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.