Friction and wear behaviors of HXLPE, PEEK and CoCrMo against articular cartilage under cross-shear motion

The friction and wear behaviors of cartilage replacement materials against articular cartilage are considered essential characteristics that determine the function and performance of the replacement. Previous studies have often been conducted under a reciprocal linear motion, while a cross-shear motion has been shown to widely exist in joints. The difference resulting between cross-shear motion and reciprocal linear motion, and the effect of bearing surface roughness on the frictional and wear behaviors of cartilage should be further investigated. In this study, experimental tribology investigations were conducted under the cross-shear motion for articular cartilage against commonly used three replacement materials, including high cross-linked polyethylene (HXLPE), polyether ether ketone (PEEK), and cobalt-chromium molybdenum alloy (CoCrMo). The experimental results showed that there was no significant difference in friction and wear behavior between cross-shear and reciprocal linear motion. For the implants with low surface roughness, the water contact angle of the bearing surface affected the friction and wear behaviors of the cartilage, while for the implants with high rough surfaces, the surface roughness of the material affected the friction and wear behaviors of the cartilage. The damage of cartilage under cross-shear motion mainly consisted of deformations and accumulations. This phenomenon was especially evident at high roughness. Of the three bearing materials considered, PEEK was more suitable for osteochondral implants.