Implanted Pulley System Could Improve Postsurgical Hand Function

A novel implanted passive engineering mechanism could improve hand function after tendon transfer surgery, according to a new study.

Researchers at Oregon State University (OSU; Corvallis, USA) and the University of Washington (Seattle, USA) conducted a cadaver study of a new tendon transfer surgical procedure that uses an implanted passive hierarchical artificial pulley mechanism for attaching multiple tendons to a single donor muscle, in place of directly suturing tendons to the muscle. The purpose of the study was to evaluate hand function in physical interaction tasks, based on the actuation force required to create a grasp and the slippage between the fingers and the object after the grasp was created.

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 results showed that when compared with the suture-based procedure, the pulley-based procedure reduced the actuation force required to close all four fingers around the object by 45%, improved the fingers’ individual adaptation to the object’s shape during the grasping process, and reduced slippage by 52% after object contact. The study was published in the September 2014 issue of the journal Hand.

“This technology is definitely going to work, and it will merge artificial mechanisms with biological hand function,” said lead author Ravi Balasubramanian, PhD, an OSU expert in robotics, biomechanics and human control systems. “We'll still need a few years to develop biocompatible materials, coatings to prevent fibrosis, make other needed advances, and then test the systems in animals and humans. But working at first with hands – and then later with other damaged joints such as knees or ankles – we will help people recover the function they've lost due to illness or injury.”

The new mechanism is not really robotic since it has no sensory, electronic, or motor capabilities, but is rather a passive technology using a basic pulley implanted within a person's hand to allow more natural grasping function with less use of muscle energy.

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Oregon State University
University of Washington