Prophylaxis for deep vein thrombosis with aspirin or low molecular weight dextran in Korean patients undergoing total hip replacement - A randomized controlled trial

150 Korean patients undergoing primary uncemented total hip replacement were randomized into 3 treatment groups for deep vein thrombosis (DVT) prophylaxis. Group A(50) Mere controls; Group B(50) received aspirin 1.2 g daily in 3 divided doses from 2 days before, to 14 days after surgery; Group C(50), received low molecular weight dextran 500 ml, infused intravenously at 50 ml/hour during surgery, and on each of the following 2 days. Contrast venograms were performed prior to surgery and 7-10 days after: The incidence of DVT was 20% in the control group, 12% in the aspirin group (p <0.1 vs control), and 6% in the dextran group (p <0.05 vs control). In patients developing DVT the ratio of proximal to distal thrombi was increased in the control group as compared to treated groups (4:1 in the control group vs 1.5:1 in the treated groups). Both aspirin and dextran were well tolerated. Obesity (p <0.05) and long-term administration of steroids (p <0.05) were risk factors for deep vein thrombosis which reached statistical significance in the control group. Intraoperative venograms performed on 10 patients, showed that hip flexion (mean 40.4 degrees) plus adduction (mean 11.5 degrees) plus internal rotation (mean 81.5 degrees), resulted in severe twisting or kinking of the femoral vein with stagnation of blood flow. Low molecular weight dextran significantly reduce the incidence of deep venous thrombosis and aspirin, though less effective, had a similar effect. Internal rotation of the hip joint should be minimized during operation in order to limit stagnation of bloodflow in the femoral vein.