In vivo production of nanosized metal wear debris formed by tribochemical reaction as confirmed by high-resolution TEM and XPS analyses.

High-resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS) were used to establish the link between particles isolated from periprosthetic tissue of metal-on-metal (MOM) bearing and the solid deposit at the surface of retrieved MOM hip components. The high resolution of TEM made it possible to identify individual CoCrMo wear particles. Two shapes were observed. Needle-shaped particles ranged from 40 to 120 nm and contained both Co and Cr. Globular particles ranged up to 90 nm and contained high levels of Cr and no Co. Ti- and Ca-based particles were also identified. XPS analysis of the areas of thick solid deposit on the retrieved femoral head showed that the base alloy was covered by up to nearly 1-microm thick layer containing carbon, nitrogen, and oxygen. This layer was organic in nature, presumably protein-related. In areas with a thinner deposit, an organic-related layer was mixed with layers of metal oxides, the latter being much thinner than the extensive organic, carbon-rich layer. Outside the area of the deposit, the passive oxidized chromium layer was thinner, less than 20 nm, and carbon was bound to nonorganic oxygen.