New 'sensitive' prosthesis gives hope to amputees

An Austrian without a leg became the first ampute to use a prosthesis that recreates the sensitivity of the missing limb and gives hope against phantom pain. "I have the impression that I have a foot again, " Wolfgang Rangger, a 54-year-old teacher who was knee-injured in 2007 after complications from a stroke, told AFP. "I no longer slip on ice, I feel the difference when I walk on gravel, concrete, grass or sand. I even feel the pebbles, " says the first patient operated by Professor Hubert Egger of the University of Linz (north).

Six months after the implant, Wolfgang Rangger runs, rides a bicycle and even climbs. When you walk, your limp is almost imperceptible. This spectacular result is the result of a technique that combines the displacement of nerve bundles with the application of sensors connected to a prosthesis of a new type. In the case of Linz's patient, doctors took, at the center of the stump, the nerve endings that initially led to the amputated foot. Then they deflected them to the surface of the thigh, where they connected them with the upper part of the prosthesis.

Signal sent to the brain

In turn, the artificial leg includes sensors under the sole attached to other cells, called simulators, that are in contact with the stump. The information transferred between the sensors and the simulators allows to mimic, and finally reproduce, the sensation of the lost limb. With each step, each time it exerts pressure on the ground, Wolfgang Rangger's artificial foot sends an accurate signal to the brain.

"In a foot with good health, it is the skin receptors that do this. An amputee doesn't have these receptors, of course. But the information transmitters, which are the nerves, continue to exist. You just have to stimulate them." sums up Professor Egger. The Austrian doctor had already innovated in 2010 by introducing a mind-controlled arm prosthesis, thanks to a connection between the motor nerves and the prosthesis. This time the principle is the same, but the course is the other way around: the information starts from the prosthesis to reach the brain.

The end of phantom pain

In addition, the Linz-tested prosthesis offers its wearer a second advantage which, at least for him, is equally important: the new system put an end to the phantom pains he had to endure for years after losing his leg in just a few days. . "With my conventional prosthesis, " recalls Wolfgang Rangger, "I could only walk. I couldn't sleep more than two hours a night and needed morphine to handle during the day."

This feeling of suffering in the limb that is no longer very common is due to a progressively developing hypersensitivity in the brain that somehow seeks the amputated limb, explains Professor Egger. Phantom pain, he goes on, is aggravated by the traumatic memory of the accident or illness that led to the amputation. The "sensitive" prosthesis remedied it by sending information back to the brain, interrupting its vain and infinite search. The cost of the prototype is estimated between 10, 000 and 30, 000 euros. Its industrialization could already begin, but Linz's team wants to study a little more the results obtained with the first patient.

Vienna, Austria

Via In Summary.