KEYNOTE: Tribocorrosion of Orthopedic Implants: Mechanisms and Consequences

Total joint replacements are one of the most important and successful orthopedic procedures today.  They provide relief from the debilitating effects of osteoarthritis, rheumatoid arthritis and degenerative joint diseases.   The mechanical, chemical and biological environment into which these metallic biomaterials-based components is placed is severe.  Metallic biomaterials (primarily titanium and cobalt-chromium-molybdenum alloys) have unique structures and properties, including surface passivating oxides, which make them ideal for use in implant applications.  However, these materials are susceptible to the conjoint effects of tribology and electrochemistry.  The body environment can also respond to the implant and generate solution conditions that may impact on the corrosion performance of these alloys.  In this presentation, the underlying fundamental tribocorrosion relationships between surface oxide film abrasion, corrosion currents, and potential transients will be described from fundamental materials-science based principles.  A model to describe these concepts will be developed using contact mechanics, Faraday’s Law, impedance spectroscopy and Duhamel (heredity) integrals.  The role of wound healing and inflammation, and the solution chemistry changes that arise during inflammation will be discussed. Inflammation-derived chemicals like hydrogen peroxide and hypochlorous acid compromise passive oxide films, shift the oxidation potential and increase the corrosion damage seen in these alloys.