Study About Wear Behavior Of Prostheses And Characterization Of Wear Particles

A hip simulator had been designed and manufactured. The investigation of motions made on the counterface of the prostheses showed the slide track in a simulator was cross-path multidirectional motion. The experiment results analysis showed there was excellent agreement between the wear rate, wear mechanisms and wear particles obtained from laboratory experiments and those derived from clinical observations. The wear mechanisms of UHMWPE in multidirectional sliding were abrasive wear, adhesive wear and microcosmic fatigue wear resulting from plastic deformation and the wear rate on this condition was 2.5 times of it in single rotating when used distilled water lubricating. Distilled water and plasma completely prevented the UHMWPE transfer to the polished Al₂O₃ counterface when they were used as lubricant in the simulator test. When using plasma as lubricant, protein was found precipitating on the interface, which can increase friction coefficient and make the wear rate 25% higher than it in distilled water lubricating. The particle sizes varied in length from 0.3μm to 180μm and 85% particles were less than 20μm. The morphological and size of wear particles varied remarkably due to different materials and wear mechanisms. Because the commonly employed statistical parameters in wear particle analysis were closely related to measuring scale and resolution, it was not always reliable due to its subjectivity. Both boundary profile and accumulation distribution of wear particle showed a strong fractal behavior. In UHMWPE-Al₂O₃ running-in period, according to the wear mechanism varying from abrasive wear to adhesive wear and microcosmic fatigue wear, the size distribution of wear particles group dispersed gradually and the size of particle which accumulative frequency was highest decreased. Correspondingly, the wear particle boundary fractal dimension Dm, small particles accumulative fractal dimension D1, large particles accumulative fractal dimension D₂ and turning point position St all had a tendency to decrease. The statistic analysis indicated that D_m, D₁, D₂ , S_t all correlated well with wear rate and wear state .