 26 pro that the afferent barrage of impulses into nervous system may disturb equilibrium. somatosomatic reflexes, and cause a somatovisceral and somatopsychic reflexes. Reflex muscle spasm is another example somatosomatic reflex. 8o This reflex has associated with the faCilitated segment, in \l muscle spasm may result from and contribUlf proprioceptive irritation. Theories8o suggest the spinal cord segments in the vicinity spinal fixation have a lower threshold lor' and therefore are neurologically hyperexci Korr refers to this concept as the facili lesion. 81 ,S2

Aberrant Somatovisceral Reflex Hypothesis The La tin mean ing of viscera is internal 0 Jn th is concept, a stim utus to nerves or r related to spinal structures produces refl responses intluencing function in the \1 organs, such as those in the digestive, cardi eular, or respiratory systems. Alternate terms this form of spinaJ reflex are somatosympal and somatoautQnomic. Lewit,53 in a review of vertebrovisceral tions in a variety of cases, cites an example which changes in spinal function (joint hi or hypomobility) are linked to tachyca Therefore when mobility of the spinal col normalized, heart rhythm also becomes n and remains so as long as no relapse oc spinal column dysfunction. Lewit states "although direct evidence of disturbed function ca using organic heart disease is la it would seem reasonable to grant it the of a possible risk factor." Lewit uses the

CHAPTER 8

Neurobiologic Relations lind Chiropractic Applications

k~e

to describe spinal movement restric­ noting that the characteristic pattern of al hypomobility in ischemic heart disease is ockage affecting the thoracic spine from T3 to , most frequently between T4 and TS, move­ I restriction being most noticeable to the and at the cervicothoracic junction," Of his­ I relevance is that as arly as the 1920s, Iropractic authors such as Vedder 83 and S4 recommended adjustment of Heart , identified as the second and third dorsal ebral segments, for treating tachycardia. I

isceral Stu.dies-Hypertension. enorrhea. Infantile Colic, and Female 'Ut), a 1988 randomized controlled trial involving hypertensive patients, Yates and coileagues8S r"ed significant short-term (1-10 minutes) s in systolic and diastolic blood presin the chiropractic adjustment group, no significant change was noted in tbe and control groups. Adjustive proce­ were applied to the T1 through. TS spinal ,Kokjohn and colleagues,S7 in a study of 45 ts, including experimental and sham 'ulation control groups, concluded that manipulative therapy lUay be an effective safe nonpharmacologic alternative for , the pain and distress of primary dys­

165

treatment resulted in "both a reduction of the daily length of colic periods and a reduction of the number of colic periods per day." Because recovery began between 5.7 and 7.7 weeks of age, the authors maintained that this finding prOVided substantial evidence that the improve­ ment might not be attributed strictly to "natural cessation of colic symptoms." In a 1999 study, Wiberg, Nordsteen, and Nilsson BB found that "spinal manipulation has a positive short-term effect on infantile colic." Researchers randomly placed otherwise healthy, colicky infants into either a chiropractic treat­ ment or a dimethicone medication group. Parents maintained a diary of symptoms and behaviors before and during the trial. Both groups received 2 weeks of treatment. The infants in the chiropractic group exhibited a "reduction of 67% on day 12" of daily hours with colic (nearly identical to the study by Klougart and col­ leagues 87 ). The "dimethicone group only had a reduction in daily hours with colic of 38% by day 12." The authors noted: [Manipulation] is normally used in treatment of mus­ culoskeletal disorders, and the results of this trial leave open two possible interpretations. Either spinal manipulation is effective in treatment of the visceral disorder infantile colic or infantile colic is, jn fact, a musculoskeletal disorder, and not as normally assumed, visceral.

ea. dras and colleagues,139 in a larger follow­ Kokjohn and colleagues' dysmenorrhea .' failed to find significant differences in (as measured by visual analog scales), dis­ . (as measured by questionnaire), or serum din levels of patients with dysmellor­ receiving side posture manipulation versus IS receiving a sham procedure. Patients in the manipulation and sham groups demon­ mild improvement. (See Chapter 2S re detailed discussion of this and other ractic research studies on somatovisceral !'S.) aplO8pective study of 316 cases of infantile reated by chiropractors, Klougart and col­ 7 found satisfactory results in 94% of within 14 days from the start of chiroprac­ . The authors found that chiropractic

Volejnikova,s9 in concert with Karel Lewit, con­ ducted a randomized trial involVing women referred for medical rehabilitation for infertility. The study population consisted of 166 women between the ages of 22 and 30, with normal spenn partners and patency of the fallopian tubes. The women in all groups had received unsuccessful infertility treatment for an average of 4 years. These women were randomly allo­ cated to five different groups. 1\\1"0 treatment groups received procedures termed Majzisova's Protocol, directed to the lumbar spine and pelvis, which included stretching and relaxation of lumbar and pelVic musculature, postisol11etric relaxation of the gluteal and pelvic floor muscles, and other exercises. In the first half of the men­ strual cyete, a physiotherapist performed mobi­ lization of hypomobile areas of the sacroiliac

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joints, lumbar spine, and ribs. Home exercises were also prescribed. Typical symptoms other than infertility were painful menstmation, bleeding with clots, dyspare­ unia (painful coitus), back pain, and headache. On examination, frequent structural and ;omatic manifestations included bad posture, scoliosis, sacroiliac dysfunction, asymmetry of the inter­ gIutealline, gluteal and levator ani muscle weak­ ness, and tenderness of coccyx, sacroiliac joints, and lumbar erector spinae. The COllrse of treat­ ment ended after six visits and was considered successful if pregnancy occurred within the study period. Other subject groups were assigned active and passive exercises or other nontreatment interventions. The two treatment groups experi­ enced 34.3% and 27.4% success rates for preg­ nancy, compared with 8% to 9% suCcess rate for each of the three minimal or nonintervention control groups. PikalQ'D Study on Duodenal Ulcers

Going beyond the consideration of visceral dys­ function and obserVing the effects of spinal adjustment or manipulation on structural vis­ ceral pathology, Pikalov and Vyatcheslav 90 in a 1994 study demonstrated improved remission rates of actual pathologic conditions in patients with observable duodenal ulcer. The statistically significant results suggest that spinal somatic dysfunction predisposes the duodenum to dis­ ease and is a cause of the true visceral disease and pathologic conditions. Andrei Pikalov, who conducted this study, is a medical physician and physiology researcher, formerly of the Medical Research Institute at the Russian r\'linistry of Internal Affairs in Moscow and a fonner member of the research faculty of Cleveland Chiropractic College, Kansas City. In this study, 35 adults attending the Gastroenterological Department at Moscow Central Hospital with acute, uncomplicated duo­ denal ulcer confirmed by endoscopic examina­ tion were examined for vertebral subluxation. Twenty three participants demonstrated charac­ teristics of subluxation, that is, displacement, spinous process tenderness, restricted Illotion, contracture, and painful paravertebral muscles. Spinal segments T9 through T12 were the most

frequently affected. Tbis finding again coi with the writings of ch,iropractors Vedder!l Firth,84 who in 1920 associated duodenal with subluxation of T9. In the Pikalov study, patients were assign either a standard medical management a spinal manipulation group. Patients in medical group received standard drug th and dietary regime over 4 to 7 weeks. For other group, a course of spinal manipulali to 14 treatments over a 3-week period undertaken along with the standard d' regime. RemiSSion or healing took an ave 16.4 days in the manipulation group, a mately 9 days or 40% faster than the 25.7 average in tbe medicaJ group. The principal come, confirmed by endoscopic exami was full clinical remission of the ulcer in of smooth healing of the lining of du (epithelialization) or healing by scar io (cicatrization). Pain resolved in 3.8 da~ average in the manipulation group. The a specuJate that possible mechanisms 10 their results include "normalization of the of the autonomic nervous system which ences both cellular metabolism and the \' tor dynamics of the stomach and duod and "stimulation of the endogenous system." These patients did not have simulat pseudoulcer (Visceral disease simulation cussed later in this chapter) but actually ited endoscopically observable duodenal confirmed by photographs. The mam applied to relieve somatic or spinal dy· not only relieved the pain, but also ap provided a healing effect significantly su that obtained from standard drug therapy.

Aberrant Viscerosomatic Reflex Hypothesis The viscerosomatic reflex is, logicall~', the site of the somatovisceral reflex. Respiral digestive dysfunction such as asthma or may cause reflex disturbances in the spine ing to muscle tension and joint subluxa dysfunction. 52 Margaret Wislowska 91 of the of Clinical Medicine in Warsaw, in a stud}'

CHAPTER 8

Neurobiologic Relations and Chiropractic Applications

tribution of pain to rotation of vertebrae in orWn and pathogenesis of lateral spinal cur­ re, determined that irritation of the nervous mresulting in pain in the abdominal cavity : rellexively cause symptomatic rotation of lumbar vertebrae. In this study, 30 patients radiographically confirmed nephrolithiasis ey stone) were examined, 15 with calculi in right kidney, 15 with calculi in the left kid­ .Radiographs were made during acute parox­ of nephrolithiasis. In most cases, rotation lumbar vertebrae was observed. For compari­ 15 patients with other kidney diseases were examined. Angles of vertebral rotation were rved in anteroposterior radiographs by ring the relationship of the pedicle to the I edge of the vertebral body. Wislowska that "... in 70% of the patients with lithiasis studied there is rotation of verte­ towards the affected kidney." A proposed nism is that a viscerosomatic reflex (Via raI afferent nerves) in the kidney resulted the muscle contraction (via somatic efferents) regmental spinal levels correlated with sym­ . segmental innervation of the affected (kidner)· ish gastroenterologists Jorgensen and een92 concluded, based on a controlled .• that a high correlation exists between pain and functional gastrointesti nal pain. A 'oned ailment is described as haVing toms that are persistent, painful, and ,"butwhere "no underlying organic problem be found." Researchers examined the 18' spines segmentaHy, testing for tender­ , skin senSibility, and range of motion. Of patients with back pain, 75% showed physi­ abnormalities during back examination, Uy skin senSibility. Most of the spinal alities were localized to the thoracic and lumbar segments, "the same segments innervate the upper gastrointestinal tract." rding to Jorgensen and Fossgreen, "This ts the existence of a connection between ina! pain and back pain." nsen and Fossgreen suggest two possible ysiologic mechanisms: (1) stimulation of 01'S in trigger areas of the abdomen, via communication to the spinal cord, causing I

167

corresponding changes in the back (visceroso­ matic reflex), or (2) irritation of nerve roots at the intervertebral foramina leading to changes in the gut (somatovisceral ret1ex). One may also speculate that given the functional nature of these clinical observations, the vertebral column is causing symptoms that are mistaken for vis­ ceral disease.

JOINT DYSAFFERENTATION The intervertebral motion segment is richly supplied with mechanoreceptive and nociceptive stroctures. 93 -97 For this reason, theories suggest that spinal biomechanic dysfunction may result in the alteration of nonnal nociception, mechanore­ ception, or both. Kent98 proposes that, "aberrated afferent input to the eNS may lead to dysponesis." To use the contemporary jargon of the computer industry, "garbage in-garbage out." Dysponesis is reversible physiopathologic state consisting of unnoticed, misdirected neurophysiologic reac­ tions to various agents (environmental events, body sensation, emotions, and thoughts) and the repercussions of these reactions throughout the organism. A similar concept once known by the outdated term, spill O'i.)er hypothesis, has been used within the chiropractic profession to imply that aberrant sensory input (i.e., undue irritation of receptors) after reaching the segmental spinal cord level may spill aver and evoke an aberrant efferent response. Seaman 99- 101 proposes that restoration of afferent Input is the probable mechanism by which the chiropractic adjustment affords symp­ tom relief and health improvement. The author asserts that joint restriction or dysfunction reduces large diameter afferent nerve fiber input from the mechanoreceptors in the articular cap­ sule and from intrinsic muscles (intertransver­ sarii and rotatores) of the spine, resulting in functional deafferentation. The prefix dys- Is used to describe actiVity that is abnormal, difficult, or disordered. In this con­ text, Seaman proposes use of the term dysaj­ jerentation to describe the abnormal afferent input associated with joint complex dysfunction. • Afferentation refers to the transmission of afferent nerve impulses,

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ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

• Deafferentation is defined as the elimination or interruption of afferent nerve impulses and is typically reserved for conditions in which peripheral nerves are eitJ1er damaged or completely severed or avulsed. • D:.ysqflerentation refers to an imbalance in afferent input such that an increase in nociceptor input and a reduction in mechanoreceptor input occur. 100 Standard texts in neurology identify two cate­ gories of somatic receptors: nociceptors and mechanoreceptors. 102 ,I03 Research indicates that abnormal joint complex function can alter the activity of nociceptors 104 and mechanorecep­ tors 10S such that nociceptive activity increases and mechanoreceptive activity decreases. Hooshmand10 5 illustrates that restricted joint mobility results in decreased firing of large diam­ eter mechanoreceptor axons (A-beta fibers) and increased firing of nociceptive axons (A-delta and C-fibers). The tenn altered somatic afferent input theory has been presented by Henderson 106 to classify the neurophysiologic theory of chiro­ practic subluxation. Henderson further proposes that chiropractic adjustive intervention may normalize articular afferent input and reestab­ lish normaJ nociceptive and kinesthetic reflex thresholds. Wyke 30 demonstrates that the results obtained from spinal manipulation are reflexo­ genic and depend on adequate stimulation of articular mechanoreceptors. Also addreSSing reflexogenic effects, Seaman 72 states that "noci­ ceptive retlexes promote the development of various components of subluxation complex." Seaman's concept of joint dysaJ]erentation describes abnormal afferent input as a result of joint restriction, involVing a functional decrease in the activity of large diameter mechanoreceptor afferent fibers and a simulta­ neous functional increase in activity of noci­ ceptive afferent nerve fibers. Siosberg107 has used the phrase altered articular input to describe this condition. Along these lines, Lewit53 states: [Changes] of mechanical functi0I! alone do not cause clinical symptoms (pain). They constitute, however,

the nociceptive stimulus which produces re changes in the segment (muscle spasm, hypera zones, etc.). If these are of sufficient intensity to the paln dueshold, pain is felt. The most likely ceptive stimulus is increased tension. Seaman lOS proposes that nociceptors are' tated by mechanical insult (trauma or in' including joint restriction) and chemical tan ts (toxi ns) (Fig. 8-3). Seaman further p poses that the associated nociceptil'c ax (A-delta and C-fibers) enter the spinal cord, veying signals that excite interneurons orig' ing in tbe dorsal horn, producing autono symptoms and pain and also exciting Ii. afferent neurons (producing sympathetic v constriction) and somatic efferent neurons ( dueing retlex muscle spasm). Tbe potential result is loeal tissue vasoconstriction andm spasm, which playa role in reduclngjoinl m ity. Local nociceptors may be further irritated this muscle spasm and sympathetic disc into the area of injury, creating even grea spasm and vasoconstriction. Seaman stal "As the joint in question becomes more h) mobile, it is likely that the various patho components of subluxation complex (his pathology, intlammation, etc.) will become pronounced and further irritate local noci tOTS." (See Chapter 9 for further detail nociception.) He further suggests: The adjustment serves to reduce the killcsiopat ical component of the subluxation complex and. result, most likely reduces mechanical lind ch irritation of articular nociceptors. Thus the resl lion of joint motion, with consequently re mechanical lind chemical irritation, appears to be direct effect the adjustment has on the subl complex. 108 Seaman describes the process: The reflex effects of mechanoreceptor ~tim include the inhibition of pain, relaxlltion of sp muscles, and reduction of vasoconstriction, Thus. adjustment appears to inhibit muscle spasm and I constriction, which are known to cause ge mechaniclu and chemical irritation of extra·a!ti nociceptors .... The adjustment directly mechanical and chemical irritation of articular'

CHAPTER 8

Neurobiologic Relations And Chiropractic Applications

CHIROPRACTIC &

THE DORSAL HORN

Rehabilitation Exercises'{,

The Chiropractic

Adjustment

169

NOCICEPTIVE IRRITANTS A. Mechanical

(trauma, injury)

B. Chemical

1. Lactic acid 2. Potassium ions 3. Prostaglandin £-2 4. Leukotriene 8-4

5. Clycosaminoglycans

Mechanoreceptor eJ
6. Histamine 7. S-hydrOxytryptamine

8. Bradykinin

Nociceptor

Muscle s~sm & vasoconstriction

imtiate & f!t!rpetuate

the subluxation complex:

J. KlneslopathoiOlY 1. Neuropalhoph~oIogy 3. Myopathol()8Y

Reflex

muscle

spasm

4. COlVt«tNe Tissue Pathology 5. Vascular Abnot'l'mlltles 6. Inflanunalory R~

7.

