Abstract

In chiropractic, vertebral subluxation is a purported misalignment of the spinal column, not necessarily visible on X-rays, leading to a set of signs and symptoms sometimes termed vertebral subluxation complex. It has no biomedical basis, lacks clinical meaningfulness, and is categorized as pseudoscientific by leading chiropractic authorities. Traditionally, the "specific focus of chiropractic practice" is the chiropractic subluxation and historical chiropractic practice assumes that a vertebral subluxation or spinal joint dysfunction interferes with the body's function and its innate intelligence, as promulgated by D. D. Palmer, the inventor of chiropractic.

The chiropractic subluxation is the heart of the split between "straight" and "mixer" chiropractors. Straight chiropractors continue to follow Palmer's vitalistic tradition, claiming that subluxation has considerable health effects and also adding a visceral component to the definition, while mixers, as exemplified by the United Kingdom's General Chiropractic Council, consider it a historical concept with no evidence identifying it as the cause of disease.

Within the chiropractic tradition, a vertebral subluxation complex is believed to be a dysfunctional biomechanical spinal segment which actively alters neurological function, which in turn, is believed to lead to neuromusculoskeletal and visceral disorders. The WHO acknowledges this difference between the medical and chiropractic definitions of a subluxation: medical doctors only refer to "significant structural displacements" as subluxations, whereas chiropractors suggest that a dysfunctional segment, whether displaced significantly or not, should be referred to as a subluxation. This difference has been noted in the proceedings of the chiropractic profession's "Mercy Center Consensus Conference": "The chiropractic profession refers to this concept as a 'subluxation'. This use of the word "subluxation" should not be confused with the term's precise anatomic usage, which considers only the anatomical relationships."

The chiropractic vertebral subluxation complex has been a source of controversy since its inception in 1895 due to the lack of empirical evidence for its existence, its metaphysical origins, and claims of its far reaching effects on health and disease. Although some chiropractic associations and colleges support the concept of subluxation, many in the chiropractic profession reject it and shun the use of this term as a diagnosis. In the United States and in Canada the term "nonallopathic lesion" may be used in place of "subluxation".

A 2009 review concluded that epidemiologic evidence does not support the chiropractic subluxation, concluding:

In 2015, internationally accredited chiropractic colleges from Bournemouth University, University of South Wales, University of Southern Denmark, University of Zürich, Institut Franco-Européen de Chiropraxie, and University of Johannesburg made an open statement which included: "The teaching of the vertebral subluxation complex as a vitalistic construct that claims that it is the cause of disease is unsupported by evidence. Its inclusion in a modern chiropractic curriculum in anything other than an historic context is therefore inappropriate and unnecessary".

Definitions | Definitions and status

The WHO definition of the chiropractic vertebral subluxation is:

The purported displacement is not necessarily visible on X-rays. This is in contrast to the medical definition of spinal subluxation which, according to the WHO, is a ""significant structural displacement"", and therefore visible on X-rays.

As of 2014, the National Board of Chiropractic Examiners states:

In 1996 an official consensus definition of subluxation was formed. Cooperstein and Gleberzon have described the situation: "... although many in the chiropractic profession reject the concept of "subluxation" and shun the use of this term as a diagnosis, the presidents of at least a dozen chiropractic colleges of the Association of Chiropractic Colleges (ACC) developed a consensus definition of "subluxation" in 1996. It reads:

In 2001 the World Federation of Chiropractic, representing the national chiropractic associations in 77 countries, adopted this consensus statement which reaffirms belief in the vertebral subluxation.

The ACC paradigm has been criticized by chiropractic authors:

In May 2010 the General Chiropractic Council, the statutory regulatory body for chiropractors in the United Kingdom, issued guidance for chiropractors stating that the chiropractic vertebral subluxation complex "is an historical concept" and "is not supported by any clinical research evidence that would allow claims to be made that it is the cause of disease or health concerns."

Definitions | ICD coding

The differences between a medical subluxation and a chiropractic "vertebral subluxation" create confusion and difficulties when it comes to following official ICD-9 and ICD-10 coding. In a 2014 article in "Dynamic Chiropractic" by a chiropractor who is a certified professional coder, these difficulties were discussed in detail. He noted that the WHO recognizes the differences between the two types of "subluxations", and also pointed out certain difficulties for chiropractors:

At the time of writing (August 2014) it was still uncertain which codes in the newer ICD-10 would be useful for chiropractors and how they would be interpreted.

Components

Traditionally there have been 5 components that form the chiropractic subluxation. The vertebral subluxation complex is differentiated by the fifth component, general systemic disturbances secondary to the spinal misalignment (vertebral subluxation).

