title: Effects of Surface Modification and Bulk Geometry on the Biotribological Behavior of Cross-Linked Polyethylene: Wear Testing and Finite Element Analysis.
abstract: The wear and creep deformation resistances of polymeric orthopedic bearing materials are both important for extending their longevity. In this study, we evaluated the wear and creep deformation resistances, including backside damage, of different polyethylene (PE) materials, namely, conventional PE, cross-linked PE (CLPE), and poly(2-methacryloyloxyethyl phosphorylcholine)- (PMPC-) grafted CLPE, through wear tests and finite element analysis. The gravimetric and volumetric degrees of wear of disks (3 or 6 mm in thickness) of these materials against a cobalt-chromium-molybdenum alloy pin were examined using a multidirectional pin-on-disk tester. Cross-linking and PMPC grafting decreased the gravimetric wear of the PE disks significantly. The volumetric wear at the bearing surface and the volumetric penetration in the backside of the 3-mm thick PE disk were higher than those of the 6-mm thick PE disk, regardless of the bearing material. The geometrical changes induced in the PE disks consisted of creep, because the calculated internal von Mises stress at the bearing side of all disks and that at the backside of the 3-mm thick disks exceeded their actual yield strengths. A highly hydrated bearing surface layer, formed by PMPC grafting, and a cross-linking-strengthened substrate of adequate thickness are essential for increasing the wear and creep deformation resistances.
authors.affiliation: Research Department, KYOCERA Medical Corporation, Osaka, Japan ; Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Watanabe
authors.affiliation: Research Department, KYOCERA Medical Corporation, Osaka, Japan ; Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan ; Department of Materials Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Masayuki
authors.initials: M
authors.lastname: Kyomoto
authors.affiliation: Research Department, KYOCERA Medical Corporation, Osaka, Japan ; Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Kenichi
authors.initials: K
authors.lastname: Saiga
authors.affiliation: Orthopaedic Surgery, Sensory and Motor System Medicine, Surgical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Shuji
authors.initials: S
authors.lastname: Taketomi
authors.affiliation: Orthopaedic Surgery, Sensory and Motor System Medicine, Surgical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Inui
authors.affiliation: Orthopaedic Surgery, Sensory and Motor System Medicine, Surgical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yuho
authors.initials: Y
authors.lastname: Kadono
authors.affiliation: Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Yoshio
authors.initials: Y
authors.lastname: Takatori
authors.affiliation: Orthopaedic Surgery, Sensory and Motor System Medicine, Surgical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Sakae
authors.initials: S
authors.lastname: Tanaka
authors.affiliation: Department of Materials Engineering, School of Engineering, The University of Tokyo, Tokyo, Japan.
authors.forename: Kazuhiko
authors.initials: K
authors.lastname: Ishihara
authors.affiliation: Division of Science for Joint Reconstruction, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan ; Orthopaedic Surgery, Sensory and Motor System Medicine, Surgical Sciences, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Toru
authors.initials: T
authors.lastname: Moro
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry* / Q000627:therapeutic use; D020342:Finite Element Analysis; D006801:Humans; D008422:Materials Testing; D009984:Orthopedic Fixation Devices; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000737:chemistry / Q000627:therapeutic use; D020959:Polyethylene / Q000737:chemistry* / Q000627:therapeutic use; D011109:Polymethacrylic Acids / Q000737:chemistry* / Q000627:therapeutic use; D013499:Surface Properties
chemical_list: D001672:Biocompatible Materials; D011109:Polymethacrylic Acids; C115766:poly(2-methacryloyloxyethyl-phosphorylcholine); D010767:Phosphorylcholine; D020959:Polyethylene