With a new prosthetic, researchers have managed to restore the sense of touch for a Denmark man who lost his left hand nine years ago.
Nine years after a Denmark man lost his left hand, electrodes surgically implanted in his nerves and connected to a prosthetic hand have allowed him to feel again.
Researchers from Ècole Polytechnique Fédéral De Lausanne, in Switzerland and the Scuola Superiore Sant'Anna, in Italy, implanted the electrodes into the amputee's arm in February 2013. The study, published Wednesday in Science Translational Medicine, details the first time sensory feedback has been restored allowing an amputee to control an artificial limb in real-time.
Dennis Aabo Sørensen lost his left hand after a firework exploded during a New Year's Eve celebration in 2004. On a whim, Sørensen said he took part in a clinical study where researchers implanted electrodes the size of a pin, into his left arm.
In March 2013 the researchers blindfolded Sørensen, and placed an object in his hand while music played in his headphones. The researchers asked him to describe each object they placed in his prosthetic hand.
"Suddenly you could see my left hand was talking to my brain again and it was magic," said Sørensen describing the first moment he could feel. "It was surreal. I grabbed the object in my hand and knew it was round. It was a baseball."
Silvestro Micera, a researcher who worked on the project for 15 years said the researchers achieved the sense of touch by measuring the tension in artificial tendons that control finger movement, and turning that measurement into an electrical current. The sense of touch was achieved by sending the electrical current through the electrodes attached to the nerves in Sørensen's arms.
"The idea was to translate the language of the prosthetic into an electrical signal the central nervous system could understand," Micera said. "So when the hand grasped an object the signals were recorded and translated into stimulation of the electrodes, creating the sense of touch."
Micera said researchers connected electrodes to two of the three main nerves in the arm, the ulnar and median nerves, which connect sensors in the hand with the brain.
After 19 days of preliminary tests, the team connected the prosthetic hand to the electrodes and to Sørensen and watched as the experiment paid off.
"It was a clear sign that we are close to developing something that can significantly improve the quality of life of those with prosthetic limbs," Micera said.
Micera said due to safety restrictions imposed in clinical trials, the electrodes were removed from Sørensen's arm after 30 days. Sørensen said he is currently using a battery operated prosthetic that does not allow him to feel the sense of touch.
"The main difference is you can actually feel what you are doing (with the bionic hand). With what I have now I am constantly monitoring to make sure I don't grasp too hard since I can't feel what I am doing," Sørensen said.
Micera said it will be years before the sensory enhanced prosthetic will be available to the public. The next step is developing a study where subjects will have the electrodes implanted for months and developing smaller sensory feedback electronics for a portable prosthetic.
For now, Micera said the study opens the door to the future of prosthetics.
"These results show the possibilities for amputees," Micera said. "It is possible that this could be expanded to lower limbs."