Abstract: “Tendon-transfer surgeries are performed for a variety of conditions such as stroke, palsies, trauma, and congenital defects. The surgery involves re-routing a tendon from a nonfunctioning muscle to a functioning muscle to partially restore lost function. However, a fundamental aspect of the current surgery, namely the suture that attaches the tendon(s) to the muscles, can lead to poor post-surgery function. For example, in the hand tendon-transfer surgery for high median-ulnar palsy, one muscle is sutured to all four finger flexor tendons. This couples finger movement, prevents the fingers from adapting to an object’s shape while grasping, and leads to poor hand function overall. This project investigates the design and use of miniature passive differential mechanisms, such as pulleys and links, as implants to attach the muscles and tendons in place of the direct suture. Results from biomechanical simulations and human cadaver experiments show that the new surgical procedure results in significantly better hand function in terms of finger movement and reduced actuator-force requirement in grasping tasks. The long-term goal is to enable re-engineering the mechanics of movement and force transmission from within the body using robotic devices.”