The Role of the Anterior Deltoid in the Stability of a Reverse Total Shoulder Arthroplasty

Mentor

Timothy Wright, PhD

Scope

Reverse total shoulder arthroplasty (RTSA) offers pain relief and functional improvement for patients suffering from glenohumeral arthropathy associated with a massive rotator cuff tear. RTSA relies on a functional deltoid for success, but the effects of a compromised anterior deltoid on shoulder abduction in RTSA are unclear. We propose to determine the sensitivity of abduction to anterior deltoid efficiency by examining the force requirements of the muscles involved in abduction at varying levels of anterior deltoid deficit. Cadaveric shoulders (obtained under IRB protocol 22121) implanted with RTSAs will be examined in a shoulder simulator to determine the distribution of forces for the rotator cuff and deltoid at various positions of abduction. The simulator links a series of stepper motors with a tracking system and software to create a control system and optimization algorithm for moving the shoulder. The humerus will be abducted to desired positions, the optimization will be run to maintain neutral rotation, and the muscle force distribution will be recorded along with the position and orientation of the arm.

To model decreased anterior deltoid efficiency, runs will be made with the force generation of the anterior deltoid successively decreased. As the force generating capacity of the anterior deltoid is compromised, we expect the shoulder to utilize other muscles to generate an abduction moment, probably the middle and possibly the posterior deltoid, resulting in increased force requirements from the affected muscles. As the anterior deltoid force decreases, we expect that the internal rotation moment will decrease, leading to coincident decreases in force through the posterior deltoid and teres minor.

Student’s role: The student will be expected to contribute to all aspects of the experiment, including specimen preparation, conducting the simulations, and data collection and analysis. Time permitting, the student may also contribute to interpretation of the findings and abstract and manuscript preparation.

Contact

Timothy Wright, PhD
email: wrightt@hss.edu