Reliability theory for load bearing biomedical implants.

At present, load-bearing implants are designed on a deterministic basis in which the structural strength and applied loading are given fixed values, and global safety factors are applied to (i) cover any uncertainties in these quantities, and (ii) to design against failure of the component. This approach will become increasingly inappropriate as younger and more active patient demands become more exacting and as devices become more complex. The present work describes a preliminary investigation in which a scientific and probabilistic technique is applied to assess the structural integrity of the knee tibial tray. It is envisaged that by applying such a technique to other load bearing biomedical devices, reliability theory may aid in future lifing procedures and materials/design optimisation.