Lumbar synovial cysts of the spine: an evaluation of surgical outcome.

OBJECTIVE: Our aim was to study the outcomes and results of surgically treated patients with synovial cysts of the lumbar spine in our institution.
METHODS: Retrospective data from 39 consecutive patients, treated during the period of December 1996 to August 2004, were analyzed. Twenty-eight men (70%) and 11 women (30%) of mean age 63.3 years were studied. All pre- and postoperative signs, symptoms, extension/flexion radiographs, magnetic resonance imaging (MRI), and computed tomography (CT) with or without myelography were reviewed. All underwent surgery for synovial cysts with excision and decompression. Additional fusion in 26 patients was performed; 22 of them had degenerative spinal spondylolisthesis. Nine (23%) patients had prior decompression procedures, with three (8%) having had prior spinal instrumentation. Surgical outcomes were evaluated according to a questionnaire scoring system (scale of 1-4; 4 = excellent, 3 = good, 2 = fair, 1 = poor). Various preoperative attributes such as gender, age, weight, and height were analyzed to see if they had any effect on the outcome of surgery. Modified musculoskeletal outcomes data evaluation and management system (MODEM), questionnaire was provided to all; 24 (62%) responded. The following categories were determined: excellent (<20), very good (21-40), good (41-60), fair (61-80), and poor (81-100). Postoperative complications were also recorded.
RESULTS: All patients had pain in their lower extremities, with 62% experiencing pain bilaterally. Ninety-five percent had pain in their back and 36% in the buttocks (36%). Eighteen (46%) patients had CT myelography. A total of 42 cysts were found. Two patients had bilateral cysts at L4-L5 level. Histology revealed two hemorrhagic cysts. The average duration of surgery was 231 minutes (range 92-391 minutes), and a mean blood loss of 930 mL (range 200-2500 mL) was recorded. Two operative dural tears and one postoperative wound dehiscence were observed. One patient had a recurrent synovial cyst at the site of original surgery. Eight patients (four each in the fusion and nonfusion group) had junctional degeneration and symptoms. A regression analysis performed on age, height, weight, and gender showed that they were not determining factors of surgical outcome. Surgery of spinal cysts at L4-L5 segment produced good and those at L5-S1 and multilevel excellent results. Patients with spinal segment fusion had superior outcomes, with 80% having excellent or good outcomes versus approximately 70% without fusion. With the modified MODEM questionnaire, 22 of the 24 (92%) patients scored between excellent, very good, and good. Two patients scored in the fair range, and none of the 24 patients scored in the range of poor.
CONCLUSIONS: Spinal cysts are commonly found at the L4-L5 level, the site of maximum instability. MRI is the tool of choice for diagnosis. The etiology is still unclear, but underlying spinal instability has a strong association for formation of spinal cysts and worsening symptoms. Synovial cysts resistant to conservative therapy should be treated surgically. Resection and decompression with fusion remain an appropriate option. The optimal approach for patients with juxtafacet cysts remains unclear. The best surgical treatment approach for each particular individual appears to remain speculative.