Editor's note: "DC" asked Dr. Vernon to adapt a presentation he made at the Sixth Annual International Symposium at the Los Angeles College of Chiropractic, March 5-6, 1993. The theme of the conference was "Neurobiological Mechanisms of Manipulation."
I'm sure conference participants came away from the meeting with a great deal more insight into the complexity of those nervous system mechanisms that play an ever-present role in our day-to-day clinical realities of treating patients in pain, and who have neuromuscular dysfunction and perhaps other disturbances of their health.
The only way for us to make progress, is to take an honest, critical view of what we really know about neurophysiological mechanisms related to chiropractic science, that is, related to the nature and effects of the spinal subluxation and its treatment by manipulation or adjustment. An honest review of this area would distinguish what we really know, from what we think we know. In the former case, what we really know will come from credible, valid scientific investigations which would, taken together, form a database from which to piece together the best picture of the mechanisms involved. In the latter case -- what we think we know -- we have the majority of our current thinking -- a large collection of varied theories, speculation and extrapolation from other research not primarily (and in some cases not even remotely) related to our particular purpose for its use. In other words, a set of very loose and convenient approximations of the truth.
Most of what we think we know has arisen from examining our patients, in other words, from post hoc clinical studies in humans. What this really means is that we are always looking for the subluxation after the fact, once we presume its already there. From doing this its very easy to get to the point where we're so convinced about what it is we're looking for, that we never fail to find it. Then we're locked into a circular process. The subluxation is all those things we find when we find what we were looking for in a subluxation.
To remedy this problem, we have to step outside this circularity and conduct investigations which start from independent positions and examine effects as they occur, that is, prospectively. Can we create "investigational subluxations" in humans and hope to solve our problems this way? Obviously not. Our work with humans must be therapeutic and must abide by the golden rule of any healer -- primum non nocerum.
This inevitable leads both the chiropractic clinician and the philosopher to the doorstep of the basic scientist, where properly conducted animal studies will answer many of our most pressing questions.
There does exist a significant number of studies in the chiropractic literature on subluxation mechanisms: certainly over 15 studies. This in itself is remarkable; most people I talked to had no idea about this body of work. We've learned a great deal from these studies, and the remarkable thing is how consistent most of them are with our theoretical predictions. The mammalian spine can be misaligned well short of a dislocation of the articular surfaces. Spinal joints can be fixated. Nerve structures can be compressed, and spinal articulations can be made painful so as to examine the effects of these states. Most of this work falls into the category of investigations into mechanisms of deep somatic pain, and of neuropathic pain -- two recent areas of pain neurophysiology which are rapidly gaining attention. The study of the spinal subluxation fits well into current pain neurophysiology; it's not voodoo science.
Most of these investigations have been singular, short-lived expeditions into "chiropractic" basic sciences. Very little of it has been carried forward and developed comprehensively. The notable exception in the past has been the work of Ken DeBoer at Palmer College. Recently, Rich Gillette of Western States Chiropractic College working with William Roberts of the Dow Neurological Institute in Portland, and myself, working with Barry Sessle of the University of Toronto, have established investigations into subluxation-like pain mechanisms which have already yielded significant findings.
What do we need to know? First of all, we need a credible, workable model of spinal subluxation, fixation, and spinal pain. The studies mentioned above were certainly working toward these goals with some very innovative approaches. It turns out that it is much easier technically to model spinal joint pain, particularly by injecting algogenic irritants into spinal tissues, than it is to mechanically recreate a subluxation and assume that pain will result from this. The same holds true for models of nerve compression both around and distal to the intervertebral foramen. These pain and compression models will probably gain the most favor amongst current and future investigations.
We need to know a great deal more about pain receptors in and around the spinal tissues. We need to know about the effects of spinal joint pain on spinal cord neurons -- dorsal horn neurons, motoneurons, and autonomic neurons. The neurobiochemistry of these mechanisms needs to be explored. We need to examine the whole facilitation model proposed by Korr with up-to-date techniques and from a modern neurophysiological perspective.
We need to pay a lot of attention to pain-related sympathetic effects: it's the theories we espouse in this area that underpin the whole somatovisceral model of chiropractic practice. This whole area is virtually untested. As an analogy, consider the competent driving of an automobile as equivalent to the amount of scientific investigation necessary to firmly establish that spinal column dysfunction can lead to visceral disorders. We are currently, like a prelicensed teenager, opening the driver's side door for the first time. We could conduct dozens of clinical trials of chiropractic treatments for asthma, dysmenorrhea, hypertension, etc., and all of that work will never be viewed as anything more than a huge exercise in validating the placebo effect, unless we can provide ourselves, our patients, and our scientific colleagues and critics with a valid, credible biological mechanism. The somatovisceral reflex mechanism is appealing, but we have a very long way to go before it is accepted.
We also need to apply animal model studies to the understanding of mechanisms related to manipulation. We need to know a lot more about the anti-nociceptive effects of a spinal adjustment -- do they derive from proprioceptive (large fiber) input? Are these mechanisms only segmental or do they involve supraspinal mechanisms as well? The "gate-control" model of Melzack and Wall has been thrown around a lot as have comparisons to acupuncture. If I were about to have surgery, I might consider acupuncture as an alternative to general anesthetic, but I sure wouldn't want to use spinal adjustments for that purpose. Different treatments, different mechanisms.
Finally, we need to explore the response of muscles to the spinal subluxation. Our theories regarding spasm, weakness and other changes in muscle function are very poorly substantiated. We have very elaborate clinical models of muscle dysfunction and of the response of muscles to manipulation. These are all very long on speculation and short on data. All of these need a great deal more investigation.
What will help us get there? The conference at LACC highlighted the necessary ingredients. We need much more basic science work in the chiropractic paradigm within our colleges. Chiropractic basic science researchers need to be nurtured and their work needs to be given the time and resources necessary to succeed.
Interdisciplinary collaborations are essential. The exchange of ideas and activities that goes on between chiropractors and basic scientists can be remarkable. I have always found basic scientists to be interested in and excited about ideas that come from the chiropractic paradigm. Interaction at conferences is vital. Scheduling more think-tanks and other opportunities for "meeting-of-the-minds" is crucial.
Finally, we have to stop telling ourselves what I call scientific children's stories. We need to stop promoting old simplistic notions about the nervous system, and we need to stop congratulating ourselves over the little bit of science that has been done, most of that by other groups.
We have a very long road ahead of us. Thankfully, some of us are at least ready to make the trip. Good science about the subluxation can be done. Get excited about it. Support it.
Howard Vernon, DC, FCCS(C)
Agincourt, Ontario
Canada
