First hand prosthesis with sensory

The 36-year-old Dennis Aabo Sørensen from Denmark regained feeling in his arm amputated by a new type of prosthetic hand, which so far only works in the laboratory.

Thanks to the new prosthesis, he could talk about how different objects looked like and if they were soft or hard - without looking at the objects. He could also customize the grip strength for this information.

Behind the new technology is a research team from Italy, Switzerland and Germany, which presents the results in the journal Science Translational Medicine. According to the researchers, this is the first time that a prosthetic hand can reproduce sensation in real time.

It works by sensors detect tension in the "sinews" of each finger when they touch an object. This information is converted to an electrical signal understands nervous system. Via four electrodes are then sent the signals on to the nerve stumps in the upper arm.

So far, the technology is too unwieldy to work outside the laboratory. But scientists now hope to make a smaller, portable prosthesis with improved sensation. In the future it may also be possible with a prosthesis which also detects the texture of objects and if they are hot or cold, they think.

Due to security restrictions in the clinical trial, the electrodes are now removed in Aabo Dennis Sørensen's upper arm. He has been released to use their usual prosthesis where his hand open and close, but that is only useful when he looks at it.

The new study is interesting, according to Goran Lundborg, senior professor of hand surgery at the University of Lund. He thinks, however, it is a bit rich that the researchers describe the technique as it provides "almost normal sensory input."

- Hand feeling can of course catch up a huge amount of information of different kinds, such as vibration, pressure, light touch, temperature and pain. For me it's a mystery how they managed to identify and encourage the right kind of nerve fibers, so that the experience does not become uncomfortable, unnatural, or even painful, says Goran Lundborg.

He doubts whether the principle in question is the way forward for the construction of prosthetic hands with sensation.

- It's very complicated to insert electrodes in intact nerves. In our own research, we believe in a completely different principle where signals from the prosthesis stimulates the skin's normal sensory receptors on the forearm, says Goran Lundborg.