THE ROLE OF BONE TRAUMATIZATION IN THE INITIATION OF PROXIMAL DEEP-VEIN THROMBOSIS DURING CEMENTED HIP-REPLACEMENT SURGERY IN PIGS

Hip arthroplasty is associated with a high frequency of postoperative solitary proximal deep vein thrombosis which seems most frequently obs erved when bone cement is used for prosthesis fixation. Eighteen pigs underwent hemiarthroplasty, eight with cement-fixed prostheses and eig ht with non-cement prosthesis installation. Levels of thrombin-antithr ombin (TAT) complexes, tissue plasminogen activator (t-PA) activity an d plasminogen activator inhibitor 1 (PAI-1) activity were determined i n femoral vein blood from both limbs during and after surgery. On the operated side, TAT increased during bone traumatization followed by a substantial rise in t-PA activity and a gradual decline in PAI-1 activ ity. This indicates a local per- and post-operative sequential activat ion of coagulation and fibrinolysis followed by a fibrinolytic shutdow n, all reflected in femoral vein blood on the operated side. In the an imals receiving noncemented hip prostheses, the same pattern of activa tion of coagulation and fibrinolysis occurred on the operated side. Th is was, however, less marked than with the cement-fixed prostheses. Po stoperative scanning electron microscopic (SEM) examination of the fem oral veins showed thrombi on the operated side in 62% of the animals i n the cement group and 25% in the non-cement group. In an additional s tudy with eight animals undergoing cement-anchored hip prosthesis oper ations the levels of TAT, t-PA and PAI-1 were analysed in femoral vein blood, mixed venous blood and arterial blood. Significantly higher le vels were found in femoral vein blood compared with mixed venous blood while no significant change was found in arterial blood compared with mixed venous blood. The hyperthermia induced by curing bone cement wa s effectively conducted by the implanted prosthesis and did not seem t o exert major influence on the activation of coagulation. Extreme rota tion of the limbs during surgery did not in itself induce visible vein wall damage as judged by SEM. These studies indicate that traumatizat ion of bone marrow during hip surgery induce a marked local activation of coagulation and a high incidence of deep vein thrombosis in proxim al veins, in particular if bone cement is used for prosthesis fixation .