Date of Award

12-2006

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Legacy Department

Bioengineering

Advisor

LaBerge, Martine

Abstract

Polymeric biomaterials are especially susceptible to changes in mechanical and surface material properties as a result of sterilization processes that involve heat, moisture and/or irradiation. This is problematic for polymeric materials used in total joint replacement bearings, as these constructs must retain their superior mechanical and tribological properties over their expected 10-20 years of implantation. A younger more active patient population has now exacerbated this longevity issue with service lifetimes of 20+ years now being expected. Supercritical phase carbon dioxide (SC-CO2) is an industrial solvent that has shown great promise as a sterilizing agent in the food industry. Recently, SC-CO2 has adapted for the sterilization of medical grade total joint replacement ultra-high molecular weight polyethylene (UHMWPE), reducing the exposure of the polymer to the detrimental effects of heat, moisture and/or radiation. Further research is needed however to evaluate the effect of SC-CO2 sterilization on the mechanical, surface and tribological properties of UHMWPE over time. This dissertation explores the use of SC- CO2 sterilization for UHMWPE for total joint applications from a tribological perspective. It seeks to investigate and quantify fundamental tribological measures that occur at the bearing contact of total joint replacements, and it formulates and develops new experimental techniques and testing systems to investigate these tribological phenomena. This dissertation explores the hypothesis that SC-CO2 sterilization does not significantly affect the mechanical and/or tribological properties of UHMWPE, making it a 'material safe' sterilization treatment for this sensitive polymer. To answer this hypothesis, this dissertation develops and employs a series of clinically relevant wear testing methodologies in conjunction with industry standard material and surface characterization techniques to evaluate the efficacy of SC-CO2 for UHMWPE sterilization.

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