Friday, January 25, 2008

Veterinary chiropractic, elusive “Vertebral subluxations”…

…and other sundry details…or a hundred years of talk and still no answers

The skills necessary to practice medicine takes years of persistent and focused effort. During the course of becoming a truly prepared doctor, aspiring students must retain an enormous mass of learned information, gather it into a working knowledge base, and successfully -with this base- bring to life a flexible and effective problem solving system. That is, aspiring doctors need to learn how to tease out meaning and develop direction in an ever changing environment of real life and death- full of unknown variables. This aptly describes the fluid state of medical practice.

One extremely important condition that has allowed this enterprise to work effectively (for the last one hundred years or so) is the fact that medicine has tempered and restrained its ego enough to keep itself within the framework of tested reality- a firm data base if you will. This medical data base has become a growing maze of interlocking bits of information, each adding to a sum total that coalesces into a robust, dependable, and usable system of knowledge.

Alas, this one critical and non-negotiable condition -key for attaining any real chance at legitimacy- is missing in chiropractic theory and practice. Since its inception, with very few exceptions, chiropractic medicine has labored under the rubric of the “subluxation” a concept that, to this day, remains elusive and mysterious.

The practice of chiropractic has been described as a diagnostic illusion; a discipline that has been constructed on very precarious foundations. Though this modality claims to treat the cause of a patients’ problem- it doesn’t at all. The core diagnosis in chiropractic practice; usually some form of the “subluxation complex”, is either non-existent or a result of a real organic disease. For example, many of the conditions interpreted as or resulting from subluxations -some of which can be localized- are actually a plethora of other maladies including bony asymmetry, conformational issues, muscular adhesions, ligamentous contracture, weak musculature, and a myriad of generalized maladies.

In veterinary medicine- and human medicine for that matter- the definition of a “vertebral subluxation” or “vertebral subluxation complex” has gone through a number of revisions over the years in what has been a futile attempt to pin this concept down and connect it to something tangible. The “subluxation”, "vertebral subluxation complex", or whatever you would like to call it is a term that describes a constellation of signs and symptoms that, chiropractors claim, result from a misaligned or dysfunctional spinal segment (and different from the rare and verifiable medical luxation describe in evidence based medicine). The Association of Chiropractic Colleges defines it as a “complex of functional and/or structural and/or pathological articular changes that compromise neural integrity and may influence organ system function and general health.” This seems to cover just about anything!

Alan Schoen DVM, a prominent promoter of Complementary and Alternative Veterinary Medicine (CAVM), defined veterinary chiropractic therapies at the 2001 World Small Animal Veterinary Association Congress “…as the art and science of diagnosis and correction of dysrelationships between the nervous system and the spinal column through manual spinal manipulation.”

He goes on to describe that the concept of a subluxation “is completely different to a veterinarian and a chiropractor, leading to numerous misunderstandings and debates. One needs to look at current definitions in order to better understand chiropractic concepts. These definitions and concepts are evolving as well… From a chiropractic perspective, a vertebral subluxation complex is defined as a disrelationship between a vertebral segment in association with contiguous vertebrae, resulting in disturbance of normal biomechanical and neurologic function.” These rather vague descriptors of the core premise for chiropractic are typical of the efforts to give this modality an air of credibility. However, they add nothing to the discussion of what a “subluxation” is, how it can be reliably diagnosed, and how it relates to the previously mentioned sum total of dependable medical knowledge.

Unfortunately, purveyors of chiropractic don’t stop with first trying to define and confirm the existence of this entity- they go on to create a huge body of detail that includes imaginative pathophysiological causal mechanisms and a whole litany of chiropractic therapies that comprises the so called “chiropractic paradigm.” The problem is if you can not independently identify the object in question, confirm and establish any effects it may produce, or consistently link it to solid evidence you are basically chasing ghosts.

Supporters of the “veterebral subluxation complex” claim that it can negatively impact general health interfering with the proper function and healing of the body because the nervous system controls a broad array of organ systems- though we are only given unproven theories as to how (fig.1).


