Implanted passive engineering mechanism improves hand function after tendon transfer surgery: a cadaver-based study.

PURPOSE The purpose of this study was to investigate if a new tendon transfer surgical procedure that uses an implanted passive engineering mechanism for attaching multiple tendons to a single donor muscle in place of directly suturing the tendons to the muscle improves hand function in physical interaction tasks such as grasping. METHODS The tendon transfer surgery for high median ulnar palsy was used as an exemplar, where all four flexor digitorum profundus (FDP) tendons are directly sutured to the extensor carpi radialis longus (ECRL) muscle to restore flexion. The new procedure used a passive hierarchical artificial pulley system to connect the muscle to the tendons. Both the suture-based and pulley-based procedures were conducted on N = 6 cadaver hands. The fingers' ability to close around four objects when the ECRL tendon was pulled was tested. Post-surgery hand function was evaluated based on the actuation force required to create a grasp and the slip between the fingers and the object after the grasp was created. RESULTS When compared with the suture-based procedure, the pulley-based procedure (i) reduced the actuation force required to close all four fingers around the object by 45 % and (ii) improved the fingers' individual adaptation to the object's shape during the grasping process and reduced slip by 52 % after object contact (2.99° ± 0.28° versus 6.22° ± 0.66°). CONCLUSIONS The cadaver study showed that the implanted engineering mechanism for attaching multiple tendons to one muscle significantly improved hand function in grasping tasks when compared with the current procedure.