Prevalence and clinical features of intraspinal facet cysts after decompression surgery for lumbar spinal stenosis.

Object: Although many cases of primary intraspinal facet cysts in the lumbar spine have been reported, there have only been a few reports of postoperative intraspinal facet cysts in the lumbar spine. The purpose of this study was to investigate the prevalence and clinical features of postoperative intraspinal facet cysts in the lumbar spine.

Methods: Data from 81 patients undergoing microendoscopic posterior decompression to treat lumbar spinal stenosis were reviewed. The development of a postoperative intraspinal facet cyst was observed using MR imaging during 1 year after surgery. If the patient demonstrated a postoperative intraspinal facet cyst, additional MR imaging was performed to evaluate the natural course of the cyst. Furthermore, the authors conducted a comparative evaluation to identify the factors associated with the causes of cyst development.

Results: A postoperative intraspinal facet cyst developed in 7 patients (8.6%) during 1 year after surgery. Spondylotic spinal stenosis, degenerative spondylolisthesis, and degenerative scoliosis were revealed before surgery in 2, 4, and 1 patient, respectively. In 5 patients, the cysts developed within 3 months after surgery. Although 3 patients exhibited symptoms caused by cyst development, all symptoms were relieved by conservative treatment. On radiographic evaluations, postoperative segmental spinal instability, including a progression of spondylolisthesis and disc degeneration, was revealed in 6 (86%) of the 7 patients. Spontaneous regression of the cysts was observed in 5 (71%) of these 7 patients. On comparative evaluation of patients with and without postoperative intraspinal facet cysts, the presence of segmental spinal instability before surgery (including degenerative spondylolisthesis) and the appearance of postoperative segmental spinal instability were related to the development of the cysts.

Conclusions: The prevalence of postoperative intraspinal facet cysts, including asymptomatic cysts, was 8.6% during 1 year after decompression surgery for lumbar spinal stenosis. The development of postoperative intraspinal facet cysts was related to the presence of segmental spinal instability before surgery (including degenerative spondylolisthesis) and postoperative segmental spinal instability, including a progression of spondylolisthesis and disc degeneration after surgery. A postoperative intraspinal facet cyst, which can be expected to regress spontaneously with a probability > 50%, should be recognized as one of the postoperative complications of decompression surgery for lumbar spinal stenosis.