There is a scarcity of literature on the performance of the stemless humeral components. This present work describes the development of a novel loading simulator for the quantification of implant performance, as well as its use in the evaluation of implant parametric design and surgical protocol decision variables.

Interface fixation of humeral components was first evaluated using computational methods to determine the optimal metric to quantify implant fixation. Distractive micromotion was found to be the defining micromotion direction in two different designs of humeral implants.

A loading simulator capable of replicating 3D physiological loads, and comprehensive loading and digital image acquisition program were successfully developed. High resolution digital tracking methods were commissioned to quantify implant fixation.

The novel apparatus was used to compare the use of bone specimens to polyurethane bone surrogate materials using the clinically relevant variable of the degree of press-fit. It was found that the polyurethane analogue materials commonly utilized for the evaluation of implant performance did not accurately replicate the results as were collected in the biological specimens, and that fixation does not linearly increase with press-fit. Moving forward, it was concluded that only bone would be employed for the fixation studies herein.

One of the most important clinical variables with respect to the fixation of stemless implants is neck shaft angle. This was evaluated in terms of primary fixation in a clinically available stemless reversed implant. This was also assessed using a computational framework for a larger range of inclinations. The results of both works were in agreement;​ finding that decreasing neck-shaft angle resulted in decreased fixation of the implant evaluated.

This present work represents an advancement of knowledge regarding the performance of shoulder arthroplasty humeral components and provides a more thorough evaluation methodology than has been previously utilized during studies of the same nature. Decreasing neck shaft angle to increase range-of-motion comes at the cost of implant primary fixation, and over-increasing implant press-fit may compromise the fixation of stemless implants. Moreover, the relevance of focusing on normal micromotion due to its prominence for the stemless implant designs was shown to be a key outcome.