Toxicology of wear particles of cobalt-chromium alloy metal-on-metal hip implants Part I: Physicochemical properties in patient and simulator studies

• Published in: Nanomedicine 2015-07, Vol.11 (5), p.1201-1215
• Main Authors: Madl, Amy K., PhD, Liong, Monty, PhD, Kovochich, Michael, PhD, Finley, Brent L., PhD, Paustenbach, Dennis J., PhD, Oberdörster, Günter, DVM, PhD
• Format: Article
• Language: English
• Subjects: Animals; Chromium Alloys - chemistry; Chromium Alloys - toxicity; Cobalt - chemistry; Cobalt - toxicity; Cobalt-chromium; Hip implant; Hip Prosthesis - adverse effects; Humans; Internal Medicine; Materials Testing; Metal-on-metal; Particle Size; Prosthesis Design; Surface Properties; Wear debris
• ISSN: 1549-9634; 1549-9642
• DOI: 10.1016/j.nano.2014.12.005

Abstract The objective of Part I of this analysis was to identify the relevant physicochemical characteristics of wear particles from cobalt-chromium alloy (CoCr) metal-on-metal (MoM) hip implant patients and simulator systems. For well-functioning MoM hip implants, the volumetric wear rate is low (< 1 mm3 per million cycles or per year) and the majority of the wear debris is composed of oxidized Cr nanoparticles (< 100 nm) with minimal or no Co content. For implants with surgical malpositioning, the volumetric wear rate is as high as 100 mm3 per million cycles or per year and the size distribution of wear debris can be skewed to larger sizes (up to 1000 nm) and contain higher concentrations of Co. In order to obtain data suitable for a risk assessment of wear debris in MoM hip implant patients, future studies need to focus on particle characteristics relevant to those generated in patients or in properly conducted simulator studies. From the Clinical Editor Metallic implants are very common in the field of orthopedics. Nonetheless, concerns have been raised about the implications of nano-sized particles generated from the wear of these implants. In this two-part review, the authors first attempted to identify and critically evaluate the relevant physicochemical characteristics of CoCr wear particles from hip implant patients and simulator systems. Then they evaluated in vitro and animal toxicology studies with respect to the physicochemistry and dose-relevance to metal-on-metal implant patients.