Electronic Thesis and Dissertation Repository

Thesis Format

Monograph

Degree

Master of Science

Program

Surgery

Supervisor

Johnson, James

2nd Supervisor

Athwal, George

Co-Supervisor

Abstract

Massive irreparable rotator cuff tears are a common cause of pain and disability. Several different treatments exist; however, they are associated with poor clinical outcomes and survivorship in younger patients without glenohumeral arthritis. The purpose of this thesis was to compare the impact of a subacromial balloon spacer, superior capsular reconstruction, and a rigid subacromial implant on the glenohumeral kinematics and mechanical efficiency of a massive rotator cuff deficient shoulder. The results indicate that each surgical state improves the glenohumeral kinematics of a massive irreparable rotator cuff tear. The subacromial implant leads to mild overcorrection of humeral head translation. No surgical state achieves the mechanical efficiency of the intact shoulder, except for the superior capsular reconstruction at 0-degrees and the subacromial implants at 60-degrees abduction. Each surgical state appears to correct the biomechanical abnormalities of rotator cuff deficiency, each with their own unique limitations.

Summary for Lay Audience

The shoulder is a complex joint in the human body. With a spherical humeral head and a shallow glenoid, it is also inherently unstable. It relies on muscles, ligaments, and joint capsule for stability. The rotator cuff is an important group of muscles that are critical to shoulder motion and stability. Disruption of the rotator cuff can lead to pain and loss of shoulder function. Tears of more than 5cm or those that involve 2 or more tendons are considered massive and can often be irreparable. Chronic loss of rotator cuff function can lead to progressive shoulder arthritis and worsened shoulder function.

The standard of care for older patients (>65 years) with massive irreparable rotator cuff tears is a reverse shoulder replacement. However, when used in younger patients (years) the clinical outcomes are worse with an increased need for reoperation. Therefore, several surgical options have been developed to treat this patient population. Common surgical procedures include the subacromial balloon spacer and the superior capsular reconstruction. There is currently no preferred surgical treatment. Recently, a metallic subacromial implant was developed which aims to improve upon the deficiencies of the subacromial balloon spacer and the superior capsular reconstruction.

The aim of this thesis was to perform a biomechanical comparison of the subacromial balloon spacer, the superior capsular reconstruction, and the metallic subacromial implant in a massive irreparable rotator cuff deficient cadaver model. Testing compared the normal intact shoulder to a massive irreparable rotator cuff tear, subacromial balloon spacer, superior capsular reconstruction, and two iterations of the subacromial implant.

Results indicate that each surgical treatment improves the stability of the humeral head compared to the massive irreparable rotator cuff tear state. The test states were unable to reproduce the mechanical efficiency of the intact shoulder, however the superior capsular reconstruction and the subacromial implants were able to improve upon the mechanical efficiency of the shoulder at 0-degrees and 60-degrees abduction, respectively. Each surgical treatment could be a viable treatment option; however, clinical studies are required.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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