Comportement à l’usure des matériaux biomédicaux : application aux prothèses

Abstract

Remarkable reduction of wear rates in wear of Metal/Metal hip implants is achieved by increasing the head diameter or the concentration of carbon composition in the alloy. The combined role of head diameter and carbon composition was studied experimentally using three different configurations(28, 32 and 36 mm) using a hip wear simulator for two million cycles(2MC) of walking under bovine calve serum as lubricant. The 28 heads and 36 mm cups were made out of low carbon(LC) CoCr alloy, while all other parts were made from high carbon(HC) alloy. Gravimetric analysis showed that all bearings have a biphasic behavior, the Run-in during one million cycles followed by the Steady state period. The cups (HC) exhibited considerable volumetric wear decrease when compared to the heads(LC) in the 28 mm bearings. It was statistically significant in the Steady state period, which was confirmed by the roughness and SEM analysis. This (LC) composition in 28 mm bearings increase the difference in wear volume between 28 and 32 mm bearings, while the (LC) composition in 36 mm bearings reduce the difference in volumetric wear between 32 and 36 mm bearings. No correlation was found between clearance and total wear at 1 LC and 5MC. The roughness parameters (Ra, Rt, Rq) of 32 mm heads were correlated to the total wear. The total roughness Rt showed an exponential regression coefficient of 0,89, while the average roughness Ra presented a value of 0,82 and the average roughness Rq presented a coefficient of 0,79.