THROMBOGENESIS DURING TOTAL HIP-ARTHROPLASTY

The activation of the clotting cascade leading to deep venous thrombos is begins during total hip arthroplasty, but few studies have assessed changes in coagulation during surgery. A better understanding of thro mbogenesis during total hip arthroplasty may provide a more rational b asis for treatment. In 3 separate studies, the following observations were made. Circulating indices of thrombosis and fibrinolysis: prothro mbin F1.2, thrombin-antithrombin complexes, fibrinopeptide A, and D-di mer, did not increase during osteotomy of the neck of the femur or dur ing insertion of the acetabular component, but rose significantly duri ng insertion of the femoral component. Thrombin-antithrombin complexes , fibrinopeptide A, and D-dimer were higher after insertion of a cemen ted component than insertion of a noncemented femoral component. A sig nificant decline in central venous oxygen tension was observed after r elocation of the hip joint and after insertions of cemented and noncem ented femoral components, providing evidence of femoral venous occlusi on during insertion of the femoral component. In patients receiving a cemented femoral component, mean pulmonary artery pressure increased a fter relocation of the hip joint, indicating intraoperative pulmonary embolism. No changes in mean pulmonary artery pressure were noted with noncemented total hip arthroplasty. Administration of 1000 units of u nfractionated heparin before insertion of a cemented femoral component blunted the rise of fibrinopeptide A. The results of these studies su ggest that (1) the greatest risk of activation of the clotting cascade during total hip arthroplasty occurs during insertion of the femoral component; (2) femoral venous occlusion and use of cemented components are factors in thrombogenesis during total hip arthroplasty; and (3) measures to prevent deep venous thrombosis during total hip arthroplas ty (such as intraoperative anticoagulation) should begin during surger y rather than during the postoperative period and be applied during in sertion of the femoral component.