Prevention of venous thrombosis in patients undergoing major orthopaedic surgical procedures.

Patients having major orthopaedic surgical procedures have a high risk of venous thromboembolism. The distribution of thrombi following hip surgery differs from most other high risk situations, as 30-40% of all thrombi occur in proximal veins and many are unassociated with distal vein thrombosis. Many of these thrombi are undetected by currently available screening tests, but are detected by venography. Of the various prophylactic methods available, oral anticoagulants, adjusted-dose heparin and low molecular weight heparins are most effective in hip surgery, and oral anticoagulants and external pneumatic compression are most effective in knee surgery.