Association between antiosteoporosis medications and risk of sacral fracture after lumbosacral fusion in adults with osteoporosis: A proportional hazards analysis.

Abstract

Sacral fracture is an uncommon complication after lumbosacral fusion, with recent evidence suggesting that osteoporosis is an independent risk factor. However, data on the association between antiosteoporosis medications and sacral fracture incidence following lumbosacral fusion remains limited. This study explored associations between antiosteoporosis medication classes and sacral fracture risk after lumbosacral fusion in osteoporotic adults, to identify possible risk mitigation strategies. This retrospective database study included osteoporotic adults who underwent first-time lumbosacral fusion between 2005 and 2023. Patients were divided into short fusion (3-6 spinal levels fused) and very short fusion (≤2 levels) cohorts to control for fusion length. The primary outcome was incidence of sacral fracture within two years postoperatively. Cumulative incidence of sacral fracture was estimated using Kaplan-Meier analysis. Hazard ratios (HRs) were derived using multivariable Cox proportional hazards modeling (p < 0.05). Antiosteoporosis medication classes evaluated in our Cox hazard model included vitamin D, denosumab, bisphosphonates, as well as teriparatide. Among 13,625 osteoporotic patients who underwent lumbosacral fusion, 347 sacral fractures occurred within two years (2.55% incidence). There were 56 sacral fractures in the short fusion cohort and 291 sacral fractures in the very short fusion cohort. Vitamin D was associated with reduced fracture risk (p = 0.047) while denosumab and teriparatide showed no significant association. However, age, a history of falls, and the use of bisphosphonates were associated with a higher risk of sustaining a sacral fracture within two years of the lumbosacral fusion. Among osteoporotic adults undergoing lumbosacral fusion, a history of falls was the strongest predictor of postoperative sacral fracture. Modest associations were observed for vitamin D (protective) and bisphosphonates (increased risk). These findings require corroboration before clinical recommendations can be made. Future studies should focus on vitamin D dose-responses and denosumab, wherein potential protective effects may have been obscured by sparse data.