Low-molecular-weight heparins have gained wide acceptance for prophylaxis and treatment of venous thromboembolism. For best protection, these agents should be started preoperatively, but this step raises concerns about intraoperative bleeding. Regional anesthesia is also more risky if preoperative heparin has been used because of the risk of epidural hematoma. Patients undergoing repair of hip fracture are at high risk for venous thromboembolism and certainly merit prophylactic measures. Eriksson and colleagues report on use of fondaparinux postoperatively for prevention of venous thromboembolism in hip fracture surgery.

Fondaparinux is a pentasaccharide molecule derived from the portion of heparin that binds activated factor X. The study authors randomly assigned 1,711 consecutive patients undergoing hip fracture surgery to enoxaparin (a low-molecular-weight heparin) in a dosage of 40 mg daily (started 12 hours before surgery) or fondaparinux in a dosage of 2.5 mg daily (started six hours postoperatively) and continued these agents for at least five days after surgery. No other anticoagulant or antiplatelet agents were allowed, but all patients were to make use of graduated compression stockings and physical therapy.

All patients underwent bilateral lower extremity venography after finishing their prophylaxis regimen. Any symptomatic deep venous thrombosis or pulmonary embolism was evaluated at the time of presentation. Approximately 25 percent of patients in both groups were excluded from analysis because of inadequate venography results.

The incidence of venous thromboembolism was 8.3 percent in the fondaparinux group versus 19.1 percent in the enoxaparin group, a difference that was statistically significant. The incidence of symptomatic deep venous thrombosis was very low and identical in both groups (0.1 percent). Pulmonary embolism was also of identical low incidence in both groups (0.3 percent). Rates of major bleeding and death from any cause were not statistically different between the two treatment arms. Minor bleeding was slightly more common with fondaparinux (4.1 percent) than enoxaparin (2.1 percent), but this difference did not reach statistical significance.

The authors conclude that use of fondaparinux is associated with a lower incidence of venous thromboembolism after hip surgery than enoxaparin, and that it has a similar safety profile.