Fracture laterality as an independent prognostic factor for clinical outcomes after hip fracture surgery : an analysis of 72,008 patients.

AIMS: Fracture laterality is routinely recorded in large hip fracture registries for administrative purposes, yet rarely evaluated as a prognostic variable. We aimed to test whether laterality is independently associated with short-term outcomes after hip fracture surgery. METHODS: This retrospective cohort study used a regional, prefecture-wide administrative database based on Japan's Diagnosis Procedure Combination system. We identified 72,008 patients who underwent primary surgery for hip fracture between 2015 and 2023. The primary outcome was in-hospital mortality. The secondary outcome was impaired independence in activities of daily living (ADL) at discharge, defined as a Barthel index (BI) score < 60. We used multivariable logistic regression to assess the association between fracture laterality and outcomes, adjusting for age, sex, BMI, smoking history, fracture type, admission BI, diabetes mellitus, and the Charlson Comorbidity Index (CCI). RESULTS: Left-sided fractures were significantly more frequent than right-sided fractures (51.5% vs 48.5%, p < 0.001). In-hospital mortality did not differ significantly between right- and left-sided fractures in either unadjusted (2.0% vs 2.0%, p = 0.093) or adjusted analyses (adjusted odds ratio (aOR), 1.10; 95% CI 0.99 to 1.22; p = 0.075). In contrast, right-sided fracture was independently associated with impaired ADL at discharge (aOR 1.09; 95% CI 1.05 to 1.13; p < 0.001). In a prespecified sub-group analysis, right-sided fracture was associated with higher mortality among patients with high comorbidity burden (CCI ≥ 2; aOR 1.29; 95% CI 1.09 to 1.53; p = 0.004; p for interaction = 0.022). A sensitivity analysis using double-selection lasso logistic regression yielded materially unchanged estimates. CONCLUSION: In our cohort, right-sided hip fractures were independently associated with impaired ADL at discharge, and with higher in-hospital mortality among patients with substantial comorbidity. These associations persisted across sensitivity analyses but, given the observational design and the inability of administrative data to capture limb dominance, require confirmation in independent cohorts. Fracture laterality, which is a variable routinely captured at presentation but seldom analyzed, nonetheless merits consistent reporting and consideration in registry-based prognostic research.