Independent Risk Factors for Sacral Fracture After Lumbosacral Fusion in Adults: A Cox Proportional Hazards Retrospective Analysis.

Abstract

Retrospective cohort study. To determine independent risk factors for sacral fracture after lumbosacral fusion. Sacral fractures are an uncommon complication after lumbosacral fusion, with recent research suggesting that osteoporosis is an independent risk factor. However, there is a paucity of data regarding other potential risk factors. This retrospective study (TriNetX) included adults (18 y or above) who underwent first-time lumbosacral fusion between 2005 and 2023, divided into 2 cohorts: the osteoporosis cohort and the no osteoporosis cohort. The primary outcome was the incidence of sacral fracture after lumbosacral fusion over 2 years, estimated using Kaplan-Meier analysis, with hazard ratios (HRs) estimated for each covariate using a multivariable Cox proportional hazards model (P<0.05). There were 592 sacral fractures (2.3%) among 25,598 adults who underwent lumbosacral fusion, with 470 cases (2.8%) in the osteoporosis cohort and 122 cases (1.3%) in the no osteoporosis cohort. Independent risk factors (P<0.05) for sacral fracture after lumbosacral fusion included previous pelvic radiation [95% CI] (HR: 3.04 [1.26, 7.36]), history of falls (HR: 2.65 [2.21, 3.18]), osteoporosis (HR: 2.02 [1.64, 2.49]), long-term systemic corticosteroid use (HR: 1.47 [1.10, 1.98]), age at index lumbosacral fusion (HR: 1.01 [1.00, 1.02] per year), while protective factors included overweight and/or obesity status (HR: 0.79 [0.65, 0.97]), and male sex (HR: 0.64 [0.48, 0.85]). Variables determined not to be independent risk factors (P>0.05) included nicotine dependence, history of total hip arthroplasty, anterior surgical approach, posterior surgical approach, long lumbosacral spinal fusion with instrumentation (7-12 vertebral levels), diabetes mellitus, bone density medications, inflammatory polyarthropathies, pelvic fixation, vitamin D prescription, chronic kidney disease, and glucagon-like peptide-1 analogues. Clinically meaningful independent risk factors for sacral fractures after lumbosacral fractures include pelvic radiation, history of falls, osteoporosis, long-term systemic corticosteroid use, and potentially increasing age, whereas being male and overweight or obese are independent protective factors. Level III-retrospective case-control study.