3 Myths of MDT
There are many misconceptions of MDT, if you regularly read this blog, I hope you don't believe them! Here are 3 MDT Myths.
1) MDT relies solely on the "disc" model.
Although they have been using the disc model to explain rapidly changing derangement syndrome for years, the McKenzie Institute faculty have stated as early as in 2001 (when I first took MDT courses) that even "if" it were completely disproved, the repeated motion exam is reliable and centralization is a valid prognosticator for outcomes. Just check out the official reference list which is updated on MDT USA's site here. That's just the lumbar section, but it remains the most studied due to the prevalence of LBP. They have been under the gun for years to prove why it works. So there are a lot of studies showing flexion postures, nuclear migration in response to postures and movement, etc.
Two studies on the cervical spine by Mercer both concluded the cervical discs do not even fit the model itself. These studies are presented as a "backup" in case the disc model is again, completely disproven. The biomechanics are still taught, and I have not taken a Part B course in many years, but I do not believe they have updated as to why end range loading and repeated motions centralize pain and improve ROM and function.
MDT for the extremities was always at a loss because very few joints have menisci that can lock, but there are often derangement syndromes classified in the shoulder. They initially presented research that I have trouble finding (it was presented in a part E course I took in 2006), that joints that have a loss of function/ROM have a capsular in-growth that normal moving capsules do not. It was theorized that end range loading of joints "reduced" this capsular in-growth. That made sense at the time, but we know from recent research that very little tissues changes are seen with multiple loading strategies and what changes are seen are transient in nature. A recent study from 2011 showed in "normal" cadaveric GH joints that cyclical loading of up 100 N was needed to make tissue changes and that was seen between 100 and 600 cycles. I don't know about you, but I don't oscillate that much!
So in the end, regardless of the model, what is taught consistently at all MDT courses is a repeated motion exam, patient education, and loading/unloading strategies that fit the recent research of self care and patient independence from passive models of care.
2) MDT is all about extension!
This is a common one. It certainly is easy to prescribe prone pressups or REIL for LBP. It's often given without first seeing if extension is the directional preference (DP). That my friends, is sloppy PT. Why not just do any treatment or exercise without first examining the patient?
However, common things happen commonly as the saying goes. It is estimated the average person flexes forward thousands of times a day. This will lead to a natural loss of extension. No... that does not always cause low back pain. We don't know why some people have the perceived threat of a disc protrusion and others have huge spinal cord compressing lesions and are asymptomatic. One thing is clear for regular practitioners of MDT, posterior derangements are more common than anterior derangements. There are physiologic reasons for this, but it most likely again comes down to loading strategies, and most people are forward flexors.
Not only that, but once nociception occurs and back pain is perceived, they start to stretch into more forward bending, and if extension is the DP, we know that is NOT going to help. One of my favorite things to tell patients is, if all the flexion you're doing was going to help, it would've helped already. Time for a change!
In the cervical spine and lumbar spine, there is definitely a predisposition toward extension being the DP, however, there is also a common lateral component of sidegliding for lumbar or sidebending for the cervical spine (less rotation in my experience). They both represent novel ways to get to end range. Neurophysiologically, this is what I think happens, flexion in the cervical and lumbar spines is often painful, whether or not this is making a disc protrude more is moot to me. It does happen to be a novel thing to explain to a patient, however. Extension "loads" the joints more, causing more type 3 mechanoreceptors to fire, bombarding the CNS with great movement information, and the CNS releases the lockdown of the area, decreasing pain and further allowing movement. Other things like downregulation and decreased CNS sensitivity and turning off some extra neurons of Mr. Homunculous could also explain why centralization occurs, not just for purely mechanical reasons.
It may commonly be extension in the cervical and lumbar spines, but in the thoracic spine, the "whip" or ballistic rotation gets to end range loading the best as there is not much extension in that area. Extension is obviously not the preferred DP for many extremities, but does remain so for the knee and the shoulder. Again, these are most likely loading strategies that the patient may not have chosen for those particular areas, so they were not getting to end range, so their chosen self Tx is rendered ineffective.
3) There are no manual techniques in MDT
McKenzie's original stat said that if you apply a careful and appropriate progression of patient generated forces, 80% of patients will most likely not need hands on techniques. If you read my blog post from Friday, I used to scoff at that. I still put my hands on over 90% of my patients, but I think my chosen Tx of IASTM, Functional Release, MWMs, and neurodynamics with the occasional thrust get patients moving to end range faster. I also treat adjacent areas of dysfunction to make overall movement more efficient and hopefully prevent future injury. Patients are also more pleased with the 1:1 time they get with OMPT care combined with MDT philosophies.
Until I began training MDT Diplomats in the fellowship program in my practice, I never saw "pure" MDT. They are EXCELLENT at getting a patient to end range without ever laying a hand on them. It's very scripted, using cause and effect, and great cuing. I never thought the 80% stat was true until I saw clinicians who had devoted a few extra years of training with the best of the best of the MDT faculty.
Of the manual techniques, there are definitely some in all areas of the spine first and foremost, and the extremities are much better now than when I took it 6 years ago. Coming from traditional OMPT programs where you literally learn hundreds of techniques, it seems inadequate what you learn with MDT. What you get in places of hundreds are a handful of techniques instead, but ones that help your patients reach that goal of self care through end range loading.
I apologize if this post seemed all over the place, I originally meant it to be simple, but I could go on for days about this stuff!