Ground felt with new artificial leg
A prosthetic leg that transmits sensations to the wearer has been fitted to a patient, enabling him to sense the ground he is walking on.
Scientists in Austria built the device for Wolfgang Rangger, an Austrian amputee, who said that it was ‘‘like a second lease of life, like being reborn’’.
Installing the leg involved two stages. In the first an operation was performed on Rangger to connect the severed nerves that previously joined his brain and foot, placing them close to the skin surface of his stump. Then the prosthetic leg, which has six sensors on the sole of the foot, was fitted to the stump.
When those sensors are put under pressure they send a signal to vibrate stimulators at the top of the artificial leg where the stump sits – and Rangger has learnt to feel as if it is a real foot pressing on the ground.
The former teacher, who lost his leg in 2007 because of a blood clot, said that it was like having a foot again. ‘‘I no longer slip on ice and I can tell whether I walk on gravel, concrete, grass or sand. I can even feel small stones,’’ he said.
Professor Hubert Egger, from the University of Linz, led the project and said that the idea was to make limbs that feel more like they are part of the body.
He said Rangger, who has spent six months testing the prosthesis, had to take time to adjust to it as his brain relearnt the connections. ‘‘This is quite unusual for him. It has come years after he lost the imagination of his real limb. He reacted very sensitively at first, but over weeks and months he got more and more familiar with it.’’
One benefit was almost instantaneous: Rangger lost the phantom pain that had been blighting his life since the amputation. It disrupted his sleep and he had to take morphine to get through the day.
‘‘A lot of people suffer very strong pain because their brain receives no more information from their limb,’’ said Egger. ‘‘The brain is searching for the leg and can’t find it so it produces the old feeling itself. This can be awful. When we provided real information, the phantom pain disappeared.’’
Egger estimates that each prosthetic foot would cost up to € 20,000 (NZ$31,687), but hopes to get companies involved in making a cheaper mass-produced version.