The fatigue properties of Simplex P and Palacos R bone cements were compared to their antibiotic impregnated counterparts AKZ' and Palacos R with gentamycin.+ The effect of porosity reduction by centrifugation of all four cement types was also assessed. Fifteen specimens of each cement type were prepared according to manufacturer's instructions and 15 additional specimens of each cement type were prepared by mixing the powder with chilled monomer (OOC) and then centrifuging the cement immediately after mixing. Fifteen fully reversed tension-compression Fatigue tests were performed at 15 MPa in stress control for each cement preparation in vitro while simulating the in uivo state (37°C and 100% humidity). The number of cycles to failure were recorded.
There was no significant difference in the fatigue life of Palacos R and Simplex P when both cements were prepared in the standard fashion. The addition of 1/2 g of gentamycin to Palacos R did not significantly alter its fatigue properties. The addition of 0.5 g of erythromycin and 0.24 g of coiistin did not decrease the fatigue life of Simplex P. Centrifugation significantly improved the fatigue properties of Simplex P and AKZ. The fatigue lives of Palacos R and Palacos R with gentamycin were not improved by centrifugation. The fatigue life of centrifuged Simplex P was significantly greater than the fatigue life of Palacos R and of Palacos R with gentamycin, whether the Palacos R based cements were centrifuged or not.
'Supported in part by EM Laboratories, 5 Skyline Drive, Hawthorne, NY 10532; and The William H. Harris Foundation.
'AKZ bone cement is the trade name used by Howmedica Inc. of Rutherford, NJ to describe Simplex P mixed with 0.5 g of erythromycin and 0.24 g of colistin methane sulphonate. Both the Simplex P and AKZ cements were obtained from Howmedica. Palacos R and Palacos R with gentamycin (0.5 g/40 g.) were supplied by E. Merck Laboratories.