His/o~lhoIogy

8. BiochemicalJ4bnormalitles

8.J Chiropractic and the dorsal hom. (From Seaman DR: Chiropractic and pain control, ed J, n'lJille, Ne, 1995, DRS Systems; with permission.) !tStoring motion to restricted joints. The adjust­ indirectly reduces mechanical and chemical lion o( extra-articular tissue by causing a rellex 'tion of muscle spasm and vasoconstriction. The ment also stimulates afferent input which drives ~pjnal pathways, spinocerebellar tracts and dorsal column system.

suggestion is one possible cause of subluxation. If these assumptions are correct, therapies such as stress management and biofeedback may have a role in case management of the subhLxa­ tion complex. lOS Limited joint motion or hypomobiJity may be associated with effects identified in Box 8_2. 37

nding inhibitory pathways, according to ,J(l.q can influence the pathogenesis of the tiOIl complex as descending fibers from Box 8-2 RESULTS OF JOINT FIXATION r centers of the nervous system stimulate • Degenerative changes same inhibitory interneurons, as does the ractic adjustment, Seaman further pro• Pain • Excitation of alpha-motoneurons: that positive emotions can influence neu­ myospasm pathways such that pain and sympathetic • Excitation of preganglionic sympathetic ti\'ity (vasoconstriction) are inhibited. neurons: vasoconstriction, nociceptive rsely, he presents the possibility that neg­ reflexes emotions and depression can have the • Deafferentation of propriospinal tract, 'le effect on these neurons, in a contempo­ dorsal columns, spinocerebellar tracts restatement of D.D. Palmer's idea that auto­

170

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ANATOMY, BIOMECHANICS, Ai\TD PHYSIOLOGY

SOMATIC VISCERAL DISEASE SIMULATION Somatic dysfunction or vertebral subluxation can often simwate, or mimic, the symptoms of visceral disease, Such mimicry may mislead the diagnostician because the clinical pattems of signs and symptoms for somatic and visceral causes may be indistinguishable from one another. Alternate names applied to this concept include pseudovisceral disease, organ disease mimicry, somatic visceral disease mimicry syndromes, and somatic simulation syndromes. Nansel aJld SzIazak 109 challenge the somatovis­ ceral theory, which claims that somatic dysfunc­ tion is capable of causing true visceral disease. The authors present instead the idea of visceral disease simulation to explain patients with appar­ ent visceral disease that responds dramatically to a spinal manIpulative thrust. Numerous authors* have proposed theories regarding a vertebrogenic or vertebrovisceral relationship associated with the dramatic changes in visceral symptoms fol­ lOWing vertebral joint adjustment or spinal manip­ ulation. A central premise of the various theories of somatovisceral disease is "that the patients involved in these rather 'miraculous' clinical situations were really suHering from true visceral disease."I09 After an extensive literature review, Nansel and Szlazall. propose that somatic pain, combined with the complex patterns of symptoms and signs, often is "virtually identical to and, therefore, eas­ ily mistaken Jar those induced by primary vis­ ceral disease." Such pseudo or simulated visceral disease syndromes may often result in misdiag­ noses. These somatic visceral disease mimict)' syndromes, as proposed, may account for per­ ceived miraculous "cures" of presumed visceral disease in response to spinal manipulation. Somatically induced visceral disease was described in the 1930s work of Lewis and Kellgren,113 in which hypertonic saline was injected into deep somatic paraspinaI structures. This action resulted in diffuse, regional pain referral patterns identical to those characteristic of certain internal organ diseases. This noxious °References 13-20, 49, 53,83-87, 110-112.

stimulation of somatic tissues often evoked variety of associated somatic and autono reflexes, including hyperalgesia, ret1ex m spasm, and increased heart rate and blood p sure. The explanation for visceral disease mim' according to Nansel and Szlazak, is that (1) logenetically primitive visceral afferent ne transmit nociceptive information from inte organs, and (2) equally primitive somatic ents are involved in transmitting nocice information from deep connective tissue ( bone, joint capsules, ligaments, tendons, f muscles). These two afferent pathways, • verge on common pools of interneurons 11" the spinal cord and brainstell1." With so afferent and visceral afferent sigtwls s quently trallsmitted into common eNS ways, afferent neuronal convergence \\ithin spinal cord may lead to clinical mallifesta' tllat are difficult to identify as being of "isceral somatic origin. That is, faCilitating the co neuronal pool by either visceral or somatic in results in common sets of somatic, anIOn and neuroendocrine responses leading to in . guishable sets of signs and symptoms (Fig.8.f Melzac1{ and WalJll4 and Milne and leagues 1l6 have shown that nociceptive s from all structures in a segment converge to in the lam.ina V of the basal spinal nucleus 01 spinal cord. This result also applies to pain naJs from receptors in the zygopophyseal j as well as pain receptors in the walls of vessels. LewH 53 therefore proposes that the motor system (spinal column) "can readily ulate visceral pain, and vice versa, and [hat constitutes an important aspect to be taken account in differential diagnosis." An iJlustrated synopsis of segmentally f pain referral patterns observed by various' tigators is presented in Fig. 8-5. 81 From a hi perspective, these pain patterns are in part Har (at least with respect to cutaneous pain tribution) to early chiropractic observa' from nerve tracing, an early chiropractic tion procedure. 84 In nerve tracing, the praetor palpated along the path of tend over impinged nerves efferently or affe (e.g., from the spinal tissues to the siteoi .

CHAPTER 8

Neurobiologic Relations and Chiropractic Applications

171

SIMULATED VISCERAL DISEASE MODEL COMMON

SETS OF

INDISTINGUISHABLE PERCEPTIVE, SOMAnc. AUTONOMIC.

Prlrnery Somatic Dysfunction Or Disuse

AND NEUROENDOCRINE RESPONSES

I

LEADING TO

+

EQUAllY INOISTlNGUISHABLE SETS Of

SIGNS AND SYMPTOMS

Central Nervous System Afferent Convergence Facllitatbn

of Common NetM"Onal Pool By EITHER Visceral OR SomatIC Inputs

Primary Visceral Dysfunction Or Disease

Schematic depiction of the basic neurologic mechanism by which dysfunction confined to purely structures is capable of producing signs and symptoms that are identic,ll to those typically associated with d}'8fullction involving various internal organs. It is now well-established that afferent fibers that transmit 'e iniormation from deep somatic structures converge on the same central neuronal pools as do the nt afferent tlbers that transmit noxious stimuli from regionally reillted visceral structureS. Jt presents a forthe diagnostician that subsequent relaying of either of these two sources of afferent infonuation by 'ergent pool of neurons into other common central pathways can often result in overt patterns of signs and that may be virtually indistinguishable with respect to their sonlatic versus visceraJ etiologies. The fact 'cdysfunction can often mimic, or simulate, the symptoms of visceral disease (and be easily mistaken Issuppol1ed by an impressive amount of experimenUlI and clinical scientific data. (From Nansel D, Szlazak Idisease simulation, J Manipulative Physiol Ther 18(6):379, 1995; ~oith permission.)

and vice versa). Nerve tracing, the tracing mess from a point of emergence from eto a point at the periphery, was an out­ of the meric systemS? (see Cbapter 2S for discussion of the meric system). Early chl­

ropractic writings9 considered such tendemess the cry ofnature or innate intelligence, indicating tbat a nerve was affected. The early practitioners considered nerve tracing not only to be a valu­ able clinical tool, but also "very convincing to the

PART TWO

172

CO toC2

ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

Fig. 8-5 Segmentally related referred pain patterns observed over the years by a number of independent investigators im mediately after the experimental noxious stimulation over purely somatic paraspinal structures. The illustrations shown herem composite representations of results obtained by (A) Campbell and Parsons;"' (B) Dwyer et al; 117 (C) Feinstein et al;l", (D) Kellgren;1l4 and (E & F) McCallelal l rnterestingly, the intensity, distribution .. affective cha Tllcteristics of the pain perceptions induced in these nomlal experimental subjects were often found to be astonishing) y similar to dIOse lypically exJlibited by patients known to be sufie~ from a variety of primary internal organ diseases or conditions. The diffuse pain referral pattems elicited in these subjectJ were also often accompanied by a number of additional secondary regional and/or global reflex-based signs and symptoms were also virtuaUy identical to (and therefore easHy mistaken for) those commonly observed in patients harbonag true primary visceral disease ( ee fig. Over the last SO years, a signiiicant am of both experimental and clinical inform,ttion has accumulated in the scientific literature concerning somatic syndromes and basic neuronal mee . thai may often conspire to create ol'en patterns of signs and symptoms tbat . or simulate those classically associaled a number of regionally related primary visceral disorders. (From iVansel D, Szlazak M: Visceral disease siTliulatiOll, J I\'Ianipulative Physiol Ther 18(6):379, 1995; with permission.)

Cl '0<::;

A B

c

o

E

F

CHAPTER 8 Neurobiologic Relations and Chiroprflctic Applications

ain

,.115 III

'on,

9,

em, for the patient is the only one who can . uish between nerves that are tender or ted and those that are not."9 Nansel and Szlazak take the position that pri­ 'dysfunction of somatic structures of the al column cannot cause regionally or seg­ tally related visceral (internal organ) disease that no clinical evidence supports the notion a regionally or segmentally induced somato­ mldisease connection. Further, the authors

Ie 8-2

173

assert that the autonomic nervous system does not seem capable of inducing frank tissue dis­ ease in any organ it innenrates. A well-refer­ enced list developed by these authors (Table 8-2) presents a correlation of regionally related pat­ terns of signs and symptoms that often result from primary somatic dysfunction, together with a collection of primary visceral conditions that such patterns of signs and symptoms have been shown to mimic or simulate.

SOME SOMATICALLY INDUCED SYMPTOMS AND THE VISCERAL DISORDERS

:rTHEY SIlI'lULATE OR MIMIC

Simulated Visceral Disorders Referred head, face, eye, ear, sinus, mouth, dental, throat pain and/or hyperesthesias and/or dysesthesias

Narrowing of the palpebral fissure Vertigo/dizziness, blurred vision, light or sou nd intolerance, tinnitus, diminished/muffled hearing, difficulty swallowing, sense of object in throat, hoarseness, dysphonia E!ythemia, sweating, nausea, vomiti ng, sinus congestion, and runny nose (coryza) Referred chest, breast, shoulder, arm pain and/or hyperesthesias, and/or dysesthesias Difficulty breathi ng/dyspnea Sweating, pallor, cardiac palpitations and arrhythmias, anomalous resti ng and/or treadmill electrocardiographic findings Abdominal pain and/or hyperesthesias and/or dysesthesias and/or cramping, pyrosis, Intestinal colic, epigastric discomfort after meals (dyspepsia) Food intolerance, irritable bowel of abdominal fullness (bloating) rperistalsis of intestines (borborygmus) sea, vomiting, belching, flatulence, constipation, diarrhea Urinary urgency/irritable bladder, renal, loin, lf8lhral, pelvic, perineal/groin/rectal pai n and/or hyperesthe'sias and/or dysesthesias, urge for defecation, dysmenorrhea, dyspare­ unia, dysuria incontinence

Pseudomigraine and cluster headache, pseudo-temporal arteritis, pseudo-trigeminal neuralgias, pseudo-Menier's, pseudo-otitis media, pseudoptosis, pseudosinusitis or rhinitis, pseudopharyngitis, pseudolaryngitis, pseudo-cranial nerve involvement

Pseudo-cardiac angina, pseudo-breast disease, pseudo asthma, pseudo pleurisy

Pseudo-peptic ulcer, pseudo-duodenal ulcer, pseudo-gastric ulcer, pseudocholelithiasis, pseudocholycystitis, pseudoappendicitis, pseudoabdominal/intestinal disorders

Pseudorenal and urinary tract disorders, pseu­ doendometriosis, pseudosalpingitis, pseudo­ pelvic inflammatory disease, pseudo-pelvic disorders

174

PART TWO

ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

Nansel and Szlazak affirm that afferent noci­ ceptive signals generated from dysfunctional deep somatic structures can often result in the referred pain patterns, along with a number of equally misleading autonomic ret1ex responses. These retlex responses have been shown to sim­ ulate (rather than cause) true visceral disease because of their convergence on the same pools of eNS neurons that also receive aH'erent input from regionally related internal organs. The coucept of somatic viscera! disease simu­ lation provides a sound alternative explanation for the apparent effectiveness of a variety of somatic therapeutic interventions in patients with presumed true visceral disease. Nansel and Szlazak conclude that the existence of these somatic visceral disease mimicry syndromes jUs­ tifies cooperation between medical physicians and health care providers such as chiropractors who specialize in the evaluation alld treatment of primary somatic dysfunction.

