Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Dr. James Johnson

Abstract

Hemiarthroplasty is a minimally invasive, cost-effective alternative to total arthroplasty in joints of the upper limb. Though these procedures reduce patient morbidity while restoring joint kinematics, their longevity is limited by wear of the adjacent cartilage. This work investigates the roles of contact geometry and implant stiffness on cartilage wear with the aim of elucidating the mechanics that contribute to cartilage damage. An in vitro study examined the influence of implant geometry on cartilage wear using a pin-on-plate wear simulator. A significant decrease in volumetric wear was observed as contact area increased, which suggests that maximizing contact area should be design target for hemiarthroplasty implants. A subsequent study examined the influence of stiffness using various clinically relevant biomaterials, and demonstrated no effect on cartilage wear for a range of Young's moduli between 200GPa and 0.69GPa. It was concluded that the disparity between the moduli of the investigated materials and that of cartilage may be too great to demonstrate the possible effects of implant stiffness on contact mechanics. A finite element simulation was conducted to further reveal contact mechanics at the implant-cartilage interface. The stress levels determined by the study were proportional to the wear observed for both implant geometry and material, with the exception of polyether ether ketone, one of the investigated biomaterials. Further studies are required to more comprehensively characterize cartilage wear, and it is necessary to examine whether stiffness has an effect on cartilage wear when caused by implant materials with moduli approaching that of articular cartilage.

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