Degenerative spondylolisthesis, synovial cyst of the zygapophyseal joints, and sciatic syndrome: report of two cases and review of the literature.

Two cases of sciatica secondary to nerve root compression by a "synovial cyst" of a zygapophyseal joint are described. In light of these 2 cases and on reviewing the literature, it appears that zygapophyseal joint osteoarthritis with degenerative (or articular) spondylolisthesis can be a predisposing factor to the formation of such synovial expansions and, consequently, the cause of nerve root compression. The coexistence of a lumbar degenerative spondylolisthesis with a radicular syndrome should therefore encourage early investigation by computed tomography scan, so that conservative treatment would not be unnecessarily prolonged.