Wear prediction of orthopaedic implants

Computational wear modelling is an efficient simulation tool for the wear assessment of artificial joints, which can be developed to investigate wear mechanisms, provide guidance for further experimental tests and optimise implant design. This chapter outlines such a tool, based on current developments in the wear modelling of artificial joints. Wear modelling consists of the development of wear equations, determination of wear factors/coefficients, contact modelling and numerical calculations of wear. In addition to the conventional Archard wear law, which is suitable for metallic/ceramic bearings, a contact-area-dependent new wear law is described for the polyethylene bearings widely used in hip, knee and spinal disc replacements. The wear predictions are illustrated with examples of metal-on-polyethylene and metal-on-metal hip joint replacements. Using such modelling, wear mechanisms can be highlighted and better understood. For example, the effect of bearing geometry design and the long-term wear performance of artificial hip joints demonstrate the efficiency and potential of wear modelling to complement or provide an alternative to experimental simulations.