Sex Differences in Patient-Rated Outcomes after Lumbar Spinal Fusion for Degenerative Disease: A Multicenter Cohort Study

Study Design. Heterogeneous data collection through a mix of prospective, retrospective, and ambispective methods. Objective. To evaluate the effect of biological sex on patient-reported outcomes after spinal fusion surgery for lumbar degenerative disease. Summary of Background Data. Current literature suggests sex differences regarding clinical outcome after spine surgery may exist. Substantial methodological heterogeneity and limited comparability of studies warrants further investigation of sex-related differences in treatment outcomes. Materials and Methods. We analyzed patients who underwent spinal fusion with or without pedicle screw insertion for lumbar degenerative disease included within a multinational study, comprising patients from 11 centers in seven countries. Absolute values and change scores (change from preoperative baseline to postoperative follow-up) for 12-month functional impairment [Oswestry disability index (ODI)] and back and leg pain severity [numeric rating scale (NRS)] were compared between male and female patients. Minimum clinically important difference (MCID) was defined as >30% improvement. Results. Six-hundred sixty (59%) of 1115 included patients were female. Female patients presented with significantly baseline ODI (51.5±17.2 vs. 47.8±17.9, P<0.001), back pain (6.96±2.32 vs. 6.60±2.30, P=0.010) and leg pain (6.49±2.76 vs. 6.01±2.76, P=0.005). At 12 months, female patients still reported significantly higher ODI (22.76±16.97 vs. 20.50±16.10, P=0.025), but not higher back (3.13±2.38 vs. 3.00±2.40, P=0.355) or leg pain (2.62±2.55 vs. 2.34±2.43, P=0.060). Change scores at 12 months did not differ significantly among male and female patients in ODI (Δ1.31, 95% CI: -3.88 to 1.25, P=0.315), back (Δ0.22, 95% CI: -0.57 to 0.12, P=0.197), and leg pain (Δ0.16, 95% CI: -0.56 to 0.24, P=0.439). MCID at 12 months was achieved in 330 (77.5%) male patients and 481 (76.3%) female patients (P=0.729) for ODI. Conclusion. Both sexes experienced a similar benefit from surgery in terms of relative improvement in scores for functional impairment and pain. Although female patients reported a higher degree of functional impairment and pain preoperatively, at 12 months only their average scores for functional impairment remained higher than those for their male counterparts, while absolute pain scores were similar for female and male patients.