1. Spinal Kinesiopathology

2. Neuropathophysiology/Neuropathology

3. Myopathology

4. Histopathology

5. Pathophysiology/Pathology

Examination

Historically, the detection of spinal misalignments (subluxations) by the chiropractic profession has relied on X-ray findings and physical examination. At least 2 of the following 4 physical signs and/or symptoms must be documented to qualify for reimbursement:

- Pain and tenderness

- Asymmetry/misalignment

- Range of motion abnormality

- Tissue/tone changes

Background

It has been proposed that a vertebral subluxation can negatively affect general health by altering the neurological communication between the brain, spinal cord and peripheral nervous system. Although individuals may not always be symptomatic, straight chiropractors believe that the presence of vertebral subluxation is in itself justification for correction via spinal adjustment.

Chiropractic treatment of vertebral subluxation focuses on delivering a chiropractic adjustment which is a high velocity low amplitude (HVLA) thrust to the dysfunctional spinal segments to help correct the chiropractic subluxation complex. Spinal adjustment is the primary procedure used by chiropractors in the adjustment. Adjustment/manipulation has been shown to help with low back pain, neck pain and tension type headaches, but further studies are inconclusive on the use of spinal manipulation outside the treatment of neuromusculoskeletal disorders.

Rationale and disagreements

In 1910, D.D. Palmer, the founder of chiropractic, wrote:

Chiropractors use and have used various terms to express this concept: subluxation, vertebral subluxation (VS), vertebral subluxation complex (VSC), "killer subluxations," and the "silent killer."

They, along with some physical therapists and osteopathic physicians, have also used another term, BOOP, meaning "bone out of place."

Some chiropractors have described the disagreements within the profession about the concept, and have written skeptically about BOOP as an antiquated idea. In 1992 one wrote:

One wrote in 1994 about the "brutal civil war":

Ten years later (in 2004) he openly disparaged the idea still propounded by "modern-day advocates of this concept":

Functional hypotheses

V. Strang, D.C., describes several hypotheses on how a misaligned vertebra may cause interference to the nervous system in his book, "Essential Principles of Chiropractic":

- Nerve compression hypothesis: suggests that when the vertebrae are out of alignment, the nerve roots and/or spinal cord can become pinched or irritated. While the most commonly referenced hypothesis, and easiest for a patient to understand, it may be the least likely to occur.

- Proprioceptive insult hypothesis: focuses on articular alterations causing hyperactivity of the sensory nerve fibers.

- Somatosympathetic reflex hypothesis: all the visceral organ functions can be reflexly affected by cutaneous or muscular stimulation.

- Somatosomatic reflex hypothesis: afferent impulses from one part of the body can result in reflex activity in other parts of the body.

- Viscerosomatic reflex hypothesis: visceral afferent fibers cause reflex somatic problems.

- Somatopsychic hypothesis: the effects of a subluxation on the ascending paths of the reticular activating system.

- Neurodystrophic hypothesis: focuses on lowered tissue resistance that results from abnormal innervation.

- Dentate ligament-cord distortion hypothesis: upper cervical misalignments can cause the dentate ligaments to put a stress on the spinal cord.

- Psychogenic hypothesis: emotions, such as stress, causing contraction in skeletal muscles.

The vertebral subluxation has been described as a syndrome with signs and symptoms which include: altered alignment; aberrant motion; palpable soft tissue changes; localized/referred pain; muscle contraction or imbalance; altered physiological function; reversible with adjustment/manipulation; focal tenderness.

Scientific investigation

Investigation by chiropractors attempting 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.

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.

Believers within the chiropractic tradition assert that spinal health and function are directly related to general health and well-being. David Seaman 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:

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:

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:

Still other chiropractic researchers state quite directly:

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.

Critiques

Edzard Ernst has stated that the "core concepts of chiropractic, subluxation and spinal manipulation, are not based on sound science."

An area of debate among chiropractors is whether "vertebral subluxation" is a metaphysical concept (as posited in B. J. Palmer's philosophy of chiropractic) or a real phenomenon.

In an article on vertebral subluxation, the chiropractic authors wrote:

Since its inception, the concept of "vertebral subluxation" has been a source of definitional debate. Tedd Koren, DC offers this explanation as a possible cause of the confusion:

Other chiropractors have declared its unproven status as an area that needs reform:

A Beth Israel Deaconess Medical Center article describes the mainstream understanding of vertebral subluxation theory:

In 2009, four scholarly chiropractors concluded that epidemiologic evidence does not support chiropractic's most fundamental theory. Since its inception, the vast majority of chiropractors have postulated that "subluxations" (misalignments) are the cause or underlying cause of ill health and can be corrected with spinal "adjustments." After searching the scientific literature, the chiropractic authors concluded:

In 2005, four leading chiropractic researchers leveled strong critiques of chiropractic dogma: