The McKenzie Examination
Procedure Found to be Accurate Way to Diagnose
In a recent study, (1) the McKenzie procedure for assessing patients with low back pain was found to be more accurate than MRI in differentiating discogenic from non-discogenic pain as well as contained from non-contained discs.
The McKenzie procedure measures the patient's symptomatic response to repeated end-range movements, with special attention to whether the pain centralizes or peripheralizes. Peripheralization is when midline back pain moves to the side of the back or to the buttocks. Further peripheralization involves pain radiating down the leg. The further it moves down the leg, the more it is said to peripheralize. Centralization is the opposite. When pain is no longer as far down the leg, it is starting to centralize. If the pain is no longer down the leg but now is only in the buttocks, it is centralizing further. If centralization continues, the pain will recede towards the lumbar midline and eventually, with continued end range movements, disappears.
With the McKenzie mechanical assessment procedures, the most common direction of testing that centralizes pain is extension, though some patients require lateral side-gliding, and a few will centralize with repeated flexion.
It is part of the McKenzie model that the most likely reason for this centralization phenomenon is that the back and referred/radiating leg is caused by displaced nuclear disc material that is mechanically stimulating the pain-sensitive annulus or the nerve root. This is referred to as the "dynamic internal disc model". As long as the annulus and the hydrostatic mechanism of the disc are intact, repeated end range loading of the spine (repeated movements) can return the displaced nuclear material, thus centralizing and reducing the pain. If no directed movements are able to centralize the pain and if multiple movements result in peripheralization of the pain, then it is theorized that the annulus is torn and that the hydrostatic mechanism of the disc is no longer functioning.
The following hypotheses were tested in this study:
This was a prospective blinded study of 63 patients with chronic LBP who were evaluated both with the McKenzie assessment procedures and with lumbar discography, which is as close as we have to a gold standard for evaluating symptomatic discs. Average age was 39.6 years. Patients had been referred for discography by neurosurgeons, orthopedists, or physiatrists because of continuing pain sufficiently severe enough to warrant invasive testing. These patients had failed a variety of conservative care programs. One or more MRI scans had been conducted without compelling indications for surgery.
The results of this study were as follows:
The McKenzie assessment methods have been criticized for being too subjective, since they rely on the patient's reports of their pain. However, while pain reporting is somewhat subjective and various psychosocial factors do influence the character, intensity, and location of pain, self-reporting of PAIN PATTERNS has been shown to be quite objective and measurable, with high intertester reliability. (various references are cited) The provoking of a patient's pain with the straight leg raise test is one example of a reliable, relevant pain response pattern.
The finding of a 50% rate of centralizers in this group of chronic patients compares with several other studies utilizing the McKenzie testing procedures. In another study of the McKenzie procedures, of patients with acute low back pain (<4 weeks pain) were found to centralize.(2) If centralizing pain is discogenic with a competent annulus, as this current study demonstrates, this suggests that the disc may be the source of pain in a high percentage of patients with LBP, as Kuslich had found in his classic paper on the pain generators in LBP.(3)
While MRI was
inconclusive in these patients and was unable to determine
whether the disc was symptomatic or not and whether the annulus
was competent or not, McKenzie assessment procedures were able to
determine these with a moderately high degree of reliability.