Postoperative mobility is associated with risk of reoperation and increased mortality after hip fracture: a nationwide cohort study of 33,486 patients

BACKGROUND AND PURPOSE: Postoperative mobilization may influence the outcome following hip fracture. We aimed to examine whether regaining pre-fracture basic mobility on discharge is associated with subsequent risk of reoperation and mortality. METHODS: Using nationwide Danish registries, we identified 33,486 patients ≥ 65 years who underwent hip fracture surgery between January 2016 and November 2021. Pre-fracture and discharge mobility were assessed with the Cumulated Ambulation Score (CAS, score 0-6 where 6 is best ambulation). The exposure was regaining pre-fracture CAS at discharge. Adjusted hazard ratios (aHRs) with 95% confidence intervals (CIs) for reoperation and mortality up to 365 days were estimated using Cox regression, adjusting for age, sex, surgery year, length of stay, and comorbidities. RESULTS: On discharge, 19,329 patients (65%) had not regained pre-fracture CAS. The 30-day reoperation risk was similar among patients who had not regained CAS (2.9%) and those who had (2.5%; aHR 1.10, CI 0.94-1.29). At 365 days, not regaining CAS was associated with a lower reoperation risk (7.1% vs 8.6%; aHR 0.98, CI 0.89-1.07). A CAS loss of 1-2 points was associated with an increased 30-day reoperation risk (aHR 1.20, CI 1.00-1.44). CAS decline was consistently associated with higher mortality at 30 days (aHR 2.07, CI 1.82-2.35) and 365 days (aHR 1.77, CI 1.66-1.89), with progressively higher rates at greater CAS decline. CONCLUSION: We found no consistent association between failure to regain pre-fracture mobility on discharge and reoperation, although patients with a 1-2 point CAS loss experienced a modestly higher 30-day reoperation risk. In contrast, failure to regain pre-fracture mobility was strongly associated with increased mortality up to 1 year after hip fracture.