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Research on shoulders of bats provides insight into the mechanisms of shoulder instability. Past research, although probing into the mechanical behaviors of the shoulders, does not provide quantitative analysis regarding the contribution of fibers to the stability of the shoulder. This report for Shicheng Li's independent study in Spring semester of 2022 includes a theoretical analysis of the interaction between the glenoid, humerus, and tendons. A Matlab program was developed for a physical model that simulates the glenohumeral system. Different tests with various parameters input show that the relationship between a external, constantly oriented force and the displacement of the bottom end of the humerus follows a non-monotonic change, with a local maximum value of F existing before the displacement reaches its maximum. The magnitude of the local maximum is positively related to the value of the angle between the tendon and the humerus in the initial condition. Future research should aim to optimize the model by adding visco-elasticity, improving the geometry of the model, and exploring the relationship between the total glenoid angle and tendon angles under constant the condition of maximum force.
Mechanical Engineering and Material Sciences Independent Study
Date of Submission
Li, Shicheng, "A Mechanical Model of Glenohumeral Stability" (2022). Mechanical Engineering and Materials Science Independent Study. 199.
Available for download on Saturday, August 09, 2025