Hip simulator wear testing according to the newly introduced standard ISO 14242

Ultra-high molecular weight polyethylene (UHMWPE) acetabular cups were test ed against alumina-ceramic femoral heads using a new type of hip joint simu lator according to ISO/FDIS 14242-1. Bovine serum as well as newborn calf s erum were used as test fluids. Total polyethylene wear was determined by we ight loss of the cups. In addition, wear depth and its distribution were re corded by means of a coordinate measurement system. Wear particle analysis and inspection of the worn polyethylene surfaces using light and scanning e lectron microscopy (SEM) were performed to analyse damage and identify the acting wear mechanisms. The total wear rate was determined to be 22.07 +/- 1.75 mg/10(6) cycles for the bovine serum group and 26.57 +/- 3.55 mg/10(6) cycles for the calf ser um group. Unexpectedly, the formation of two wear vectors corresponding to recent clinical findings was detected. Retrieved polyethylene wear debris w as comparable in size and shape with clinical findings. The test method des cribed by ISO/FDIS 14242-1 produced reliable and reproducible wear data usi ng UHMWPE acetabular cups articulating against alumina-ceramic heads. In th e authors' opinion, the lubricant composition should be described in more d etail, since the protein and additive content seem to have a high impact on the wear results. It needs to be emphasized that the findings of this stud y cannot be regarded as a general validation of hip wear tests according to ISO/FDIS 14242-1 but are limited to the material combinations investigated herein. Further testing of other clinically relevant materials and interla boratory ring tests must follow.