Date of Award

Spring 2023

Document Type


Terms of Use

© 2023 Cole D. Smith. This work is freely available courtesy of the author. It may be used under the terms of the Creative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0) license. For all other uses, please contact the copyright holder.

Creative Commons License

Creative Commons Attribution-NonCommercial 4.0 International License
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License

Degree Name

Bachelor of Arts


Engineering Department

First Advisor

Joseph D. Towles


It is believed that 65-75% of the persons diagnosed with tetraplegia would benefit from reconstructive surgery to regain the ability to perform activities of daily living. This surgery would improve their functional independence and reduce the annual assistive care costs ($80 million) in the US. Tendon transfer surgery, a reconstructive surgical procedure involving surgical transfer of a healthy muscle–such as the pronator teres (PT) or the brachioradialis (Br) muscle–to the paralyzed flexor pollicis longus (FPL) muscle of the thumb, is commonly performed to restore lateral pinch grasp. Functional outcomes, however, have been mixed. Previous research suggests that using muscle combinations could produce more optimal thumb-tip force characteristics, however research is needed to quantify the movement these combinations produce throughout pinch. The goal of this project was to develop a way to determine whether these muscle combinations producing stronger force characteristics could generate natural lateral pinch movement. Preliminary execution of a mathematical model determined whether individual muscles and muscle combinations could begin to move the thumb from an extended posture to the index finger in a natural way. The model predicted that only muscle combinations, and not individual muscles, have the capacity for the desired movement. Moreover, muscle combinations should consist of both a flexor and an extensor, and one of those muscles should be the FPL. I adapted an OpenSim model using the Elastic Foundation Method to investigate these findings and found them to be true. Simulations in my adapted model yielded 3 muscle combinations yielding better interphalangeal (IP) joint flexion and comprable thumb ab/adduction throughout pinch in 3D, all within known anatomical constraints. All combinations were composed of a flexor, including the FPL, and an extensor. Further in-situ cadaveric simulation work will further refine these muscle combinations by considering natural lateral pinch movement in 3D and throughout the full range of grasp motion.

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Engineering Commons