Engineering Commons^™

The Effect Of Humeral Short Stem Positioning, Humeral Head Contact, And Head Positioning On Bone Stress Following Total Shoulder Arthroplasty, Amir Tavakoli

Electronic Thesis and Dissertation Repository

Uncemented humeral stems cause stress shielding which result in bone resorption when used in total shoulder arthroplasty (TSA). Shorter length stems show a decrease in stress shielding, however the effect of humeral short stem positioning and humeral head contact and positioning on bone stress is currently not known, hence CT-based tools and Finite Element (FE) methods are used to quantify the effects of the mentioned variables on bone stresses after TSA.

Eight male cadaveric humeri were virtually constructed from computed tomography (CT) data, with a generic short humeral short stem as the implant.

The results of this work show that …

An Investigation On The Influences Of Radial Head Hemiarthroplasty Stem Fixation Techniques On Articular Mechanics, Jakub Szmit

Electronic Thesis and Dissertation Repository

Radial head hemiarthroplasty design has been extensively studied with a focus on utilizing the geometrical characteristics of the native radial dish as a guide of implant placement and design. Although implant design has been studied, optimal radial head implant fixation technique remains unknown. This thesis focused on the effect of stem fit on radiocapitellar contact mechanics, using both finite element and experimental bench-top approaches. Additionally, investigation into the impact of varus/valgus malalignment of the radial head in both the native state and following hemiarthroplasty was conducted. It was found that loose fitting a smooth stem axisymmetric radial head implant through …

A Computational Investigation Into Acromial Fractures After Reverse Total Shoulder Arthroplasty, Jason Lockhart

Electronic Thesis and Dissertation Repository

Acromial fractures are a debilitating complication following reverse total shoulder arthroplasty (RTSA). The purpose of this work is to (1) improve the current state of FE bone stress estimates after RTSA and to investigate the effects of (2) plane of elevation, (3) hand loads, and (4) baseplate screw position on scapular spine stress. The FE method used was validated against an in-vitro strain gauge based experiment and found to be accurate in the prediction of stress increases and decreases after RTSA. The coronal plane of elevation was found to increase scapular spine stress compared to more central planes of elevation. …

Lower Stiffness Orthopaedic Implants For Hemiarthroplasty, Carolyn Berkmortel

Electronic Thesis and Dissertation Repository

One of the main drawbacks of hemiarthroplasty is that it involves the articulation of a foreign material against the native cartilage, and hence the native cartilage experiences accelerated wear. It is hypothesized that lowering the stiffness of hemiarthroplasty implants will decrease contact pressure and increase contact area, thus decrease wear. Lowering the stiffness was done using finite element analysis to lower the stiffness of the implant materials, and then to change the internal structure of the implants to increase their compliance. Structural changes produced no noticeable or favourable results, whereas material produced improved results for stiffnesses below a Young’s modulus …