Factors contributing to rapid wear and osteolysis in hips with modular acetabular bearings made of hylamer

There have been several reports of osteolysis associated with rapid wear of Hylamer. A detailed analysis of retrieved implants and tissues can identif y factors contributing to rapid wear and osteolysis. The mean linear wear r ate of 12 liners was 0.49 mm/y, and II of 12 hips had progressive retroacet abular osteolysis. The average patient age was 50 years, and the mean impla ntation time was 50 months. All liners were sterilized by gamma irradiation in air. There was an Ii-month difference in the average shelf-life of the 3 liners that were white and those that were darker in color. The volumetri c wear rate of the white liners was 30% less than that of the others, sugge sting a difference in the wear resistance of the liners as a function of sh elf life. The mean average surface roughness (R-a) and the mean maximum sur face roughness (R-max) of the femoral heads were increased 3-fold and 50-fo ld compared with typical values for unused femoral heads. Evidence of 3-bod y wear, such as metal particles embedded in the liners, was commonly presen t. The pattern of backside liner deformation and burnishing was consistent with relative motion between the liner and the shell. In addition to genera ting Hylamer wear particles, repetitive axial motion between the liner and shell could generate fluid pressure, which transmitted through holes in the acetabular shell could cause or contribute to the development of retroacet abular osteolysis. Hylamer particles of variable shape and size, consistent with generation by several wear modes, were isolated from periprosthetic t issues.