Risk Factors for Failed Decompression in Degenerative Lumbar Spondylolisthesis

Study Design: Retrospective cohort study. Objective: To identify clinical, radiographic, and early postoperative factors associated with successful and unsuccessful outcomes following isolated lumbar decompression for low-grade degenerative spondylolisthesis (DS). Summary of Background Data: Although decompression alone has demonstrated outcomes comparable to decompression with fusion in select patients with DS, a proportion of patients experience limited functional improvement or require subsequent fusion. Predictors of durable success following decompression alone remain poorly defined. Methods: Patients underwent a one- or two-level lumbar decompression for grade I/II DS at a single institution between July 2020 and October 2024. Surgical success was defined as achievement of patient-reported outcomes Measurement Information System - Physical Function (PROMIS-PF) minimal clinically important difference (MCID; 5 points). Unsuccessful surgery was defined as failure to achieve MCID progression to lumbar fusion within one year. Demographics, comorbidities, clinical presentation, surgical variables, radiographic features, complications, and outcomes were compared. Facet joint angles and facet tropism were measured by MRI. Results: Fifty-six patients were included, with a mean age of 65.4 13.2 years; 58.9% were female. MCID was achieved in 50.0% of patients. Demographic, clinical, and surgical characteristics did not significantly differ between successful and unsuccessful groups. Patients with unsuccessful outcomes had higher preoperative PROMIS-PF scores (37.5 6.1 vs . 33.5 6.0, P =0.017) and significantly more emergency department visits and readmissions within 90 days compared with the successful group ( P =0.012). Reoperations occurred exclusively in the unsuccessful group. Unsuccessful outcomes were associated with larger facet angles ( P =0.046), greater inter-facet asymmetry ( P =0.002), and higher rates of facet tropism ( P =0.002). Conclusion: In our cohort, only half of patients achieved meaningful functional improvement following isolated decompression for low-grade DS. Unsuccessful outcomes were associated with higher baseline function, early postoperative health care utilization, and specific facet morphology features. These findings highlight the need for improved predictors to optimize patient selection for decompression alone.