Posterior lumbar interbody fusion versus posterolateral fusion with instrumentation in the treatment of low-grade isthmic spondylolisthesis: midterm clinical outcomes

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The purpose of this study was to compare the methods of posterior lumbar interbody fusion (PLIF) and posterolateral fusion (PLF) in cases of isthmic Grades 1 and 2 lumbar spondylolisthesis, and to evaluate the clinical efficacy of the procedures. Operations were performed in 50 patients with lumbar spondylolisthesis in the authors' clinics between 2001 and 2007. Indications for surgery were low-back pain with or without sciatica and neurogenic claudication that had not improved after at least 6 months of conservative treatment. The study included 33 female and 17 male patients, with mean ages of 50.6 years in the PLIF group and 47.3 years in the PLF group. These patients were randomly allocated into 2 groups: decompression, posterior transpedicular instrumentation, and PLF (Group 1; 25 patients) and decompression, posterior transpedicular instrumentation, and PLIF (Group 2; 25 patients). In the PLIF group, titanium cages were used, and autograft material was obtained from the decompression. In the PLF group, bone fragments collected from the iliac crest were used as autografts. A minimum 18-month follow-up was available in all patients. For clinical evaluation, a visual analog scale, Oswestry Disability Index, and the 36-Item Short Form Health Survey were used. Improvements in pre- and postoperative spondylolisthesis, segmental angles, fusion ratios, and postoperative complications were evaluated radiologically. The average follow-up period was 3.3 years. Based on the etiologies, isthmic spondylolisthesis was detected in all patients. The spondylolisthesis levels in the patients who underwent PLIF were located at L3-4 (5 patients, 20%); L4-5 (14, 56%); and L5-S1 (6, 24%), whereas the levels in the ones treated with PLF were located at L3-4 (4 patients, 16%); L4-5 (13, 52%); and L5-S1 (8, 32%). In the clinical evaluations, good or excellent results were obtained in 22 (88%) cases in the PLIF group and 19 (76%) cases in the PLF group. Fusion ratios were 100% in the PLIF group and 84% in the PLF group. Both lumbar lordosis and the segmental angle showed greater improvement in the PLIF group. There was no difference in the complication rates for each group. Based on early clinical outcomes and the fusion ratios of adult isthmic spondylolisthesis, the authors found PLIF to be superior to PLF.