Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Biomedical Engineering

Collaborative Specialization

Musculoskeletal Health Research

Supervisor

Lalone, Emily A.

2nd Supervisor

Johnson, James A.

Co-Supervisor

Abstract

The shoulder is the most mobile joint in the human body, with the glenohumeral joint specifically allowing a wide range of motion and a high incidence of instability due to its ability to translate, as well as rotate in its socket. However, the extent of translation in a healthy glenohumeral joint is not well-established. Additionally, it is unclear if subluxation correction after anatomic total shoulder arthroplasty (TSA) with posterior augmented glenoid (PAG) implants remains consistent throughout active motion. This thesis aimed to evaluate healthy glenohumeral arthrokinematics to benchmark normal joint proximity and translation, and to assess if a TSA with PAG implants correct subluxation and maintain joint mechanics throughout motion post-surgery. Using four-dimensional computed tomography, 3D Slicer, and ICP registration, the study found that healthy glenohumeral proximity and translation were mostly consistent across ages and that a TSA with PAG implants effectively restored and maintained corrected joint mechanics throughout active motion.

Summary for Lay Audience

The shoulder joint, also known as the glenohumeral joint (articulation between the humeral head and glenoid) is the most mobile joint in the human body and enables people to move their arms freely in many directions. Due to the unique makeup of the shoulder joint, it can slide (translate) in addition to rotate in its socket. This makes the joint prone to instability, which can eventually lead to a greater chance of needing a shoulder replacement. Currently, it is not well-established how much translation occurs in the healthy glenohumeral joint and how that changes overtime as people age. Additionally, it is unknown if shoulder stability, corrected by a specific type of shoulder replacement surgery (anatomic total shoulder arthroplasty) using special implants (posterior augmented glenoid implants), stays consistent during activities of daily living.

This thesis aimed to understand how a healthy shoulder joint moves throughout different motions and to determine if these special implants can correct shoulder displacement and keep the joint stable during movement after surgery. Advanced imaging techniques, such as four-dimensional computed tomography (4DCT), were used to observe these movements in detail. Three-dimensional bone models were made from these scans and were used in the analyses to see how the glenohumeral joint moves within different people.

In the first study, the research findings highlighted the importance of translation within the joint during movements of daily living, which can then be used in the design and optimization of shoulder implants. In the second study, patients who received the shoulder replacement, due to conditions like osteoarthritis (where the shoulder joint erodes and becomes unstable), found the implants to be effective. These implants corrected the dislocation and kept the shoulder stable throughout movement.

Overall, the findings in this thesis showcased how important translation is within the healthy glenohumeral joint to achieve good functional movement. As well, this work demonstrated that the special shoulder implants are effective at restoring and maintaining proper shoulder alignment during daily movements. These results allow for better-informed clinical decisions, improved patient care, and enhanced outcomes in treatment of shoulder instability.

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