Fatigue behaviour of fine-grained alumina hip-joint heads under normal walking conditions

In prosthetic applications, the reliability of implant materials over a period of thirty years is absolutely essential. Calculation of the lifetimes of alumina ceramic heads is generally made on the basis of experimental fatigue and slow crack growth tests using finite element analysis. This investigation is aimed at understanding the fatigue behaviour of fine-grained alumina heads of hip joints. The service conditions of cyclic stress experienced by hip joints during walking are used in evaluating the fatigue behaviour of alumina femoral heads. These femoral heads have successfully withstood 10(7) cycles at a maximum walking stress of 17.2 kN, which is equivalent to a body weight of 400 kg. The femoral heads did not exhibit any sub-critical crack growth at the maximum walking load of 10 kN, indicating the quasi-infinite performance life in patients up to a body weight of 250 kg. The details of proof testing designed for evaluating the performance of femoral heads over 40 years are also presented