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Technique & Analysis

The Upper Cervical Subluxation Complex

By Kirk Eriksen, D.C.

In the January/February 2002 issue we covered the history of the Grostic/Orthospinology Procedure and provided an overview of the X-ray analysis. This was followed by the March/April 2002 Today’s Chiropractic which discussed the Orthospinology adjustment and outcome assessments. This issue will provide an overview of the upper cervical subluxation complex, which is the sole focus of the Orthospinology spinal correction. An introduction to a new textbook published by Lippincott Williams & Wilkins, Upper Cervical Subluxation Complex, is also presented.

Anatomy and Biomechanics
A thorough understanding of the anatomy, biomechanics and neurophysiology of the upper cervical spine is a prerequisite to being able to appreciate the clinical manifestations of the occipito-atlanto-axial subluxation complex. White and Panjabi describe the upper cervical articulations as “the most complex joints of the axial skeleton, both anatomically and kinematically.”1 The two upper cervical vertebrae differ in shape and function from the remainder of the spine as they are two of nine atypical vertebrae. The configuration of the atlanto (C1) and axial (C2) joints, enables these structures to carry the head and determine its movement. These vertebrae also provide protection for the intimate neurologic and vascular structures. The atlas articulation is diarthrodial and is the most freely movable segment in the spine, in relation to C1-C2 rotation and occipito (C0)-C1 flexion-extension. The C0-C1 articulation consists of reciprocally curved superior facets of the lateral masses of the atlas and the ellipsoid synovial joints of the occipital condyles. The atlas vertebra has a condyloid articulation with the axis that allows for 45-50 percent of rotation in the cervical spine, but the consensus of the studies show that little motion occurs between the atlas and occiput in lateral flexion and rotation. The small amount of atlanto-occipital movement that does occur is found at the end point of the range of motion. This is a critical point when discussion is made about the misalignment component of the subluxation.

It is well understood that the spine does not move in only one plane of motion. During normal cervical movement, coupled motion occurs. Coupling is defined as motion in which rotation or translation of a rigid body about or along one axis is consistently associated with simultaneous rotation or translation about or along another axis.2 During normal range of movement, coupled motion helps reduce tension on the nervous system. This is accomplished by offsetting pure lateral flexion or rotation, with small amounts of movements in the x, y or z axes. One feature of an upper cervical subluxation is that the occipito-atlanto-axial articulations have misaligned in an uncoupled fashion. This condition is measured radiographically in a neutral posture, with the spine at rest. The body must continually adapt, from a biomechanical and neurological standpoint, to this type of subluxation.

Neurology
Neuroanatomy and physiology related to the upper cervical region is exceptional as the upper cervical cord represents a transitional area between the brainstem and subjacent cord levels. Neurological dysfunction related to the upper cervical subluxation can be explained by a few different mechanisms. However, it is likely that these mechanisms manifest concurrently in many patients. The two most plausible hypotheses involve spinal cord tension and mechanoreceptive dysafferentation. The upper cervical spinal cord is directly attached to the circumference of the foramen magnum, to the second and third cervical vertebrae and by fibrous slips to the posterior longitudinal ligament.3 Hinson4, Grostic5 and others have demonstrated dissection evidence showing a dural attachment at the atlas level. The uppermost denticulate ligaments are arranged almost horizontally, as compared to the inferiorly angled ligaments found around the rest of spinal cord. The most cephalad ligaments are also thicker and stronger to help anchor the spinal cord around the foramen magnum. These ligaments are so strong that they have been found to sever the upper cervical spinal cord in some cases of hydrocephalus.6 A rigid attachment at the foramen magnum is vital to prevent the brainstem from being pulled through the opening during the end point of cervical flexion. Recent studies have also revealed a connective tissue bridge between the rectus capitis posterior minor muscle and the dura mater of the upper cervical spinal cord.7 A similar attachment has also been found to the spinal cord via the ligamentum nuchae.8 The spinal dura mater has been found to be innervated and a possible source of pain and neurological dysfunction.9,10

