A clinical evaluation, with the crosslinked UHMWPE that is a part of this study, suggests that larger head sizes do produce increased wear volume over smaller heads, meaning that the use of crosslinked polyethylene, while it may reduce the wear rates over non-crosslinked material, still may suffer from the effect of increasing head size. Finite element analysis modelling the predicted stresses in conventional and highly crosslinked polyethylene and Fuji film pressure analysis suggested that the stresses in highly crosslinked UHMWPE with large head sizes might be less than for 28 mm conventional polyethylene. It has been suggested that the detrimental effect of head size on wear rates may not exist for highly crosslinked UHMWPE, which may allow for the use of larger femoral heads to achieve the potential benefits. Research has shown that the crosslinking of UHMWPE will reduce the wear rates in both laboratory testing and in clinical experience.
However, larger femoral heads have been advocated to reduce dislocation and improve the range of motion and stability of total hip replacements. Previous clinical studies have shown that head size had an effect on wear rates of gamma-irradiation-sterilized UHMWPE with larger heads exhibiting greater linear and volumetric wear rates. This preliminary screening study compares the wear properties of an electron beam crosslinked ultra high molecular weight polyethylene (UHMWPE) when bearing against a 32 mm cobalt/chromium alloy femoral head with the properties of a gamma-irradiation-sterilized UHMWPE utilizing a 26 mm ceramic head.
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