(look for part II in february)
I wanted to kick off the New Year by focusing on some of the science behind the postural paradigm of chiropractic. The idea of a postural approach to chiropractic actually has a long, although admittedly, sparse history for nearly a century now. Over the past two decades, the concept has gained popularity as a result of publication of a fairly large body of scientific papers supporting various aspects of posture based chiropractic. In spite of this, the idea remains foreign to many doctors.
Resistance to incorporating postural analysis and rehab into daily practice probably stems from the fact that most of us were educated in colleges still clinging to the traditional, but outdated, concept of subluxation as a single segment phenomenon. I am referring here to the traditional concept of subluxation as a single bone which has lost "normal juxtaposition" with its immediate neighbors. Add to that the more recent rise in popularity of the new "motion paradigm" during the seventies and eighties and you have a recipe for professional confusion.
Early proponents of the "motion" approach basically advocated that vertebral position (structure) was largely irrelevant as long as spinal motor units were able to move freely. Later research would show this to be less than accurate but, unfortunately, the idea stuck in the collective chiropractic mind. Certainly, segmental motion (dynamic function) is important, but now we also have a good basis in the scientific literature supporting the clinical importance of healthy human posture (static structure). Unlike many fads that have come and gone in chiropractic, posture is quite different. Posture, the way in which human beings sit, stand, and generally hold their bodies, is so fundamental to how we live, move and feel, that the profession can ill afford to ignore it. Accordingly, this year will address some of the science supporting a postural approach to chiropractic. A great place to start is with a discussion of why such an approach is scientifically valid in the first place.
Maybe your pre chiropractic education prepared you well in the fields of scientific thought and critical thinking, but mine sure didn’t. Add to that an educational environment in chiropractic college, which encouraged students to be “open minded” and chastised those who dared to be skeptical as “negative.” The rather predictable outcome was a group of otherwise bright young doctors with a tendency to be less discriminating than we probably should have been. It is one thing to be open minded. It’s quite another to just be gullible.
Here’s an example. We were all taught the basic prone (Derifield) leg check in school. You were probably told something like a “short leg” means an inferior sacrum, or possibly a PI ilium. But is it possible there could be other, valid explanations for the phenomenon? Isn't it possible the patient just laid down on the table incorrectly? Could tight trunk musculature on one side draw the hip and leg upward? What if there were more degeneration in one knee joint than another? And, dare I even say it, isn’t it possible that sometimes a "short leg" is really just a short leg? All are potentially valid theories, so let's explore just a bit more.
Validity is defined as the relationship between a given conclusion and the premises used to reach that conclusion. Any analysis or test, then, is valid only to the extent that the conclusions reached are actually warranted. So, assuming the Derifield test was highly reliable (It's not particularly, but "reliability" is a completely different issue), the validity of the test would still be compromised by the simple fact that there are other competing hypotheses which could also explain the results. The most obvious of these is that the "short leg" finding on the leg check is simply due to one leg actually being shorter than another!
This brings us to what's known as face validity. Simply put, it's whether or not something makes sense on the “face of things." In this case, had we been trained in critical thinking skills in college, we might well have asked ourselves which of the possible competing hypotheses in our example made the most sense...sacral subluxation vs. anatomical short leg. Certainly, on the face of things, it appears that an actual shortness of the limb might be a distinct possibility, while the concept of sacral subluxation is a bit more removed anatomically. Note that I didn't say it's impossible... just a bit more of an abstract possibility.
And that's the bad thing about tests and procedures with poor face validity; they compel us to avoid obvious conclusions and make leaps in logic to more abstract conclusions. The result is often a lot of unnecessary wear and tear on our imaginations!
All of which leads us to a basic tenet of science and logic known since the 14th century: Occam's razor. The original principle has been expanded and modified over the centuries, but the idea is very simple. Whenever there are two or more theories for something, the simpler one is more likely to be correct. Or restated, the explanation requiring the fewest assumptions is most likely to be correct. In the case of the Derifield leg check, the “validity” of the test is dependent upon the truth of the assumptions we have made (i.e., that the test actually detects sacral subluxation). Again, I’m not saying that assumption is/are wrong (or right), but as a general rule, the greater the degree of abstraction, the more tortured the assumptions which must be made to complete a line of logic. My point here is that, whenever we are confronted with tests or procedures which involve several degrees of abstraction, it should give us pause to think and question the underlying validity.
The postural approach to chiropractic has an inherently high degree of face validity. Consider this: Whenever you observe patients whose postures appears bent or twisted in some manner, the most obvious conclusion is that their body's internal structural framework is somehow bent or twisted. Could it be something else? Well, maybe, if you want to strain really hard. Just be sure to use Occam's Razor to trim away unlikely, competing theories. But, as a chiropractor, if you happen to believe that abnormal structure/posture is clinically significant (I'll provide support for this in future columns), then the validity of actually being able to directly see and observe that which you seek to remedy or treat is obvious.
Our profession has spent a hundred years looking for tiny, often invisible, subluxations of individual vertebrae, while ignoring large, global misalignments of the column as a whole. Where, I ask, is the validity of that approach? When you visually analyze posture, you are observing the direct manifestation of spinal imbalance, not some abstract representation of it. Only spinal X rays allow the doctor a more direct means of observing and measuring the patient’s standing biomechanics. In short, posture matters because of its inherent underlying validity. In fact, few methods and procedures in chiropractic will ever carry the degree of face validity as does the postural approach to corrective care. That doesn’t mean it’s the only way of practicing, just that it’s a logical way of approaching things, and that highly valid procedures are worth incorporating into our daily practices.
Dr. Mark Payne is president of Matlin Mfg., a manufacturer and distributor of postural rehab products since 1988. For a FREE, unabridged copy of this article or other information on postural chiropractic, please contact Matlin Mfg. Inc. at 1-334 448 1210 or on the web at