Surgical treatment of degenerative lumbar spondylolisthesis: Effect of TLIF and slip reduction on sagittal alignment

The surgical treatment of lumbar degenerative spondylolisthesis (LDS) remains controversial. The aim of this study was to determine the effect of adding transforaminal lumbar interbody fusion (TLIF) to posterolateral fusion (PLF) on the local lordosis, sagittal alignment and potential complications. The second aim was to evaluate the effect of slip reduction on the same parameters.The initial hypothesis was that TLIF provides better correction of the local lordosis and that reducing the slip improves the global sagittal balance.In this retrospective, single-center study, patients who had been operated on for LSD at one or two levels by laminectomy and PLF, with or without a TLIF cage, were included. Data collected consisted of age, sex, number of levels fused and whether or not a TLIF cage was used. Fusion was defined as the absence of indirect nonunion signs on radiographs at 2 years postoperative. The occurrence and time frame of any complications and the need for reoperation were documented. Lateral radiographs of the entire spine were analyzed preoperatively, in the early postoperative period (3 to 6 months) and at a minimum follow-up of 2 years. The following parameters were measured: pelvic parameters, C7 sagittal tilt (C7ST), spinosacral angle (SSA), maximum lumbar lordosis (LL), lordosis at slipped level (LS), slip percentage. The analysis compared patients treated by PLF and TLIF and determined the impact of slip reduction.One hundred and three patients were included in the study (71% women). The mean follow-up was 38 months. The mean age was 69 years. Seventy-seven patients (75%) underwent PLF. Comparing the preoperative and early postoperative data identified 5.4% better spondylolisthesis reduction in the TLIF group than the PLF group (-8.9±9.5% vs -3.5±7.6%; p=0.04) that was not maintained at the final follow-up. The fusion rate was comparable between groups: 94% in APL and 89% in TLIF (p=0.7). The overall complication rate was 46% in the TLIF group versus 33% in the PLF group (p=0.35). A comparison based on whether or not the slip was reduced found significant improvement in the reduction group of the SSA by more than 6° (6.8°±6° vs 0.5°±7.4°; p=0.04). The fusion rate was 91% in the reduced group and 95% in the non-reduced group (p=0.81); the complication rate was 44% versus 28% in the non-reduced group (p=0.10).This study shows that slip reduction helps to improve the sagittal alignment by increasing the SSA when treating LDS. Posterolateral fusion and TLIF produce comparable radiographic outcomes at 2 years postoperative in the segmental lordosis, slip reduction, global sagittal alignment and fusion rate.IV.