Synovial facet joint cysts after lumbar posterior decompression surgery

OBJECTIVE Numerous studies have reported on synovial facet joint cysts of the spine as a primary lesion. The exact pathogenesis of those cysts is still controversial, but degeneration and destabilization seem to be underlying mechanisms. However, only a few reports have thus far investigated synovial cysts of the spine as postoperative complications of decompression surgery. In this retrospective clinical study, the authors focused on synovial cysts of the lumbar facet joints as complications after lumbar decompression surgery, with the aim of elucidating their pathophysiology. METHODS A total of 326 patients with 384 segments treated with posterior decompression surgery without fusion were included in the study. Of these segments, 107 were surgically decompressed unilaterally and 277 were decompressed bilaterally. After surgery, 18 of the 384 segments developed a complication of symptomatic facet synovial cyst. The anatomical and morphological evaluations of these segments were performed using functional plain radiographs, CT scans, and MR images. RESULTS All of the 18 segments with postoperative lumbar facet synovial cyst were treated with bilateral lumbar posterior decompression. There was no significant radiological lumbar spinal instability in any segments, although 17 of 18 segments demonstrated facet articular spondylotic changes. Moreover, 12 of 18 patients demonstrated lumbar retrolisthesis in the neutral position. CONCLUSIONS Based on the authors’ results, they propose that patients with lumbar degenerative disease who have a potential biomechanical lumbar instability such as disruption of the facet articular surface and hydrarthrosis or lumbar facet tropism might have a high risk for formation of lumbar facet synovial cyst after bilateral posterior decompression surgery.