[The effect of spinal distraction and immobilization on the facet joint cartilage--experimental and clinical studies].

The effects of spinal immobilization and distraction on the facet joint cartilage was studied in 49 young Wistar rats which were kept in the specially made lumbar-pelvic distraction apparatus from two to twelve weeks' duration. After two weeks' immobilization and distraction, histologic examinations revealed early regressive degeneration in superficial layers of the facet joint cartilage. Thereafter, the degeneration progressed further and became irreversible between 4 and 8 weeks' immobilization. After release of immobilization, the facet joint cartilage finally resulted in osteoarthrosis. Six clinical cases with thoracolumbar spinal fracture treated by posterior instrumentation without arthrodesis were investigated. Following removal of the instrumentation, the spinal mobility recovered temporarily then decreased gradually afterwards. Histologic examinations on the facet joint in the clinical cases showed pathological changes which were very similar to those of the experimental rats. From these results, we have concluded that the spine without arthrodesis appears to develop into symptomatic arthrosis by internal fixation.