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Mckenzie Science

Robert Medcalf, PT, Dip MDT

This is the era of Evidence-based Medicine. Sufficient time has passed to allow the scientific scrutiny to be applied to the various assessment and treatment methods available to patients. Though further studies are forthcoming and are necessary to build a full evidence base, there are many studies published in peer reviewed journals that support various aspects of the McKenzie Approach of MDT. This approach continues to be the most researched physical therapy based method available. The following is the selection of some of the most important studies on the approach to date with an explanation of their significance.

Assessment
It is fundamentally important that any system of assessment and treatment have two key components of the assessment-
1. reliability and
2. diagnostic validity

Reliability means that two different examiners will agree on the assessment findings and come to the same conclusion when assessing each patient. Since treatment decisions rely exclusivey on the patient assessment this is critical. The following two studies demonstrate that the McKenzie Approach, when applied by Credentialled therapists, has very good agreement.
  • Kilpikoski S, Airaksinen O, Kankaanpaa M, Leminen P, Videman T, Alen M.; Interexaminer reliability of low back pain assessment using the McKenzie method. Spine; Apr 15;27(8):E207-14, 2002. 
  • Ramjou H, Kramer JF, Yamada R; Intertester reliability of the McKenzie evalutation in assessing patients with mechanical low-back pain. J Orth & Sports Phys Ther; Ju;30(7):368-383, 2000.
When the above two studies are combined with a previous study of untrained therapists - Riddle, Rothstein 1993 it is clear that the only way therapists can consistently agree is if they are properly trained and Credentialled. Therapists who lack full training in MDT do not have accurate or reliable assessments and therefore are unable to deliver consistent, appropriate treatment to their patients with this method.
The second part of the diagnostic process is the accuracy of the assessment when compared to a diagnostic standard. The following two studies demonstrate the accuracy of key findings in the McKenzie assessment and their relation to diagnostic injection. These are the first studies to our knowledge to find any physical examination process can accurately predict injection findings.
  • Donelson R, Aprill C, Medcalf R, Grant W.; A prospective study of centralization of lumbar and referred pain. A predictor of symptomatic discs and anular competence. Spine; May 15;22(10):1115-22, 1997.
  • Laslett M, Young SB, Aprill CN, McDonald B.; Diagnosing painful sacroiliac joints: A validity of a McKenzie evaluation and sacroiliac provocation texts. Aust J Physiother; 49(2):89-97, 2003.
The McKenzie approach also has a very important feature which many other approaches do not and that is the ability to predict patient treatment outcome. Centralization or lack of centralization is a key predictor of patient treatment outcome. More specifically, if a patient with lumbar or cervical pain can have their symptoms centralized in a short time after initiating MDT, the prognosis for a rapid and lasting improvement is likely.
  • Skytte L, May S, Peterson P; Centralization: its prognostic value in patients with referred symptoms and sciatica Spine; 30:E293-E299, 2005
  • Werneke M, Hart DL; Centralization phenomenon as a prognostic factor for chronic low back pain and disability Spine; Apr 1;26(7):758-65, 2001.
  • Werneke MW, Hart DL; Categorizing patients with occupational low back pain by use of the Quebec Task Force Classification system versus pain pattern classification procedures: discriminant and predictive validity Phys Ther; 84:243-253, 2004.
Treatment
  • Long A, Donelson R, Fung T; Does it matter which exercise? A randomized control trial of exercises for low back pain. Spine; 29:2593-2602, 2004.
This is a study that more closely replicates what we experience clinically. The results are dramatic and ensure that the case for non-specific exercises will be much harder to make.
In this study, we have a clear endorsement for the value of subclassifying our patients using a McKenzie assessment, establishing directional preference and giving our patients specific exercises based upon these findings, which will significally affect patient outcomes in regard to, among other things ... pain, function and medication use.
This is probably one of, if not the, most important MDT study to date. It certainly helps us to justify the MDT assessment and the specific interventions based on individual patients presentations. It shows that it is what we do with our patients that determine their outcom. It is not simply that centralizers have a superior outcome with any treatment provided. The treatment must match the assessment findings or the results are inferior.
  • Alexander AH, Jones AM, Rosenbaum Jr D H:; Nonoperative Managment of Herniated Nucleus Pulposus: Patient Selection by the Extension Sign-Long term Follow-up. Orthopaedic Review; 21;181-188, 1992.
Patients who had a confirmed lumbar herniated disc with loss of strength and/or sensation, achieved a successful nonoperative resolution with MDT if they could centralize their symptoms and achieve full passive extension (a press-up). The results showed that 91% of persons who achieved this were able to avoid surgery at 5 year follow-up.

Prevention
  • Larsen K, Weidick F, Leoboeuf-Yde C.; Can passive prone extensions of the back prevent back problems?: a randomized. controlled intervention trial of 314 military conscripts. Spine; Dec 15;27(24):2747-52, 2002.
In a military poplation, the regular performance of passive extensions exercises (press-ups) resulted in a decrease in the report of low back pain as well as a reduction in disability related to low bak pain over a one year timeframe.

Fortino Gonzalez, PT, Dip MDT, FAAOMPT, OCS  

McAllen Physical Therapy