[Fat embolism during total hip arthroplasty. Cementless versus cemented--a quantitative in vivo comparison in an animal model].

Thrombembolic complications,which include the fat embolism syndrome, are well-known consequences of cementless and cemented femoral total hip replacement. Thrombembolic phenomena have been demonstrated in clinical and experimental situations with both these fixation techniques, but so far no exact quantification of the intravasated fat emboli has been performed. In a standardized animal model in 15 Merino sheep we investigated the intravasation of fat into the bloodstream during simultaneous bilateral prosthetic implantation (cemented versus cementless). After identical preparation of the intramedullary canal on both sides, a cement restrictor was additionally inserted on the cemented side and the canal was cleaned by 250 ml jet lavage. Catheters in the external iliac veins made it possible to collect the drained blood in two phases, after preparation of the intramedullary canal and during insertion of the prosthesis, and the fat content of these blood samples was measured. The amount of fat that passed into the venous draining system of the femur induced by cemented implantation (2.2749 g; S=+/-1.0079) was twice the amount seen with cementless implantation (1.1586 g; S=+/-0.4555) ( P=0.0002). An obvious effect of the canal preparation was recognizable with the cemented implantation, 8 of the 13 animals evaluated showing a peak in the fat intravasation caused by application of the cement restrictor. Our results emphasize the importance of a thorough preparation of the intramedullary canal, particularly when cemented fixation is performed. The jet lavage,which should be considered mandatory standard in cemented total hip arthroplasty, should be implemented before the insertion of the cement restrictor in order to further reduce the risk of fat embolism.