DECREASED AXOPLASMIC TRANSPORT The consequences of vertebral subluxation or spinal biomechanical impainnents include pain and other sensory manifestations, as well as motor and autonomic disturbances. Manifestations dis­ cussed thus far have related to disturbances in excitation and conduction of nerve impulses. The impulse-based mechanisms underlying these clinical manifestations seem to be initiated through either direct insult to nerves and nerve roots or altered sensory input from affected joints, ligaments, tendons, and muscles. Another component of neural function, also proposed to be affected by vertebral subluxation and related musculoskeletal problems, is axoplas­ mic transport. This component is a nonimpulse mechanism based not on transmission of signals along the surface of the neuron's neurolemma, but rather on the intraaxonal transport and exchange of macromolecular materials. This action involves a neurotrophic relationsltip between neurons and end organs or target cells. 56 Tenns such as end organs, target cells, and postsynaptic cells refer to organs supplied or affected by a nerve. It is now well estabIished llfi.l2J that macro­ molecular substances are synthesized in the

nerve cell body, packaged by Golgi apparalllS, and transported within the axon to the lerminal ending of the neuron. These substances are released at the synapse and then exert a subde int1uence to maintain proper vitality and iuno­ tion of the target tissues. The axoplasmic lr8/lJo port system may convey material at a rate up 10 400 mm/day.120,121 Chemicals transported ~ this process are coUectively known as tropbio substances, and have been found to he cssenlii for the maintenance of proper tissue funclkt and morphology (structure or frame\Vork).II~ Within the context of this discussion,lro means relating to growth. In the neuroscie literature,119 trophic influence on the peri nervous system refers to (I) the intluence oi nervous system on differentiation and devel ment of structures into mature end organs (2) the role of trophic function in maintcn of end organs. To distinguish trophic function from the ron's function of conducting nerve iIllpulses the end organ, Guth'sI27,128 definition of ITO function-"those interactions between lie and other cells which initiate or control mol lar modification in the other cell."-is appropriate. This definition may be reslaled follows: trophic function influences the deve ment and maintenance of chemical changes cells supplied by the nerve. The nerve impulse is a fast acting membrane phenomenon (120 m/sec), in trast to the much slower (up to 400 mm/day. 50)120,121 intracellular or intraneuronal t mechanism conveying trophic inlluences to get end organs. Swartz 116 describes the complex transpon terns that have evolved to carry laq,ic rna fanned in the nerve cell body. These ch are carried the full length of the axon 10lbe minals, after which materials from the te are returned to the cell body for rep Two forms of intracellular transport are ideo The slower ltind, axoplasmic fiow, conveys rials only from the cell body toward lhe fiber terminals; the faster form, axonal I carries materials in both directions (Fig. 8-6 Studies by Weiss and colleagues in I descrlbed by Swartz,1I6 first proved ex tally that substances originating in the 0

CHAPTER 8

Neurobiologic Relations and Chiropractic Applications

body move at a steady rate along the axon 8-7). The experimental procedure involved . I constriction of branches of the sciatic e in rats, chickens, and monkeys. After sev­ weeks, examination of the region just above lima! to) the constricted axon demon­ swelling, suggesting that "axoplasm had mulated behind the blockade." ennore, "the portion of the axon beyond ) the constriction had degenerated." Weiss \'ed the constriction, timed the movement rerial, and observed that, "the accumulated Iasm progressed down the regenerating at a constant rate of one or two millime­

aday,"116

175

Chiropractors may note a similarity between this observation and I3.J. Palmer's simplifiedjoot on hose analogy, historicaUy presented to the public as a description of the effects of nerve compression.

Trophic Influences on End Organ Growth and Function Examples of trophic intluences on target tissues as adapted from Korr S5 include: 1. Atrophy of denervation. An example is the atrophy skeletal muscle undergoes after denervation, Apparently, the integrity of the connection between tlw nerve and

8-6 Life cycles of vesicles and other membranous organelles illvolwd in the transmission of nerve signals aynapse (the specialized region of contact between a nerve terminal and another neuron or a muscle cell) With their synthesis in the cell body. Organelles move outward along the axon by fast axonal transport. ofilie material is deposited along the axon to maintain the a;
--'t;.;:·_..::·::·,~::; .~::::;,,::~\-,;!_:;:;~>::;:X( '-ii, 2

'--'~""~'Y_~I_-"._~~~;:\'

"'.:­ 3

7 Constriction experiments done at the University of Chicago in 1948 by Paul A. Weiss and his

demonstrat.ed that material from the cell body of a neuron moves along the axon at a steady rate. The enl is depicted here schematically for a single mature nerve fiber (1), with the cell body at t.he left and leading away from it to the nerve terminal at right. A constricting cuff was applied to the fiber rseveral weeks the axon was swollen above the constriction (3) and reduced in size below it, showing axoplasm (the material from the cell body) had been dammed up by the constriction. It flowed again nthe cuff Ivas taken off. (Fmm Schwartz HI: The tmnsport ql substances in nRT'De cells, SCI Am 52,1980; with pennissimt. Illustration by Alan D. Iselin.)

176

PART TWO

ANATOMY, BIOMECHANlCS,

muscle, rather than the impulses to the muscle, is the critical factor. WlIen observing the effects of removing the nerve supply from the sensory organ, the connectedness between two kinds of cells has been demonstrated to be the crucial issue. Sensory organs are the initiators of the nerve impulses, not receivers. In the case of gustatory organs (taste buds), these structures undergo trophic changes or even complete dedifferentiation on denervation. I22 ,123 Recovery or restoration of the taste buds follows soon after reinnerva tion. 119 2. Morphogenetic influences. In embryonic development, complete differentiation and development of muscle requires that nerve supply reach the muscle and that a myoneural junction be established. Hix l24 demonstrated that renal innervation prepares the kidney for response to circulating growth factors. When a pup is deprived of that preparation by denervation in the first few days of postnatal life, kidney development is arrested. 3. Role of nerve io regeneration. Certain amphibians are capable of regenerating entire limbs and tails after amputation. Singer 12S has demonstrated that deoervation of the fibers coursing towards the amputated stump prevents regeneration of the amputated forelimb of the newt. Furthcnnore, only portions of the fibers are required to sustain regeneration and sensory fibers serve thiS function. 4. Regulation of genic expression. Gutman 126 and Guth 127 propose that the nerve that grows into a muscle in the course of embryonic development determines which genes of that muscle's cells wi)] be repressed and which will be expressed. For example, red and white muscles are known to differ morphologically, functionally, and chemically. Their chemical differences include those related to proteins, enzymes, and metabolic pathways. 128 Surgical section of nerves and cross-reinnervation of red and white muscles are followed by a high degree of cross transformation. Korr55

Ai~D

PHYSIOLOGY

interprets this metabolic transiormalioD be an expression of neurally mediated genetic influence, in which the nerve instructs the muscle what kind of muscle to become. S. Nerve-to-muscle transmission. Another example of neurally influenced genic expression and repression occurs in lhe transmission from nerve to muscle at the myoneural junction. Receptor molecules for acetylcholine, which is released by nerve terminals, are normally restricted the area of the muscle surface where the myoneural junction is located. 55 Cutting the nerve causes the emire surface or muscle cell to become acetylcholine sensitive, in response to removal of the repressive influence of the nerve on the synthesis of the protein receptor mol in the extrajunctional areas. 129

CLINICAL IMPLICATIONS OFAXOPLASMIC TRANSPORT According to multiple aurnorities,lI6-l29 pe eral nerves not only conduct impulses 10 or nooneuronal cells and tissues that they i vate, but they also exert long-term intluences these end organs through trophic or rotrophic influences that are essential Cor development, growth, and maintenance. Korr.'i5 proposes: [Any] factor that causes derangement of t mechanisms in the axon or that chronically the quality or quantity of the axonally trans substances could cause the trophic influences become detrimental. This alteration in turn produce aberrations of structure, function, metabolism. therehy contributing to dysfunction disease.

One such cause is direct mechanical insult, as deformations of nerves and roots, incl compression, stretching, angulation, and sion, "that occur commonly and that .... the intraaxonal transport mechanisms, . neural microcirculation." Moreover, "0 structures are especially vulnerable in passage over highly mobile joints, through

CHAPTER 8

to

e

e

Neurobiologic Relations and Chiropractic Applications

a1s, intervertebral foramina; fascial layers, tonical contracted muscles." An additional factor, also biomeclumic in ori­ is, "sustained hyperactivity of peripheral rons (sensory, motor, and autonomic) ted to those portions of the spinal cord asso­ dwith intervertebral strain or other types of tic dysfunction."lJO Korr concludes: ainedl high rates of impulse-discharge place d energy demands on the affected neurons affecting their metabolism and... their synthesis turnover of proteins and other macromolecules... Intense activity does impair axonal transport, .. trophic interchange with other cells.

CRODYSTROPHIC POTHESIS rodystrophy is the proposition that neural clion is stressful to viscera and other body ures, which may modify immune responses alter the trophic function of involved 'es. 1Jl ·JJ2 In its most basic fonn, the con­ may be reduced to D.D. Palmer's asser­ that "lowered tissue resist3JICe is the cause disease."13 According to the neurodystrophic thesis, spinal biomechanical insult to es may affect intraneural a..,xoplasmic truns­ mechanisms and, in turn, affect the quality neurotrophic influence and Illolecul fir (chern­ ) changes in the cells. This de<,;reas<,; in hie factors is understood to render innerstructures vulnerable to dysfunction or

text has now examined a variety of eses that seek to explain the cause-and­ relationship between altered spinal biome­ and clinical manifestations, dysfunction, disease. How may these hypotheses be con­ ly applied so as to enhance the chiro­ r's understanding in a particular clinical tion? l.e\\it presents the following explanations of eblWisceral correlations in his text, tit'e Thempy in the Rehabilitation of

Locomotor System: 53

177

1. The vertebral column (locomotor system)

is causing or mimicking, symptoms that are mistaken for visceral disease. 2. The visceral disease is causing a reflex reaction, resulting in the hypomobility or fixation of the corresponding, vertebral segment. 3. The visceral disease that refleXively caused restricted segmental mobility has subsided, but the hypomobility remains, causing symptoms simulating visceral disease (as in item 1). 4. Disturbance of the vertebral locomotor segment is causing visceral disease . Readers may consult Lewit's text for an expanded presentation on a variety of visceral disorders and their associated segmental spinal relationships. Keeping, Lewit's four choices in mind, the fol­ lOwing clinical experience presented by Chapman­ Smith.'s in The Chiropractic Report might be considered: Mr. A.T., a S6 year old dairy farmer complaining of chest pain that feels like "a tire around my chest," is referred by his family physician to a cardiologist. Examinations Induding imaging, ECGs, and exercise stress tests, reveal many dassic signs and symptoms of myocardial ischemia-deep chest a.nd arm pain, paleness, sweating, cardiac dysrhythmia, and coro­ nary arteriosclerosis. Mr. A.T. is told he has a heart problem and is treated accordingly. He is advised to stop strenuous physical work and change his occupation. However, tJle med­ ications prescribed, nitrates, then beta-blockers, are ineffective. Faced with the sale of his farm and anx­ ious to find something that might help, he seeks the adVice of a chiropractor. Chiropractic eXflmination reveals joint subluxation, with restricted joint range of motion and muscle ten­ sion in the lower cervical and upper thoracic spine. Palpation of the two top segments in the thoraCic spine reproduces the cardiac pain. Radiographs show marked narrowing of the intervertebral foramina at C6/C7. Following a short course of spinal manipulation, designed to restore normal function to the spinal seg­ ments ~Uld paraspinal muscles and to relieve irritations of the spinal nerve roots, joint function is normal and pain relieved. Mr. A.T. returns to his normal farm work and lifestyle, and has no further symptoms.

178

PART TWO

AKATOMY. BIOMEiCl-L\.I\1lCS. AND PHYSIOLOGY

Chapman-Smith adapted this case from one cited by Kunert, a German cardiologist. In his paper, "Functional Disorders of the Internal Organs Due to Vertebral Lesions"13J Kunert states: [We] have records of numerous cases Similar to the one described here, in which a definite connection appears to ex.ist between a functional disorder in an intenml organ and a spinal lesion ... lesions of the spinal col­ umn are perfectly capable of simulating, accentuating, or making a major contribution to (organic) disorders. There can, in fact, be no doubt that the state of the spinal column does have bearing on the functional sta­ tus of the internal organs.

Chapman-Smith then applies Lewit's vertebrovis­ ceral cOlTelations as possible explanations for Mr. AT's case. The author proposes these possibilities: 1. The spinal or somatic problem (subluxation) is simulating or mimicking heart disease. 2. Heart disease and pain have caused a reflex reaction in the spine and paraspinal muscles. The resulting spinal dysfunction (subluxation) then exaggerates or mimics cardiac pain. 3. Heart disease has reflexively caused subluxation as in (2), the underlying disease has now subSided, and the spinal lesion gives symptoms simulating continuing heart disease. 4. Spinal subluxation is causing heart disease, maybe through altered somatovisceral reflexes that, either alone or together with other stressors, cause ischemia and disease. In view of the explanations proposed previously regarding patients such as Mr. A.T., cardiologists and other health practitioners must be educated regarding the possible role of subluxation or spinal biomechanical lesion and its potential role in presumed cardiac pain and other visceral manifestations.

OVERVIEW OF BIOMECHANICAL AND NEUROPHYSIOLOGICAL MECHANISMS OF SPINAL ADJUSTMENT/MANIPULATION Various hypotheses proposing explanation for the apparent effects associated with subluxation

and nerve system function have been present in the chapter. A close interface between s ' biomechanics and nerve function has established. SJ ,5s.)J<1-1Ji The nervous system been identified as a major and central medi of the clinical effects of spinal manipulativet apy, chiropractic adjustment, or both.ii,l. Gutziet, as cited by Lewit,53 characterizes spinal column as the initiat01; provoker, m pliel; and localizer of the pathogenesis of ce diseases. LewitS3 maintains that any distur of function in a single 1110tor segment will repercussions throughout the body ~xis must be compensated and that once the becomes painful, tbe nervous system dele . how intensely the spinal segment will rna . clinically. Symptoms resulting from biomechanical i ments of the musculoskeletal system that responsive to spinal manipulative therapy or adjustment encompass sensory maniicslil' including pain, as weU as motor and aul disturbances." Spinal biomechanic dysfu (vertebral subluxation) and concomit<'lIlt ne system manifestations appear to be associated and affect both the impulse-based and nonim based mechanisms of nerve function.;;

Impulse-Based Neurall'vlechanisms Insult to the jmpulse-based neural meeh ' occurs through: • Direct insult to the nerves and nerve roots resulting from compression, torsion, stretching, or angulation resulting from adhesions 54 or foraminal encroachment.' Neuf31 structures are vulnerable in their passage over highly mobile joints, intervertebral foramina, fascial layers. and tonically contracted muscles. * • Altered sensory input (sustained hyperactivity) from affected muscles, tendons, ligaments, and joints produces aberrant somatosomatic and somat0\1 spinal reflexes. § Undue irritation to ~Rderences 27, 53, 55, 63, 66-68, 130, 134·l37.

tReferences 13-18, 20-24, 51.

tRcferences 48,51,54,55,59,62.

