The Effects of Estrogen-Based Hormone Replacement Therapy on Women Aged ≥55 Years Undergoing 1- to 3-Level Posterior Lumbar Spinal Fusion Surgery

BACKGROUND: The effect of estrogen-based hormone replacement therapy (HRT) on patient outcomes following posterior lumbar fusion (PLF) is not clear. The purpose of this study is to evaluate the effect of preoperative HRT on older women undergoing PLF. METHODS: A retrospective review of 4596 patients undergoing PLF in the PearlDiver database was performed. Patients prescribed HRT within 1 year preoperatively were matched 1:3 on demographics and pertinent comorbidities with patients not taking HRT; 1149 patients were taking HRT and 3447 were not. Univariate analyses were performed to compare postoperative complications at 90 days and reoperations at 2 years with and without false discovery rate (FDR) adjustment. RESULTS: At 90 days postoperatively, those taking HRT were 41% more likely to experience a urinary tract infection (UTI) within 90 days postoperatively (OR: 1.41, 95% CI: 1.12-1.79; P = 0.005, FDR-adjusted P = 0.090). At 2 years postoperatively, those taking HRT were 65% more likely to have a decompression (OR: 1.65, 95% CI: 1.14-2.38; P = 0.009, FDR-adjusted P = 0.090) and were 35% more likely to have any reoperation (OR: 1.35, 95% CI: 1.04-1.74; P = 0.027, FDR-adjusted P = 0.180). However, these differences were not statistically significant after FDR adjustment. CONCLUSIONS: Patients taking HRT prior to PLF had increased rates of UTI within 90 days of surgery and increased rates of subsequent decompression and any reoperation within 2 years postoperatively, although these trends did not reach statistical significance after FDR adjustment. These results suggest an overall favorable safety profile of HRT use in female PLF patients aged ≥55 years old; however, further surveillance of risk for 90-day UTIs and 2-year reoperations is warranted. CLINICAL RELEVANCE: With the recent removal of most black-box warnings from estrogen-based HRT for menopausal symptoms, it is likely that the number of older female patients taking HRT will increase. It is important to identify the implications of the concurrent use of the medication in patients undergoing spinal fusion surgery.