Investigating the Relationship Between Estrogen Replacement Therapy and Postoperative Complications Following Single-Level Lumbar Fusion: A Propensity Matched Analysis

Study Design Retrospective Cohort. Objectives The objective of this study was to investigate the relationship between preoperative estrogen replacement therapy and postoperative complications following single level lumbar fusion. Methods The TriNetX Research Network was queried for menopausal patients aged ≥ 50 years who underwent single level lumbar fusion. Patients issued ERT within the 12-month preoperative period were separated from patients with no documented ERT use. Propensity score matching was performed 1:1 based upon demographic characteristics and medical comorbidities. Rates of medical complications were assessed within 90 days postoperatively. Secondary outcomes include pseudarthrosis and revision surgery, which were evaluated within one and two years postoperatively. P < 0.05 indicates statistical significance. Results A total of 1,570 matched pairs were included. The incidence of PE was more than doubled in the ERT-positive cohort (RR 2.167, 95% CI 1.097 – 4.279, P =0.022). Rates of pseudarthrosis were elevated in the ERT-positive cohort within one (12.9% versus 9.9%, RR 1.303, 95% CI 1.070 – 1.587, P =0.008) and two years postoperatively (14.8% versus 11.6%, RR 1.275, 95% CI 1.064 – 1.528, P =0.008); reoperation rates were similar at both intervals. ERT use was also associated with increased rates of ED utilization within 90 days postoperatively (15.4% versus 11.1%, RR 1.377, 95% CI 1.148 – 1.651, P =0.001). Conclusions Patients on preoperative ERT may represent a higher-risk cohort amongst single-level lumbar fusion candidates. Further studies are warranted to explore causality and the potential mechanistic underpinnings between ERT and unsuccessful bone healing and thromboembolic complications.