Oxidation in Ultrahigh Molecular Weight Polyethylene and Cross-Linked Polyethylene Acetabular Cups Tested against Roughened Femoral Heads in a Hip Joint Simulator

摘要

This study was aimed at comparing the oxidative degradation of commercial acetabular cups made of cross-linked polyethylene (XLPE) and conventional ultrahigh molecular weight polyethylene (UHMWPE).After testing against deliberately scratched CoCrMo femoral heads in a hip joint simulator,the cups,microtomed parallel to the articulating surface,were analyzed by IR spectroscopy.Due to the potential for artifacts caused by absorbed contaminants,the IR spectra were compared only after hexane extraction; actually,XLPE was found to absorb more serum than UHMWPE.The two sets of unworn acetabular cups showed different oxidation patterns with consequently different distributions of carbonyl species; unworn XLPE was characterized by lower contents of carbonyl species and hydrogen-bonded alcohols and higher contents of trans-vinylene species than unworn UHMWPE.Upon simulator testing,UHMWPE showed more significant changes in oxidation indexes and distribution of carbonyl compounds than XLPE,confirming a better wear behavior for XLPE under the adopted testing conditions.