[Spinal stenosis and instability of the lumbar spine. Current aspects of pathophysiology and pain mechanisms].

The pathophysiology of spinal stenosis and segmental instability is discussed. The critical magnitude of the cross-sectional area of the cauda equina in the lower part of the vertebral canal is related to the dynamic loading of the spine, nerve impulse conduction and nerve root nutrition. Present knowledge of segmental instability is discussed, and an account is given of findings obtained during dynamic measurements with an intervertebral motion device (IMD), which indicate pathological motion patterns to differ from one pair of vertebrae to another.