It’s a common plot point in science fiction stories – someone loses an arm and gets a prosthetic limb that can move and feel just like the original. And, that’s exactly what researchers at the University of Pittsburgh are working toward.
Clinicians, engineers and scientists have teamed up to develop prosthetic arms that not only move naturally, but also allow the wearer to experience the sensation of touch.
Researcher Robert Gaunt, an assistant professor in the Department of Physical Medicine and Rehabilitation at Pitt, said without touch, prosthetics are seen as tools as opposed to part of an amputee’s person.
“They don’t exist in your body’s schema,” he said. “It’s this thing that’s attached to you. And so, we hope that the addition of sensation will help integrate this into their sense of self.”
According to Gaunt, the prosthetic will be designed for those amputated below the elbow because the muscles required to manipulate the wrist and fingers are still intact. This allows the amputee to have greater control over the movement of the prosthetic limb.
Researchers are currently gathering baseline muscle movement data from volunteers who are not amputees through electrodes inserted into the forearm muscles. This will allow researchers to see the electrical signals required to move a prosthetic thumb, as well as open and close a prosthetic hand.
To study sensation, researchers are stimulating the portion of the spinal cord nerves responsible for forearm and hand sensation in amputated volunteers. If an electrical signal is sent through the right nerves, the amputees should be able to feel the sensations of touch and movement in their “phantom limbs,” according to Gaunt.
Once it’s determined an amputee is capable of feeling with their phantom limb, electrodes will be implanted into their remaining forearm muscles. Those electrodes will connect to the prosthetic, which will accept the brain’s movement and sensory signals.
“A lot of the benefit and the motor control that we’re talking about here will be achieved because we have these fully implanted systems where we have a very stable interface with the muscles and the nervous system,” Gaunt said.
Similar prosthetic movement technologies use electrodes applied to the surface of the skin, but according to Gaunt, the data gathered from these sensors can vary depending on where they are placed and how dry the wearer’s skin is.
“The level of control that people can achieve with these devices is still, generally, fairly low,” he said. “They can be clumsy and awkward devices to operate.”
The new prosthetics should be ready for in-home testing within four years, according to Gaunt. And, if successful, the technology could be adapted to prosthetic legs and feet.
Parts of the prosthetic are being designed by researchers at West Virginia University and Ripple LLC in Salt Lake City.
The Defense Advanced Research Project Agency’s Hand Proprioception and Touch Interfaces program, the National Institutes of Health, the National Science Foundation, and the Food and Drug Administration put more than $110 million towards the project in fiscal year 2014.