How to Treat Adjacent-Segment Pathology Following Lumbar Fusion Surgery: Decompression Alone or Decompression With Extended Fusion Surgery?

OBJECTIVE: This study aims to compare the risk of subsequent surgery following surgical treatment of clinical adjacent-segment pathology (CASP) after lumbar fusion, specifically evaluating decompression alone versus decompression with extension of the fusion. METHODS: Using the Swespine registry, we included patients who had surgical treatment for CASP following index lumbar fusion surgery, 1997-2019. The cohort was divided according to CASP treatment: decompression alone or decompression with extended fusion. A comparison of subsequent surgeries was made with Kaplan-Meier analysis and Cox regressions adjusted for potential confounders (age, sex, body mass index, smoking status, number of operated levels at CASP surgery, number of fused levels at index fusion surgery, and diagnosis for CASP surgery). RESULTS: A total of 2,521 patients were included, 1,176 (47%) in the decompression-group and 1,345 (53%) in the extended fusion group and the mean follow-up was 6.1±4.4 years. Mean age at CASP surgery was 61 years and 1,588 (63%) were females. The median time to subsequent surgery was 1.7 years (range, 0.9-3.7 years). Kaplan-Meier-estimated probability of subsequent surgeries at 5 years was 18% (95% confidence interval [CI], 15%-20%) for the decompression-group and 25% (95% CI, 22%-27%) for the extended fusion group. The hazard ratio was 1.26 (95% CI, 1.02-1.56; p=0.032) for those with extended fusion. CONCLUSION: Extension of fusion for CASP was associated with significantly higher risk of subsequent surgery, but causality should be interpreted with caution as radiographic information on instability, deformity, or foraminal stenosis could not be verified.