The John Charnley Award. Thrombogenesis during total hip arthroplasty.

The activation of the clotting cascade leading to deep venous thrombosis begins during total hip arthroplasty, but few studies have assessed changes in coagulation during surgery. A better understanding of thrombogenesis during total hip arthroplasty may provide a more rational basis for treatment. In 3 separate studies, the following observations were made. Circulating indices of thrombosis and fibrinolysis: prothrombin F1.2, thrombin-antithrombin complexes, fibrinopeptide A, and D-dimer, did not increase during osteotomy of the neck of the femur or during insertion of the acetabular component, but rose significantly during insertion of the femoral component. Thrombin-antithrombin complexes, fibrinopeptide A, and D-dimer were higher after insertion of a cemented component than insertion of a noncemented femoral component. A significant decline in central venous oxygen tension was observed after relocation of the hip joint and after insertions of cemented and noncemented femoral components, providing evidence of femoral venous occlusion during insertion of the femoral component. In patients receiving a cemented femoral component, mean pulmonary artery pressure increased after 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 unfractionated heparin before insertion of a cemented femoral component blunted the rise of fibrinopeptide A. The results of these studies suggest 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 arthroplasty (such as intraoperative anticoagulation) should begin during surgery rather than during the postoperative period and be applied during insertion of the femoral component.