AVS 47th International Symposium
    Biomaterial Interfaces Monday Sessions
       Session BI+MC-MoA

Paper BI+MC-MoA9
Molecular Orientation of Annealed Artificial Joint Polymers: Characterization by Soft X-ray Absorption

Monday, October 2, 2000, 4:40 pm, Room 202

Session: Characterization of Biomaterial Interfaces
Presenter: D.A. Fischer, National Institute of Standards and Technology
Authors: S. Sambasivan, SUNY Stony Brook
D.A. Fischer, National Institute of Standards and Technology
M. Shen, University of Maryland
J.A. Tesk, National Institute of Standards and Technology
S. Hsu, National Institute of Standards and Technology
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For the past 30 years ultra-high molecular weight polyethylene (UHMWPE) has remained the dominant polymer in artificial joints due to its outstanding wear resistance properties. It has been recognized that wear of UHMWPE contributes to the loosening of the implants and is the main cause for the failure of long-term implants. Hence, there is an urgent need to understand the mechanism and the surface morphology leading to wear and failure of the artificial joint. Hubbard et al.@footnote 1@ and Hastings et al.@footnote 2@ have demonstrated that the molding and annealing the UHMWPE at safe elevated temperatures resulted in increased mechanical strength. Also, cross-linking of UHMWPE has been demonstrated to reduce wear significantly. We have previously measured molecular orientation as a function of wear motion.@footnote 3@ Molecular orientation in biomaterials is thought to be critical in characterizing the precursors of wear and the production of debris during the wear process. While the link between molecular orientation and wear has not been clearly established, molecular orientation has been recognized as an important parameter in wear resistance. This study examines the change of molecular orientation caused by annealing UHMWPE. Our technique utilizes soft x-ray absorption spectroscopy at a synchrotron beamline to non-destructively characterize the molecular orientation of the UHMWPE surface layer. Current methods of inferring or deducing orientation are not accurate and often rely on staining and cutting specimens.@FootnoteText@ @footnote 1@Hubbard et al., Trans. 25th Soc. For Biomaterials, 325(1999). @footnote 2@Hastings et al., Trans. 25th Soc. For Biomaterials, 328(1999). @footnote 3@Fischer et al., Trans. 25th Soc. For Biomaterials, 351(1999).