SPINAL INSTABILITY

SPINAL INSTABILITY - Spinal Instability is a term coined to describe abnormal movement between one vertebra and another. As a disc degenerates it loses tension or ‘turgor’ which allows the disc to bulge and permits increasing movements to take place between the vertebrae. The loss of disc height causes the facet joints to displace and override beyond their correct congruent alignment. This overriding and abnormal slipping of the facet joints induces arthritic overgrowth of the joints and the production of bone spurs around the joint margins.

Abnormal sliding between vertebrae may occur during flexion, lifting or extension and cause pain. This produces significant back pain, attended by a ‘catch’ sign where the patient is suddenly startled by a stabbing pain. This usually occurs when the sufferer is halfway through getting out of a chair and standing upright. It is often associated with a spasm and sometimes locking up of the back.

The pain is caused when movement such as flexion or extension causes the vertebrae to slide forward and backward or rotate abnormally. This directly irritates the nerve which has become tethered to the disc, vertebra, facet joint margin and ligaments in the foramen. Since the nerve cannot move freely to accommodate these abnormal movements, it becomes irritated causing back and/or leg pain. The abnormal movements cause arthritic overgrowth of the joints and bone spurs to develop. The ‘catch’ occurs when the facet joint bone spurs dig into the nerve.