Degenerative lumbar scoliosis with stenosis: how should Cobb angle inform decompression versus fusion? A systematic review.

Background: Degenerative lumbar scoliosis (DLS) with stenosis is a three-dimensional disorder in which the magnitude of the coronal curve informs, but does not, by itself, determine operative planning. Objective: To assess how the preoperative Cobb angle should be interpreted when choosing decompression alone versus fusion in adults with DLS and stenosis. Methods: Ovid MEDLINE and Embase databases were searched from 1996 to April 25, 2025. The search in Ovid was created by combining keyword and subject heading terms for adult degenerative scoliosis/adult spinal deformity, lumbar scoliosis, Cobb angle, stenosis, decompression, and fusion. Studies eligible for inclusion were adult surgical cohorts that either provided explicit data on preoperative Cobb angles or included patients based on a preoperative Cobb angle threshold, and that reported at least one outcome measure following surgery for decompression and/or fusion. Cohorts consisting of mixed populations were excluded unless an analysis of the appropriate subset of adults with DLS could be performed independently. Heterogeneous studies were synthesized using narrative methods. Results: Four observational studies met the inclusion criteria. In mild curves, generally below 20°, decompression alone produced acceptable outcomes when stenosis predominated and instability was limited. In the limited comparative evidence, fusion appeared more favorable when curves were larger or when mechanical features such as instability or more substantial deformity were present. Across the included studies, important modifiers beyond Cobb angle included foraminal stenosis, lateral listhesis, disc wedging, and sagittal alignment. Follow-up ranged from approximately 1 to 4.6 years. Conclusions: Cobb angle is a useful decision aid, but not a stand-alone indication. Operative choice in DLS with stenosis should integrate curve magnitude with stenosis pattern, instability, sagittal alignment, symptoms, comorbidity, frailty, and the expected burden of surgery.