Rheumatoid arthritis of the lumbar spine leading to anterior vertebral subluxation and compression of the cauda equina.

A 71-year-old woman with rheumatoid arthritis suffered a spontaneous anterior subluxation of the fourth lumbar vertebra with compression of the cauda equina. The patient was operated upon with a decompressive lumbar laminectomy and a stabilizing posterior interbody fusion of L4 and L5. Histological examination of the unstable L4-L5 motor segment showed that the apophyseal and discovertebral joints had been destroyed by rheumatoid granulation tissue.