Impact of Pre-operative Estrogen Replacement Therapy on Clinical Outcomes After Lumbar Spine Fusion Surgery

Study Design Retrospective cohort study. Objective There is a lack of contemporary evidence evaluating the influence of estrogen replacement therapy (ERT) on clinical outcomes following lumbar spine surgery. We hypothesized that ERT would be associated with lower rates of pseudoarthrosis following lumbar spine fusion. Methods A multi-institutional electronic medical record database was queried for female patients >50 years old undergoing single- and multi-level lumbar spine fusion surgeries. Propensity score matching (1:1) resulted in evenly distributed ERT and non-ERT cohorts. Exclusion criteria included history of previous lumbar spine surgery, spine neoplasms, trauma, inflammatory, or infectious bone conditions. Comparisons were made with independent sample t-tests. Results There were 2268 patients in the single-level and 2776 patients in the multi-level lumbar spine fusion cohorts. During the thirty-day post-operative period, patients in the ERT cohorts demonstrated significantly higher rates of emergency department utilization following single-level and multi-level lumbar spine fusion. Significantly lower rates of postoperative blood transfusion were observed in the non-ERT cohort following multi-level lumbar spine fusion. At 5 years, patients in the non-ERT cohort demonstrated significantly higher rates of pseudoarthrosis following single-level and multi-level lumbar spine fusion. However, at 5 years patients in the ERT cohort demonstrated similar rates of adjacent segment disease and lumbar spine reoperation following single-level and multi-level lumbar spine fusion. Conclusions Pre-operative ERT exposure was associated with lower rates of pseudoarthrosis following lumbar spine fusion with similar rates of lumbar spine reoperation. These findings can enhance pre-operative counseling and risk stratification prior to lumbar spine fusion.