Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine
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The wear of a model metal-on-metal ball-and-socket total disc arthroplasty was measured in a simulator. The ball had a radius of 10 mm, and there was a radial clearance between ball and socket of 0.015 mm. The model was subjected to simultaneous flexion-extension, lateral bending, axial rotation (frequency: 1 Hz) and compression (frequency: 2 Hz, maximum load: 2 kN). ⋯ Wear occurred in two stages. In the first stage (duration about 1 million cycles), there was a linear wear rate of 2.01 ± 0.04 mm(3) per million cycles; in the second stage, there was a linear wear rate of 0.76 ± 0.02 mm(3) per million cycles. Surface roughness increased linearly in the first million cycles and then continued to increase linearly but more slowly.