Fatique testing of bone cements - comparison of 4-point-bending and uniaxial tensile arrangements

In joint replacement one of the most important demands for the save function is a sufficient strength of the bone cement. Besides the standardized characterizat ion by quasistatic tests, fatigue investigations should be performed. Three test ing procedures are discussed: The four-point-bending arrangement, a uniaxial pur e tensile test with flat tapered specimens and a uniaxial compression-tension te st with cylindrical tapered samples. S-N-curves were measured for Palacos R and Simplex P. The three procedures and their results are compared. The results show that the strength levels in the testing arrangements differ markedly which can be explained by differences in the loaded volume. However the three test methods seem to be equally suited to characterize the fatigue behaviour.