Microsurgical excision without fusion as a safe option for resection of synovial cyst of the lumbar spine: long-term follow-up in mono-institutional experience.

Spinal synovial cysts are cystic dilatations of the synovial membrane that may arise at all levels of the spine. We describe our experience, paying attention to diagnosis, surgical treatment, and long-term follow-up. Between 1995 and 2007, 18 patients were surgically treated. Of these, three patients were excluded from the study because they presented spinal instability at pre-operative assessment. All patients were evaluated pre-operatively with CT, MRI, and dynamic X-rays, and underwent surgery for removal of the cyst by hemilaminectomy and partial arthrectomy. All patients were evaluated with early MRI and had a minimum 2-year follow-up by dynamic X-rays. None of the patients required instrumented fusion due to the absence of radiological signs of instability on the pre-operative dynamic tests. In all patients, there was an immediate resolution of the symptoms, with evidence of complete removal of the cysts on post-operative MRI. At 2-year follow-up, all patients underwent dynamic X-rays and responded to a questionnaire for evaluation of outcome. None of them showed signs of relapse. The gold standard for treatment is surgery, even though other conservative treatment regimens have been proposed. Correct surgical strategy relies on pre-operative assessment of biomechanical stability for deciding whether patients need instrumented fusion during cyst removal. Patients with no instability signs are suitable for hemilaminectomy with partial arthrectomy, preserving 2/3 of the medial portion of the articular facet, because this represents a valid option of treatment with a low risk of complications and a low rate of relapse.