~References 27, 50, 55, 75, 108,

CHAPTER 8

Neurobiologic RelHtions and Chiropractic Applications

nociceptors in visceral organs is proposed to trihute to aberrant sensory input at intersegmental spinal levels, resulting in abnormal viscerosomatic reflexes and sin paraspinal musculature that may tribute to spinal joint hypomobility, b!uxatioll, or both. 19,55,80, 108 Given that atic afferent and visceral afferent signals ilOnverge equally into common central l'\'OU8 system pathways at intersegmental allevels, vertebral subluxation or spinal sfunction may simulate or mimic

ptoms of visceral disease, potentially

leading diagnosticians in all health

essions.) lO,m

. pulse-Based Neural

hanisms

erence with nonimpulse-based neural nisms results in decreased axoplasmic rt of neurotrophic factors to the terminal of the nerve. S5 Such trophic factors inJ1u­ chemical changes at the molecular level, affects the development, growth, and Ienance of end organs in tissue supplied hy Derve. II7·131 This mechanism is not based on lransmission of nerve impulses. Rather, it is on the transport and exchange of macro­ lar materials via intraaxonal transport Deurotrophic relationships between neurons lhe postsynaptic or target cells. >1< The SllS­ high rates of impulse discharge proposed ult from altered joint function place energy demands on the affected nell­ lhU8 affecting synthesis and the turnover of and other macromolecules, as well as axonal transport and trophic inter­ with other cells. The intraaxonal trans­ mechanisms may be affected either by direct tion of the nerve through mechanical or by altered activity or sustained hyperac­ olsensory receptors. This alteration may, in produce aberrations of structure, function, bolism, thus contributing to dysfunction

179

Fig. 8-8 outlines the theoretical progression of joint complex dysfunction's effects on neural mechanisms associated with the neuropatho­ physiologic component of vertebral subluxation complex. The neurophysiological and biomechanical mechanisms underlying the effects of spinal manip­ ulation/adjustment are reviewed by Pickar1+S,149 and conceptualized in the theoreticaJ model presented in Fig. 8-9. Picka r proposes that s tructu ral dysreJalion­ ships between vertebral segments may hypo­ thetically produce biomechanical overloads and stimulate the receptive endings of mechanically or chemically sensitive neurons in the paraspinal tissues. Sustained afferent input could result in abnormal or aberrant neural reflexes. Pickar 149 states the following; These changes in sensory input are thought to modify neural integration either by directly affecting reflex. activity and/or by affecting central neural integration withiJI motor, nociceptive and possibly autonomic neuronal pools_ I':ither of these changes In sensory input may elicit changes in efferent somatomotor and visceromotor actiVity. Pain, discomfort, altered mus­ cle function or altered visceromotor activities com­ prise the signs or symptoms that might cause patients to seek spinal manipulation. Spinal manipulation, then, theoretically alters the innow of sensory signals from paraspinal tissues in a manner that improves physiological function.

In addition, endogenous metabolites such as bradykinin, substance P, and related intlamma­ tory mediators may result from joint dysfunc­ tion. These substances are noxious stimuli that likely activate paraspinal afferents.99-101, 14S Altered vertebral segment mechanics may result in compression of nerve roots within the intervertebral foramen. It is known that spinal nerve roots and the dorsal root ganglia are more susceptible to the effects of mechanical com­ pression than the axons of peripheral nerves 60 -63 and that mechanical compression of the dorsal roots and dorsal root ganglia may alter both impulse-based and non-impulse-based neural mechanisms. 54 ,55.14<) Pickar examines the neurophysiological basis for the effects of manual procedure, presenting a theoretical model describing the relationships

180

PART TWO

ANATOMY, BIOMECH.ANICS. AND PHYSIOLOGY

NEUROPATHOPHYSIOLQGY OF VSC'

I. SUSTAINED RECEPTOR HYPERACTIVITY Posterior horn Irritation _

Sensory manifestations

Facilitation£ Lateral horn _ _ Sympathetic vasomotor ~ construction Anterior horn- Muscle hypertonicity

II. NERVE COMPRESSION ~ Atrophy Pressure_ Degeneralion~Sympathetic Atonia Anesthesia

lit. DECREASED AXOPLASMIC FLOW Compression or irritation

Adverse effect on _ axoplasmic transport mechanism

Adverse trophic influences on development. growth, and maintenance of end organs

'Vertebral Subluxation Complex

Fig. 8-8 Neuropathophysiology of vertebral subluxation complex (VSC). (Adapted by Carl S. C/ei.,'(?lalldlH from ~~aye model of VSC. From Schafer Re, Paye LJ: Motion palpation and chiropractic, technic principles dynamic chiropractic, Huntington Beach, Calif, 1989, The Motion Palpation Institute, with permission.)

between spinal manipulation/adjustment, seg­ mental biomechanics, the nervous system, and end-organ function (see Fig. 8-9). As conceptualized through this model, the biomechanica! changes influenced by spinal manipulation are thought to have physiological consequences by means of their effects on inflow of sensory information (via paraspinal sensory receptors, see Fig. 8-9, 1) into the central nerv­ ous system. Muscle spindle afferents and Golgi tendon organ afferents are stimulated by spinal manipulation and smaller-diameter sensory nerve fibers are likely activated. Mechanical and chemical changes in the intervertebral foramen (see Fig. 8-9, 2) may result from a herniated intervertebral disc affect­

ing the dorsal roots and dorsal root Whereas the direct effect of Illanipula' these changes is not understood, indi~ with herniated lumbar discs have shown improvement in response to spinal m tion/adjustment. The phenomenon of central facilita' central sensitization (see Fig. 8-9, J) described as an increased excitability of horn neurons within the spinal cord due sistent aberrant afferent input, is kn increase the receptive field of central enabling either subthreshold or nonnoxious uli access to central pain pathways. It is that spinal adjustment/manipulation' pain tolerance and/or threshold of ex

CHAPTER 8

Neurobiologic Relations and Chiropractic Applications

181

IStructural dysrelationship I

t

I Mechanical overload I

1

1"

Parasplnal

sensory receptors

c

~

)( ~

2

'I<

II

Nerve roots in intervertebral foramen

Stimulated by and/or sensitized to vertebral motion, compression, and endogenous metabolites

:0 ~

(/J

Group I and II afferents

Group III and IV afferents

and

/S'

Central

31 facilitation

iI t Pain, tenderness, altered paraspinal muscle tone. altered vertebral movement and abnormal reflexes responses 4

Somata-somatic reflexes

8-9 Atheoretical model showing components

thll!

II

Somata-visceral reflexes

5

describe the relationships between spinal manipulation,

ental biomechanics, the nervous system, and physiology, The neurophysiological effect of spinal

pu]ation could be mediated at any of the numbered boxes.

mechanism underlying the effectiveness of pulalion may be the effect of altering censensory processing by removal of subthreshmechanical or chemical stimuli from the pinallissues. Spinal manipulation/adjustment is proposed affect reflex neural outputs in both muscle Fi~. 8-9, 4) and visceral organs (Fig. 8-9, 5). manual procedures evoke paraspinal mus­ rellexes and alter motorneuron excitability cing both excitatory and inhibitory effects. s il is known that sensory input, espe­ • noxious irritants, from paraspinal tissues refleXively elicit sympathetic neural activ­ the understanding regarding the effect of IpulationJadjustment on somato-visceral es and visceral end-organ function is lim­

It Is difficult to know which operational mod­ or combination of hypotheses provides the plausible explanation for the effects of 081 adjustive procedures in a given clinical ion, What is known is that a close interface between spinal biomechanics and nerve

function and that additional basic and clinical research will assist in understanding the mecha­ nisms affected through the intervention of spinal manipulation and the adjustive techniques.

Review Questions 1. Discuss the anatomic differences among

2.

3.

4. 5.

the intervertebral foramina in the cervical, dorsal, and lumbar regions. How do these differences influence the relevance of the nerve compression hypothesis for these three areas?

What was a flaw in Crelin's attempt to

refute chiropractic claims regarding spinal nerve pressure? How might the presence of transforaminal ligaments affect the course of a back pain patient's recovery? Discuss the knee-jerk reflex as an example of a somatosomatic reflex. Identify two studies that prOVide clinical

support for the assertion that chiropractic

adjustments effect somatovisceral reflex responses.

182

PART TWO

ANATOMY. BIOMECHANICS, AND PHYSIOLOGY

6. What is the significance of Pikalov's study on duodenal ulcers? 7. Discuss Seaman's theory of joint

dysafferentat ion.

8. What are some arguments for and against Nansal and Szlazak's presentation on somatic viscera I disea se si m u lation? 9. How does axoplasmic transport differ from nerve impulse transmission? 10. What are Lewit's four explanations of verte brovi Scera I co rrelation s?

1. If a patient's visceral symptoms disappear after a chiropractic adjustment, does this mean that the adjustment cured or relieved a visceral disorder? What other possible explanations exist? What kind of evidence is necessary to justify a claim that chiropractic did in fact bring resolution of a visceral disorder? 2. How might enhanced cooperation between chiropractors and medical physicians benefit patients with visceral symptoms? 3. In the Wiberg, Nordsteen, and Nilsson study on infantile colic, the authors noted that "... manipulation is normally used in treatm ent of m uscu loskel eta I disorders, and the results of this trial leave open two possi bl e i nte rp retations. Either spi na I manipulation is effective in treatment of the visceral disorder infantile colic or infantile colic is, in fact, a musculoskeletal disorder, and not as normally assumed, visceral:' Of the theories discussed in this chapter, which may best describe the observations in this study?

REFERENCES 1. Meeker WC, Haldeman S: Chiropractic: a profession at the crossroads of mainstrl:aru and alternative med­ Icine, Ann Tnt Med 136(3):217,2002. 2. Vernon H: Basic scientific evidence for chiropractic subluxation. In Glltterman M, ediror: Foundations of chiropractic.- subltlXation, St Lou is, 1995, Mosby. 3. Harrison DE et al: A review of biol11echanlcs of the cenlral nervous syStem. Part I: spinal canal deforma­ tions due w changes In posture, J Manipulative Physiol Ther 22(4):227, 1999. 4. Harrison DE et al: A revIew of biomechanics of the central nervous system. Part II: slmins in the spinal

cord from postural loads, J Manipulative Ther 22(5):322. ) 999. 5. Harrison DE et al: A review of biomechanictl central nervous system. Part III: neurologic stresses and strains, J Manipula.tit'e Phj'sill/ 22(6):.1')9, 1999. 6. Haldeman S et al: Spinal manipulative the Frymoyer JW, editor: The adult spine: p' and practice. vol 2, Philadelphia, 1997, Li Raven. 7. Lopes MA, Plaugher G: Vllrtebral subluxation In Plaugher G, ediror: Te..wbook oj clinical c ' tic: a specific biomechanical approach, }993, Williams and WilluJls. 8. Peterson DB, Bergmann TE: Chiropracl.ic~ prirlciples and procedures, ed 2, St LQuis, Mosby. 9. Leach RA: The chiropractic theories, princi clinical applications, ed J, Baltimore, 1994, ~ & Wilkins. 10. Osterbauer PJ: Technology assessment of the practic subluxation. In Mootz RD, Hansen DT, Thpics in dinicaJ chiropractic series, tic technologies, Gaithersburg, ~ld, 1999, Puhlishers. 11- Marsarsky CS, Todres-Masarsky M: Sub and the special senses. In Marsarsk)' CS, Masarsl\y lvI, editors: SomatO'l)isceral aspec~rI practic.- an e
ropractic-the chiropractor's ad:illster, 1910, Portland Pri nti ng House. 14. Palmer BJ: The science 0/ chiropractic-ita pies and philosophies, vol I, Davenport, 10 Palmer 8cl1001 of Chiropractic. 15. Bllatty HG: Anatomical eu(justing techn' Denver, 19J 7, (seLf-puhlished). 16. Firth IN: A textbook on chiropractic s) ogy, Rock {sland, J1I, 1914 (self.published), 17. Forster AL: P.rinciples and practice oj spilllll ment Jor the use oj students allli . Chicago, 1915 (self-published), 18. Laban JM: Technic and practice oj chi Davenport, Iowa, 1912 (self-published). 19. Janse J, Houser R, Wells B: Chiropractic and technic, Chicago, 1947, National Chi ropractic. 20. Cleveland CS Sr: Chiropractic principles rice-outline, Kansas City, 1950, Clel'elaacl practic College. 21. Kent C: Models of vertebral subluxation: a Vertebral Subluxation Res 1(1): 11, 1996, 22. Cramer G, Darhy 8: Anatomy related to luxation. In Gatterman M, editor: foUl chiropractic:: subluxation, St Louis, 1995,

Nociceptors, Pain,

and Chiropractic

Geojfrey M. Bove, DC, PhD, Rand S. Swenson, DC, MD, PhD

Key Terms,

_

AFFERENT

LONc-TERM DEPRESSION

ONGOING ACTIVITY

ALLOIJY:-.IIA

LUMBAR FACET

OPIATES

AXON REFLEX CO\,OliCTJON VELOCITIES

ORTH:OPEDIC TESTS

SYNDROME

M ICRONEUROGRAPHY

PAIN

EFFERENT

NER% SHEATH

PLASMA E}"'"TRAVASATJON

ENDOGENOlS OPIATES

NERVI NERVORUM

RADIATING PAIN

EI\'DORPJIIl\

NEURITIS

RADICU LO PAT I-I Y

NEUROCENIC INfLAMMATION

RECEPTIVE FIELDS

GROliP

IfI

GROUP

IV NOCICEPTOR

NOCICEPTOR

HYPERALGESIA LONG-TER\1

POl'E:-.ITlATION

NOCICEPT)ON

REFERRED PAIN

NOCICEPTIVE

SENSITIZ,\TION

NOCICF..I'TOI{

WINDUP

NoxIous STIMULUS

P

ain and its relief are critical to the chiro­ practic profession. Chiropractic doctors lid ludcnts need a strong background in the concepts of the neurophysiology underly­

"pain, The purpose of this chapter is to pres­

lIund clarify issues related to tbe basic science i~n and to direct the reader to more com­ fIele works on the major issues in pain physiol­ ICY and control. All of the information in this i1apter is clinically relevant, although it may tllseem so on first reading. If the reader perse­ , the final section will be very rewarding, ~use the concepts presented will aid in rslanding the reasons patients seek care will also proVide a clinical rationale for chi­ qrraclic trcatmen t. First, pain and several associated terms are 00. Subsequent discussion considers the 1elements involved in pain, describing anatomically and functionally. An overview lite changes in the central nervous system noxious stimuli is prOVided, and an intro­ 'on to 'the psychology of pain is offered.

