In terms of the SC, centrists have as their cornerstone the clinical reality of the “painful sticky joint” that, in essence, may be our layperson's description of a mild facet joint syndrome. This concept is well described within our contemporary texts,15-18
but the reality of its existence is essentially based upon the published evidence combined with the personal clinical experiences chiropractors have had as both a patient and a doctor. The centrist perspective of the construct is broader than this though and extends to many possibilities of motion segment dysfunction, from the clinically unstable “orthopedic subluxation” to the completely fixated motion segment as a result of bony ankylosis or congenital fusion. This model encompasses the functional, structural, and pathoanatomical changes to the various components of a spinal motion segment as well as the other pelvic and peripheral motion segments. Therefore, in terms of a working definition of the SC, centrists are comfortable with the Association of Chiropractic Colleges presidents' definition of subluxation19
and may be equally as comfortable with the consensus definition proposed by Gatterman and Hansen20
because, essentially, they say the same thing: a subluxation is a change in joint motion that affects the nervous system. Centrists are comfortable with the ambiguity of these definitions because they recognize the strength of words that are broad and inclusive. They recognize that even though the definitions are unsuitable as the basis for a research endeavor, they are a work in an evolutionary process that leaves the clinical door open for patients with any manner of articular problem to enter their offices and be cared for. In regard to subluxation causing nerve interference
, centrists recognize that it is an antiquated term that is more appropriately recast as neural reactivity
. Essentially it is the appreciation that many of the signs and symptoms associated with motion segment dysfunction are likely the result of reactions to mechanical or chemical insults to neural tissue or, more commonly, through reflexes generated within the nervous system as a result of nociceptor or proprioceptor activity initiated in the tissues comprising the motion segment.
As for evidence-based health care, certainly, the peer-reviewed journals stand at the top of the list as sources of important information; but centrists read these understanding that they only provide a narrowly focused glimpse of the subject at hand and that each research study has its own strengths and limitations. Even a well-written systematic review or meta-analysis is a selective interpretation of the accessed literature, and these will be written based on the criteria and biases the authors bring to the study. Therefore, in addition to the peer-reviewed journals, centrists recognize that the other critically important source of literature would include the profession's most recent textbooks. In this case, it is within our textbooks that the depth and breadth of a well-evidenced contemporary perspective of the SC are available. Indeed, the current chiropractic textbooks are of excellent quality and are founded on the best available evidence that existed just before the point of publication. Of course, journal articles help fill the void regarding more recent advances; but a true contemporary understanding of the SC includes both textbooks and journal publications.
In addition to the published literature, centrists are pragmatic and recognize the importance of clinical observation and patient values, which completes the evidence-based practice triad. Centrists essentially are open-minded yet skeptical practitioners attempting to do what is best for their patients. They have an interest in reading about the newest research findings in regard to the SC, however, they are struck by how little we have evidenced than by the meager evidence itself. This is primarily because as they earnestly treat the human condition, they recognize that only a sliver of what they have observed in clinical practice has yet to be studied in any detailed fashion and this is primarily because of the limitations of most of the clinical studies that chiropractors have been involved in. Certainly, a growing number of randomized clinical trials exist evidencing the benefits of manipulation for various types of spinal pain.21
But a shortcoming of most of these is that they failed to report on the changes in subluxation/joint dysfunction pre- and posttreatment while other outcomes were being measured. This is not to say that the clinicians did not analyze the motion segments first to determine the target area of their treatment, it is that the subluxation data were not analyzed and published, and this is particularly lamentable. Therefore, regarding investigating the subluxation clinically, most of this has occurred in conditions not involving low back pain, neck pain, or headaches, and has typically appeared as part of a case study publication.
