Sex Differences in Adjacent Segment Disease Following Spinal Fusion Procedures: A National Retrospective Cohort Analysis

Introduction: Many studies have reported differences in outcomes by sex following spinal fusion procedures and often report worse outcomes in female patients, although a clear relationship has not yet been established. One complication of spinal fusion procedures is adjacent segment disease, which includes outcomes such as disc degeneration and spondylolisthesis. Here, we compared the development of adjacent segment disease in patients by sex using TriNetX, a national health record database.

Methods: We used TriNetX to compare male and female patients who had undergone any spinal fusion procedure and had no prior history of disc degeneration or spondylolisthesis. We then stratified further by comparing sex across only cervical and lumbar fusion procedures. Propensity score matching was performed, yielding 65,080 patients in each cohort for the analysis of any fusion procedure, 7,440 for the lumbar fusion analysis, and 13,053 for the cervical fusion analysis. The outcome examined in each case was adjacent segment disease, classified as disc degeneration or spondylolisthesis, that occurred within 10 years of the procedure.

Results: Female patients had a higher risk of developing adjacent segment disease than male patients after any fusion procedure (23.1% vs. 20.3%, p< 0.0001), after lumbar fusion procedures (23.5% vs. 21.0%, p=0.0012), and after cervical fusion procedures (20.7% vs. 19.0%, p=0.0018).

Conclusion : Our results suggest that female patients are more likely to develop adjacent segment disease following spinal fusion procedures. This aligns with previous reports of worse outcomes in female patients and lends further validity to a causal link with sex. More work is needed to uncover the exact mechanisms that could explain this difference in outcomes.