Polyurethane Load Bearing Surfaces for Total Hip Joint Replacement

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DESCRIPTION (provided by applicant): As total hip arthroplasty (THA) is being performed on increasingly younger patients, there is a need for THA implants that can sustain higher patient activity and number of loading cycle. UHMW-PE used in most common THA implants have been shown susceptible to high rates of wear, generating billions of sub-micron wear particles associated with the osteolysis-mediated implant failures. The objective of this study is to replace the UHMW-PE components of THA implants with polyurethane (PUR) elastomers specifically developed for this load-bearing application. The PUR elastomers were specifically developed with higher toughness, hardness, and modulus than the UHMW-PE, which should lead to lower deformation, adhesion, and abrasion. PUR elastomers are also significantly more hydrophilic than the UHMW-PEs, which should translate into more effective "fluid-film" lubrication between the articulating surfaces of THA implants, lower friction and ultimately lower wear. In Phase I we propose to compare the wear rates of selected PUR elastomers and UHMW-PE in a physiological hip joint simulator to demonstrate the potential of PUR elastomers to reduce the surface wear rates in THA implants and formation of sub-micron wear particles. Additionally, a study will be completed to compare the oxidation-mediate degradation of selected PUR elastomers and UHMW-PE, which is the primary cause for in vivo polymer degradation that can lead to considerable wear rate increases. PUR elastomer with the best combination of wear characteristics and resistance to oxidation will be selected for further optimization and evaluation in Phase II. Wear-property correlations and oxidation resistance-composition correlations determined in Phase I will be used as bases for further material optimization in Phase II. PROPOSED COMMERCIAL APPLICATIONS: With the expected lower wear rates and reduced potential for osteolysis, THA implants with PUR elastomer liners are expected to capture a significant portion of the THA implant market, which numbers over 270,000 THAs in the US and over 1.5 million world-wide. Successful application in THA is expected to lead to use of PUR elastomers as load bearing surfaces in total knee and shoulder implants and other joint replacements. PUBLIC HEALTH RELEVANCE: The overall goal of this project is to develop new load-bearing polyurethane surfaces for total hip replacement implants. The new load-bearing polyurethane surfaces will improve the durability and life- span of the replacement implants, significantly reducing the risk of failure. The technology developed in this study has the potential to improve lives of over 1.5 million new patients who each year undergo hip replacement surgeries.