Given the hierarchy of evidence, case studies sit near the bottom and are seldom included when considering the evidence regarding the SC.22
Yet centrists will not dismiss case reports as having absolutely no value especially because they have witnessed many positive clinical responses that are not satisfactorily explained by the competing hypotheses. Hartman23
has ruefully pointed out that a number of alternative mechanisms could be at work when patients appear to improve under care, and these have nothing to do with the effectiveness of the treatment itself. Included in this list are the placebo effect, the self-limiting nature of the disease, regression toward the mean, the effect of known or unknown cotreatments, and/or reporting biases of the patient or the doctor. Centrists accept that these phenomena could be at work, but they also realize that one important possibility is that there truly was a treatment effect from their adjustment of the patient's subluxation. In terms of the SC, possibility rises to the level of probability as the presenting complaint mirrors the signs and symptoms associated with the painful sticky joint or even one of the more complex musculoskeletal subluxation syndromes identified by Gatterman17
and patients respond to treatment with dramatic and immediate responses.
One might ask why it is that these musculoskeletal clinical conditions actually form the basis for the centrist perspective in regard to the SC instead of broadening this to include nonmusculoskeletal conditions. Firstly, chiropractors treat patients with musculoskeletal pain approximately 90% of the time24,25
; and painful subluxations are simply encountered in their offices as one of the most common causes of musculoskeletal pain. This has been documented by Smith and Carber26
when DCs were surveyed about their perspectives on subluxation. They found that more than 75% of chiropractors' clinical approach to addressing musculoskeletal or biomechanical disorders such as back pain was “subluxation based.”
Secondly, I suggest that there is another important criterion related to the causation of disease: temporality.27,28
The clinical observations that chiropractors make either as patients themselves or as doctors rendering care and the dramatic results obtained immediately after analysis and adjustment at the site of the lesion tip the scales of belief. Positive clinical responses in acute, subacute, and even chronic cases are occurring within seconds and minutes, not hours, days, weeks, or months; and it is this evidence that causes centrists to shake their heads when the existence of subluxation is questioned. These repeated observations have convinced the doctors beyond all reasonable doubt that segmental dysfunction exists and that they have the means for treating it. To centrists, the SC is simply the most rational model used to explain the clinical observations that occur daily and thousands of times per year in their patients.
Essentially, centrists recognize that clinical anecdote, expert opinion, and the case reports, which eventually flow from these observations, are acceptable forms of evidence that must be considered along with all other evidence if one is truly going to consider the best available evidence. Naturally, one must be ever mindful of the shortcomings of clinical observations and continue to look for evidence that falsifies these hypotheses if one is truly a practitioner-scientist. But this is one of the strengths of the centrist position: to date, there has been no compelling falsification of the joint dysfunction hypothesis. It is granted that some of the earlier hypotheses regarding nerve impingement have been debunked. But even the claims that the reliability studies investigating the diagnostic tools used to identify the manipulative lesion are wanting or that the validity studies are too sparse do not falsify the SC. They only inform the debate and help create the demand for better research. For the time being, the chiropractic subluxation is the most credible reason to explain the clinical results obtained in these patients, which is primarily why centrists will not abandon the SC, much to the chagrin of the evidentialistas.
In a similar sense, the same can be said for some nonmusculoskeletal cases. Centrists are particularly skeptical of visceral conditions being caused by subluxation, which is particularly irksome to the uncritical observationalists in the profession who view subluxations as being far more involved in these. In this case, Smith and Carber26
found that most chiropractors reported that less than 20% of their clinical approach was “subluxation based” for patient complaints deemed to be principally problems with circulation, digestion, or similarly “visceral” in nature. Centrists recognize that subluxation could often present as a condition that mimics a visceral condition and in fact no true visceral disease exists,18
such as in the case of pseudoangina.29
Centrists however also view treatment of some selected nonmusculoskeletal conditions as simply a therapeutic trial that patients have a right to choose to participate in. Given that proper clinical procedures (including informed consent) have been followed and given consideration for the current state of the evidence, there truly is no compelling reason to refuse chiropractic management (including manipulative care) for these conditions if patients decide they want it. Ultimately, though, I would suggest that beyond the clinical reality of subluxation, it is the social utility of the construct that has caused it to remain as a cornerstone of the profession. In this sense, it is reminiscent of a similar cultural phenomenon, namely, the Santa Claus construct (SCC).