Reoperation in Long Lumbar Constructs with and Without Iliac Fixation

Study Design. Retrospective cohort study. Objective. To evaluate the association between iliac fixation and long-term reoperation risk in patients undergoing multilevel lumbosacral fusion for degenerative pathology. Summary of Background Data. Spinopelvic fixation using iliac screws is commonly employed to improve construct stability in long lumbar fusions involving the sacrum. While biomechanical benefits are well established, clinical evidence regarding long-term reoperation risk and failure mechanisms in degenerative populations remains limited. Methods. We identified adult patients undergoing primary elective multilevel lumbosacral fusion (>4 levels) between 2009 and 2023 from a large integrated healthcare spine registry by using iliac fixation. Primary outcome was all-cause reoperation. Secondary outcomes included reoperation for adjacent segment disease (ASD), nonunion, and hardware-related complications. We used Multivariable Cox proportional hazards regression models adjusted for patient and surgical factors to evaluate reoperation risk. Time-stratified analyses addressed nonproportional hazards. Results. A total of 1,301 patients were included, including 483 with iliac fixation and 818 without. Mean follow-up was 6.3 years. At 10 years, crude all-cause reoperation incidence was 26.0% with iliac fixation versus 31.1% without. Iliac fixation was associated with reduced long-term all-cause reoperation risk (>1 y) (HR 0.63, 95% CI 0.43–0.92, P =0.018), but not early reoperation risk. Nonunion-related reoperation risk was significantly lower with iliac fixation (HR 0.30, 95% CI 0.13–0.67, P =0.004). No significant differences were observed in ASD-related reoperation risk. Conclusions. In patients undergoing multilevel lumbosacral fusion for degenerative pathology, iliac fixation was associated with significantly lower long-term reoperation risk, driven primarily by reduced nonunion-related reoperation. These findings support the role of iliac fixation in improving long-term construct durability. Level of Evidence. III