Subluxation: Dogma or Science?
Subluxation syndrome is a legitimate, potentially testable, theoretical construct for which there is little experimental evidence. Acceptable as hypothesis, the widespread assertion of the clinical meaningfulness of this notion brings ridicule from the scientific and health care communities and confusion within the chiropractic profession. We believe that an evidence-orientation among chiropractors requires that we distinguish between subluxation dogma vs. subluxation as the potential focus of clinical research. We lament efforts to generate unity within the profession through consensus statements concerning subluxation dogma, and believe that cultural authority will continue to elude us so long as we assert dogma as though it were validated clinical theory.
Historical Overview and Update on Subluxation Theories
These challenges to the “subluxation concept” are in their early days and, in many instances, are based on only one or a few studies. In several instances, these studies have involved healthy subjects or those with relatively mild symptom severity. In several studies, the manual therapy intervention might be regarded as nonspecific and, therefore, would not qualify as an “adjustment.” On the other hand, critiques could be made of the quality of many of the studies that formed the basis for what might be called the “standard model” in chiropractic and the other manual therapy professions, including those which extend back several decades. Indeed, some of the modern challenges, especially in the area of manual diagnostic procedures, appear to derive precisely from the poorer quality of prior studies. The only way forward is to strengthen our efforts to investigate the “subluxation concept” with high-quality scientific studies including animal models and human clinical studies.
The Basis for Spinal Manipulation: Chiropractic Perspective of Indications and Theory
It is reasonable to think that patients responding to spinal manipulation (SM), a mechanically based therapy, would have mechanical derangement of the spine as a critical causal component in the mechanism of their condition. Consequently, SM practitioners routinely assess intervertebral motion, and treat patients on the basis of those assessments. In chiropractic practice, the vertebral subluxation has been the historical raison d’etre for SM. Vertebral subluxation is a biomechanical spine derangement thought to produce clinically significant effects by disturbing neurological function. This paper reviews the putative mechanical features of the subluxation and three theories that form the foundation for much of chiropractic practice. It concludes with discussion of subluxation as an indicator for SM therapy, particularly from the perspective that subluxation may be one contributory cause of ill-health within a “web of causation”.
Subluxation Reviewed, Revisited, Revitalized
Our understanding of the biomechanics and neurology of the subluxation continues to evolve as more research is published which helps explain the nature of this lesion. Historically, the subluxation has been at the heart of the identity and purpose of the chiropractic profession. Contemporary models provide new insights into this elusive and sometimes mysterious problem which we attempt to find by various clinical means and correct by the application of high-velocity, low-amplitude thrusts. Let’s review past models, but focus primarily on the latest evidence concerning the subluxation published in the recent scientific literature in order to improve our understanding, insight, and application of clinical interventions to improve patient outcomes with chiropractic care.
The Short-term Effect of Spinal Manipulation in the Treatment of Infantile Colic: A Randomized Controlled Clinical Trial with a Blinded Observer
By trial days 4 to 7, hours of crying were reduced by 1 hour in the dimethicone group compared with 2.4 hours in the manipulation group (P = .04). On days 8 through 11, crying was reduced by 1 hour for the dimethicone group, whereas crying in the manipulation group was reduced by 2.7 hours (P = .004). From trial day 5 onward the manipulation group did significantly better that the dimethicone group. The authors then conclude: Spinal manipulation is effective in relieving infantile colic.
Epilepsy and Seizure Disorders: A Review of Literature Relative to Chiropractic Care of Children
Chiropractic care may represent a nonpharmaceutical health care approach for pediatric epileptic patients. Current anecdotal evidence suggests that correction of upper cervical vertebral subluxation complex might be most beneficial. It is suggested that chiropractic care be further investigated regarding its role in the overall health care management of pediatric epileptic patients.
Chronic Pediatric Asthma and Chiropractic Spinal Manipulation: A Prospective Clinical Series and Randomized Clinical Pilot Study
After 3 months of combining chiropractic SMT with optimal medical management for pediatric asthma, the children rated their quality of life substantially higher and their asthma severity substantially lower. These improvements were maintained at the 1-year follow-up assessment. There were no important changes in lung function or hyperresponsiveness at any time. The observed improvements are unlikely as a result of the specific effects of chiropractic SMT alone, but other aspects of the clinical encounter that should not be dismissed readily. Further research is needed to assess which components of the chiropractic encounter are responsible for important improvements in patient-oriented outcomes so that they may be incorporated into the care of all patients with asthma.
