A laboratory study of friction in hip implants

One of the most promising methods of reducing wear and extending the useful life of artificial joints is by regular microrelief treatment, a novel finishing technology based on the formation of a system of fine grooves by means of plastic deformation of surfaces with a ball-tipped diamond. Laboratory friction testing of treated joint prostheses is an essential component in the developmental process of this application. In order to evaluate the friction characteristics of hip prostheses made up of metal ball heads treated with regular microrelief, a computer-monitored friction tester was developed. The ball head was pressed against the cup by a load. The friction torque was measured by means of a load cell. Distilled water was used as the lubricant. Before the friction test, all balls were tested in a specially developed wetting ability tester, to evaluate the effect of regular microrelief treatment on the wetting behaviour of the head surface in water. The results obtained showed that the wetting ability of balls treated with regular microrelief was higher by 30% as compared with non-treated hip heads. The articulating pairs with heads treated with regular microrelief showed a 25–35% reduction in the friction torque, when compared with conventional, non-treated joints.