(Fig 1) Example of unsubstantiated etiologic theories for how a “subluxation could cause disease: V. Strang, D.C., “Essential Principles of Chiropractic”1.

  • 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.


Dr Schoen states that “The pathophysiology of subluxation complexes includes compression of spinal nerve roots or the spinal cord, vertebrobasilar arterial insufficiency, somatovisceral dysfunction, and decreased mobility.” This is similar to many of the anatomical and functional theories described by other practitioners- sound nice, but where is the proof?

These “dysfunctions” are treated by a plethora of therapies some of which seem reasonable (i.e.; rest, massage, stretching excersizes) but most -in their majority- appear to be based on dubious alternative recommendations and techniques (i.e.; acupuncture, muscle testing, unusual hair and blood analysis testing, laser therapy, magnetic therapy, nutritional supplement therapy). Still, by far, the core treatment modality used by chiropractors in animals and humans remains the familiar “adjustment or manipulation”.

Schoen defines these two modalities successively as follows“<an adjustment is > a ‘short-lever, high-velocity, quick thrust’ with specific force applied in a specific direction to a specific vertebra and designed to deliver maximal force with minimal tissue damage. Manipulation distributes the force to multiple segments via “long-lever, slow velocity, non-thrust” techniques. These are all based on Wolf’s Law that ‘structure follows function.’ In other words, that functional problems precede actual structural defects.”

The mention of Wolfs law is a good example of how tangentially related concepts are cherry picked and mentioned in the same breath with implausible notions- such as the above described manipulations.2 Wolfs law describes a physiological response over time of bone to a variety of loading situations- not including periodic chiropractic adjustments or manipulations.Stating that functional problems precede structural defects is like saying all diseases are caused by nutritonal deficiencies. Broad sweeping statements are often incomplete or false and may reflect a profound misreading of what scientific observations actually reveal.

“Vertebral subluxations” are thought to involve one or more spinal units (two vertebral articar faces and all the corresponding tissues). The fuzzy “vertebral subluxation complex”, though more abstract is still approached primarily through manipulations. Chiropractic treatment is therefore oriented at targeting the affected part or parts of the spine in order to reduce a “subluxation” or correct physiological disruption.

Dr Schoen goes on to imply that by adjusting an animal and correcting the subluxation the affected neurological pathways are no longer hindered or compressed and the flow of impulses improves thereby resulting in a healthier status. This is reminiscent of the original vitalistic “energy” related beliefs invented by DD Palmer; the originator of chiropractic therapy.

In medicine, it is important to localize and identify the systems involved in disease and to monitor the evolution and effects of treatment- all important criteria for science based medical treatments. The problem is veterinary chiropractic is not dependant on the findings of modern medical problem solving techniques -though it will often “piggy back” and be “integrated” with those findings- it can also just as easily be implemented independently of any established science. This is because chiropractic medicine is not threaded and tied into the robust system of modern medicine- not a good thing.

In this vein, Dr Schoen correctly adds “Veterinary chiropractic research is limited.” and notes that “Most recent research has been conducted by Dr. Kevin Hausler at Cornell Veterinary School, where he documented mobility of the equine spine and demonstrated equine spinal movement following a chiropractic adjustment.” This may refer to a small study published later in 2007 regarding the relationship between spinal kinematics (movement) and specific spinal manipulations after attempting to surgically induce back pain in a group of ten horses. This study found a very modest improvement in spinal “flexibility” in the thoracolumbar region when treated horses were exercised on a treadmill as compared to a control group.

Though intriguing, this observation does not constitute any type of explanation or validation for the “subluxation complex” and the results may or may not even be real.3 In any event, the data is indeed minimal with respect to a establishing any scientific underpinning for veterinary chiropractic theory. It is worth noting, that the present scarcity in humans of validated research regarding the “subluxation complex” makes animal research even less promising.