It has been shown that the average occipito-atlantal misalignment in the frontal plane is almost three degrees, which equates to about one-eighth of an inch of linear movement. This is significant due to the upper cervical spinal cord having a diameter of about one-half inch. Dr. John D. Grostic’s Dentate Ligament—Cord Distortion Hypothesis5 provides a compelling hypothesis for how these anatomical connections can lead to spinal cord distortion, in the presence of upper cervical misalignment. It is posited that the neurological dysfunction can occur via two mechanisms: 1) direct mechanical irritation of the nerves of the spinal cord, and/or 2) collapse of the small veins of the cord, producing venular congestion with a loss of nutrients necessary to carry on the high energy reactions necessary for nerve conduction. Indeed, a mechanical irritation of the nerve tracts may be aggravated by localized hypoxia and increased sensitivity to the effects of cord tension during the initial phase. This neurological dysfunction could be the cause of many clinical signs and symptoms observed in patients with upper cervical subluxations.

The spinocerebellar tracts are located along the lateral edge of the spinal cord (see Fig. 3) and are located at the most probable site of maximal mechanical irritation via the dentate ligaments. These proprioceptive tracts are primary pathways for regulating muscle tone and joint position sense. The spinocerebellar tracts are arranged in a laminar fashion (although somewhat angulated) with the most lateral fibers innervating the most caudal structures [i.e. legs—sacral—lumbar—thoracic—cervical (very limited)]. Irritation of these tracts could lead to muscle tone imbalance of the pelvic girdle resulting in a functional short leg.

The spinothalamic tracts are also located close to the attachment of the dentate ligaments and are organized in a laminar arrangement as well (see Fig. 3). These tracts are responsible for conveying pain and temperature into the neuroaxis. Mechanical irritation and/or ischemic compromise to the spinothalamic tracts could possibly explain particular cases of severe low back and leg pain being caused by an upper cervical subluxation. This is a possible mechanism for the rapid amelioration of sciatic-type pain in specific patients, particularly those without any demonstrable clinical findings attributed to the lower back.

Afferent/efferent joint mechanoreceptive neurology has interesting implications in the upper cervical spine. The cervical spine has more mechanoreceptors per surface area than any other region of the spinal column.11 It is thought that the upper cervical articulations have the greatest amount or receptors in the cervical spine. This may give the region the greatest potential for spinal mechanoreceptive afferentation into the neuraxis. Mechanoreceptive innervation has been found in the cervical facet joints12, ligaments13, intervertebral discs.14-17 The muscle spindle may be the most important proprioceptive receptor in the upper cervical spine (see Figure 4). The spindles are intrafusal fibers that are imbedded within all muscles of the body, however, they are extremely dense in the suboccipital muscles.18-24 The human experience is governed by receptors of all types. Cerebral cortical firing initiates efferent activity. However, the thalamus regulates the cerebral cortex through summation and integration. It should be noted that all sensory information goes through the thalamus (except aspects of olfaction).25 Mechanoreception is the primary input into the cerebellum due to life in a gravity environment. The primary load to the thalamus is via the cerebellum due to the vast amount of afferent input required to maintain upright posture. Studies have shown that the upper cervical afferents feed directly into the vestibular and other high order nuclei.26-35 This enables a less modified input of information from the upper cervical articulations into the brainstem nuclei, as opposed to the lower segments of the spine. Inappropriate afferentation (i.e. subluxation) and appropriate input (subluxation correction) into the vestibular nuclei is yet another plausible explanation for the functional short leg/pelvic distortion that is observed clinically with patients under upper cervical chiropractic care. This can occur by way of upper cervical mechanoreceptive functional integrity through the cuneocerebellar tracts, cerebellum, vestibular nuclei, descending medial longitudinal fasciculus (medial and lateral vestibular spinal tracts), regulatory anterior horn cell pathway which affects postural motor tone. It is plausible to theorize that stimulating or regulating mechanoreceptive activity can have a significant impact on the neurological activity of the brain and many bodily functions. The previous facts and details demonstrate the vulnerability of the upper cervical spine to neurological insult, and the potential impact of the chiropractic adjustment on health. This helps to explain many of the clinical signs (i.e. postural and functional pelvic distortion, paraspinal thermal asymmetry, muscle spasm, specific pain syndromes) doctors of chiropractic observe in patients.

