Influence of coronal lumbar Cobb angle and surgical level on short-segment lumbar surgery outcomes in degenerative scoliosis

Purpose: This study investigates the relationship between surgical levels and coronal deformity to identify risk factors for failing to achieve a minimal clinically important difference (MCID) in the Oswestry Disability Index (ODI) following short-segment isolated decompression or fusion surgery in patients with degenerative scoliosis (DS) and concurrent lumbar canal stenosis (LCS), without severe sagittal deformity malalignment.

Methods: Patients with degenerative scoliosis who underwent 1- or 2-level lumbar isolated decompression or fusion surgery were included. Surgical level was labeled as "Cobb-related" when decompression or surgical levels spanned or were between end vertebrae, and "outside" when the operative levels did not include the end vertebrae. Logistic regression analysis was conducted to assess the factor associated with MCID achievement in ODI at 1 year postoperatively.

Results: A total of 129 DS patients with LCS and preoperative ODI > 30 were included. At 1-year follow-up, 91 patients (70.5%) achieved MCID in ODI. No significant differences were found in demographics or overall spinal alignment between patients who did and did not achieve MCID. Logistic regression analysis revealed that Cobb-related decompression was independently associated with decreased odds of achieving MCID in ODI (adjusted Odds Ratio 0.18, 95% CI 0.42-0.79, P = 0.025).

Conclusion: In patients with mild to moderate coronal deformity and minimal sagittal deformity, decompression alone at or across end vertebrae significantly lowers the likelihood of achieving the MCID in ODI compared to fusion surgery, with an 84% reduction in odds. No significant difference in MCID achievement was observed between decompression and fusion surgeries outside the Cobb angle.