The wear pattern in metal-on-metal hip prostheses

The accumulated data suggest that there is a strong correlation between pol yethylene wear and osteolysis, which ultimately leads to prosthetic looseni ng. Second-generation metal-on-metal prostheses have been introduced, with an eye toward resolving this wear-induced osteolysis problem. The metal par ticles and ions are biologically active and can affect the cell homeostasis . Thus, defining the wear pattern and ratio of a given metal-on-metal prost hesis system is desirable. An early high-wear or run-in phase followed by a low-wear phase or steady state has been suggested for metal-on-metal hip p rostheses. The aim of this study was to define the wear pattern of metal-on -metal bearings. The prosthesis systems were tested in a joint simulator. A n early accelerated wear phase transformed to a slower wear phase after 700 ,000 cycles. The run-in and steady-state wear rates for combined head and l iner averaged 2.22 mm(3)/Mc and 1.0 mm(3)/ million cycles, respectively. Th e metal-on-metal prosthesis featured a biphasic wear trend with the wear ra tio in run in being more than twofold higher than the steady-state phase. ( C) 2001 John Wiley & Sons, Inc.