A prosthetic hand could allow amputees to feel sensations by sending patterns of electrical signals to their nerves and brains.
Igor Spetic, who gets goose bumps when he touches cotton, felt the hair on the back of his arms stand up when a cotton ball was brushed over the back of the prosthetic hand, Case Western Reserve University reported. Spetic lost his hand in an industrial accident four years ago and was able to feel for the first time since then.
"I knew immediately it was cotton," he said.
Spetic was also happy to find the "phantom pain" he experienced in his missing hand disappeared; the same was true for a second patient who lost his forearm in an accident.
"The sense of touch is one of the ways we interact with objects around us," said Dustin Tyler, an associate professor of biomedical engineering at Case Western Reserve and director of the research. "Our goal is not just to restore function, but to build a reconnection to the world. This is long-lasting, chronic restoration of sensation over multiple points across the hand."
The prosthesis reactivates the part of the brain that produces the sense of touch, and the ability to feel these sensations improves over time. The nerves used to send the sense of touch to the brain are stimulated by contact points on cuffs that encircle major nerve bundles in the arm. The researchers developed algorithms that convert input sensors taped to the patient's hand into different patterns and intensities of signals to provide the most natural feeling sensations.
Keith Vonderhuevel, of Sidney, Ohio, who lost his hand in 2005 and had this prosthesis implanted in 2013 was able to tell how hard he was squeezing grapes and cherries, and even pulled out the stems.
The team hopes to develop a system that could be used at home within five years, and may even move on to develop prosthetic legs that receive input from the ground.
The findings were published Oct. 8 in the journal Science and Translational Medicine.
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