Finally, an example is given that demonstrates

how these basic scientific concepts fit with the

day-to-day practice of cbiropractic.

"Ie

DEFINITIONS Taxonomy is important for any discipline, and discussions of pain are most frUitful when appro­ priate terms are used. The following terms have been defined by a committee of experts from diverse specialties, in association with the International Association for the Study of Pain (IASP), and the definitions are used wit.h per­ •.

miSSIOn.

1

Pain. An unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in tenus of such damage.

BiologiSts agree that pain is a sensation; however,

because it is unpleasant, it is also emotional.

Thus the foundation of this definition is that pain is always subjective and mayor may not have an objective component. It is possible to

187

188

PART TWO

ANATOMY. BIOMECHANICS. AND PHYSIOLOGY

have pain without peripheral noxious stimuli; the definition purposely avoids linking pain to any specific stimulus. Therefore each individual defines pain on the basis of his or her experi­ ences, usually related to injury. However, a report of pain in the absence of apparent cause cannot be dismissed, because central mecha­ nisms, including psychologic factors, are often sufficient to cause pain. Nociception. Activity in a neural structure considered capable of leading to or contributing to a sensation of pain. Nociception is objective because the activity in nociceptive neurons and axons can be meas­ ured, at least in the laboratory. Nociception does not necessarily lead to pain, especially when the nociceptor activity is found in the peripheral nervous system. To cause pain, the nociceptor activity must be of sufficient intensity or fre­ quency to activate central elements of tbe noci­ ceptive pathways. Noxious stimulus. Noxious is defined as harmful, and a noxious stimulus is defined as a stimulus that damages, Or even potentially damages, nonnal tissue. Unfortunately, there are stimuli that are noxious by this definition that are not painful, such as radiation injury and cutting the wall of a normal small intestine, but there is no descriptive term for this subset of noxious stimuli. Nociceptor. A receptor preferentially

sensitive to a noxious stimulus or to a

stimulus that would become noxious if

prolonged.

A nociceptor is a sensory stmcture that senses noxious stimuli; in response, it generates neural activity to communicate to the central nervous system that a potentially hannfuJ stimulus has occurred. Terms like pain sensor or pain recep­ tor have been applied to nociceptors, but they should be avoided. Some nociceptors have been reported to respond to nonnoxious stimuli as well, but this discussion falls outside the scope of this text. Nociceptive. Although not defined by the IASP, this adjective is often misused to modify stimulus. A stimulus cannot be nociceptive, but it can be noxious. However,

a nociceptor is considered to be nocice when activated. Allodynia. Pain due to a stimulus which not nonnally provoke pain. Pain as a result of a stimulus that does not malty cause pain is termed allodynia. Allod) is the loss of specificity of any sensory m such as light touch or thermal sensitivity, the final perception being pain. Examples mechanical allodyn ia are the pain of light b ing when the skin is sunburned and the caused by lightly squeezing a muscle the after unaccustomed exercise. Hyperalgesia..An increased'or prolonged response to a stimulus which is normally painful. Hyperalgesia is distinct from allodynia. W allodynia, the modality of stimulus (such light touch), differs from dIe perceptual m ity (pain). In hyperalgesia the modalities the same, but the intensity of the perception greater. Both hyperalgesia and allodynia commonly experienced simultaneously. In clinically, tbe use of the term hypersensirifJitJ often more appropriate to avoid possible m nistic implications of hyperalgesia versus aU nia. Although rare, certain conditions destroy pain nerve fibers in an area while lea touch and pressure sensors intact. In such the patient may not be sensitive to pin stimulation that is commonly used to test pain pathways, but a simple touch may pr an intensely unpleasant sensation. The common clinical example of this occurs in cases of postherpetic neuralgia (most cases both hyperalgesia and aJlodynia). Radiating. referred, and radicular pain. These terms are often used incorrectly, perhaps because published definitions are rare. A requirement of radiating pain ist the symptom is perceived to radiate away from the site of the pathology or the site of presumed patbology. Radiating pain can follow pathology of any component of the nervous system. Radicular pain is resen'ed for pain due to pathology of one or more nerve roots (the Latin word for nerve rool radix, hence the word radicular). Radi pain is perceived distal to the pathology

CHAPTER 9

onged ormaUy

pain. ecdy, ions are laill is that lte away he site pain can It of the s reserved ,r more ~rve root i Radicul hology o

Nociceptors, Pain, and Chiropractic

8IId is thus a subset of radiating pain. Radicular pain has also been termed projected pain, because the pain is perceived to be spccificaHy localized to the distal ental distribution of the aJfected nerve lOOt (Fig. 9·1). leferred pain is reserved for symptoms that occur in portions at' the body that are DOl directly innen1ated by damaged nerves ornerve roots. Thus the arm pain that often occurs with angina is referred; the cause of the amI pain is thought to be that the sensory nerve from the heart muscle and mn project to similar areas in the central ner..ous system; thus under some circumstances, an inappropriate "spillover" of neuronal activation occurs. Clinicians are urged to use the term referred pain sparingly, unless they are confident that !here is no pathology in the peripheral nervous system.

189

NOCICEPTORS Primary Afferent Nociceptors Nociceptors serve a primordial function for an organism, providing infonnation about harmful or potentialJy harmful events that may cause loss of function or life. Even simple organisms essen­ tially have nociceptive function. For example, protochordates display the coihng reflex, a with­ drawing from a noxious stimulus. 2 Through evo­ lution, this defense mechanism was conserved and refined, although the basic function of sig­ naling harmful events remained unchanged. The importance of nociceptors is reveaJed in rare cases in which children have been born Without nociceptorso These children are constantly being injured and often die from complications of minor infections or trauma. Similarly, rats whose noci­ ceptors have been destroyed by neonatal treat­ ment with capsaicin have a short life span and are always bmjsed and incautious.

rv. 9·1 Innervation patterns (left wright) of peripheral nervt!S, dermatomes, myotomes, and sclerotomes are DIlIIIJl3red. Symptom descriptions by patients, including depth of sensation and location, are invaluable to is. 1 and 2, Supraclavicular nerves; 3, axillary; 4, intercostohrachial and intercostals; 5, llledial brachial eraneous; 6, posterior brachial cutaneous; 7, medial antebrachial cutaneous; 8, lateral antebrachial cutaneous; t 1Idial; 10, median; 11, ulnar. (Dermatomesfrom Foerster 0: The derrnatornes in man, Brain 56:1-39, 1933. ~omes and sclem/ames 1 edrawn and used 'With permission. Inman VT, Saunders JBcIM: Referred pain "slwlelul Slrlie/UTeS, J Nen'e Ment Dis 99:660-667, 1944.) 0

190

PART TWO

AJ~ATOM'l.

BIOMECHANICS.

On a moment-to-moment basis, nociceptors signal that a stone that needs removing is in a shoe, that the time to go to the dentist has arrived, or the time has come to shift from a position tJlat may cause a leg to "go to sleep" (possible beginnings of sciatic or peroneal neu­ ropathy). Inflammation causes pain that is per­ ceived, in part, through activity of nociceptors responding to chemical mediators released by the process. In general, nociceptors exist where it makes sense for them to be, which is any­ where that the organism may be subjected to harmful stimuli. Nociceptors in the peripheral nervous sys­ tem are pseudounipolar dorsal root ganglion neurons with unmyelinated or thinly myelinated axons (Fig. 9-2, A). The unmyelinated axons are referred to as C-fibers, with conduction velocities of less than 2.5 mlsec; and tbe thinly myelinated axons are referred to as Ao-fibers, with conduction velocities of 2.5 to approxi­ mately 15 m/sec. 3 An unfortunate nomenclature exists regarding cutaneous and noncutaneous nociceptors. Cutaneous nociceptors are called C-nociceptors when they have unmyelinated (C-fiber) axons or Ao-nociceptors when they have thinly myelinated (Ao-fiber) axons. Nociceptors innervating deep structures such as muscle and joint are called Group IV or Group III nodcep­ tors. Group IV nociceptors have unmyelinated axons (C-fibers), and Group III nociceptors have thinly myelinated axons (Ao-fibers, Fig. 9-2, B). To make things slightly more complicated, the ceotraJly and peripherally projecting a..xons from a nociceptor cell body can be of a differ­ ent caliber, and an individual A-fiber can thin to a C-fiber caliber as it passes distally.4,s This ter­ minology is presented in this text because it will be encountered in tlle literature. Cutaneous C- and Ao-nociceptors are typi­ cally discussed as subserving slow andfast pain function, respectively. These functions may have some physiologic and clinical differences, with C-nociceptor activity being more likely to give rise to burning or aching sensations a.nd Ao-nociceptor activation to better-localized sharp, stahbing, or pricking pain. However, sig­ nificant overlap in function occurs. Furthermore, this differentiation was determined from studies

A.t~D

PHYSIOLOGY

A

B

Fig. 9-2 A. Dorsal root ganglion section is labeled with a sodium chaJUlel antibody. The single pseudounipolar axon leaves a primary afferent neuron (arrow) to branch into peripheral and centrally projecting processes (nol on sectlrm). axon is approximately 4 Mm in diameter and thus classified as an Ao axon; scale bar'" SO lim, seclkG 11m thiclL B. Electron photomicrograph of ac section of a nerve branch is demonstrated within cranial dura mater. Individual C-axons (a1TfJWs) less than 111m in diameter and are, with their neighbors, combined by one SchWalm ceU into a Remak bundle. Myelin sheath of an Ao axon is demonstrated (arrowhead); scale bar =2 Jim. :0

(Image courte..<;y Dl·. Andrew Strassman.)

of cutaneous innervation, and this distin may not apply to pain in subcutaneous f Althougb several subcategories of nocice exist, a discussion of these is beyond the of this text, and the reader is referred to lent reviews by Cervero, Kumazawa, Mense, Schaible. 6-9 For the purposes of this text,a11 categories of nociceptors are considered t under the heading nociceptor. The distal projection of nocicepti\'e ne tenninates in what has historically been

section is labeled The single imary afferent >eripheral and ~ot on section). Th liameter and thus Ir '" 50 111ll, section icrograph of a cro IOnstrated within th -axons (arrows) are are, with their lwalln cell into a , an Ao axon is Ie bar'" 2 11m.

CHAPTER 9

191

Nociccptors. Pllil;l, and Chiropmctic

jree-,leT'VC ending. This unfortunate term implies • nonspecialized structure. The anatomic spe­ cialization of these terminals remains elusive, especially for C-fiber llociceptors. However, the terminals are sufficiently specialized to discrimi­ nate among mechal1ical, chemical, and thennal stimuli, or they may respond to all these stimuli, depending on the type of nociceptor. The termi­ nals of cutaneous nociceptors usually split InlO numerous small branches in the skin, yield­ Ing one or more very small (<1 mm 2) points on Ihe skin surface at which they respond most strongly. A zone of lesser sensitivity usually sur­ rounds these points. The receptive fields of noci­ ceptors in subcutaneous tissues have sim.ilar properties bllt branch more freely, thereby having more complex receptive fields,1o These fields could be partially responsible for the rela­ tive difficulty in localizing deep, painful stimuli (Fig. 9-3). As implied by the preceding definitions, the simple anatomic presence of small nerve fibers ending in free-nerve endings does not prove that the structure is a nociceptor; a number of proce­ dures are needed for confirmation, discussed briel1y below. It should be kept in mind that SIons belonging to the autonomic nervous sys­ tem are also unmyelinated (C-Bber), but they ba\'e purely efferent functions. Afferent fibers that are intermingled with autonomic nerves, such as those accompanying splanchnic nerves, are not part of the autonomic nervous system; they are simply following a convenient path to their innervation target. For the most part, their ceO bodies reside in a dorsal root ganglion, and

they are part of the peripheral nervous system. Some of these neurons are probably nociceptors. The skin is the largest organ in the body and most subject to external stimuli. It follows tJIat the s]
Tlssman.)

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FIg. 9-3 Schematic of primary afferent innervation pattern. 1Wo neurons are depicted, one innervating skin (A) and the other innervating deep structures. The cutaneous neuron extends to one area of the skin, and the deep neuron branches extend to innervate muscle (B), tendon (C), and even the nerve in which it passes (D). Both neurons are depicted as extending to a single neuron in the dorsal horn, which would be tenned a wide d)'lIQmic range neuron.

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functional testing using specific stimuli is usu­ ally necessary to prove that the nerve fiber or neuron is indeed nociceptive. Knmvledge of nociceptors for different. tissues varies. For instance, much is known about the nocioeptors innervating skin; less is known about subcuta­ neous and visceral nociceptors. Interestingly, functional information on the innervation of paraspinal tissues is soarce. Only relatively recendy have studies shown a substantial noci­ ceptor population, supporting these stnlCtures as potential pain sources. 10,12.17

How Nociceptors Are Studied Nociceptors can be studied in a variety of ways in humans and animals. In humans, testing can be as simple as applying a stimulus and getting a subjective report from the subject. However, because the stimuli that are known to evoke responses from nociceptors also evoke responses from mechanoreceptors and often thermorecep­ tors, the results are somewhat nonspecific. Capsaicin, the hot ingredient in peppers, has gained popularity for use in experimental studies because it is fairly specific for activating noci­ ceptors. Numerous studies of the psychophysical parameters of pain have used subdermal injec­ tions of capsaicin to activate nociceptor termi­ nals. Tn animals, the selective response of a nociceptor terminal to application of this chem­ ical has been used as eVidence that the receptor is a nociceptor. Studying the response of individual nocicep­ tors is possible in both animals and humans. In

Table 9-1

animals, a nerve can be exposed and small nefl'e filaments (S to 15 Ilm) can be carefully teased apart and placed over electrodes connected to amplification and recording devices. This proce· dure isolates a small population ofaxons, \\;th the process being repeated until only one neuron or axon is found to be active. The recepti\'t field(s) and sensitivities of this neuron or axon are then determined. In humans, a similar process, called microneurography, can be per· formed. Fine needle electrodes are placed uuo nerves, and the receptive fields of identified ax OilS are characterized. Yet another process in animals uses microelectrodes to record irom individual oells in ganglia. In this case, a fine electrode is advanced into the ganglion, and used (0 record the electrical activity of individ· ual cells. Much of the information that 1'011 Oil'S was gathered using methods similar to these.

