Prosthetics That Feel: The Next Generation Arrives

One of the greatest challenges facing amputees is not only the missing limb, which can be remedied with any simple prosthetic, but the absence of touch and sensation within the prosthetic. Recently, researchers at a university in Ohio developed a new prosthetic system that enables amputees to experience a variety of sensations.

In a release from Case Western Reserve University news, researchers spoke about their work with Igor Spetic, an amputee who lost his right hand in an industrial accident in 2010. While blindfolded during an experiment, researchers brushed his prosthetic hand with a cotton ball, and watched as Spetic reacted instantaneously, identifying the ball of cotton.

"The sense of touch actually gets better," said Keith Vonderhuevel, another amputee patient in Ohio that had the system implanted. "They change things on the computer to change the sensation. One time, it felt like water running across the back of my hand."

Though this isn't the first foray into prosthetic limbs with nerve sensation technology, it truly is the first of its kind to provide various sensations.The system, which is still limited to laboratory use, uses electrical stimulation to provide the sense of feeling, with a few distinct differences from previous efforts.

For starters, the nerves used to relay the sense of touch to the brain are stimulated by contact points on cuffs, whichencircle major nerve bundles in the arm. Surgeons inserted three of these electrode cuffs in Spetic's arm, enabling him to feel sensations in 19 distinct locations.

Doctors also altered the algorithms that convert the input from the sensors into varying patterns and intensities of electrical signals. This enabled users to experience less of a tingling sensation, and more of a natural sense of touch. The goal is that this can eventually lead to improved sensations that aren't only limited to pressure sensations, but ones that can detect textures as well.

The system has even been refined to help patients gauge how tightly they can grasp and squeeze objects. When Vonderhuevel was blindfolded, he was able to hold a grape or cherry, grasp the fruit, and pull out the stems without crushing the object.

"When the sensation is on, it's not too hard," he said. "When it's off, you make a lot of grape juice."

Given the progress that has been made up to this point, some doctors are optimistic that the system can lead to a lifetime of improved experiences for amputees. The team that developed the arm is even optimistic that the system can be ready for outpatient use within the next five years.

Dustin Tyler, an associate professor of biomedical engineering at CWRU and director of the study, believes that the research can be extended to help those using prosthetic legs as well. The same principles could help leg amputees receive input from the ground, assisting patients with the discernment of gravel and other uneven surfaces.

"The sense of touch is one of the ways we interact with the objects around us," Tyler said. "Our goal is not just to restore function, but to build a reconnection to the world. This is a long-lasting chronic restoration of sensation."

Specific details on how the system works, as well as the full extent of the study's results were published online in the journal Science Translational Medicine on October 8.

Kristopher Sturgis is a contributor to Qmed and MPMN.

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