Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article


Master of Engineering Science


Mechanical and Materials Engineering


Johnson, James A.

2nd Supervisor

Athwal, George S.



Massive irreparable rotator cuff tears are a common cause of pain and disability. Several different treatment options are available for this pathology; however, these treatments have been associated with poor clinical outcomes when used to treat younger (<65 years), more active patients. The purpose of this thesis was to design and evaluate a subacromial implant in its ability to restore normal glenohumeral stability and range of motion. The implant was created as a modular device, which captured different implant thicknesses (5mm and 8mm) and constraints (high and low) within its design. In-vitro testing compared the ability of these implants to restore normal shoulder biomechanics. The results indicated the 5mm high constraint implant to be the most effective in restoring normal joint position. Furthermore, range of motion increased when the implant was paired with a tuberoplasty procedure. These results suggest this implant may be advantageous in treating younger patients.

Summary for Lay Audience

One of the primary joints in the human shoulder is the glenohumeral joint, defined as the articulation between the humerus and scapula. This joint is largely supported by a group of muscles called the rotator cuff. However, when large tears occur in two or more of the units connecting these muscles to bone, patients can experience pain and loss of function. These tears can also cause unnatural translation of the humerus at the glenohumeral articulation, which can lead to further injury. Several surgical interventions are available for treating this type of injury, which have shown to have promising results when treating older (years), less active patients. However, for more active patients who are younger than 65 years of age, the effectiveness of these treatments has been called into question as poor results have been shown when treating this patient group. Recently, the concept of a subacromial implant has been proposed for this patient demographic, as it may contain several attributes that are advantageous to this specific patient population. Therefore, this thesis served to design and evaluate a subacromial implant in its ability to prevent translation of the humerus and restore normal range of motion. Four different implant models were created with varying thickness (5mm and 8mm) and constraint (high and low constraint) to determine which model was most effective at treating this injury. Testing was performed using a series of cadaver shoulders, which compared the normal, healthy shoulder to an injured shoulder state treated with the four different implant designs. Further testing was also conducted that paired the insertion of the subacromial implants with a tuberoplasty procedure which is used to improve the articulation at the glenohumeral joint. The results indicated the 5mm high constraint implant to be most effective in restoring the normal position of the humerus within the shoulder. Furthermore, it was found that the addition of the tuberoplasty procedure increased the shoulder’s allowable range of motion. These early results suggest this device may be an effective treatment options for younger, more active patients, and could improve their quality of life.

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Creative Commons Attribution 4.0 License
This work is licensed under a Creative Commons Attribution 4.0 License.