Do first-generation highly crosslinked XXXX oxidize in vivo?

@entity691 @entity273 @entity3061 @entity30375
BACKGROUND: Highly crosslinked and thermally treated @entity30375 were clinically introduced to reduce wear and @entity3061 . Although the crosslinking process improves the wear performance, it also introduces free radicals into the polymer that can subsequently oxidize. Thermal treatments have been implemented to reduce oxidation; however, the efficacy of these methods with regard to reducing in vivo oxidative degradation remains to be seen. @entity691 oxidation is a concern because it can compromise the ultimate strength and ductility of the material. QUESTIONS/PURPOSES: We analyzed the oxidation, oxidation potential, and mechanical behavior of thermally treated highly crosslinked @entity691 retrieved acetabular liners. METHODS: Three hundred seven acetabular liners were collected from consecutive revision surgeries at six institutions over a 10-year period. Twenty-four were sterilized using nonionizing methods, 43 were sterilized in an inert environment, 80 were highly crosslinked and annealed, and 160 were highly crosslinked and remelted. Oxidation and oxidation potential were assessed by Fourier transmission infrared spectroscopy. Mechanical behavior was assessed by the small punch test. RESULTS: Oxidation and @entity273 (oxidation potential) indices were elevated in the annealed and gamma inert sterilized groups compared with those of the remelted liners and uncrosslinked gas sterilized controls, particularly at the rim. We also detected an increase in oxidation over time at the bearing surface of the remelted group. Ultimate strength of the @entity691 at the bearing surface was negatively correlated with implantation time for the annealed liners. CONCLUSIONS: Within the first decade of implantation, the clinical outlook for first-generation highly crosslinked @entity691 remains promising. However, ongoing research continues to be warranted for first-generation highly crosslinked @entity691 bearings to monitor the implications of elevated oxidation at the rim of annealed liners as well as to better understand the subtle changes in oxidation at the bearing surface of remelted liners that occur in vivo.
