Hip Fracture Risk Following Lumbar Fusion: A Retrospective Cohort Study of Construct Length and Age-Stratified Outcomes.

Abstract

Lumbar fusion alters spinal biomechanics and may increase hip loading, especially with long-segment constructs. We used a large administrative database to evaluate hip fracture risk after lumbar fusion and assess whether fusion length influences this risk in younger and older adults. Using PearlDiver, we identified patients ≥ 50 with lumbar degenerative disorders across three cohorts: nonoperative controls (n = 66,603), 1-6 level fusion (n = 44,402), and ≥ 7 level fusion (n = 22,201), matched by age and sex. Five-year hip fracture-free survival was estimated via Kaplan-Meier analysis, stratified by age (< 65 vs. ≥ 65) and compared with log-rank tests. Hip fractures were uncommon across all groups (~ 1-2 per 1,000 person-years), with no significant overall differences between controls and fusion groups. In patients aged < 65, long-segment fusion was associated with significantly lower hip fracture-free survival (χ²=22.11, p < 0.00001) and a threefold higher hazard compared with short-segment fusion (HR 3.07, 95% CI 1.89-4.99; incidence 2.01 vs. 0.62 per 1,000 person-years). In patients ≥ 65, hip fracture rates were higher overall but did not differ significantly by fusion length (χ²=0.455, p = 0.50). Lumbar fusion was associated with a small increase in hip fracture risk, with long constructs conferring substantially higher risk in adults < 65.