title: Structural modifications induced by compressive plastic deformation in single-step and sequentially irradiated UHMWPE for hip joint components.
abstract: Structural modifications were studied at the molecular scale in two highly crosslinked UHMWPE materials for hip-joint acetabular components, as induced upon application of (uniaxial) compressive strain to the as-manufactured microstructures. The two materials, quite different in their starting resins and belonging to different manufacturing generations, were a single-step irradiated and a sequentially irradiated polyethylene. The latter material represents the most recently launched gamma-ray-irradiated polyethylene material in the global hip implant market. Confocal/polarized Raman spectroscopy was systematically applied to characterize the initial microstructures and the microstructural response of the materials to plastic deformation. Crystallinity fractions and preferential orientation of molecular chains have been followed up during in vitro deformation tests on unused cups and correlated to plastic strain magnitude and to the recovery capacity of the material. Moreover, analyses of the in vivo deformation behavior of two short-term retrieved hip cups are also presented. Trends of preferential orientation of molecular chains as a function of residual strain were similar for both materials, but distinctly different in their extents. The sequentially irradiated material was more resistant to plastic deformation and, for the same magnitude of residual plastic strain, possessed a higher capacity of recovery as compared to the single-step irradiated one.
authors.affiliation: Ceramic Physics Laboratory and Research Institute for Nanoscience, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan. Electronic address: puppulin@chem.kit.ac.jp.
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: Nobuhiko
authors.initials: N
authors.lastname: Sugano
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: Ceramic Physics Laboratory and Research Institute for Nanoscience, Kyoto Institute of Technology, Sakyo-ku, Matsugasaki, 606-8585 Kyoto, Japan; The Center for Advanced Medical Engineering and Informatics, Osaka University,Yamadaoka, Suita, 565-0871 Osaka, Japan.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Pezzotti
mesh_terms: D019245:Compressive Strength / Q000528:radiation effects; D055119:Elastic Modulus / Q000528:radiation effects; D019544:Equipment Failure Analysis; D005720:Gamma Rays; D006244:Hardness / Q000187:drug effects; D006622:Hip Prosthesis; D008422:Materials Testing; D008968:Molecular Conformation / Q000528:radiation effects; D011095:Polyethylenes / Q000737:chemistry* / Q000528:radiation effects; D011829:Radiation Dosage; D013059:Spectrum Analysis, Raman / Q000379:methods*; D013499:Surface Properties / Q000528:radiation effects
chemical_list: D011095:Polyethylenes; C111601:ultra-high molecular weight polyethylene
keywords: Compressive plastic deformation; Cross-linking; Hip arthroplasty; Orientation distribution function; Raman spectroscopy; UHMWPE