Influence of the femoral head surface hardness on abrasive wear mechanisms in the combination with polyethylene total hip replacement

The problem of wear has become a major issue in total joint replacement. A correlation between biomaterial hardness and abrasive wear mechanisms may be assumed. To investigate the effect of hardness, cobalt-chromium (CoCr) femoral heads coated with hard amorphous-hydrogenated carbon (a-CH) were tested against uncoated heads under conditions of abrasive wear. The heads were paired with polyethylene (UHMWPE) discs in a ball-on-disc machine. The abrasive wear resistance of the heads increased with surface hardness, and qualitatively differing patterns of wear were observed on the UHMWPE surfaces, depending on the abrasive wear of the matching areas of the heads. Accordingly, when evaluating biomaterials for their suitability for use in total joint replacement, hardness should be considered one of the relevant factors among the material properties with an influence on wear.