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The bionic hand sends electrical signals to allow Dennis Sorensen to feel what he is touching. Photograph: Patrizia Tocci
A man who lost his left hand in a fireworks accident has described how he could feel things that he had not been able to feel for more than nine years after testing a bionic replacement with a sense of touch.
Dennis Sorensen, from Denmark, felt the shape and texture of objects during a month's trial in Rome of the robotic hand developed by Swiss and Italian scientists. "The sensory feedback was incredible," said the 36-year-old, whose experience may help pave the way for artificial "feeling" limbs. "When I held an object I could feel if it was soft or hard, round or square."
The artificial hand picks up electrical signals from artificial tendons controlling the movement of its fingers, which are sent down fine wires to four electrodes implanted in sensory nerves in the upper arm.
"This is the first time in neuroprosthetics that sensory feedback has been restored and used by an amputee in real-time to control an artificial limb," said Silvestro Micera, of the Federal Polytechnic School of Lausanne, Switzerland, who leads the Life Hand 2 project.
Scientists hope they can eventually streamline the equipment into a more discreet prosthetic using miniaturised equipment under the skin.
The experiment detailed in the journal Science Translational Medicinetook place in January last year at the Gemelli hospital in Rome. Safety rules for trials meant the electrodes had to be removed from Sorensen's arm after a month but scientists think they would have continued to function without harm for several years.
They said the hand had allowed him to experience "almost natural" sensory feelings comparable to those he felt in his remaining hand. He had distinguished hard, medium and soft objects and recognised basic shapes such as the cylinder of a bottle and the sphere of a baseball.
The team plan to do further trials with more patients, saying these could open up the chances of far more dexterous artificial hands, even though it could be years for the equipment to be miniaturised and available for everyday use. Since his accident, Sorensen had been wearing a conventional prosthesis that detects muscle movement in the stump of his arm, allowing him to open and close the hand but he was unable to feel objects he had grasped. "I was more than happy to volunteer for the clinical trial, not only for myself, but to help other amputees as well," he said.
Alastair Ritchie, a lecturer in biomaterials and bioengineering at Nottingham University, welcomed the "very interesting work" taking research on upper-limb prosthetics "into the next stage".
"Our hands are one of our principal interfaces with the world, and in recent years we have seen real advances. This technology would enable the user to know how firmly they are gripping an object, which is vital for handling fragile objects – imagine picking up an egg without any feeling in your fingers. Another exciting aspect is the ability of the human brain to learn, allowing the user to become more proficient as he gains experience in using the prosthesis."
However, rigorous wound care would be needed to prevent infection, including from electrodes embedded next to the peripheral nerves and wires running through the skin.
David Gow, director of rehabilitation engineering services and bioengineering at NHS Lothian, said: "Although based on a single case study, the results look like a practical surgical-based method of delivering spatial and force information from a robotic hand's sensors back to the user to allow him fine control of force and to gain some knowledge of the shape and stiffness of the object in his artificial grasp.
"This opens up exciting possibilities for artificial-limb users and takes us a step closer to a clinically viable man-machine interface."

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