Larger diameter femoral heads used in conjunction with a highly cross-linked ultra-high molecular weight polyethylene: a new concept.

The design of femoral and acetabular components of metal-on-polyethylene total hip arthroplasty implants has been dominated by the limitations of the wear properties of ultra-high molecular weight polyethylene (UHMWPE). As a result, the commonest femoral head diameters used range from 22 to 32 mm, the latter producing maximal volumetric wear. Cross-linking has been shown to improve significantly the wear resistance of acetabular components when tested in vitro against conventional femoral head sizes (22-32 mm). We expanded the study of the wear behavior of 1 type of electron-beam cross-linked UHMWPE with femoral head diameters ranging from 22 to 46 mm. The simulated gait studies showed that wear was independent of head size for the range of femoral head sizes studied. Even for the 46-mm femoral head, wear was reduced significantly using criteria of gravimetric and geometric measurements and morphologic appearance of the machining marks out to 11 million cycles of simulated gait.