I couldn't resist entering the frey...
First let's not forget that osteopathy (the forerunner of osteopathic medicine) predates chiropractic in the US by several decades. Palmer visited Kirksville and observed several classes and enjoyed conversations with AT Still, before sneaking across the border to set-up his own school in Iowa. This is well known.
<a href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11620051&dopt=Abstract" target="_blank">http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=11620051&dopt=Abstract</a>
While the biomechanics of manipulation is the same regardless of who performs it (MDs, DOs, DCs, PTs, LMTs, etc) there are important differences between OMT practiced by DO's and SMT practiced by chiropractors. First, chiropractors use SMT within the framework of a "nerve model" to remove subluxations. These subluxations are believed to actually exist and affect whole-body physiology via interaction with the CNS.
Historically, DO's used OMT to improve blood flow and fascilitate tissue waste-product removal; this is AT Still's, "rule of the artery is supreme." As a whole, DO's gave up this etiological theory decades ago, though some hold onto it for its heuristic value. Now, DO's use OMT to remove somatic dysfunction, broadly defined as "impaired or altered function of the somatic system; its skeletal, arthroidal, or neurovascular related elements. It is believed that by removing somatic dysfunction, a host may better recruit its own healing mechanisms. These approaches (removing somatic dysfunction versus removing subluxations) are not the same.
More importantly, DO's are trained as medical doctors and use OMT within a much broader context than chiropractors do. There are DO's who only have inpatient OMT practices using OMT to treat hospitalized patients with pneumonia, post-operative ileus, chronic ventilator patients, non-cardiac chest pain. Again, being medically-trained allows them to treat patients in the hospital and get paid by Medicare, something chiropractors cannot do.
I think that there are other important advantages to being a medically-trained manipulator in terms of ones experience with more complicated diseases, inpatient hospital care, sicker patients, etc. In many European countries, non-medical osteopaths and chiropractors do not hold professional doctorate degrees. They are more like master degree level PT's. They practice under the supervision of a medically-trained physician. I think the same could be arranged here in the US. Chiropractic schools could stop awarding a professional doctorate degree, and start awarding a Master's degree and chiropractors could work under the supervision of a medically-qualified practitioners as do licensed PT's.
I think the issue of medically versus non-medically trained manipulators is analagous to having PhD psychologists prescribe psychotropic medicines (as is happening in New Mexico and some other states). Yes, it is possible to teach a non-physician to prescribe, but is it good medicine? Certainly there are very, very gifted non-medical manipulators, but is this safe and effective patient care?
DO's were so concerned with keeping up with MD's that the profession let chiropractors sneak off with manipulation. The fact that the chiropractic profession has evolved and thrived the way it has is due to, in part, a failure of organized osteopathic medicine to stand-up 100 years ago and forecibly argue that manipulation *IS* the practice of medicine. The MD's would have probably thrown a fit over that assertion since they denied any utility of manipulation at all, but no one could predict the way things would end-up: MD's and DO's would learn to play nice-nice, and DC's would make a tidy bundle popping people's necks and backs, and we would still not know what works and why.
Now, we have a situation where a variety of different practitioners are treating patients with a variety of different manipulative therapies and no one knows what good any of it is for anyone. Just like studies of psychotherapy have shown that psychotherapy is, in general, effective for a vareity of psychological problems, these same studies have also shown that are few differences between specific "brands" of psychotherapy (psychoanalytic versus interpersonal versus cognitive behavioral). I think studies will eventually show the same general benefits for manipulation---regardless of its particular brand name.
Chiropractors keep pushing for a broader scope of practice: Manipulation under anesthesia, access to hospitals, prescription privileges, the right to practice "primary care", etc. Unfortunately, these issues will probably not be decided by science, but by politics and influence. I think organized medicine (MDs and DOs) need look critically at this situation.
