Routine use of LMWH prophylaxis is associated with a lower incidence of venous thromboembolic events following an ankle fracture

Background: Venous thromboembolic events (VTE) are well-known and serious complications following a trauma to the lower extremities. There is an ongoing debate on the benefit of low-molecular-weight heparin (LMWH) as prophylaxis following ankle fracture treatment. We examined the association between the incidence of VTE and the use of LMWH-prophylaxis following an ankle fracture, as well as factors affecting the risk of VTE. Methods: In this retrospective cohort study, data on ankle fractures and fracture treatment from the Swedish Fracture Register was linked to data from the Swedish National Patient Register and the Swedish Prescribed Drug Register. Patients with VTE and patients who received LMWH prophylaxis were identified. The treating orthopedic departments were sent a questionnaire about their guidelines regarding the use of LMWH prophylaxis. Results: 222 cases of diagnosed VTE were identified among 14,954 ankle fractures. Orthopedic departments with higher-than-average use of LMWH prophylaxis among non-operatively treated ankle fractures had a lower incidence of VTE (OR 0.60, CI 0.39–0.92). Among operatively treated patients, departments with a guideline for the routine use of LMWH prophylaxis also had lower incidence of VTE (OR 0.56, CI 0.37–0.86). A later onset of VTE was seen among patients prescribed LMWH prophylaxis, with a mean of 56 days to onset (CI 44–67), compared to 39 days (CI 33–45) in patients without prescribed prophylaxis. During the first two weeks following injury, there was only one case of VTE in patients with prescribed LMWH, compared to 39 cases of VTE among patients without prescribed prophylaxis. Conclusions: Routine use of LMWH in patients with operatively treated ankle fractures was associated with a lower incidence of VTE. A more frequent use of LMWH among patients with non-operatively treated ankle fractures were associated with a lower incidence of VTE. The onset occurred later among patients with LMWH-prophylaxis who still suffered a VTE