Study of twenty skeletons and two hundred patients with degenerative
spondylolisthesis established that it occurred four times more frequently
in females, six to nine times more frequently at the interspace between the
fourth and fifth lumbar vertebrae than at adjoining levels, three times
more frequently in blacks than in whites, and four times more frequently
the fifth lumbar vertebra was sacralized. It did not occur before the fifth
decade or in conjunction with spina bifida or isthmic spondylolisthesis.
The slipping occurs as a result of degenerative disease of the articular
processes, but it never exceeds 30 per cent. When symptoms are severe and
unrelieved by conservative treatment (10 per cent of our patients),
decompression laminectomy and excision of the medial portion of the
articular processes affords relief of pain. The predisposing factor is a
straight, stable lumbosacral joint which puts abnormal stress on the
intervertebral joint between the fourth and fifth lumbar vertebrae, leading
to decompensation of disc and ligaments, hypermobility, and degeneration of
the articular processes allowing forward slipping.