Early mobilisation after hip fracture surgery reduces the risk of infection: an inverse probability of treatment weighted analysis

BACKGROUND: Mobilisation within the first day following hip fracture surgery is recommended. However, an in-depth analysis of the association between early mobilisation and the risk of infection is lacking. OBJECTIVE: To examine the association between early mobilisation and the subsequent risk of hospital-treated infections following hip fracture surgery. METHODS: Using nationwide registries, we included 36 229 patients aged ≥65 who underwent surgery for hip fracture (2016-21). Exposure was time from surgery to first mobilisation in hours. Outcomes were any hospital-treated infection, pneumonia, urinary tract infection and sepsis within 2-30 days and reoperation due to surgical-site infection within 2-365 days of surgery. We calculated cumulative incidences (risks), risk differences (RD) and hazard ratios (HR) with 95% confidence intervals (CIs) using the inverse probability of treatment (IPT) weighted method to account for confounding. RESULTS: Overall, 27 174 (75%) patients were mobilised ≤24 h, 2890 (8%) between 24 and 36 h, and 6165 (17%) were mobilised >36 h of surgery or had no registration of mobilisation time.In the weighted analysis, the risk of any infection was 12.9% (CI 11.7%-14.2%) in patients mobilised 24-36 h of surgery and 10.9% (CI 10.5%-11.7%) in those mobilised ≤24 h, corresponding to RD of 2.0% (CI 0.7-3.3) and HR of 1.2 (CI 1.1-1.3). Similar associations were observed for pneumonia and urinary tract infection but not for sepsis and reoperation. CONCLUSIONS: Infection is a common complication after hip fracture surgery. Mobilisation within 24 h is clearly associated with reduced infection risk. Our results emphasise the importance of early mobilisation and suggest a possible pathway for reducing complications and mortality after hip fracture.