Low wear and friction in alumina/alumina total hip joints - A hip simulator study

We studied the wear of state-of-the-art alumina/alumina total hip joints wi th the uniaxial five-station, and the three-axis single-station hip joint s imulators of Helsinki University of Technology. The diameters of the joints were 26, 28 and 32 mm. Visual examination and weighing of the components s howed no wear. Scanning electron microscopy showed that (a) the wear marks were slight, consisting of removal of grains, multidirectional grooving and mild abrasion, (b) the wear mechanisms were similar to those seen in compo nents removed from patients, and (c) there was no marked difference in the specimens worn in the uniaxial vs. three-axis simulator. The coefficient of friction was measured throughout the 5 million cycle wear test with the th ree-axis simulator. The average value was 0.007. We conclude that alumina/a lumina joints had low wear and friction under the present test conditions. The results are promising, since minimal wear is one of the prerequisites f or long-term success in prosthetic joints.