Comparison between in vitro and in vivo UHMW-PE degradation

There is an increasing interest in orthopedics for clinical problems associated with wear and failure of ultra-high-molecular-weight (UHMW) polyethylene devices. Wear not only affects the implant performance but, more importantly, produces the release of particulate debris in the surrounding tissues and fluids. The debris in turn cause a deleterious biological response that can include an inflammatory reaction with subsequent loosening of the implant components. Surface wear is certainly promoted from the oxidation process that can occur during the prosthesis life. However, the oxidation mechanism involved during the implantation period has not been described yet for the UHMW-polyethylene devices. Here, the comparison of FT-IR spectra of a retrieved acetabular cup (9 years in a human body) and thin UHMW-PE films treated respectively with: H2O2, KO2/THF, and Fe[II]/H2O2 solutions indicates the effect of the high reactive hydroxyl radicals as the most important cause of in vivo polymer degradation.