Prolonged thromboprophylaxis with oral anticoagulants after total hip arthroplasty - A prospective controlled randomized study

Background: The optimal duration of thromboprophylaxis after major orthopedic surgery is controversial. Although oral anticoagulants are still widely used for the prevention of venous thromboembolism after hip replacement, to our knowledge no study has assessed the benefit of prolonging anticoagulation beyond the hospital stay. Methods: Consecutive patients who had received warfarin sodium prophylaxis after total hip arthroplasty were randomized to stop taking the drug at the time of hospital discharge or to continue taking it for 4 more weeks. The rate of symptomatic and asymptomatic venous thromboembolic events (as shown by compression ultrasonography of the proximal-vein system) occurring during the study period was compared between the 2 groups. The study was prematurely terminated after the inclusion of the first 360 patients because a statistically significant and clinically relevant superiority of extended over short-term thromboprophylaxis was observed. Results: Objectively confirmed venous thromboembolic complications were recorded in 10 patients: 9 (5.1%) in the group of 176 control patients, and 1 (0.5%) in the group of 184 patients who continued the warfarin treatment. The absolute difference in the incidence of events was 4.57% (95% confidence interval [CI], 1.15-7.99). The relative risk of venous thromboembolism developing in control patients compared with patients assigned to extended thromboprophylaxis was 9.4 (95% CI, 1.2-73.5). The number needed to treat was 22. Major bleeding developed in I patient who was randomized to the extended prophylaxis group (0.5%; 95% CI, 0.02-3.0) compared with none in the control group. Conclusion: Extending prophylaxis with warfarin for a few more weeks beyond the hospital stay has the potential to considerably improve the outcome of patients who undergo hip arthroplasty.