Extended thromboprophylaxis following lower limb arthroplasty: what do the clinical trials mean?

Patients undergoing major orthopaedic surgery are at high risk of thromboembolic complications. Of the available options for pharmacologic prophylaxis, the low-molecular-weight heparins (LMWHs) have been shown to be most effective in reducing the incidence of venous thromboembolic complications and are well tolerated. However, as the risk of venous thromboembolism persists for several weeks post-discharge, there is controversy regarding the ideal duration of prophylaxis. Six recent studies have examined the efficacy and safety of prolonged prophylaxis in this setting. Five of these studies have demonstrated that prolonged LMWH prophylaxis (either enoxaparin or dalteparin) for 4--5 weeks is beneficial and significantly superior to conventional prophylaxis for 7--15 days. The other study, using ardeparin, examined clinical endpoints and showed a minor trend but no significant reduction in these events. Furthermore, two of the studies -- one with enoxaparin and one with dalteparin -- also demonstrated a significant reduction in the incidence of proximal deep vein thrombosis. Analysis of all clinical events from the five studies that have published that information shows a halving or 51% reduction in favour of prolonged prophylaxis. On the basis of current evidence, prolonged thromboprophylaxis with LMWH for up to 35 days after major orthopaedic surgery is recommended.