title: Microstructural modifications induced by accelerated aging and lipid absorption in remelted and annealed UHMWPEs for total hip arthroplasty.
abstract: Three types of commercially available ultra-high molecular weight polyethylene (UHMWPE) acetabular cups currently used in total hip arthroplasty have been studied by means of Raman micro-spectroscopy to unfold the microstructural modification induced by the oxidative degradation after accelerated aging with and without lipid absorption. The three investigated materials were produced by three different manufacturing procedures, as follows: irradiation followed by remelting, one-step irradiation followed by annealing, 3-step irradiation and annealing. Clear microstructural differences were observed in terms of phase contents (i.e. amorphous, crystalline and intermediate phase fraction). The three-step annealed material showed the highest crystallinity fraction in the bulk, while the remelted polyethylene is clearly characterized by the lowest content of crystalline phase and the highest content of amorphous phase. After accelerated aging either with or without lipids, the amount of amorphous phase decreased in all the samples as a consequence of the oxidation-induced recrystallization. The most remarkable variations of phase contents were detected in the remelted and in the single-step annealed materials. The presence of lipids triggered oxidative degradation especially in the remelted polyethylene. Such experimental evidence might be explained by the highest amount of amorphous phase in which lipids can be absorbed prior to accelerated aging. The results of these spectroscopic characterizations help to rationalize the complex effect of different irradiation and post-irradiation treatments on the UHMWPE microstructure and gives useful information on how significantly any single step of the manufacturing procedures might affect the oxidative degradation of the polymer.
authors.affiliation: Department of Molecular Cell Physiology, Kyoto Prefectural University of Medicine, Kamigyo-ku Hirokoji Agaru, Kyoto, Japan.
authors.forename: Leonardo
authors.initials: L
authors.lastname: Puppulin
authors.affiliation: Department of Orthopedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita 565-0871 Osaka, Japan.
authors.forename: Wenliang
authors.initials: W
authors.lastname: Zhu
authors.affiliation: Department of Orthopedic Surgery, Osaka University Medical School, 2-2 Yamadaoka, Suita 565-0871 Osaka, Japan.
authors.forename: Nobuhiko
authors.initials: N
authors.lastname: Sugano
authors.affiliation: Ceramic Physics Laboratory and Research Institute for Nanoscience, Kyoto Institute of Technology, Sakyo-ku, Kyoto, Japan The Center for Advanced Medical Engineering and Informatics, Osaka University, Yamadaoka, Osaka, Japan pezzotti@kit.ac.jp.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pezzotti
mesh_terms: D065966:Absorption, Physicochemical; D001672:Biocompatible Materials / Q000032:analysis* / Q000138:chemical synthesis*; D019544:Equipment Failure Analysis; D006244:Hardness; D006361:Heating / Q000379:methods; D006622:Hip Prosthesis; D008055:Lipids / Q000737:chemistry*; D008422:Materials Testing; D010084:Oxidation-Reduction; D010100:Oxygen / Q000737:chemistry; D044367:Phase Transition; D011095:Polyethylenes / Q000032:analysis / Q000138:chemical synthesis*; D011474:Prosthesis Design / Q000379:methods; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D008055:Lipids; D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene; D010100:Oxygen
keywords: Polyethylene; Raman spectroscopy; hip replacement; lipid absorption; oxidation