Low-molecular-weight heparin versus compression stockings for thromboprophylaxis after knee arthroscopy - A randomized trial

Background: Knee arthroscopy, the most common orthopedic operation worldwide, carries a definite risk for deep venous thrombosis; however, postsurgical thromboprophylaxis is not routinely recommended. Objective: To evaluate whether low-molecular-weight heparin (LMWH) better prevents deep venous thrombosis and does not cause more complications than graduated compression stockings in adults having knee arthroscopy. Design: Assessor-blind, randomized, controlled trial. Setting: The Department of Knee Surgery, Abano Terme Clinic, Abano Terme (knee surgery, random assignment, and bleeding event survey), and the Unit- of Angiology, University Hospital of Padua, Padua (efficacy outcomes evaluation, follow-up,* data management, and analysis), Italy. Patients: 1761 consecutive patients undergoing knee arthroscopy between March 2002 and January 2006. Intervention: Patients were randomly assigned to wear full-length graduated compression stocking for 7 days (660 patients) or to receive a once-daily subcutaneous injection of LMWH (nadroparin, 3800 anti-Xa IU) for 7 days (657 patients) or 14 days (444 patients). The data and safety monitoring board prematurely stopped the 14-day heparin group after the second interim analysis. Measurements: Combined incidence of asymptornatic proximal deep venous thrombosis, symptomatic venous thromboembolism, and all-cause mortality (primary efficacy end point) and combined incidence of major and clinically relevant bleeding events (primary safety end point). All patients had bilateral whole-leg ultrasonography at the end of the allocated prophylactic regimen or earlier if indicated. All patients with normal findings were followed for 3 months, and none was lost to follow-up. Results: The 3-month cumulative incidence of asymptornatic proximal deep venous thrombosis, symptomatic venous thromboembolism, and all-cause mortality was 3.2% (21 of 660 patients) in the stockings group, 0.9% (6 of 657 patients) in the 7-day LMWH group (absolute difference, 2.3 percentage points [95% CI, 0.7 to 4.0 percentage points]; P = 0.005), and 0.9% (4 of 444 patients) in the prematurely stopped 14-day LMWH group. The cumulative incidence of major or clinically relevant bleeding events was 0.3% (2 of 660 patients) in the stockings group, 0.9% (6 of 657 patients) in the 7-day LMWH group (absolute difference, -0.6 percentage point [CI, -1.5 to 0.2 percentage points]), and 0.5% (2 of 444 patients) in the 14-day LMWH group. Limitations: The study was not double-blind or double-dummy. Almost half of the events making up the composite outcome measure were distal deep venous thromboses. Stockings were used instead of placebo because of local prophylaxis policies. Conclusion: In patients undergoing knee arthroscopy, prophylactic LMWH for 1 week reduced a composite end point of asymptomatic proximal deep venous thrombosis, symptomatic venous thromboembolism, and all-cause mortality more than did graduated compression stockings.