Mid-term effects of posterior versus oblique lumbar interbody fusion on spinopelvic alignment and clinical outcomes in lumbar spinal stenosis: a retrospective comparative cohort study.

Mid-term evidence directly comparing posterior lumbar interbody fusion (PLIF) and oblique lumbar interbody fusion (OLIF) for degenerative lumbar spinal stenosis (LSS) remains limited. It is also unclear whether radiographic restoration relates to disability improvement differently between techniques. We retrospectively included 100 patients who underwent one- or two-level fusion between 2018 and 2020 (PLIF, n = 53; OLIF, n = 47). ODI, visual analog scale (VAS), and Japanese Orthopaedic Association (JOA) scores and standing lateral radiographs were collected preoperatively and at mid-term follow-up (mean follow-up, ~ 52 months). ODI improvement (ΔODI) was defined as ODI_pre-ODI_final. Radiographic parameters included lumbar lordosis, sacral slope, segmental lordosis angle, disc height (DH), and foraminal height (FH). Between-group comparisons were performed, and a covariate-adjusted ANCOVA modeled final ODI with baseline ODI adjustment. Both procedures significantly improved ODI, VAS, and JOA from baseline. Unadjusted final ODI did not differ significantly between groups, whereas ΔODI was greater after PLIF (19.6 ± 8.4 vs. 14.6 ± 8.8; P = 0.004). In adjusted ANCOVA, OLIF was associated with a higher final ODI (β = 5.04, 95% CI 1.60-8.49; P = 0.005). Radiographic improvements were observed in both groups; final FH was higher after OLIF. Perioperative complication profiles differed: surgical-related events were more frequent after PLIF, whereas approach-related events were more frequent after OLIF. At mid-term follow-up, PLIF and OLIF provided sustained improvement in pain and function. PLIF showed greater unadjusted ODI improvement, while baseline-adjusted analyses suggested higher final ODI after OLIF. OLIF achieved a higher final foraminal height.