Artificial hand brings back sense of touch

The amputee can feel and feel again thanks to the innovative hand prosthesis

06/02/2014

In the future, hand amputees can hope to feel and feel again with the help of a new type of prosthesis. According to researchers, Dennis Aabo Sørensen is the first person in the world to feel something again thanks to such a substitute hand.

Accident with fireworks
The Dane Dennis Aabo Sørensen had lost his left hand in an accident with fireworks about nine years ago. According to researchers, the Scandinavian is now the first person in the world to feel and touch again thanks to a novel prosthesis without time delay. Sørensen is quoted in a communication from the Swiss Federal Institute of Technology in Lausanne (Switzerland): „When I held an object, I could feel it was soft or hard, round or angular.„ He was enthusiastic about the new test hand: „The sensory feedback was incredible.„

Conventional prostheses work pretty well
Since his accident, the Dane has been wearing a standard prosthetic arm that allows him to open and close the artificial hand. In the meantime, such prosthetics work quite well, but still provide no indication of how strong the artificial hand has to grab or how an object feels. Under the direction of the Italian Silvestro Micera from the École Polytechnique Fédérale de Lausanne (EPFL), a prototype of a prosthesis has been developed by an international research team from several European universities and clinics that can feel. In the journal „Science Translational Medicine„ They reported about their work.

Sensations to the pain threshold
The then 36-year-old Dane was operated at the end of January 2013 at the Gemelli University Hospital in Rome. Surgeons at the upper arm implanted electrodes to the median nerve and ulnar nerve, which are responsible for various finger and hand movements. Less than three weeks later, the scientists attached the artificial hand and wired it with the implanted electrodes, so that the tactile sensations when gripping an object can be conveyed directly to the brain. These sensations led to the pain threshold.

His children called him the cable man
In the following tests, Dennis Aabo Sørensen was blindfolded and put on headphones to separate him from those senses. Thus, only the sense of touch remained to him. Stanisa Raspopovic from an Italian university in Pisa (Scuola Superiore Sant'Anna) explained: „We feared that the sensitivity of the patient's nerves would have diminished because he had not used them for more than nine years.„ But the worries proved unfounded. In a video, the Dane explained: „Suddenly I could feel something that I had not felt for nine years.„ His children were also enthusiastic and called him the cable man.

„I feel the closing of my missing hand!„
During the experiments, Sørensen had to feel various objects such as a tangerine, delicate plastic cups, wooden cubes or dressing material. His brain quickly registered that something was happening on his thumb, little finger and forefinger. The reaction was that he could adjust his grip, for he could see what he held in the artificial hand. The Dane said: „And suddenly, I actually felt what I was doing.„ The art hand enabled him to feel the size, shape and hardness of objects. Raspopovic remembered the results at the time: „It was a very exciting moment when Dennis, after endless hours of artificial hand testing, turned to us and said in disbelief, 'This is magic! I feel the closing of my missing hand! '„

Works like a motorcycle brake
Sørensen controls the fingers of the prosthesis with his muscles. „It works like a motorcycle brake„, he explains the principle. „If you pull it, the hand closes. When you let go, it opens.„ He controls his fingers by watching them and adjusting his movements. The researchers made more than 700 experiments with the Danes, all in the last week of the test series.

Because of safety regulations only for four weeks
However, since the safety regulations required for clinical trials, Sørensen had to remove the electrodes of the new, sensible prosthesis after just four weeks. However, the researchers say that they could stay in the body for years without causing damage to the nerves. Thomas Stieglitz from the University of Freiburg im Breisgau explained: „The subject would have preferred to keep the feeling hand.„

Prosthesis with feeling only in a few years
The scientists are optimistic by the successes that their artificial hand could also help other amputees in the future. As they wrote in their journal article, in the future the stimulation apparatus should be made smaller and then completely implanted in the arm. They now want to test their procedure on numerous patients. However, many more years would pass before the prosthesis with feel on the market could exist. (Ad)