Enhanced wear resistance of modified cross-linked polyethylene by grafting with poly(2-methacryloyloxyethyl phosphorylcholine).
We developed a cross-linked polyethylene (CLPE) modified with a phospholipid polymer in order to address the serious problem of osteolysis caused by wear particles derived from the polyethylene components of artificial hip joints. Our goal of preventing aseptic loosening could be achieved by avoiding any formation of CLPE wear particles or suppressing the activation of cell systems by the wear particles. We investigated the surface and wear resistance properties of 2-methacryloyloxyethyl phosphorylcholine (MPC) polymer grafted onto the surface of CLPE (CLPE-g-MPC). The relative density of MPC polymer chains was determined by the P-O group index. Generally, polymerization times correspond to the number of polymer chains in radical polymerization. After 3.0 x 10(6) cycles in a hip joint simulator test, the steady wear rates of the untreated CLPE and CLPE-g-MPC cups with a low P-O group index were as high as 4 mg/10(6) cycles; those of the CLPE-g-MPC cups with high P-O group indexes, that is, 0.46 and 0.48, markedly decreased to -1.12 and 0.16 mg/10(6) cycles, respectively. Therefore, the grafting of an MPC polymer with high density would be essential in order to maintain the long-term wear resistance of CLPE-g-MPC as an orthopedic bearing material.
Kyomoto
Masayuki
M
Research and Development Corporate Division, Japan Medical Materials Corporation, Osaka, Japan. kyomotom@jmmc.jp
Moro
Toru
T
Konno
Tomohiro
T
Takadama
Hiroaki
H
Yamawaki
Noboru
N
Kawaguchi
Hiroshi
H
Takatori
Yoshio
Y
Nakamura
Kozo
K
Ishihara
Kazuhiko
K
D001672:Biocompatible Materials / Q000138:chemical synthesis* / Q000737:chemistry*; D003432:Cross-Linking Reagents; D006622:Hip Prosthesis; D006801:Humans; D066298:In Vitro Techniques; D008422:Materials Testing; D008689:Methacrylates / Q000138:chemical synthesis* / Q000737:chemistry*; D018613:Microscopy, Confocal; D008854:Microscopy, Electron; D010767:Phosphorylcholine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D011095:Polyethylenes / Q000138:chemical synthesis* / Q000737:chemistry*; D011109:Polymethacrylic Acids; D017550:Spectroscopy, Fourier Transform Infrared; D013057:Spectrum Analysis; D013499:Surface Properties; D014965:X-Rays
D001672:Biocompatible Materials; D003432:Cross-Linking Reagents; D008689:Methacrylates; D011095:Polyethylenes; D011109:Polymethacrylic Acids; C115766:poly(2-methacryloyloxyethyl-phosphorylcholine); D010767:Phosphorylcholine