Environmental effect on fretting of metallic materials for orthopaedic implants

The environment of orthopaedic implants sometimes induces vibrations at the contact of the modular prostheses components. These microdisplacements contribute to the total failure of the implant. The necessary optimisation of orthopaedic device life requires a better knowledge of the damages induced by fretting corrosion. The aim of this paper is to describe the damage mechanism at the head–neck contact of a total hip joint with a neck in Ti–6Al–4V alloy and a head in austenitic stainless steel (AISI 316L SS). Simple tests were performed at the ambient air and in an artificial physiologic medium in order to reveal the damage induced by the physiological medium. The presence of a solution containing chloride ions activates a localised corrosion phenomenon which leads to the modification of the displacement accommodation regime. The consequences of electrochemical phenomena on this evolution are discussed. A quantitative energetic approach shows the lubricant effect of the artificial physiological environment. The different materials are ranked according to their wear rates. The result shows that fretting regime, accumulated dissipated energy and corrosion activated at the interface are interdependent.