Electronic Thesis and Dissertation Repository

Degree

Master of Engineering Science

Program

Biomedical Engineering

Supervisor

Dr. James Johnson

2nd Supervisor

Dr. John Medley

Co-Supervisor

3rd Supervisor

Dr. George Athwal

Joint Supervisor

Abstract

Scapular notching is a common complication of reverse total shoulder arthroplasty (RTSA) wherein the predominant focus of current literature has been on changes in osseous anatomy. However, the implications on RTSA performance from the damaged humeral cup is largely unknown. Therefore the present work describes the effects of the initiation and propagation of the humeral cup defect resulting from scapular notching through the use of finite element modeling and wear simulation, in order to assess changes in RTSA contact mechanics and tribological properties. A significant decrease in articular contact area and increase in maximum contact stress values was found for the tested abduction range of motion for damaged humeral cups. Wear testing of high-mobility RTSA implants indicated a relatively low wear rate, which decreased with the propagation of the scapular notching defect. However, the simulated defect from notching also resulted in a more visibly concentrated secondary wear region within the inferior aspect. Through inferior tilting of the glenosphere, articular contact mechanics were improved, with a significant increase in contact observed, without affecting maximum contact stress values, indicating that this intraoperative parameter may be beneficial beyond the reduced risk for developing scapular notching. Overall, it was indicated that scapular notching damage of the humeral cup may well be detrimental to the assessed articular implant performance parameters, possibly attributing to a decreased lifespan of the implant.

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