Rationalizing the In Vivo Degradation of Metal-on-Metal Artificial Hip Joints Using Tribocorrosion Concepts

In this study, the in vivo degradation of metal-on-metal (MoM) artificial hip joints was assessed based on the present state of the art concepts of tribocorrosion. A recently developed tribocorrosion model, based on the combination of mechanical and corrosion concepts, was used in order to rationalize experimental observations and clinical outcomes. This analysis permitted one to identify and assess the relevance of crucial mechanical (load, velocity), material (hardness, Young's modulus), chemical (oxidation valence, passivation charge density, electrode potential), and geometrical (head radius, clearance) parameters and synovial fluid viscosity affecting hip joint degradation. Moreover, the tribocorrosion approach taken here shows that in vivo degradation is highly dependent on individual patient features and reveals that in vivo characterization of the corrosion and chemical reactivity of implant materials as well as of synovial fluid properties are needed for predicting degradation of MoM implants.