The influence of weight-bearing status on post-operative mobility and outcomes in geriatric hip fracture

PURPOSE: We hypothesized that unrestricted or full weight-bearing (FWB) in hip fracture would increase the opportunity to mobilize on post-operative day 1 (POD1mob) and be associated with better outcomes compared with restricted weight-bearing (RWB). METHODS: Over 4 years, 1514 geriatric hip fracture patients aged 65 and above were prospectively recruited. Outcomes were compared between FWB and RWB patients. The primary outcome was 30-day mortality. Secondary outcomes were immobility-related adverse events, length of stay (LOS), and reoperation for failure. Causal effect modelling and multivariate regression with mediation analyses were performed to examine the relation between weight-bearing status (WBS), POD1mob, and known mortality predictors. RESULTS: FWB was allowed in 1421 (96%) of 1479 surgically treated patients and RWB enforced in 58 (4%) patients. Mortality within 30 days occurred in 141 (9.9%) of FWB and 3 (5.2%) of RWB patients. In adjusted analysis, RWB did not influence 30-day mortality (OR 0.42, 95% CI 0.15–01.13, p = 0.293), with the WBS accounting for 91% of the total effect on mortality and 9% contributed from how WBS influenced the POD1mob. RWB was significantly related to increased DVT (OR 7.81, 95% CI: 1.81–33.71 p = 0.002) but no other secondary outcomes. Patients that did not have the opportunity to mobilize had increased 30-day mortality (OR 2.31, 95% CI 1.53–3.48 p < 0.001). CONCLUSION: Restricted weight-bearing was not associated with increased 30-day mortality. Only a small proportion of this effect was mediated by POD1mob. Whilst post-surgical WBS may be difficult to influence for cultural reasons, POD1mob is an easily modifiable target that is likely to have a greater effect on 30-day mortality. LEVEL OF EVIDENCE: Level III, observational study.