Date of Award

7-2018

Document Type

Dissertation

Department

Mechanical Engineering

First Advisor

Ryan Willing

Abstract

Reverse total shoulder arthroplasty was developed to restore range of motion (ROM) and joint stability to patients with pre-operative conditions that are not addressed by conventional replacements. Although reverse total shoulder arthroplasty is the current gold standard for treating a range of indications, the effects of varying its design on functional outcomes of the procedure are still not well understood.

To that end, it is not yet clear which configurations, in terms of both design and surgical placement parameters, maximize range of motion and stability of the joint. It was hypothesized that there is trade-off between the two. These types of relationships may be elucidated using multi-objective design optimization to generate a Pareto front. Pareto optimal points represent those where neither performance metric can be further improved without detriment to the other.

Multi-objective optimization requires 1) metrics to characterize the objectives to be optimized and 2) an automated computational framework capable of assessing the metrics for any candidate implant design. As such, the pre-cursory goals to performing multi-objective optimization involved the development, validation, and automation of computational tools to predict the performance of reverse should designs with respect to range of motion and joint stability.

Characterization of the Pareto front with multi-objective optimization confirmed that there is in fact a trade-off between range of motion and stability. Designs that maximize one functional outcome differ from those that maximize the other. Designs that resulted in intermediate performance in terms of both objectives were variable. This indicates that functional factors other than range of motion and stability, such as mechanical implant stability (fixation) and avoidance of inferior impingement, could serve as deciding factors between implant configurations that achieve similar range of motion and stability results.

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