[Long-term Results Regarding the Instability of Decompressive Surgery without Fusion for Degenerative Spondylolisthesis].

PURPOSE: The long-term results of decompressive surgery for degenerative spondylolisthesis (DS) were evaluated with reference to instability. MATERIALS AND METHODS: Patients (n=48) undergoing decompressive surgery without fusion were studied. The diagnosis of spondylolisthesis was made based on the presence of sagittal vertebral slippage greater than 3mm. Instability was defined as translation more than 2mm on lateral functional radiography. Surgical interventions were divided into two groups: bilateral laminotomy (n=25)and laminectomy (n=23). Clinical results were evaluated according to the McCulloch's classification and Japanese Orthopedic Association(JOA)score. RESULTS: Of 48 patients, 25 showed preoperative instability. Eleven patients showed both pre-and postoperative instability. The mean pre-and postoperative slippages were 7.5 and 7.6mm, respectively. Of 23 patients without preoperative instability, nine developed postoperative instability. In this group, slippage changed from 6.2 to 6.1mm. Instability was not related to slippage progression. Surgical results of patients undergoing laminotomy were superior to those undergoing laminectomy. The mean pre-and postoperative JOA scores and recovery rate were 14.5, 20.9, and 63.1 in instability group patients with laminotomy and 15.6, 23.2, and 59.0 in the non-instability group, respectively. Surgical results were similar and not related to preoperative instability. Low back pain (LBP) showed no correlation to the degree of slippage, instability, and surgery type. LBP improved in each group. CONCLUSIONS: Instability, defined by vertebral translation on lateral functional radiography, did not affect the surgical results of patients with DS treated with laminotomy.