Acid and potassium Prostaglandins Leukotrienes Bradykinin Histamine

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CHAPTER 9

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Nociceptors, Pain, and Chjropractic

nociceptors that have already sustained some injury, These substances have been tested on

animal and human nociceptors in a variety of preparations20 and can evoke discharge from indi­ lidual nociceptors, calise behavioral changes, and e\'oke reports of pain. Among the cytokines, the best studied are tumor necrosis factor-alpha (T~T-a) and interleukin lop, which are released irom llumerous celis during immune-mediated inIlammation. When injected into the skin, these chemicals are noxious. 21 \Jv1Ien TNF-a is placed 0113 peripheral nerve, nociceptors develop ongo­ ing discharge,22 and rat feet demonstrate allody­ nia.2.J Although individual chemicals will elicit responses from varying populations of nocicep­ tors, the combination of mediators, found in vivo, is most effective. In diseased or damaged tissue, the properties oj nociceptors may change. In a phenomenon called sensitization, they develop ongoing activ­ kyo along with a decrease in the thresholds to IIOIious stimuli and an increase in the size of receptive fields. The effect can occur with even abrief stimulus and can last for hours. 24 In skin, Ibis effect is observed in response to bums, even • small-sized burn. The spontaneous pain and cased sensitivity of the damaged area is mediated by sensitized nociceptors, though other types of receptor may also be active and p1a~' a role during injury. Sensitization has been shown to occur in both nociceptors from cuta­ neous and deep tissues, but the full mechanism of the process remains poorly understood. Stimulation of sympathetic nerves can affect nociceptors in certain situations. Normally, noci­ l:eptors may be sensitized by sympathetic stim­ u1ation/s,26 but they do not directly respond roinereased sympathetic activity or to the appli­ cation of norepinephrine. Zi ,2S However, during ehronic int1ammation or after nerve injury, S)'DIpathetic stimulation can directly activate G-ftber nociceptors. 29 -33 Pain and psychologic iressors increase sympathetic discharge, lead­ Ing to increased levels of norepinephrine. 34 -36 This well-known response provides at least a plrtial explanation for the clinical observa­ ~s that redUCing psychologic stress responses may decrease pain and facilitate a more rapid

193

At the beginning of tlle twentieth century, jt vas discovered that electrical stimulation of dorsal roots caused cutaneous vasodilation and plasma extravasation whenever the stimulus intensity was high enough to excite unmyeli­ nated fibers. 3i This response was termed the axon reflex. Later, this neurally controlled and reflexive release of initiators and inflammatory mediators was termed the nocifensor system. 38 More recently, the nerves contributing to the axon reflexes were found to be nociceptors,:l9 strongly suggesting that nociceptors have both sensory and efferent functions. Calcitonin gene­ related peptide (CGRP) and substance P (SP), which are co-localized in the nociceptor termi­ nal (Fig. 9-4), are the two most important medi­ ators that these nerves release. ~O·'12 Substance P and CORP are potent vasodilators, and CGRP potentiates the effects of SP.~J·48 Moreover, SP contributes to nociceptor sensitization 49 and is thought to participate in tbe immune response. 50 Electrical stimulation of nociceptor axons any­ where along their course will CHllse the release of these peptides from distal terminals, result­ ing in a focal inflammation, termed neurogenic inflammation . Nociceptors may be essential for an animal to mount an int1ammatory response through neurogenic iutJammation. For example, it has been shown that tlle development of peripheral experimental arthritis is at least in part depend­ ent on the presence of afferent innervation. 51 Additionally, the severity of experimental arthri­ tis is reduced in animals depleted of nocicep­ tors tb rough neo natal injection 0 f capsaiei n. 52 Finally, the increased cerebral blood flow as a result of meningitis is greatly attenuated by denervation of tbe primary afferents innervating the intracranial structures. 53 These lines of evi­ dence support a critical role of nociceptors in the organism's response to injUry. Although the role of nociceptors in neuro­ geoic inflammation is undisputed, less is known about the role of the sympathetic nervous sys­ tem in this process. However, sympathetic nerves are clearly important to the generation of experimental inlmune arthritis. They are also known to participate in the localized edema that occurs in certain models of chroniC neuropathic

194

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ANATOMY, BIOMECHANICS, AND PHYSIOLOGY

Fig. 9-4 Release of substance P and calcitonin gene-related peptide (CGRP) by primary afferent nociceptors. \\lnen an appropriate stimulation elicits an action potential, the action potential is propagated to the central nervous system and to other branches of the neuron (arrows). Simultaneously, the endings release substance I' and CGRP (small closed and open symbols) from the terminals, which are co-localized in vesicles that are transported from the ceU body. This process is thought to occur in terminals that are invaded by the action potential even when they are not directly stimulated. Substance P and CGRP cause plasma extravasation and vasodilation, respectively, which are necessary components of the inflammatory response. This process is termed neurogen'ic 'ilIflammation.

pain. This participation may explain why stress­ ful situations may exacerbate int1ammatory con­ ditions and increase pain.

Differences between Deep and Cutaneous Nociceptors AJthough most studies of nociceptors have been performed on skin, few clinically important pain conditions exist that primarily affect the skin. Even among conditions felt in the skin, most are neuropathic (the term neuropathic refers to a nerve pathology or functional disturbance of a nerve or some axons within a nerve) and may not involve cutaneous nociceptors at all. CUUmeous neuropathic pain is very possibly mediated by sensitization of neurons that are normally not responsive to noxiolls stimuli, sllch as neurons that respond to light touch. Recently, the authors of this chapter interviewed 25 peo­ ple with diagnoses of lumbar radiculopathy (Le., radiating pain due to a pathology of one or more dorsal roots). The participants were asl{ed to identify the perceived location of the radiating leg pain. In every case, tlle pain at rest and the pain evoked during a straight leg raise test were reported to be "deep" rather than "on the skin."

Thus studies of cutaneous nocicept.ors may nOI be fully applicable to deep nociceptors. Indeed. studies that have compared nociceptor sensitiv­ ity by innervated structure have shown criticti differences. The response to pinch was found 10 be dramatically great.er after a stimulus dellv· ered to a muscle nerve rather than to a cuta­ neous nerve. 54 Deep nociceptor aXOllS also seem to respond differently to inflammation. Durint neuritis, or nerve inflammation, axons of deep nociceptors become mechanically sensitive, whereas cutaneous nociceptor axons do not. li The percentage of deep nociceptors that develop ongoing activity during neuritis is also greater than their cutaneous counterparts. After axonal damage, recordings from nociceptors in muscle nerves reveal ongoing discharge more often than do recordings from cutaneous neurons. 56.51 These data point to fundamental differences in deep versus cutaneous nocicept.or physiology.

Neuronal Response to Injury When their peripheral a:wns are injured, the central projections of myelinated and unmyeJi. nated dorsal root neurons can sprollt into \\1 territories in the spinal cord. 58,59 The sprou'

CHAPTER 9

s.

Nociceptors, Paio, and Chiropractic

of presumably nociceptive terminals in the superficial dorsal horn could explain hyper­ algesia, because the discharge of an individual sensory axon would be transmitted to more sec­ ond-order neurons, with their sum predictably leading to an increased perception of pain. The sprouting of larger fibers, usually nonnocicep­ tive, into the laminae (layers) of the spinal cord, which is usually reserved for nociceptor input, may explain aUodynia, because their discharge may now activate nociceptive neurons. Indeed, possibly the allodynia that often accompanies chronic regional pain syndromes is mediated by myelinated fibers. 60 ,61

Spinal Cord Projections of Nociceptors

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Xociceptive dorsal root ganglion neurons project into the dorsolateral portion of the spinal cord where they branch T-wise, sending branches 1 through 5 segments rostral and caudal (1 to 2 for C·fiber nociceptors, 1 through 5 for Ao-nocicep­ tors).62 The region of the spinal cord white mat­ ter located adjacent to the dorsal horn that contains these ascending and descending fibers has been termed the Lissauer's zone. C-fiber noci­ ceptors ultimately terminate in the dorsal horn in the most dorsal part of the dorsal horn, termed laminae I and ll,6J whereas Ao-nociceptors addi­ tionally project to laminae V and X. 64 Most dor­ sal horn neurons are classified as wide dynamic range, which means they respond to both nox­ ious and innocuous stimuli, with more intense and Widespread stimuli producing greater acti­ vation (see Fig. 9-3). A smaller percentage of dorsal horn neurons, particularly located within the most superficial laminae of the dorsal horn, are nociceptive specific. It is believed that the nociceptive specific neurons are more impor­ tant (0 signal the presence of pain and its pre­ cise location, whereas the wide dynamic range neurons are more important to the recogni­ tion of intensity of pain. Nociceptors from the limbs terminate ipsilaterally. However, para­ spinal tissue nociceptors project bilaterally to dorsal horn neurons. 65 ,66 This projection pre­ dicts the typically poorly defined nature of back pain and emphasizes the need for bilateral spinal examination.

195

Molecular Changes in the Spinal Cord Related to Nociception \Vhell nociceptors are stimulated, their central terminals release SP, CGRP, and glutamate onto spinal cord neurons. Besides transmitting infor­ mation to these high-order neurons, genes in second and higher order neurons increase their expression of some proteins. With even a brief stimulus, some genes are known to be upregu­ fated. The c-fos and c-jun genes have been intensely studied, and their protein products can be visualized indirectly using immunohisto­ chemical techniques. Studies using these tech­ niques have confirmed the projection of the nociceptive primary afferents, though t.he stimuli used are not usually specific for nociceptors. 67.69 The protein products of c-fos and c-jun initiate a cascade of biochemical reactions in the neu­ rons, result.ing in the production of enkephalins and dynorphin (endogenous opiates) in the cen­ tral nervous system (see the follOWing text). 70 Enkephalin is an inhibitor of dorsaJ hom cells, but dynorphjn is known to have variable responses, inhibiting one third of neurons, sensitizing ODe t.hird of neurons, and increasing the receptive fields of many spinal cord neurons. 71 ThiS effect could also contribute to hyperalgesia :mJ to chronic pain, as well as to their modulation. The generation of neuronal action potentials requires the opening and closing of numerous ion channels. An electrical charge passing through these channels changes the membrane potential, and if this is changed enough, the neu­ ron will generate an action potential (for details, see allY neurophyslolog~ text). Alteration in the number and type of ion channels will change the resting potential and excitability of the neu­ ron. For instance, an increase of tonically open sodium channels or a decrease of tonically open potassium channels would be expected to depolarize the membrane. A depolarized mem­ brane reqUires less additional depolarization to induce an action potential; a neuron that had sucb changes in ion channels could be consid­ eredfacilitated. Evidence is building that in pathologic states, dorsal root ganglion cells undergo numer­ ous changes in the expression of ion channels,

196

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ANATOMY, BIOMECHANICS, Al'ID PHYSIOLOGY

especially sodium channels. Sodium channel expression has been reported to change after axonal injury and during inflammation (reviewed by Waxman et a!. 72), and some of these channels have also been -linked to pain. 7J -76 Increased cation channel production may lead to increased insertion in axonal membranes and axonal hyper­ eXCitability. Such changes were proposed to account for the recovery of mechanical sensitivity in the tips of preViously cut mechanoreceptive axons. 77 ,78 Increased cation chaJlllel production was also proposed to lead to ongoing activity in sensory neurons from muscle, but not from skin, after damage to neighboring axonsY

Central Mechanisms Related to Nociception Nociceptors are not the only neurons active in response to painful stimuli. In a classic study, Adriaensen and collea,gues 79 demonstrated that sustained pinch of the skin led to increasing reports of pain with time, whereas the neural dis­ charge from nociceptors supplying the area actu­ ally decreased. Explaining this paradox is difficult, but other nociceptors are probably recruited and the spinal cord and higher centers are chang­ ing their "gain" (I.e., amplifying the signal) in response to the input from the nociceptors. Substantial evidence suggests that peripheral noxious stimulation leads to changes in the cen­ tral nervous system, collectively called spinal cord plasticity (for reviews, see Coderre,so Woolf,S I and Chen et a1. 82 ). These changes lead to sensitization of central nervous system neu­ rons and may result in hyperalgesia, allodynia, and spontaneous discharge of neurons. Under some conditions, these symptoms may be sus­ tained even if the sensory input from the origlnal source is terminated. All of the characteristics of stimuli that are capable of prodUcing these changes are not yet known, although some experimental models, such as ligating the sciatic nerve, readily produce long-term sensory facili­ tation. Additionally, because spinal cord neurons have receptive fields that converge from many tissue types (sometimes bilaterally),65 allodynia and hyperalgesia may be perceived very broadly from uninjured and even rather remote tissues.

[ndeed, these symptoms are observed among the plethora of acute and chronic back pain presen­ tations; central nervous system plasticity could help explain tllese variable presentations. '

Concepts of Plasticity The principal concepts of spinal cord plasticity include windup. loug-term potentiation (LTP), and long-term depression (LTD). A brief presen­ tation of these processes follows, and further details can be found in a review by l'ockett.&l Windup is a term that was coined for the phe­ nomenon of increasing the response of a spinal cord neuron to repeated stimuli. 84 When depo­ larized by the primary afferent neuron, dorsal horn neurons do not always fully recover their resting potential before tlie arrival of another volley from the primary afferent neuron. Therefore the threshold for firing of the neuron is lower (facilitated). This process typically lasts seconds to minutes. LTP is similar to windup, but it lasts much longer; indeed, some consider LTP to be pennaoent. This process requires a high-frequency conditioning discharge from the primary afferent neuron 85 and results in increased synaptic efI'iciency mediated by acti­ vation of a specific type of glutamate receptor, the N-methyl-D-aspartate (NMDA) receptor. It differs from windup in that the increased synap­ tic efficiency is not related to a change in tbe .resting membrane potential of the postsynaptic cells; rather, jt involves complicated changes Within the postsynaptic dorsal horn neurons that can best be described as a type of memory. For example, there are changes in postsynaptic receptor properties and possibly numbers. so These changes are accompanied by alterations in the expression of messenger ribonucleic acid (RNA), as well as in the expression of specific gene products. Once established, there is noth· ing known that will reverse LTP, except the induction of LTD. LTD can be eswblished by both high- and low-frequency conditioning stim· uli, and it involves a long-lasting decrease in synaptic efficacy (thus it is the mirror image oi LTP). Repeated episodes of Windup may possibly induce LTP or LTD, but tbis response has not been studied.