Self-reported Nonmusculoskeletal Responses to Chiropractic Intervention: A Multination Survey
A minority of patients with self-reported nonmusculoskeletal symptoms report definite improvement after chiropractic care, and very few report definite worsening. Future studies should use stringent criteria to investigate a possible treatment effect and concentrate on specific diagnostic subgroups such as digestive problems and tinnitus.
Cerebral Metabolic Changes in Men After Chiropractic Spinal Manipulation for Neck Pain
Research on chiropractic spinal manipulation (CSM) has been conducted extensively worldwide, and its efficacy on musculoskeletal symptoms has been well documented. Previous studies have documented potential relationships between spinal dysfunction and the autonomic nervous system and that chiropractic treatment affects the autonomic nervous system. The authors hypothesized that CSM might induce metabolic changes in brain regions associated with autonomic nervous system functions as assessed with positron emission tomography (PET). PET is a nuclear medicine imaging technique that allows quantification of cellular and molecular processes in humans such as cerebral glucose metabolism which is thought to reflect regional neuronal activities.
Cerebral Perfusion in Patients with Chronic Neck and Upper Back Pain: Preliminary Observations
Group 1 (mild) consisted of 14 patients. Cerebral perfusion measured by SPECT was normal in all 8 brain regions. Group 2 (moderate)consisted of 16 patients. In this group, a decrease in cerebral perfusion was observed (range, 20%-35%), predominantly in the parietal and frontal zones.Group 3 (severe) consisted of 15 patients. In this group, the decrease in cerebral perfusion observed was from 30% to 45%, again predominantly in the parietal and frontal zones. A significant difference was found between NDI groups (“moderate” and “severe” showed significantly greater hypoperfusion than “mild”). Total blockage score correlated with SPECT scores at r = 0.47, P = .001. In a multivariate analysis, NDI scores contributed 39% of the variance of SPECT scores.
Biomechancial Quantification of Pathologic Manipulable Spinal Lesions: An In Vivo Ovine Model of Spondylolysis and Intervertebral Disc Degeneration
Quantifiable objective evidence of spinal lesions and their response to SMT were confirmed in this study. Neuromechanical alterations provide novel insights into quantifying manipulable spinal lesions and a means to biomechanically assess SMT outcomes.
Does Inter-vertebral Range of Motion Increase After Spinal Manipulation? A Prospective Cohort Study
This study found no differences in cervical sagittal IV-RoM between patients with mild nonspecific neck pain and matched healthy controls and motion palpation over-estimated the prevalence of hypomobile segments. There was, however, a modest positive relationship between the number of spinal manipulations given and detectable increases in sagittal segmental IV-RoM. The patient-reported outcomes of spinal manipulation were not related to this, nor was there any relationship between increase in range and improvement in pain and disability, even though these improvements were generally large.
Nociception and Subluxation
When discussing subluxation with our patients, the great majority of DCs still describe it in terms of a bone-out-of-place that pinches or chokes nerves. There are two major problems with this explanation: It is inaccurate because subluxations rarely, if ever, pinch or choke nerves. Secondly, by repeating this erroneous explanation again and again, DCs eventually come to believe it. Repetitive exposure to information embeds in the mind.
Nociception, Mechanoreception and Proprioception … What’s the Difference and What Do They Have to Do with Subluxation?
Nociception is the process by which nociceptive receptors receive tissue damaging stimuli that is then carried into the CNS by nociceptive axons (A-delta and C fibers). Potential outcomes of nociceptive input to the cord include pain, autonomic symptoms, vasoconstriction and muscle spasm. Nociceptive input to the cord appears to be the driving force behind the pathogenesis of subluxation (see Figure A). We must remember that nociception and pain are two completely different animals. However, a devastating consequence of both pain and nociceptive stimulation of the hypothalamus, is the release of cortisol by the adrenal glands. Over time, elevated levels of cortisol will promote glucose intolerance, inhibit collagen formation, increase protein breakdown, inhibit secretory IgA output, and inhibit white blood cell function. Clearly, the clinical importance of pain and nociception should not be minimized.
How Does Subluxation Affect the Nervous System?
In 1976, Drs. Vert Mooney and James Robertson set out to confirm the earlier research on referred pain and discussed their findings in a well-known paper, “The Facet Syndrome.”3 Their attention was directed toward the facet joints rather than spinal muscles and ligaments. The subjects in this study included five normal individuals and 15 patients with low back pain. To make a semi-long story short, Mooney and Robertson discovered that, indeed, injecting hypertonic saline into facet joints resulted in local and referred pain. They also discovered that, “slightly increasing the volume of injection would consistently increase the amount of pain radiation.”
