In vitro wear testing of the PyroCarbon proximal interphalangeal joint replacement: Five million cycles of flexion and extension.

Clinical results of the PyroCarbon proximal interphalangeal joint replacement are inconsistent with various complications reported. To address this, in vitro testing was conducted using finger joint simulators. Two PyroCarbon proximal interphalangeal prostheses were tested in a lubricant of dilute bovine serum to 5x10(6) cycles of flexion-extension (90 degrees-30 degrees) with dynamic forces of 10N applied. At intervals of 3000 cycles testing ceased and a static load of 100N was applied to simulate gripping. In addition, two control' prostheses were immersed alongside the test prostheses to account for lubricant absorption. Wear and roughness averages (Ra) were measured every 1x10(6) cycles. Minimal wear for all of the components was measured with a negligible increase in Ra for most of the components. One condyle of one component increased in Ra over the 5x10(6) cycles with a value above the recommended 50nm. Unidirectional marks were visible on the condyle from micrographs, consistent with an abrasive wear mode.