Engineering and Design of Upper Limb Joint Arthroplasties with Special Interest in Tribology, Load Transfer, and Contact Mechanics

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Joint arthroplasty replaces damaged cartilage with articulating implants to alleviate pain and restore motion. However, failure of these devices in the body results in the need for costly and painful revision surgery to replace the implant. To reduce this risk, the current research proposal aims to investigate and address several of the most common upper limb arthroplasty implant failure modes with the aim of improving implant design and the long-term goal of improving the quality of life of Canadians and reducing cost to the healthcare system. Furthermore, moving forward the resulting research methodologies developed herein can also be extended to other emerging areas of orthopaedics.******Reverse total shoulder arthroplasty (RTSA) is growing in use, however articular wear and scapular notching remain a concern. While the use of cross-linked polyethylene (XLPE) has reduced wear in hip arthroplasty, the tribological performance of both XLPE and non-XLPE in RTSA has not been fully explored for varying loads. To address this, a shoulder wear simulator will be used to perform wear testing of XLPE and non-XLPE humeral cups subjected to normal and adverse loads. Scapular notching arises due to contact of the humeral cup with the scapula, which could be prevented if humeral cups had an inferomedial cut-out. To assess the feasibility of this concept, finite element modelling will be used to estimate the degree of cut-out that can be removed without significantly altering contact mechanics, and the resulting cut-outs will then be made on humeral cups and subjected to wear testing to assess their impact on RTSA wear.******Radial head hemiarthroplasty (RHH) replaces only one side of the joint, however the substitution of cartilage with a stiff metallic implant results in degeneration of the opposing cartilage. The use of new RHH materials may help to reduce this, however their tribological performance against cartilage is not fully understood. To address this, wear testing of Bionate, a compliant material, and pyrolytic carbon (PyC), a smooth reduced modulus material, will be performed using an OrthoPOD wear apparatus. The long-term fatigue of Bionate and the tribological performance of PyC against cartilage will be evaluated.******Humeral stress shielding following shoulder arthroplasty is common and is a result of the unloading of bone following insertion of a stiff metallic humeral stem. Although humeral stem design has been improved somewhat, the optimal short stem geometry has yet to be defined. To address this, humeral stem geometry will be optimized using finite element methods employing a novel modelling technique which permits the estimation of expected stress shielding following stem implantation.******The proposed innovative research program incorporates several novel approaches to advance the tribology and design of upper limb arthroplasty, contributing to the long-term vision of improving patient outcomes and quality of life while reducing healthcare costs.**