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CHAPTER 9

among the presen­ icity could ons. ~in

1 plasticity

tion (LTP), rid presen­ .nd further . Pockett. S3 )r the phe­ of a spinal {hen depo­ ron, dorsal cover their of another It neuron. the neuron ~ically lasts to windup, ~e consider requires a ~e from the results in :ed by acti­ tc recept.or, rcceptor. It ~sed synap­ Ulge in the ostsynaptic ~d changes 'n neurons of memory. ostsynaptic numbers. 86 alterations lUcleic acid of specific ~re is !loth­ except the Iblished by Dning stim­ lecrease in )r image of ay possibly se has not

Nociceptors. Pain. and Chiropractic

Hypotheticall);, LTP is at least partially respon­ sible for chronic pain; and, if so, LTD induc­ tion by stimulating an appropriate nerve may relieve it. 1k1 This mechanism may be behind the anecdotal effectiveness of various forms of clini­ cal electrical stimulation, but it remains to be demonstrated. Several additional mechanisms may be important to the changes that occur in the sensitivity of spinal cord pathways in pain syndromes. For example, the expression of inl1ammatory cytokines by the glial cells of the spinal cord increase during an experiment~tl model of nerve injury.s7 Indeed, the interactions between the two great communication systems In the body, the immune system and the nervous system, are substantially more complex and bidirectional than had been previously appreci­ ated. 88 .89 However, it must be remembered that the role of long-term changes that occur after experimental injuries, and indeed whether they occur in clinical problems in humans, remain to be determined. However, painful stimuli can IHlve potent and long-lasting effects on the func­ tions in the spinal cord and other levels of the nervous system.

Descending Modulation of Nociception The ability to perceive pain is critical to the sur­ vival and general well being of the individual. However, it is also important to be able to mod­ ulate pain. An example taken from common experience is the ability to "shal{e off' an injury that produces severe tissue damage until any immediate threat is past. At that time the pain may become severe or even immobilizing, although the injury itself has not changed. What, tben, explains this ability to modulate pain transmission and processing? The earliest hints as to the mechanisms behind pain modulation arose from studies of the most potent pain-suppressing drugs, the opi­ atesYo Receptors for opiates have been localized to several brain regions (notably the periaque­ ductal gray [PAG], dorsal hom of the spinal cord, ventral medullary raphe nuclei, and basal gan­ glia). Electrical stimulation of some of these regions (notably the PAG and raphe nuclei) was

197

found to inhibit nociceptive responses in ani­ maJs and produce analgesia in humans. 9 ! Of course, the presence of these receptors begs the question of why the nervous system would have specific receptors (apia te receptors) for an exogenous compound (opium). derived from a Middle Eastem poppy. Investigation of this question led to the discovery of a group of transmitters contained in small interneurons that bind to these receptors and activate them. These "endogl'nous opiates" consist of a famHy of very small peptides (enkephaHns) that are synthesized in small neurons of the central nerv­ ous system, as well as a larger compound (endorphin) that is found in the region of the pituitary gland and is released into the circula­ tion. Injection of these compounds into portions of the nervous system that have opiate receptors produces powerful analgesia. As previously dis­ cussed, these compounds are also directly pro­ duced by spinal cord neurons aJter intense activity of primary afferent neurons. It became apparent that some of the enkephalin neurons directly inhibit the pain transmission neurons in the dorsal horn of the spinal cord. For example, intense nociceptive input results in the release of enkephalin from the dorsal horn, providing at least a partial explanation for the inhibition of pain that can occur shortly after the onset of a powerful nox­ ious stimulus. However, that does not adequately explain the role of opiates at the level of the PAG, because the endogenous opiate contain­ ing neurons do not have axons that leave the PAG and also because the PAG does not have direct neuronal connection with the pain pathway. Further investigation revealed that the influence of PAG on pain transmission is rather complex, involVing excitatory projections from the PAG to the caudal medulla. These projec­ tions, in turn, excite descending projections to the dorsal horn that release norepinephrine and serotonin from their terminals in the spinal cord dorsal horn. Norepinephrine and serotonin, called mono­ amine transmitters, have complex effects at the dorsal horn, both by directly affecting the pain transmission neurons and by activating other neu­ rons at the spinal level (e.g., small enkephalinergic

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ANATO.MY, BIOMECHANICS. AND PHYSIOLOGY

intemeurons). Of course, in understanding this system tbe regions that connect with and thereby influence the PAG became important considerations. Many brain regions connect with the PAG, including the frontal and insular cor­ tex, amygdala, hypothalamus, reticular forma­ tion, locus ceruleus, and collateral branches of the spinothalamic tract. This connection illustrates tbe diverse brain regions that can play a part in regulating pain transmission. This descending system, based on the endoge­ nous opiates and monoamines, has become the best-known inhibitory circuit for pain modu­ lation. It defines the analgesic effects of opi­ ates, such as morphine, but it also explains at least some of the role that serotonin and nor­ epinephrine play in pain control. Despite the fact that descending inhibition is the best characterized of all pain-suppression mecha­ nisms (notwithstanding the known effects of various drugs on this system), less well known mechanisms are other physiologic factors that are capable of activating this potent pain-suppression mechanism. Although, undoubtedly, endogenous opiates playa powerful role in controlling pain, other inhibitory systems are also found in the nervous system. For example, gamma aminobutyric acid (GABA) is the most common inhibitory neuro­ transmitter in the central nervous systen,.92 Activation of GABAergic intemeurons appears to be at least one important mechanism of anal­ gesia provol{ed by the stimulation of large diam­ eter sensory nerve fibers (e.g., proprioceptive nerve fibers).9J Glycine, another neurotransmit­ ter, has a significant inhibitory influence at the spinal cord level with at least some of its effect produced by inhibition of excitatory neurotrans­ mission through :N1\1DA receptors. 94 This effect may be important not only in inhibiting the ini­ tial Signal but also in preventing the kind of LTP that can accompany activation of l\T1JDA recep­ tors. Recent studies have shown that activation of spinal facet joint receptors can powerfuUy inhibit the reflex effects of noxious stimulation of the spine. 95 Although the mechanisms of this inhibition are not known, the inhibitory trans­ mitters in the spinal cord represent prime can­ didates for investigation.

Psychology and Nociception \\lhy is it that two individuals can be injured in exactly the same manner, with dramatically dif· ferent results (at least in tenns of pain and suf· fering)? Although, undoubtedly, some of these different results are the result of the differences in the peripheral pain systems and the pain transmission systems in t.he central nervous sys­ tem, the experience of pain goes well beyond the mere activation of a nociceptor and the conduc­ tion of an impulse to the cerebral cortex. Pain is defined as an unpleasant sensory ami emotional experience. In addition, the issue 01 suffering, which is the behavioral and psycho­ logic component that is reflected in tlle patients outward affect, is expressed. The patient typi· cally describes his or her suffering as the conse· quence of the painful disorder. Although all of the mechanisms involved in suffering or in the psychologic ramifications of pain are not under· stood, several lines of evidence indicate that the frontal lobes of the cerebral cortex are critical in thiS regard. The first hints of tllis conclusion arose from the clinical evaluation of patients with frontal lobe injuries and those who had been subjected to frontal lobectomy. Patiems with frontal lobe damage can describe the inten· sity of a painful stimulus, indicating that the principal transmission pathways are intact; how· ever, they do not appear to suffer in proportion to the degree of pain. In such patients, both behavioral and autonomic responses to pain are blunted. Evidence suggests that some of the analgesic effects of some sedatives and antianxi· ety drugs may have their primary effect at the level of the frontal lobe rather than (or in addi­ tion to) affecting pain transmission through nociceptive pathways. Other lines of investigation have also directed attention to areas of the frontal lobe. These include experimental pain models that have been shown on functional magnetic resonance imaging to activate selectively specific portions of the frontal 10bes. 96 Additionally, it has been shown that patients with pain who were effec­ tively hypnotized to block the unpleasantness, but not tlle intensity of their pajn, showed changes in the anterior cingulate cortex (I.e., the medial portion of the frontal lobe).?7 It is interesting to

CHAPT~R

njured in Ically dif­ and suf­ of these ffercnces the p
9

Nociceptors. Pain. and Chiropractic

note that similar areas of the medial frontal lobes, particularly in the areas of the anterior cingulate and subcallosal gyri, havc been shown to be metabolically altered in certain affective disorders, particularly depression. It is we)] known that a complex interaction between depression and pain exists, and it would appear tbat at least some physiologic basis for this inter­ action is evident. Alt.hough much has been writ­ tcn ,lbout the capacity of depression to magnify pain, some evidence also suggests that. effective treatment of chronic pain is capable of amelio­ rating depression. 98 Most of the interest in cortical mechanisms of pain has been focused on the issue of sufferin~ rather than pain perception, and there is reason to believe that. behavioral factors might have some influence over pain transmission as well. For example, several studies indicate that placebo analgesia is real and is probably medi­ ated via endogenous opiate mechanisms. 99 Certainly, the connections between the frontal cortex and PAG (among other places) might pro­ I'ide the substrate for this effect, though the pre­ cise mechanisms remain unl<nowIl. Overall, there is good reason to believe that cortical mechanisms playa role in analgesia, and excel­ lent evidence suggests that suffering is a cortical phenomenon that is largely based in the frontal lobes. These findings provide some theoretical underpinning for behavioral interventions in pain management.

,sory and ~ issue of I psycho­ : patient's ient typi­ he conse­ .Igh all of or in the ot under­ ~ that the critical in Dnclusion : patients who had Patients the iuten­ that. the tact.; how­ roportion nts, both ) pain are Ie of the antifUlxi­ ~ct at t.he r iu addi­ t.hrough

Local Tissue Damage

) directed >e. These hat have 'esonance : port.ions has been ere effec­ tness, but I changes 11e medial resting to

Of course, local tissue damage can lead to pain through direct activation of the peripberal nerv­ ous system. Acute activation is usually second­ ary to direct activation of nociceptor terminals. Persistent pain can be the result of continued direct activation, the result of chemical excita­ tion by inflammatory mediators, or in some cases, maintained at least in part by the central nervous system. A few common sources of somatic pain need mentioning. First, the intervertebral disk has been blamed for most spinal pain, usually sec­

SOURCES OF PAIN

199

ondary to its ability to compress nerve roots when herniated. However, compression alone is not painful, and patients can recover from so­ called compressive radiculopathy without reso­ lution of the compression. 100 The source of pain is int1ammation induced by the discal pathology; when the intlammation subsides with healing, the pain also subsides. The inner part of the intervertebral disk is caIJed the nucleus pulpa­ sus and contains TNF-Cl. IOI \\Then released from the disk, this substance promotes an immune­ mediated in tlanuuation , which generates more local noxious chemicals. Persist.ent. pain from dil'cal herniation probably means tllat the disk is still releasing noxious material, maintaining suf­ ficient inflammation to sensitize the nociceptors in the neighboring tissues. Additionally, in older people the nucleus pulposus dries and therefore cannot herniate; consequently, the prevalence of disk-related pain also decreases with age. Chronic muscle pain also presents a problem. Two familiar incidences of muscle insult that lead to pain are conSidered: (1) injury as a result of excessive stretch during an automobile acci­ dent, and (2) pain after the overload of muscle dUring unaccustomed exercise. Although the acute stretch during an automobile accident is at least t.ransiently painful, pain during unaccus­ tomed exercise is not common. In both cases, symptoms start within 12 to 24 hours and ren­ der the muscle anodynic. Why, then, does tbe pain of an injury often persist, whereas the pain after ex.ercise resolves rapidly and without inci­ dent? In the case of accidental injury, nerves are damaged through stretch. In the case of nor­ mal exercises, nerve injuries are far less likely to occur, This major difference between these two scenarios appears to be the cause of the different results. Afferent activity of damaged or even intact but injured a..xons would be perceived as coming from the t..'l..rget muscle. ThiS could even be responsible for maintaining a low-grade int1am­ mation in the region through the neurogenic mechanisms preViously outlined. The authors of this chapter propose that persistent pain probably requires a source of persistent nociceptor activity, called a peripheral generator. Indeed, many cases of persistent severe pain will follow nerve injuries, especially stretch injudes.

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Although a complicated layering of connective tis­ sues protects the axons within nerves, the nerves can be damaged by direct trauma or stretch. (For further reading, see SWlderiand. 102) Such damage leads to mechanical, chemical, and thermal sensi­ tivity at the cut and regrowing terminal. However, it is not necessary for the axon to be completely intermpted for axonal injury and illtlammation to lead to action potential generation.

Radiating Pain Mechanisms Nerve injury and inflammation result in the per­ ception of radiating pain (radicular pain, if the nerve roots are involved). Neurobiology texts present sensory neurons as having a transducer or receptor in the periphery, an 3..'(on, a cell body, another axon, and a synaptic terminal in the spinal cord (Fig. 9-5, A). The axons are pre­ sented as simple electrical conduits. Normal sen­ sation occurs when the transducer is suffiCiently stimulated by touch, generating, for example, an action potential that is propagated to the spinal cord for possible transmission to higher centers. If perceived, the sensation will be in the area of the original transducer. Wben the axon has been cut, no pOSSibility of action potential conduction is left from the transducer. The regenerating tip of the severed axon can become chemically and mechanically

sensitive. Touching this tip will generate action potentials (Fig. 9-5, C). These action potentials will be perceived as coming from the tissue that contains the now dead transducer, because the signal will follow pathways that originally con­ ducted impulses from that tissue. This mecha· nism is the likely cause of "phantom" sensations that often follow limb amputation. The only excep­ tion would be if the nervous system reorganizes to accommodate the amputation. More recently, it has been shown that at least some injured axoru; can develop ongoing activity and mechanical sen­ sitivity without intermpdng their normal conduc­ tion, secondary to inflammation (Fig. 9-5, B). Neurons thus have two potential sources of action potential generation-their receptors in tbe innervated tissue and their axon. It is critical to remember that activity generated at either site will be perceived as coming from the tissue innervated and will probably be difficult or impossible for the patient to distinguish. Such ectopiC activity can also arise in injured axons in the dorsal root ganglion and will be similarly per­ ceived as coming from the innervated tissue. for example, inflammation within the intervertebral foramen or TNF-o: applied to the dorsal rootgan· glion causes hyperalgesia of the foot, as well as ongOing activity localized to the dorsal root gan­ glia. HlJ,J04 These data further support that the radiating or projected pain associated with discal

Fig. 9-5 A, Typical representation of primary afferent neuron, with (right to liift) a receptor, a peripherally projecting axon, the cell body, a centrally proj~cting axon, and a terminal in the dorsal horn of the spinal cord. Sufficient stimuJi of the receptor lead to the generation of action potentials, which are propagated along the axon to the central nervous system. B, The axon is an alternate source of action potential generation for slowly conducting neurons innervating deep tissues. Importantly, any sensation arising from stimulation of the axon at such a sensitive site will be perceived as coming from the distal receptive area, not from che site of action potential generation. C, A damaged and regroWing axon is another source of action potentials. If numerous axons are cut, the regrowth can cause a mass called a neuroma. Regrowing 8..'{ons are very sensitive to chemical and mechanical stimuli. As in B, sensations arising from such stimuli would also be perceived as coming from the innervated tissue.

CHAPTER 9

tion ials that the con­ ICha­ lions :cep­ cs to 1y, it xons senIduc­ cs of rs in 'itical ~ither

tissue .It or Such ~ns in ~ per­ e. For tebral t gan­ 'oll as t gan­ It the disca)

y

cord. 'Ie

;lowly xon at

IS

emiclil

from

Nociceptors, Pain. and Chiropractic

herniation probably arises as a result of ectopic activity of the dorsal roots or ganglia and there­ iore is not referred.

Referred Pain Mechanisms Acommon human experience is the perception oi pain radiating into the scapula, posterior head, or upper limb after pressure over so-called "trig­ ger points" in tile muscles of the shoulder girdle. Of course, if this pressure were to be placed on nerve trunks (e.g., upper brachial plexus), the explanation would have to consider radiating pain as described in the preceding section. However, because most of the stimuH that produce such pain do not directly activate the nerve trunks projecting to these areas, what can explain this perception of pain? Referred pain is the perception of pain in locations other than tile site of generation and not localized to the distribution of a damaged nerve. 105 It is a direct result of activation of nociceptive endings in somatic tissues or internal organs. The process depends on the activation of nociceptors that project to the wide dynamic range neurons that receive highly convergent input from the many sites that make input to that particular part of the spinal cord. These projection neurons seem to be primarily designed to relate the intensity rather than the location of a painful stimulus. Typically, the nervous system relies on other clues as to the origin of pain and, in the absence of adequate clues, often "paints" the pain on the body in a manner that may be at some dis­ tance from the actual site of pain generation. Because activity in the wide dynamic range neu­ rons is usually perceived as a deep aching or burning sensation, referred pain is rarely sharp, even though it can be both intense and very unpleasant. Additionally, it is not well local­ ized and has indistinct borders that overlap the distribution of several nerves and nerve roots.

CLINICAL RELEVANCE Lumbar Facet Syndrome The preceding sections have described physio­ logic mechanisms for the initiation and mainte­

201

nance of nociception and pain. However, how are these principles relevant to a patient's condition? This section describes how these mechanisms may apply to a common clinical condition, the lumbar facet syndrome. LlUubar facet syndrome is described as a sprain of the zygapophyseal joints and can be either acute or chronic. The acute form can fol­ Iowan excessive movement in any plane or com­ bination of planes of motion and more likely involves pinching or excessive stretching of the articular capsule. AJthough this structure is rela­ tively small, why can the pain be hard to localize and difficult to manage? Assuming that the injUry is restricted to the left LS-Sl joint and is, in fact, from pinching of the joint capsule itself or an intraarticular meniscoid arising from the capsule, the joint capsules are innervated by nociceptors,17.66 which respond to noxious mechanical stimula­ tion with a high-frequency discharge. This injury leads to mast cell degranulation, releasing hista­ mine that can amplify the neural response and can also lead to the recruitment of macrophages to clear the damaged tissue. Macrophages pro­ duce a multitude of prointlammatory cytokines that call directly elicit discharges from nocicep­ tors and their axons. 22 The activated primary afferent neurons release SP and CORP into the surrounding tissue. The end result is an inflam­ matory reaction in the joint and perhaps in other surrounding tissues. Increased concentra­ tions of noxious chemicals and reduced pH, which are also effective stimuli for nociceptors, are also present in the inflammatory milieu. 106 At the same time, nociceptors that have been damaged or senSitized may now respond to prod­ ucts of increased sympathetic activity; indeed, the inflammation may be affecting the sympa­ thetic axons directly, though no data exist to support tilis possibility. These pain fibers relay through nociceptive specific neurons in the dor­ sal hom of the spinal cord (to Signal the pres­ ence and location of pain) and through wide dynamic range neurons (to signal its intensity). Although the majority of pain will be felt in the region and on the side of the injured facet, the divergence of nociceptive afferent input over several spinal cord segments and the bilateral

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ANATOMY, I3JOMECHANICS. AND PHYSIOLOGY

input of some nociceptors fTOm axial tissues, such as paraspinal muscles and zygapophyseal joints, will mean that the aching component of pain will probably be perceived over a broader area. The preceding scenario describes the genera­ tion of acute pain after a noxious incident. However, in the absence of continued or main­ tained noxious input, the inflammation is expected to subside and the injury is expected to heal. Indeed, in most cases, the acute injUry and pain do resolve. Subsequently, why do many patients have what appears to be chronic facet syndrome with the addition of other typically poorly defined symptoms extending to other areas? Two possible explanations eXist, explana­ tions that are not mutually exclusive. First, the symptoms may continue because of continued activity of the nociceptor. This explanation would imply some ongoing mechanical or inflam­ matory process that continually irritates the nociceptor. In this case, the job of the clinician is to determine the peripheral generator of the afferent discharge and to do whatever is neces­ sary to reduce or terminate the neuronal activity. This might occur if the joint capsule was being intermittently impinged by bony stnJctures, with movement reinforcing or worsening the damage. Interventions that remove the impingement would be expected to remove the source of affer­ ent discharge, allowing the inflammation and the pain to subside. One possible mechanism of action of spinal adjustment and manipulation is the removal of such impingements. Second, and more problematic, would be the persistence of pain symptoms in the apparent absence of afferent discharge. In this case, the practitioner is always urged to continue the search for a peripheral generator, because this represents the more easily correctable problem. Only after a diligent search should it be assumed that the cen­ tral pain transmission pathways have been facili­ tated and are now responsible for the prolonged pain. Persistent pain, hyperesthesia, or allodynia would be expected if LTP has resulted in pro­ longed sensitization. Unfortunately, no available diagnostic tests are currently available to deter­ mine the role of such central mechanisms in pain. When all other options have been exhausted, the

clinician may have to rely on tbe previously described (and clinically hypothetical) mecha­ nisms to explain the persistence of symptoms. However, it is proposed that spinal adjustmclll and manipulation may be an effective source of high-frequency neural discharge that could con· ceivably reverse LTP. As prevjously discussed, nociceptor activity stimulates neurons in the central nervous sys­ temj otherwise, there would be no perception at all. The innervation of the facet joint in question is predominantly through the posterior ramus of the spinal nerve from L4-S1, though there is some evidence from animal studies for even greater spread via sensory fibers that follow hUll· bar sympathetic nerves. The nociceptive nerve fjbers likely synapse with neurons over at least the cord levels L2-S2, with most but certainly not all terminating in the ipsilateral spinal cord dorsal hom. This anatomy has two possible effects: (1) spinal cord neurons receive com'cr­ gent input from many structures, contributing to poor localization of the pain; and (2) axon reflexes may be propagated to any tissue inner· vated by these levels. As mentioned, these axon reflexes cause the release of SP and CGRP by antidromic mechanisms, with the development of at least some degree of neurogenic inl1amma­ tion. Paraspinal, gluteal, and even leg pain are common and might be explained by these mech­ anisms in cases where facet joint syndrome is diagnosed. These two theories of chronic pain are often regarded as mutually exclusive, and a great deal of controversy remains regarding the relative importance of ongoing nociceptor activation ver­ sus plastic changes in pain systems in chronic pain. However, tbese theories are not mutually exclusive and, even in cases with clear sensitiza· tion of the central nervous system, evidence also typically suggests ongoing peripheral iJ.l1puJs~ generation.l°7 Important]y, wltil the processes of sensitization are clearly understood and until such time as there are methods for expediting the reversal of such sensitization, therapy will be predominantly directed at the peripheral pain generators. To the extent that central sensitiza­ tion has occurred, slower improvement in the condition would, of course, be anticipated.

OJ, least tests

late these the C1 it rer: new ( nosis. moUo pedic prcte( with I or a s to re Howe' cant f tion ' nocic{ the m, nia. B have I, and II( tiate 0 ther . orthop severe Des] ments sugges inhibit: situati( to the that pI are imr of coll~ ventiol1 manipt:

Neuro

The iss tor pro in the to dire( inflanm oases of ber of r from pI

CHAPTE:R 9

Nociceptors, Pain. and Chiropractic

Diagnosis of the facet syndrome is based, at least partially, on orthopedic testing. Orthopedic tests are simple motions that are designed to iso­ late particular tissues to determine whether these tissues are responsible for the symptom. In the case of pain, the test is considered positive i.f it reproduces the pain. (Note: Production of a new or different pain does not help in the diag­ nosis.) Unfortunately, in the case of the spine, no motions isolate a single tissue. Therefore ortho­ pedic tests of the spine must be carefully inter­ preted. Nonetheless, in the case of the patient \\ith facet syndrome. motions that place a load or a stretch on the injured Joint would be Ii!l:ely to reproduce tbe pain, aiding in diagnosis. However, it must be remembered that if signifi­ cam facilitation of pain pathways eXists, activa­ tion of sensory nerve fibers that are not nociceptive may be capable of provoking pain by the mechanisms previously described for aUody­ nia. By this mechanism, the initial injury may have left the patient with hypersensitive tissues, and normally innocuous movements COlltd rein i­ tiate or aggravate the processes, which gives fur­ ther justification for care in in.terpreting orthopedic tests, particularly in patients with severe or chronic pain. Despite pain with movement, not flll move­ ments are bad. For example, substHntial evidence suggests that stimulating mechanoreceptors inhibits nociceptor activity, at least in the acute situation. Therefore movement may be beneficial to the control of pain. In addition, rnovements that place normal stresses on an injured tissue are impOrL'lnt for directing tbe proper orientation oi collagenous tissue dUring repair. Such inter­ ventions could include spinal adjustment and manipulation, mobilization, and exercise.

203

Historically. some changes in tissue texture and consistency and in temperature and sweating patterns associated WitJl various musculoskele­ tal lesions (e.g., vertebral subluKation complex) have been observed. At least some of these observations could be explained by neurogenic int1ammation. However, thiS process would require significantly more investigation before anything more than speculative explanations could be offered.

Unanswered Questions about Chronic Pain The previous sequence of events describes the pain-dysfunction cycles so often used to illus­ trate musculoskeletal disease processes. It is thought that eli nieal efforts directed at breali­ ing these cycles will help the patient's recov­ ery. However, most musculoskeletal injuries do get better on their own, probably through the gradual spontaneous resolution of the events described. One major problem with this theory is that it does not explain the significant popula­ tion of musculoslieletal pain sufferers with chroniC pain in the absence of detectable pathol­ ogy. In many cases tJlese patients are thought to have suffered permanent plastic changes in tJleir central nervous system, leading to the percep­ tion of spontaneous pain thought to be originat­ ing from a peripheral site. However, it seems likely that in the majOlity of cases, there is at least some persistent peripheral pathology that hus remained undetected and maintains the peripheral noxious input and associated pain. It also seems likely that the persistent peripheral generator is arising from damaged nerve tissue.

CONCLUSION Neurogenic Inflammation The issue of neurogenic inflammation as a fac­ tor prolonging pain is not settled, particularly in the deeper tissues that are less accessible 10 direct observation. Nonetheless, neurogenic inl1ammation is probably important in many cases of prolonged pain, as witnessed by the num­ ber of patients who receive at least some relief from powerful antiinflammatory medications.

Pain and nociception are related but different events. The neural events leading to pain usually involve activation of nociceptors innervating a threatened or damaged tissue. Once activated, nociceptors transmit information to the spinal cord for processing and may also participate in the generation of the inflammatory reaction. The response properties of nociceptors are plastic, and they can become sensitized by continued

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stimulation. This sensitization also occurs in the central nervous system, evidenced by the devel­ opment of windup and LTP. Several mechanisms in the central nervous system can suppress pain transmission. These have been best studied at the level of the spinal cord, although similar mechanisms probably exist at higher levels, such as the thalamus. The high degree of convergence of nociceptors from various parts of the body on projection neurons in the spinal cord provides a substrate for referred pain. Additionally, axon retlexes from nociceptive neurons are capable of producing neurogenic infiammation in tissues that are not involved in the initial injury. The neural basis for the affective (emotional) compo­ nents of pain and suffering are localized to the frontal lobes, in areas known to be affected in depression and anxiety disorders. This i~ the physiologic substrate for the common and com­ plex clinical interaction between pain and mood.

[j{~view Question..~ 1. What is the difference between pain and nociception? 2. What is the conduction velocity of the neurons that subserve nociception? 3. What is an axon reflex? How is it related to neurogenic inflammation? 4. Where are nociceptors located? 5. Damage to nociceptor axons leads to what anatomic changes? 6. To what levels of the spinal cord can a C­ fiber nociceptor projecting through the L4 dorsal root project? 7. What is a possible clinical effect of long­ term potentiation? 8. Describe the nervi nervorum. 9. What nOclceptors are likely to be activated during a positive straight-leg raise? 10. How can light brushing cause pain?

Concept Questio'ns 1. A local herbalist gives you a poultice that he claims reduces the pain of sprains, You use it on the next patient that you see and not only does the patient report less pain within 30 minutes but also you observe that local redness and swelling are

reduced. Being familiar with nociceptor physiology, you think that it may be affecting them directly. How would you investigate your hypothesis? 2. A patient presents with bilateral foot pain. The symptoms started on the right; after exacerbation 2 weeks ago, the left side started hurting. Your examination indic a biomechanical lesion on the right, but. normal left foot, although it is somewhlll tender to palpation. You make a diagnosis of right plantar fascitis. Why does the patient have symptoms on the left? Do treat the left foot?

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1(12):1426,1981. .3. L,l\vson SN: Phenotype and function of somatic mary afferent nociceptive neurones with C" A or l\ a1phalbeta-fibres. Exp Physiol 8i(2):239, 4, Duclaux R et a1: Conduction velocity along the

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5. Morrison JFB: Splanchnic slowly adapting mec

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6. Cerverol": Sensory innervation of tlle \;scera:

era1 basis of vlsceraJ pain, Physiol Rcl..' i4:95, I

7. J
IHmrons, Jpn J PhyS'ioI40(I):I, 1990.

8. Mense S: Nociception from skeletal muscle in

tiOll to clinical pain, Pain 54:241, 1993,

9. Schaible HG, Grubb BD; Afferent and spinal

nisms of joint pain, Pain 55:5, 1993,

10. Bove GM, Light AR: Unmyelinated Jlociceploll paraspinal tissues, J Neuropll:ysiol 73:1752.1 11. Bazett He, McGlon.e B: Note on the pain sen which accompany deep punctures, Brain

1928. 12. Cavanaugh JM et al: Sensory innervation oflhe tiSsues of the lumbar spine of the nil, J 7:378,1989. 13. EI-Bohy A ot al: Localization of substance PaDd rofilament Im01unoreactl ve fibers in th~ hunblr joint capsule and supraspinous Jj~all1ent of bit, Brain Res 460:379, 1988. 14. Giles LG et aJ: Human zygapophyse:JI joint. folds, Acta r\nac 126: 110, 1986. 15. Giles LG, Harvey AR: Immunohistological tion of nociceptors in the capsule and srn~