Subluxation and the Nervous System
The important point to appreciate now is that the subluxation complex will alter the firing of spinal tissue nociceptors and mechanoreceptors, and this will lead to various symptoms that we often encounter in the clinical setting that respond to chiropractic care. So, when we think about subluxation, the subluxation complex, or joint dysfunction, we need to think about receptors and afferent fibers.
Somatic Dysfunction and the Phenomenon of Visceral Disease Simulation:
The proper differential diagnosis of somatic vs. visceral dysfunction represents a challenge for both the medical and chiropractic physician. The afferent convergence mechanisms, which can create signs and symptoms that are virtually indistinguishable with respect to their somatic vs. visceral etiologies, need to be appreciated by all portal-of-entry health care providers, to insure timely referral of patients to the health specialist appropriate to their condition. Furthermore, it is not unreasonable that this somatic visceral-disease mimicry could very well account for the “cures” of presumed organ disease that have been observed over the years in response to various somatic therapies (e.g., spinal manipulation, acupuncture, Rolfing, Qi Gong, etc.) and may represent a common phenomenon that has led to “holistic” health care claims on the part of such clinical disciplines.
Dysafferentation: A Novel Term to Describe the Neuropathophysiological Effects of Joint Complex Dysfunction. A Look at Likely Mechanisms of Symptom Generation
Since the founding of the chiropractic profession, very few efforts have been made to thoroughly explain the mechanism(s) by which joint complex dysfunction generates symptoms. Save for a few papers, only vague and physiologically inconsistent descriptions have been offered. The purpose of this article is to propose a precise and physiologically sound mechanism by which symptoms may be generated by joint complex dysfunction.
The Somatosensory System of the Neck and its Effects on the Central Nervous System
Studies involving human and nonhuman vertebrates have provided considerable information about the anatomy of the sensory receptors located in the neck and about where information from these receptors is relayed in the spinal cord and brain. Physiological experiments involving electrical and natural stimulation of the head and neck regions have identified a role for some of these receptors in neck-evoked reflexes. It is clear that in addition to signaling nociception, the somatosensory system of the neck may influence the motor control of the neck, eyes, limbs, respiratory muscles and possibly the activity of some preganglionic sympathetic nerves.
Reflex Effects of Subluxation: The Autonomic Nervous System
Autonomically mediated reflex responses to noxious stimulation of spinal tissues have been clearly demonstrated. Where parasympathetic influences dominate, a segmental organization has not been apparent. Where sympathetic mediation has been significant, it has been possible to demonstrate the existence of spinal reflex centers and, to some degree, a measure of segmental organization.
Certain findings cited are consistent with the observations of chiropractic clinicians about the effects of spinal dysfunction on visceral disorders. On the other hand, the bulk of the positive data obtained was elicited with noxious stimulation. There is still little support for the contention that painless spinal dysfunction can affect organ function. This is scarcely surprising considering that all the basic physiologic work cited was performed in anesthetized animals. However, new evidence suggests that muscle spindles in cervical paraspinal muscles may in fact be capable of eliciting somatoautonomic reflexes. [12] In addition, there is recent evidence from studies in conscious human beings that innocuous somatic stimulation of the neck may influence cardiovascular function.13 Additional and similarly well-conceived studies of basic physiology and clinical phenomena are needed to construct an explanation for the promising observations of practitioners of spinal manipulation.
Neurophysiologic Response to Intraoperative Lumbosacral Spinal Manipulation
Monitoring mixed-nerve root discharges in response to spinal manipulative thrusts in vivo in human subjects undergoing lumbar surgery is feasible. Neurophysiologic responses appeared sensitive to the contact point and applied force vector of the spinal manipulative thrust. Further study of the neurophysiologic mechanisms of spinal manipulation in humans and animals is needed to more precisely identify the mechanisms and neural pathways involved.
Mechanical Force Spinal Manipulation Increases Trunk Muscle Strength Assessed By Electromyography: A Comparative Clinical Trial
The results of this preliminary clinical trial demonstrated that MFMA SMT results in a significant increase in sEMG erector spinae isometric MVC muscle output. These findings indicate that altered muscle function may be a potential short-term therapeutic effect of MFMA SMT, and they form a basis for a randomized, controlled clinical trial to further investigate acute and long-term changes in low back function.
Neuromechanical Characterization Of In Vivo Lumbar Spinal Manipulation. Part II. Neurophysiological Response
Vertebral motions and resulting spinal nerve root and neuromuscular reflex responses appear to be temporally related to the applied force during SMT. These findings suggest that intersegmental motions produced by spinal manipulation may play a prominent role in eliciting physiologic responses.
