Vertebral Subluxation - Scientific Investigation

Scientific Investigation

Investigation to confirm the existence of vertebral subluxations has been ongoing since it was first postulated in 1895. The early practitioners used palpation and the anatomy of the nervous system as a guide (meric system). In their efforts to be more specific, they seized the newly discovered X-ray technology and introduced the neurocalometer (a heat sensing device). It was during those early years that the medical establishment first criticized the chiropractic profession, saying that the conditions that those early chiropractors were treating were only psychophysiologic disorders. To prove that chiropractic patients had real conditions, BJ Palmer opened a research clinic as a part of the Palmer College of Chiropractic. When a patient entered the clinic, they were first examined by medical doctors and a diagnosis was formulated. They were then sent to the chiropractic part of the clinic, treated, and sent back to the medical doctors for evaluation. Since then, chiropractors have sought a greater understanding of the mechanisms and effects of the vertebral subluxation. Today we see motion x-rays, surface EMG, and digital thermography though none of these methods have been proven to be reliable or valid in the detection of vertebral subluxations.

As research projects are able to employ new techniques and technologies to evaluate nervous system function and effects, further support for chiropractic principles has surfaced. Chiropractors have long suggested that spinal joint fixation that results from subluxation will result in degenerative effects that compromise the spinal joints. A 2004 research team at the National University of Health Sciences evaluated changes of the lumbar vertebral column following fixation (immobility) by surgically fusing spinal joints in experimental rats. The fixated joints showed significant degeneration compared to the mobile joints, confirming that surgical fixation results in time-dependent degenerative changes of the zygapophysial joints.

Chiropractic also asserts that spinal health and function are directly related to general health and well-being. Preliminary research concerning the intricate functioning of the nervous system suggests that this speculation may have some support. David Seaman, DC, MS reviewed the work of several researchers concerning autonomic nervous system relationship to the somatic tissues of the spine. He noted that Feinstein et al. were the first to clearly describe some symptoms associated with noxious irritation of spinal tissues. They injected hypertonic saline into interspinous tissues and paraspinal muscles of normal volunteers for the purpose of characterizing local and referred pain patterns that might develop. His observations included:

"The pain elicited from muscles was accompanied by a characteristic group of phenomena which indicated involvement of other than segmental somatic mechanisms. . . . The manifestations were pallor, sweating bradycardia, fall in blood pressure, subjective faintness, and nausea, but vomiting was not observed. Syncope occurred in two early procedures in the series of paravertebral injections and was subsequently avoided by quickly depressing the subject's head or by having him lie down at the first sign of faintness. These features were not proportional to the severity of or to the extent of radiation; on the contrary, they seemed to dominate the experience of subjects who complained of little pain, but who were overwhelmed by this distressing complex of symptoms."

Feinstein referred to these symptoms as autonomic concomitants. It is likely that these autonomic concomitants were caused by nociceptive stimulation of autonomic centers in the brainstem, particularly the medulla. Feinstein indicated that "this is an example of the ability of deep noxious stimulation to activate generalized autonomic responses independently of the relay of pain to conscious levels." In other words, pain may not be the symptomatic outcome of nociceptive stimulation of spinal structures. Such a conclusion has profound implications for the chiropractic profession. Clearly, patients do not need to be in pain to be candidates for spinal adjustments.

The efficacy and validity of spinal manipulation to address visceral disorders systems remains a source of controversy within the chiropractic profession. Although research is ongoing on this topic, conclusions that support the usefulness of spinal manipulation for organic disorders remains to be seen. Additionally, to complicate matters, chiropractic professors and researchers, Nansel and Szlazak, found that:

"the proper differential diagnosis of somatic (musculoskeletal) vs. visceral (organ) 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, suggest 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."

Considering this phenomenon, Seaman suggests that the chiropractic concept of joint complex (somatic) dysfunction should be incorporated into the differential diagnosis of pain and visceral symptoms because these dysfunctions often generate symptoms similar to those produced by true visceral disease and notes that this mimicry leads to unnecessary surgical procedures and medications.

Other chiropractic researchers have also questioned some of the claimed effects of vertebral subluxation:

"The literature supports the existence of somatovisceral and viscerosomatic reflexes, but there is little or no evidence to support the notion that the spinal derangements (often referred to as subluxations by chiropractors) can cause prolonged aberrant discharge of these reflexes. Equally unsupported in the literature is the notion that the prolonged activation of these reflexes will manifest into pathological state of tissues, and most relevantly, that the application of spinal manipulative therapy can alter the prolonged reflex discharge or be associated with a reversal of the pathological degeneration of the affected reflexes or tissues. The evidence that has been amassed is largely anecdotal or case report based and it has attracted much intra disciplinary debate because of its frequent association with certain approaches to management (largely described as being traditional or "philosophical" in nature)."

Still other chiropractic researchers state quite directly:

"... early chiropractic philosophy ... considered disease the result of spinal nerve dysfunction caused by misplaced (subluxated) vertebrae. Although rejected by medical science, this concept is still accepted by a minority of chiropractors... Indeed, many progressive chiropractors have rejected the historical concept of the chiropractic subluxation in favor of ones that more accurately describe the nature of the complex joint disfunctions they treat."

Researchers at the RMIT University-Japan, Tokyo studied reflex effects of vertebral subluxation with regards to the autonomic nervous system. They found that "recent neuroscience research supports a neurophysiologic rationale for the concept that aberrant stimulation of spinal or paraspinal structures may lead to segmentally organized reflex responses of the autonomic nervous system, which in turn may alter visceral function."

Professor Philip S. Bolton of the School of Biomedical Sciences at University of Newcastle, Australia writes in Journal of Manipulative and Physiological Therapeutics, "The traditional chiropractic vertebral subluxation hypothesis proposes that vertebral misalignment cause illness, disease, or both. This hypothesis remains controversial." His objective was, "To briefly review and update experimental evidence concerning reflex effects of vertebral subluxations, particularly concerning peripheral nervous system responses to vertebral subluxations. Data source: Information was obtained from chiropractic or, scientific peer-reviewed literature concerning human or animal studies of neural responses to vertebral subluxation, vertebral displacement or movement, or both." He concluded, "Animal models suggest that vertebral displacements and putative vertebral subluxations may modulate activity in group I to IV afferent nerves. However, it is not clear whether these afferent nerves are modulated during normal day-to-day activities of living and, if so, what segmental or whole-body reflex effects they may have."

Conclusions: 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.

Researchers at the Department of Physiology, University College London studied the effects of compression upon conduction in myelinated axons. Using pneumatic pressure of varying degrees on the sciatic nerves of frog specimens, the study supported the idea of nerve conduction failure as a result of compression.