Sensing Localized Surface Corrosion Damage of CoCrMo Alloys and Modular Tapers of Total Hip Retrievals Using Nearfield Electrochemical Impedance Spectroscopy.

Wear and corrosion damage of biomedical alloys alters the structure and electrochemical properties of the surface heterogeneously. It was hypothesized that local regions on the same surface systematically differ from one another in terms of their impedance characteristics. To test this hypothesis, CoCrMo disks exposed to electrosurgical and inflammatory-species-driven damage were characterized using a localized impedance technique, nearfield electrochemical impedance spectroscopy (NEIS), to assess point-specific surface integrity in response to applied damage. It was found that electrosurgical damage, as may arise during primary arthroplasty and revision surgeries, and hydrogen peroxide concentrations of 5-10 mM significantly alter the corrosion susceptibility of the local surface compared to the as-polished CoCrMo surface. A CoCrMo retrieved neck taper (Goldberg score of 4) was scored in different local regions on the basis of visual appearance, and it was found that there is a direct relationship between increasing debris coverage and decreasing impedance, with the global surface impedance closest to the most severely scored local region. This noninvasive method, which uses a millielectrode configuration to test localized regions, can measure the heterogeneous electrochemical impedance of an implant surface and be tailored to assess specific damage and corrosion mechanisms revealed on retrieval surfaces.