An international research team led by the Cleveland Clinic engineered a novel bionic arm for patients with upper-limb amputations that they say allows wearers to think, behave, and function as though they did not have an amputation.
According to a study published in Science Robotics, the researchers developed the bionic system that combines three functions—intuitive motor control, touch and grip kinesthesia, and the intuitive feeling of opening and closing the hand.
“We modified a standard-of-care prosthetic with this complex bionic system which enables wearers to move their prosthetic arm more intuitively and feel sensations of touch and movement at the same time,” said Paul Marasco, PhD, lead investigator and associate professor in Cleveland Clinic Lerner Research Institute’s Department of Biomedical Engineering. “These findings are an important step towards providing people with amputation with complete restoration of natural arm function.”The system is one of the first to test all three sensory and motor functions in a neural-machine interface all at once in a prosthetic arm. The neural-machine interface connects with the nerves in the user’s residual limb. It enables patients to send nerve impulses from their brains to the prosthesis when they want to use or move it, and to receive physical information from the environment and relay it back to their brain through their nerves.
The artificial arm’s bidirectional feedback and control enabled the participants to perform tasks with a similar degree of accuracy as people without amputations.
“Perhaps what we were most excited to learn was that they made judgments, decisions, and calculated and corrected for their mistakes like a person without an amputation,” said Marasco, who leads the Laboratory for Bionic Integration. “With the new bionic limb, people behaved like they had a natural hand. Normally, these brain behaviors are very different between people with and without upper-limb prosthetics.”
The researchers tested the limb on two study participants with upper-limb amputations who had previously undergone targeted sensory and motor reinnervation—procedures that establish a neural-machine interface by redirecting amputated nerves to remaining skin and muscles. While wearing the advanced prosthesis, participants performed tasks reflective of basic, everyday behaviors that require hand and arm functionality. With their newly developed advanced evaluation tools, the researchers assessed how performance with the bionic limb compared to people without amputations and people with amputations who have traditional prosthetic devices. They also compared how people with the advanced prosthesis fared when the three sensory and motor modalities were enabled together versus individually. With the new artificial arm and the advanced evaluation tools, the researchers said they could see that the study participants’ brain and behavioral strategies changed to match a person without an amputation.
Collaborators for this research also included University of Alberta and University of New Brunswick, and due to the study’s small size, more research will be necessary.