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

STUDY

DESIGN

Retrospective cohort study.

OBJECTIVE

To determine independent risk factors for sacral fracture after lumbosacral fusion.

SUMMARY OF BACKGROUND DATA: 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.

METHODS

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).

RESULTS

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.

CONCLUSIONS

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 OF EVIDENCE: Level III-retrospective case-control study.