Prognostic Factors of Surgical Outcome after Spinous Process-Splitting Laminectomy for Lumbar Spinal Stenosis

STUDY DESIGN: A retrospective case review. PURPOSE: To assess the clinical and radiographic outcomes and identify the predictive factors associated with poor clinical outcomes after lumbar spinous process-splitting laminectomy (LSPSL) for lumbar spinal stenosis (LSS). OVERVIEW OF LITERATURE: LSPSL is an effective surgical treatment for LSS. Special care should be taken in patients with degenerative lumbar scoliosis (DLS). METHODS: A consecutive retrospective case review of patients undergoing LSPSL for LSS with a minimum 2-year follow-up was performed. Mild DLS and mild degenerative spondylolisthesis (DS) were included in the study. The Japanese Orthopedic Association (JOA) score and recovery rate were reviewed. Poor clinical outcome was defined as a recovery rate <50% using Hirabayashi's method. RESULTS: A total of 52 patients (mean age, 72 years) met the inclusion criteria and had a mean follow-up of 2.6 years (range, 2-4.5 years). The preoperative diagnosis was LSS in 19, DS in 19, and DLS in 14 cases. The mean JOA score significantly increased from 14.6 to 23.2 at the final follow-up. The overall mean recovery rate was 60.1%. Thirteen patients (25%) were assigned to the poor outcome group. A higher rate of pre-existing DLS was observed in the poor outcome (poor) group (good, 15%; poor, 62%; p=0.003) than in the good outcome (good) group. None of the patient factors examined were associated with a poor outcome. A progression of slippage ≥5 mm was found in 8 of 24 patients (33%) in the DS group. A progression of curvature ≥5° was found in 5 of 14 patients (36%) in the DLS group. The progression of scoliosis and slippage did not influence the clinical outcome. CONCLUSIONS: The clinical and radiographic outcomes of LSPSL for LSS were favorable. Pre-existing DLS was significantly associated with poor clinical outcome.