McKenzie Derangement Syndrome
The third syndrome which McKenzie distinguished was derangement syndrome. This syndrome has its theoretical basis in the effect of repetition of movement on the nucleus of the intervertebral discs. The outer covering of the disc, the annulus fibrosus, is firm and resilient to withstand the stresses on the structure and contain the nucleus when it is under pressure. The nucleus is much higher in water content and develops pressures in its fluid matrix when put under postural and activity stresses. These stresses can alter the position of the nucleus to a minor degree so that it has a greater or lesser effect on the posterior wall of the disc which is the main areas which suffers from stresses which cause pain.
McKenzie''s idea was that the nucleus is dynamic to some degree and that repeated movements can change the dynamics of the nucleus, altering the symptoms of the patient in a rational and consistent fashion. He developed the idea of centralisation and peripheralisation to describe the symptom changes. In centralisation the symptoms of the patient reduced or disappeared in a farther part of the pain distribution and concentrated more towards the low back to a degree. In peripheralisation the reverse occurred with symptoms perhaps spreading from the low back to the buttock or down the leg.
Centralisation implies improvement in the disc mechanics while peripheralisation implies a worsening and the physiotherapist will test a patient using a variety of repeated movements in particular directions to see what effect this has on the symptoms. Commonly the patient will display a directional preference, in other words a particular movement which, when repeated, improves their symptoms and will likely be the basis their treatment. Sitting and bending over both involved repeated or sustained flexion and it is to correct these problems that much therapy is aimed.
The physiotherapist will give the patient postural correction again, as poor posture allows the vertebrae to hold an unhelpful position, impacting on the nucleus and allowing it to be displaced in the painful direction. Repeated movements of the directional preference will also be prescribed, with the centralisation as a guide to improvement. This syndrome can be unstable, with rapid worsening of symptoms if posture or activity is wrongly performed, so patients need to persist until the symptoms are well under control and the disc mechanics are more stable. Later the physio will want the patient to perform movements in the aggravating direction to ensure that a dysfunction does not develop.
Author: Jonathan Blood-Smyth