An example of how some chiropractors have responded to this criticism includes an article by Ted Koran DC in which he states “Subluxations, genes, gravity, the ego and life are all heuristic devices, "useful fictions" that are used to explain phenomenon that are far larger than our understanding. We use them as long as they work for us and discard or limit their application when they become unwieldy or unable to account for new observations... Critics of chiropractic have incorrectly assumed that chiropractic is based on the theory or principle that vertebral subluxations cause "pinched" nerves that cause disease. They have it backwards. Chiropractic is based on the success of the spinal adjustment. The theory attempting to explain the success of the adjustment (nerve impingement, disease, subluxations) followed its clinical discovery.” 4 The problem with this position is that the subluxation has no where near the foundation and usefulness this doctor thinks. Associating “success” to spinal adjustments is an unsubstantiated assumption- a fallacy- making the rest of his argument rather tenuous and meaningless.

To date, the “vertebral subluxation complex” has no documented natural history (you can not feel it, see it, nor follow its evolution clearly) making it impossible to objectively grade and classify5 and is not a verifiable pathological entity in animals (nor humans). So, if you can’t describe it and you can’t truly localize it- how can you treat it?

Dr Schoen notes that “The future of chiropractic is to include it in a professional manner as an integral part of veterinary medicine.” Sadly, this is another example of a therapeutic modality making an unearned and premature rush towards the world of legitimacy typical of Complementary and Alternative therapies.

The concept of chiropractic vertebral subluxation remains a uniquely chiropractic model not associated or supported by the scientific consensus in human and veterinary medicine. Any benefits from “adjustments” or other chiropractic therapies are likely to be coincidental and actually a result of -among other things- complex placebo effects and the waxing/waning course of chronic disease (natural history of disease).

An article written by supporters of the “subluxation” as a valid- albeit unproven- theory lamented the “dogmatic” approach the chiropractic establishment holds with regards to this concept. Though we may disagree on whether “subluxation” is a valid theory, the authors do candidly and correctly note that “…What must be avoided... is the unreasonable extrapolation of current knowledge into speculation and presentation of theory as fact. Given the current deficiency of empirical data, the only sound scientific-epistemological position that we can conceive of is to acknowledge our ignorance: we don't know if subluxation is clinically meaningful or not. We suggest that this is a requisite first step toward greater wisdom concerning subluxation." 6 On that at least, we can agree.

That chiropractic theory is built on such a tenuous and fragile premise makes it an interesting- yet fictional- belief based enterprise in human ingenuity. Ultimately, veterinary (and human) chiropractic is like the story of the naked king surrounded by worshiping servants. No matter how beautiful their description of his “dress” is- the fact remains that the emperor still has no clothes.


1) Strang, V (1984) Essential Principles of Chiropractic Davenport : Palmer College of Chiropractic, OCLC: 12102972

2) Wolffs' law states “that bone in a healthy person or animal will adapt to the loads it is placed under. If loading on a particular bone increases, the bone will remodel itself over time to become stronger to resist that sort of loading. The external cortical portion of the bone becomes thicker as a result. The converse is true as well: if the loading on a bone decreases, the bone will become weaker due to turnover as it is less metabolically costly to maintain and there is no stimulus for continued remodeling that is required to maintain bone mass.”

3) As with any study, this one needs to be critically analyzed and possibly pooled with other research in equine spinal kinematics. Any significant findings, if found, would then need to be looked into. If there are benefits they should be noted. However, assuming there was some type of positive effect it is more likely due to more readily explainable phenomena such as relaxation or counter irritation than to actions related to the theory behind the “manipulation”. Additionally, other studies researching normal equine kinematics can shed light on the validity of this particular study. On top of that, we have to deal with how this may or may not relate to the rest of the animal kingdom!

4) Chiropractic's Elusive Subluxation - Does the Vertebral Subluxation Exist? - Tedd Koren.

5) For example there is no way to grade different levels of subluxation based on severity, cause, age of patient, anatomical region where it is found, whether it affects populations differently, or if there is any genetic involvement.

6) Keating J, Charlton K, Grod J, Perle S, Sikorski D, Winterstein J (2005) Subluxation: dogma or science? Chiropr Osteopat. 2005; 13: 17. available online

Other ref:

Chirotalk: The skeptical chiropractic discussion forum

Ramey, D. Veterinary chiropractic.

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