[Notated references are available from the author upon request.]

About the author: Kirk Eriksen, D.C., a 1991 Life Chiropractic College graduate, is president of the Society of Chiropractic Orthospinology. A lecturer and author, he manages a private practice in Dothan, Ala. For more information, call (334) 793-7992; e-mail to drkeriksen@ala.net; or access the web site at www.orthospinology.org.

Upper Cervical Subluxation Complex—the textbook

Lippincott Williams and Wilkins has published the Upper Cervical Subluxation Complex: A Review of the Chiropractic and Medical Literature. This landmark text is the most comprehensive book ever published on the vertebral subluxation complex. This textbook is the culmination of several years of detailed research and review of chiropractic and medical literature on the topic of the cervical spine, the occipito-atlanto-axial subluxation, and upper cervical chiropractic care. The book reviews the anatomy and kinematics of the upper cervical spine and explains how impaired biomechanics causes neurological dysfunction and physiological concomitants. This reference is not intended to be about chiropractic technique; rather, the text provides the “why” as opposed to the “how” of upper cervical chiropractic care. However, the scientific and clinical rationale for orthogonally-based upper cervical care (and other methods) is presented, making a compelling case for this being a chiropractic specialty. The procedures involved have been around for over 50 years, but they have not been fully understood or properly evaluated by either the chiropractic or medical professions at large. This type of care is supported by over 100 peer-reviewed, indexed references, as well as unparalleled gentleness and safety. The quantification of the subluxation and its assessment enables the spinal adjustments to be reproduced from one doctor to the next. Indeed, the nature of this care allows it to be fine-tuned to satisfy the individual needs of patients, and usually results in fewer visits to achieve therapeutic goals.

The format and treatment of the Upper Cervical Subluxation Complex permits its use as a text, a reference, an atlas or a guide. The first half focuses on anatomy and neurophysiology, exploring the theme that “structure dictates function.” The second half shifts the focus to clinical procedures and related issues. The insights that this book provides into the role of the occipito-atlanto-axial subluxation complex in establishing accurate spinal conformation, and the role that proper spinal alignment plays in maintaining quality of life issues may bring about a paradigm shift in our understanding of many health problems. The extensive clinical reports will open the eyes of many in the medical as well as chiropractic professions to the fact that the upper cervical specific procedures are not only safe and effective; they are inspiring research that is opening a new chapter in our understanding of health and well-being. This textbook attempts to show the integration and mutual dependency of the science, art and philosophy of upper cervical chiropractic care.

In this reference text the reader will find quotes from and reviews of over 1,200 research papers, books and presentations; and almost 400 illustrations and images will help the reader conceptualize this abundance of information. Over 90 percent of the reviewed research papers are from peer-reviewed and indexed sources. Topics range from a review of upper cervical anatomy and physiology to clinical analyses of spinal corrective care. The text ends with extensive appendices portraying dramatic spinal corrections as portrayed with radiography, postural assessments, and surface electromyograms and thermograms. This one of a kind textbook has earned these words from Dan Murphy, D.C., vice president of the International Chiropractic Association:

“Now, a comprehensive text has been produced that can be used by all chiropractors and other interested parties as a resource to enhance the understanding of the upper cervical spine, basic science, theoretical science, and published case studies,” said Murphy. “The result is a unique assembly of information that will not only benefit individual chiropractors, but will also benefit our entire profession because of the sharing of the science that supports the observations of clinical chiropractic.”

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© Copyright 2004 Today's Chiropractic

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