Joint Manipulation Reduces Hyperalgesia By Activation of Monoamine Receptors But Not Opioid or GABA Receptors in the Spinal Cord
Joint manipulation has long been used for pain relief. However, the underlying mechanisms for manipulation-related pain relief remain largely unexplored. The purpose of the current study was to determine which spinal neurotransmitter receptors mediate manipulation-induced antihyperalgesia. Rats were injected with capsaicin (50 microl, 0.2%) into one ankle joint and mechanical withdrawal threshold measured before and after injection. The mechanical withdrawal threshold decreases 2 h after capsaicin injection.
Does Facet Joint Inflammation Induce Radiculopathy? An Investigation Using a Rat Model of Lumbar Facet Joint Inflammation
When inflammation was induced in a facet joint, inflammatory reactions spread to nerve roots, and leg symptoms were induced by chemical factors. These results support the possibility that facet joint inflammation induces radiculopathy.
Preliminary Morphological Evidence That Vertebral Hypomobility Induces Synaptic Plasticity in the Spinal Cord
These preliminary data suggest for the first time that chronic vertebral hypomobility at L4 through L6 in the rat affects synaptic density and morphology in the superficial dorsal horn of the L2 spinal cord level. More definitive studies are warranted, and the biologic significance of these finding should be investigated.
Immobilization Induces Changes in Presynaptic Control of Group Ia Afferents in Healthy Humans
Although the present study involved limb immobilization in able-bodied subjects, the findings may also be of clinical relevance. This is especially the case in relation to neurological disorders leading to physical inactivity. It is noteworthy that the findings of increased H-reflexes, decreased GABAergic presynaptic inhibition and decreased post-activation depression following immobilization to some extent matches the findings of previous studies in spastic patients and it is worth considering the effects of reduced physical activity in itself. As mentioned previously, it is possible that the decreased presynaptic inhibition and post-activation depression observed in patients with cerebral or spinal lesions may at least in part be a consequence of the disuse of motoneurons and Ia afferents.
Exploring the Neuromodulatory Effects of the Vertebral Subluxation and Chiropractic Care
Over the past 15 years our research group has been conducting a variety of experiments aimed at testing out the theory that adjusting subluxations improves central nervous system functioning and overall expression of health and well being. To do this the theory was first formulated into a model (Figure 2) that could be scientifically tested with a programme of research studies. This model became the basis for the lead author’s PhD research, [5] and continues to be a foundational premise that our research group is attempting to elucidate with our work. The model was constructed using early chiropractic research data and a thorough review of the neurophysiology scientific literature.
Spinal Motor Neuronal Degeneration After Knee Joint Immobilization in the Guinea Pig
We conclude that motor neuronal degeneration in the spinal cord and axons in this study was the result of knee joint immobilization. Increases in motor neuronal nitric oxide-mediated oxidative stress level after reduction of target tissue activity may contribute to the mechanism for degenerative changes in the motor neurons in adult spinal cord of the guinea pig.
Cerebral Metabolic Changes in Men After Chiropractic Spinal Manipulation for Neck Pain
Research on chiropractic spinal manipulation (CSM) has been conducted extensively worldwide, and its efficacy on musculoskeletal symptoms has been well documented. Previous studies have documented potential relationships between spinal dysfunction and the autonomic nervous system and that chiropractic treatment affects the autonomic nervous system. The authors hypothesized that CSM might induce metabolic changes in brain regions associated with autonomic nervous system functions as assessed with positron emission tomography (PET). PET is a nuclear medicine imaging technique that allows quantification of cellular and molecular processes in humans such as cerebral glucose metabolism which is thought to reflect regional neuronal activities.
Cerebral Perfusion in Patients with Chronic Neck and Upper Back Pain: Preliminary Observations
In this group of patients with neck and/or upper back pain, NDI scores strongly predicted cerebral hypoperfusion. Spinal joint dysfunction may be involved via hyperactivity in the regional sympathetic nervous system.
What is Different About Spinal Pain?
This thesis addressed the question “what is different about spine pain?” Neuroanatomic and neurophysiologic findings from studies in the last twenty years provide preliminary support for the thesis that deep spine pain is different from deep pain arising from peripheral limb structures.
Spinal Manipulative Therapy and Somatosensory Activation
The goal of this article is to briefly update our knowledge regarding several physical characteristics of an applied SMT, and review what is known about the signaling characteristics of sensory neurons innervating the vertebral column in response to spinal manipulation. Based upon the experimental literature, we propose that SMT may produce a sustained change in the synaptic efficacy of central neurons by evoking a high frequency, bursting discharge from several types of dynamically-sensitive, mechanosensitive paraspinal primary afferent neurons.
Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited
The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.
Articular Cartilage Surface Changes Following Immobilization of the Rat Knee Joint. A Semiquantitative Scanning Electron-microscopic Study
Normal articular cartilage surfaces are not flat and smooth, but are contoured with various degrees of roughness. We applied the articular surface classification system developed by Jurvelin to evaluate contour and surface quality changes in rat patellae after varying periods of knee joint immobilization. Numerous studies have demonstrated that joint immobilization induces degenerative changes in articular cartilage. We found a correlation between the duration of immobilization and changes in the measured area of contour and surface quality subclasses.
Degenerative Changes Following Spinal Fixation in a Small Animal Model
Degenerative changes were found in the Z joints following spinal fixation in this animal model. In addition, degenerative changes of the articular surfaces preceded the slower formation of new bone required for the development of osteophytes. The average severity of the degenerative changes (degeneration severity parameters) supports the findings from the total number of osteophytes per animal and facetal surfaces showing signs of degeneration per animal (degeneration occurrence parameters). These results support the hypothesis that degenerative changes follow hypomobility of the Z joints and are consistent with the theoretical model shown in Figure 1. Future studies are planned to evaluate the effects of spinal adjusting on the time profiles of the degenerative changes found in this study and on the development of adhesions following fixation (hypomobility) of the Z joints.
We conclude that Z joint changes occur following spinal fixation in this rat model, and the amount and severity of degeneration is time-dependent with a threshold of between 4 and 8 weeks for the development of osteophytic changes that showed no signs of reversal and between 1 and 4 weeks for ASD changes of a similar magnitude.
Introducing the External Link Model for Studying Spine Fixation and Misalignment: Part 1— Need, Rationale, and Applications
The great promise of basic chiropractic “subluxation” research is that it will clarify for clinical researchers the mechanisms by which spine fixation or malposition may cause harm and show or suggest effective therapeutic remedies. Answers are needed to pressing and fundamental questions such as: Does chiropractic subluxation actually occur? If so, does chiropractic spinal subluxation significantly threaten a patient’s health? Are there features that will allow researchers and clinicians to determine its accurate and precise location as well as its specific nature? Can spinal manipulative therapy prevent, stop the progression, or reverse adverse health effects related to chiropractic subluxation? Are there “time windows” that might influence the outcome of treatment? When these questions are answered, clinicians will be able to more objectively match the unique features of a patient’s presentation to the diversity of chiropractic techniques, treatment frequency, number of visits, and treatment duration.
Preliminary Morphological Evidence That Vertebral Hypomobility Induces Synaptic Plasticity in the Spinal Cord
These preliminary data suggest for the first time that chronic vertebral hypomobility at L4 through L6 in the rat affects synaptic density and morphology in the superficial dorsal horn of the L2 spinal cord level. More definitive studies are warranted, and the biologic significance of these finding should be investigated.
What is Different About Spinal Pain?
This thesis addressed the question “what is different about spine pain?” Neuroanatomic and neurophysiologic findings from studies in the last twenty years provide preliminary support for the thesis that deep spine pain is different from deep pain arising from peripheral limb structures.
Introducing the External Link Model for Studying Spine Fixation and Misalignment: Part 2, Biomechanical Features
This study suggests that the external link model can be a valuable tool for studying the effects of spine fixation and misalignment, 2 cardinal features of what has been historically described as the chiropractic subluxation. Significant residual stiffness and misalignment remained after the links were removed. The progressive course of this lesion is consistent with subluxation theory and clinical chiropractic experience.
Introducing the External Link Model for Studying Spine Fixation and Misalignment: Current Procedures, Costs, and Failure Rates
It has been our experience that individuals with basic animal research training will become proficient at producing the ELM after observing 3 to 4 implant procedures and performing 4 to 6 procedures on their own.
Zygapophyseal Joint Adhesions After Induced Hypomobility
We conclude that hypomobility results in time-dependent ADH development within the Z joints. Such ADH development may have relevance to spinal manipulation, which could theoretically break up Z joint intra-articular ADHs.
Basic Science Research Related to Chiropractic Spinal Adjusting: The State of the Art and Recommendations Revisited
The summaries of the literature for the 6 topic sections (anatomy, biomechanics, somatic nervous system, animal models, immune system, and human studies related to the autonomic nervous system) indicated that a significant body of basic science research evaluating chiropractic spinal adjusting has been completed and published since the 1997 basic science white paper. Much more basic science research in these fields needs to be accomplished, and the recommendations at the end of each topic section should help researchers, funding agencies, and other decision makers develop specific research priorities.
