A Comparison of Unilateral and Bilateral Laminotomies for Decompression of L4-L5 Spinal Stenosis

Study Design. A retrospective review of clinical and radiographic data was performed at a single institution. Objectives. To compare clinical and radiologic outcomes between unilateral and bilateral laminotomies for bilateral decompression in patients with L4-L5 spinal stenosis. Summary of Background Data. Laminotomy has been shown to be comparable with laminectomy with the advantage of potentially maintaining more stability by preserving more of the osseous structures. However, the comparison between unilateral and bilateral laminotomies is available only for short-term follow-up. Methods. Fifty-three patients at one institution having decompressive surgery for L4-L5 spinal stenosis, including grade 1 degenerative spondylolisthesis without instability, were entered into this study with a minimum of 3-year follow-up. Clinical outcomes were assessed with visual analog scale for back and leg pain and the Oswestry disability index. Radiographic measurements were performed and included translational motion, angular motion, and epidural cross-sectional area. Results. The average age of the patients was 62.4 years (range: 31-82). The mean follow-up period was 49.3 months (range: 40-61). Clinical outcomes and complication rates were similar in both groups. Intraoperative blood loss and operative time were less in the unilateral laminotomy group. Radiographically, the amount of increased translational motion was significantly increased in the bilateral laminotomy group (P = 0.012), but the amount of increased angular motion was not significantly different (P = 0.195) between the two groups. Postoperative radiographic instability was detected more frequently in bilateral laminotomy group than in the unilateral group, without statistical significance. Conclusions. Both unilateral and bilateral laminotomies provide sufficient decompression of spinal stenosis and excellent pain reduction. However, unilateral laminotomy can be performed with shorter operative times and less blood loss. Radiologically, the use of a unilateral laminotomy induces less translational motion increase after surgery; thus, it may reduce the risk of late instability when compared with a bilateral laminotomy.