MPC-grafted highly cross-linked polyethylene liners retrieved from short-term total hip arthroplasty: Further evidences for the unsuitability of the MPC method.

Abstract

An analysis is presented of four short-term retrieved highly crosslinked polyethylene (HXLPE) hip liners grafted with 2-methacryloyloxyethyl phosphorylcholine (MPC) on their bearing surfaces, which were recently commercialized as a new generation of artificial hip joints. Straightforward evidences by X-ray photoelectron spectroscopy (XPS) confirmed that the MPC layer peeled off on the bearing surface of all short-term liners in both main wear and nonwear zones. Analyses by Fourier-transform infrared spectroscopy with attenuated total reflection assessed the extent of surface oxidation and revealed the type of oxidative species. Electron spin resonance analyses, which compared retrievals and as-received samples, revealed the presence of different species of alkoxyl CO^• radicals. This study suggests that MPC grafts on polyethylene do not offer any additional protection from oxidation and can delaminate prematurely after short-term in vivo exposure.