Oxidative Degradation after Implant Manufacture

The oxidative process initiated during sterilization can continue during shelf storage and implantation. The rate and the extent of the process will depend on the storage temperature in the shelf and on the human body temperature, together with the amount of available oxygen in vivo. 

In addition, oxidative degradation related to poor consolidation has been found in both in vivo and shelf-aged prostheses that were either gamma sterilized or ethylene oxide gas (EtO) sterilized (Costa et al. 2002). When oxidation related to consolidation occurs, the oxidation profile through the cups section is inhomogeneous and the maximum oxidation is observed near the center of the prosthesis. It is worth mentioning that this consolidation-related oxidation mechanism is often accompanied by whitening of the material, visible to the naked eye. 

The origins of consolidation-related oxidation are not clear yet, but the processing conditions of the UHMWPE bar or sheet, together with the influence of the machining of the prosthetic component, have been proposed as contributing factors. Poor consolidation of the UHMWPE powder during processing. 

FTIR map collected along the cross-section of an EtO-stehlized, shelf-aged UHMWPE acetabular cup. 

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