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Characterization of wear in composite material orthopaedic implants. Part I: The composite trunnion/ceramic head interface.

Carbon fiber reinforced polyetheretherketone (C/PEEK) composite materials are being investigated as an alternative to metal in the femoral component of a total hip arthroplasty. Wear is among the issues that must be addressed before introducing a new orthopaedic implant material. This study examines the generation of wear debris when zirconia femoral heads are mechanically attached to C/PEEK trunnions and loaded under simulated physiological conditions. Mechanical testing was performed on a trunnion/head assembly loaded from 445 to 4450N at an angle of 39 degrees to the long axis of the trunnion. The trunnions were tested at a frequency of 20 Hz for 10 million cycles. After completion of the fatigue test, solution from the test assembly was characterized by laser scattering and by SEM image analysis to determine the size, shape, total number, and identify of the particles. In addition, the peak load to pull the head from the trunnion was measured. The total number of particles generated during the test was in the range of 10(5) as indicated by both laser scattering and (SEM) image analysis. Both carbon fiber and PEEK particles were found in an average proportion of about 1:13, respectively. The carbon fiber particle size average was 153 microns and the PEEK particle size average was 2.2 microns. The zirconia heads remained well attached to the C/PEEK trunnions as indicated by a mean peak distraction force of 1942 +/- 116N.