Investigation of the effects of electrochemical reactions on complex metal tribocorrosion within the human body.

Although total hip arthroplasty (THA) is considered to be the most successful orthopedic operation in restoring mobility and relieving pain, common Metal-on-Metal (MoM) implants developed in the past decade suffer from severe inflammatory reactions of the surrounding tissue caused by the premature corrosion and degradation of the implant. A substantial amount of research has been dedicated to the investigation of mechanically driven fretting and crevice corrosion as the primary mechanism of implant failure. However, the exact mechanism by which hip implant breakdown occurs remains unknown, as current fretting and crevice corrosion studies have failed to completely replicate the corrosion characteristics of recovered implants. Here, we show that minor electric potential oscillations on a model hip implant replicate the corrosion of failed implants without the introduction of mechanical wear. We found in a controlled lab setting that small electrical oscillations, of similar frequency and magnitude as those resulting from ambient electromagnetic waves interacting with the metal of the implant, can force electrochemical reactions within a simulated synovial fluid environment that have not been previously predicted. In lab testing we have shown the replication of titanium, phosphorous, and oxygen deposition onto the surface of ASTM astm:F75 CoCrMo metal alloy test specimens, matching the chemical composition of previously retrieved wear particles from failed patient prosthetics. Our results demonstrate that the electrical activity and ensuing electrochemical activity excites two corrosion failure modes: direct dissolution of the medically implantable alloy, leaching metal ions into the body, and surface deposition growth, forming the precursor of secondary wear particles. We anticipate our findings to be the foundation for the future development and testing of electrochemically resistant implantable material.