Postoperative Sagittal Alignment in Degenerative Lumbar Spondylolisthesis: A Prospective Pilot Study

Background: Degenerative lumbar spondylolisthesis (DLS) commonly affects the elderly and may require lumbar fusion when conservative treatments fail. Restoration of sagittal alignment has gained attention as a determinant of postoperative outcomes, but its impact in DLS-specific populations remains under-investigated. Objective: The objective of the study was to evaluate the relationship between postoperative sagittal alignment and functional recovery in patients undergoing lumbar fusion for symptomatic DLS. Material and Methods: This prospective single-center pilot study included 16 patients with DLS who underwent lumbar decompression and fusion between April 2022 and May 2023. Postoperative sagittal alignment parameters – sagittal vertical axis (SVA), pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt, sacral slope, and PI–LL mismatch – were measured using standardized radiographs. Functional outcomes were assessed with the Oswestry Disability Index (ODI) at baseline and 12 months postsurgery. Results: Mean ODI scores improved significantly from 60.6 ± 13.9 preoperatively to 16.5 ± 13.1 postoperatively ( P < 0.001; Cohen’s d = 2.3). Patients with SVA <50 mm had better ODI scores, and those with PI–LL mismatch <10° tended to do better functionally, though statistical comparisons were limited due to small subgroup sizes. Conclusion: Optimizing sagittal alignment, particularly achieving SVA <50 mm and minimizing PI–LL mismatch, may enhance early functional recovery in DLS patients undergoing lumbar fusion. Larger multicenter studies are needed to confirm these findings and guide alignment-based surgical planning.