Graduate Research and Discovery Symposium (GRADS)


Glenoid Loading and Stability of the Inlay versus Onlay Shoulder Implant Systems


John DesJardins, PhD

Document Type




Publication Date

Spring 2013


The glenohumeral joint of the shoulder is the most freely moving joint in the body. The large range of pathology associated with the glenohumeral joint has motivated the innovation for the development of new technology. Current options for improved stability of the glenohumeral joint include a total shoulder arthroplasty (TSA), a reverse total shoulder arthroplasty (RSA), a humeral hemiarthroplasty, or a soft-tissue allograft. Each option has its risks and benefits, but when considering a TSA, an additional choice must be made: the onlay or inlay glenoid component. The purpose of this research study is to examine the contact pressures and implant stability associated with fatigue loading of these two types of glenoid components. The current standard of choice is that of the onlay design, which sits proud to the surrounding native bone. This design has a tendency to exhibit a rocking-horse loosening phenomenon as the humeral head articulates across the implant. The inlay design matches the surrounding anatomy with a fit that leaves it flush with the surrounding native bone and should therefore limit the rocking-horse loosening of the implant. Functional comparisons of these two components were made in the present experimental study.

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