Venous Thromboembolism and Bleeding Adverse Events in Lower Leg, Ankle, and Foot Orthopaedic Surgery with and without Anticoagulants

Background: Currently, there is insufficient knowledge about the benefits of anticoagulant use for primary prevention of venous thromboembolism (VTE) and its inherent risk of bleeding adverse events in patients undergoing surgery distal to the knee. Methods: The study included patients who had undergone an orthopaedic procedure distal to the tibial articular surface when they were 18 years of age or older. Using retrospective information from a tertiary care referral center, we compared patient demographics, clinical findings, diagnostic reports, procedures performed, and the rate of symptomatic VTE and bleeding adverse events between patients who had and those who had not received anticoagulant prophylaxis. Propensity score matching was used to minimize selection bias due to prophylactic treatment allocation. Results: A total of 5,286 patients who had received anticoagulant prophylaxis for below-the-knee surgery were successfully matched with 5,286 patients who had not received anticoagulant prophylaxis for such surgery. After propensity score matching, the standardized difference between the groups was <0.1 for all baseline characteristics, indicating a negligible difference between the groups. Patients who received anticoagulant prophylaxis had a significantly lower risk of developing a VTE compared with patients who did not (39 patients [0.7%] versus 99 patients [1.9%]), with an odds ratio (OR) of 0.38 (95% confidence interval [CI], 0.25 to 0.56; p < 0.001). In contradistinction, patients who received anticoagulant prophylaxis had a significantly higher risk of developing a bleeding adverse event than those who did not (115 [2.2%] versus 55 [1.0%]; OR, 2.18 [95% CI, 1.55 to 3.09]; p < 0.001). Conclusions: Anticoagulant prophylaxis reduced the risk of VTE after surgery distal to the tibial articular surface by 3-fold but resulted in a concomitant 2-fold increase in the risk of a bleeding adverse event. Large-scale, prospective studies are necessary to better understand the true incidence of such events, associated patient-specific risk factors, efficacy of various thromboprophylactic regimens, and patient-reported implications of such events.