Date of Award

8-2013

Document Type

Thesis

Degree Name

Master of Science (MS)

Legacy Department

Bioengineering

Advisor

DesJardins, John D

Committee Member

LaBerge , Martine

Committee Member

Colbath , Gregory

Abstract

The large range of pathology associated with the glenohumeral joint has motivated the development of innovative technology to improve stability of the glenohumeral joint. When considering a total shoulder arthroplasty (TSA), an additional choice may be considered: the onlay or inlay glenoid component.
The purpose of this 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 tissue and has a tendency to exhibit a rocking-horse loosening phenomenon. A newer option on the market is the inlay design that sits flush with the surrounding tissue and seeks to limit the rocking horse loosening of the implant. Functional and biomechanical comparisons of these two components were made in the present pilot study.
Two matched pair shoulders (four specimens) were dissected of all soft tissue and were potted in aluminum alloy fixtures and positioned on a custom testing apparatus. The glenoid was positioned perpendicular to the floor, with the humerus secured for testing in abduction angles of 10¡ (neutral carrying angle), 30¡, and 60¡. Biomechanical testing of the specimens was carried out using dynamic and fatigue materials testing software that articulated the humerus with respect to the superior-inferior and anterior-posterior axis of the glenoid. A flexible force sensor was positioned in the glenohumeral joint to record the location of glenohumeral contact area and contact pressure during a ±5 mm humeral articulation under an applied joint compression force. Testing was performed in the native shoulder and again, following implantation. TSAs were performed on all shoulders, one of each matched pair implanted with the onlay glenoid and the other with the inlay glenoid. The study concluded with fatigue loading until clinical loosening was observed.
Appropriate methods and testing have been established to test the glenoid loading and stability through contact areas and pressures associated with the inlay and onlay shoulder implant system. Future work will look to expand this protocol to a larger study to determine the implant stability associated with the onlay versus the inlay glenoid component.

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Engineering Commons

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