An artificial leg has sensors to let people feel when it flexes and lands on the ground – which helps them to walk more quickly and confidently.
The first two people to use the new kind of prosthetic legs found they also had less phantom limb pain, the mysterious phenomenon when amputees get rogue sensations that seem to come from their missing limb.
Many people with an artificial leg find it hard to use, especially those who have lost their leg above the knee. Part of the problem is that it feeds back no sensations, making it hard to judge its position and motion.
Stanisa Raspopovic of the Swiss Federal Institute of Technology in Zürich, Switzerland, and colleagues took a commercially available artificial leg and put sensors on the sole of the foot and inside the knee that could be connected by wires to nerves in the person’s thigh.
The team gave two men the chance to test out their legs, by connecting up their nerves to the wires. For the first month they tested the best way to stimulate their nerves to generate the most realistic sensations. “They described it as close to lifelike,” says Raspopovic.
Then the men tested out the legs on an outdoor track. Both walked faster with the new limbs than when the feedback was turned off, by up to 6 meters per minute and they felt more confident in the limb. “Being able to perceive the motion of your joints is incredibly important,” says Aadeel Akhtar of the University of Illinois at Urbana-Champaign, who was not involved in the work. “It makes you feel like the prosthetic becomes your own.”
Over three months, one man’s phantom limb pain went completely and the other’s fell by 80 per cent. “I would argue that’s an even bigger benefit,” says Akhtar.
Journal reference: Nature Medicine, DOI: 10.1038/s41591-019-0567-3
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