Artificial hands connect with the world

"Smart" artificial hands have been moving and feeling objects in two men with amputated limbs for 1,5 and 2,5 years

Bionic prosthetic arms and legs are becoming more "alive" – they can not only make a variety of movements, getting more freedom, but they also began to feel. Dennis Sorensen from Denmark is the first person with an amputated hand who got an opportunity of not only movement, but also the feeling that he had been deprived of for nine years. The unique construction was developed by the Swiss and Italian bioengineers.

Dustin Tyler, Ph.D. Associate Professor and his colleagues from the Case Western Reserve University published the following achievements in the Science Translation Medicine magazine –

the results of the first long-term test of bionic sensitive hand prostheses of two patients.

Igor Spetic from Madison, Ohio, lost his arm four years ago because of work-related injury. The artificial arm has served him for two and a half years. Keith Vonderhuevel lost his arm in 2005, he has been wearing a "smart" prosthesis for 1,5 years. During all this time, both men were doing their daily activities.

With the help of the artificial arm, they could open the door, cook, tie their shoes, brush their teeth, and even chop wood.

Interestingly, after starting using the "smart" prostheses, two men stopped feeling phantom pain in the residual limbs.

Each month, the men visited the laboratory where they underwent a variety of sensitivity tests blindfolded. For example, the sense of a tennis ball with fibrous covering in the artificial hand evoked goosebumps on Spetic"s residual arm. Vonderhuevel carefully took grapes and cherries from the bowl on the table without crushing them. "He would have turned them into juice without sensory feedback," says Dustin Tyler, the Professor of Biomedical Engineering at Case Western Reserve University.

"The tactile sense is one of the most important ways of our interaction with the outside world," emphasizes the scientist.

"We aimed not only to restore the motor function, but also to restore the patient"s communication with the world."

Tactile sense in the prosthesis occurred due to the electrodes implanted under the skin, which were attached to the nerves of the remaining part of the arm. Artificial hand was equipped with a number of sensors. The scientists have developed an algorithm that converts the input from the sensors while touching a variety of objects. This sensory feedback adjusted the intensity of each artificial finger fastening.

Spetic had three electrodes implanted into his body that provided sensation in 19 points. Two electrodes implanted in Vonderhuevel"s body gave him a tactile sense in 16 points. Thanks to them, the sense of the patients has improved with time. First, both patients described them as tingling, but as they got used to the artificial hand this feeling became more and more natural. The scientists are improving the setting of the device and are working on the naturalness of sense.

In the end, both men began to perceive the prostheses as the parts of their own body.

It is the world"s first evidence that the bionic sensitive prostheses can work for such a long time. Until now, such system tests lasted no more than a month.

Besides prosthetic hands, scientists are currently working on "smart" prosthetic legs that would feel the earth"s surface, as well as on the device that would release the patients, suffering from Parkinson"s disease, from tremor.