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Bionic Leg Controlled By Brain Is Tested
An American man who lost the lower part of his leg in a motorcycle accident has been fitted with the first thought-controlled bionic leg.
Zac Vawter has been testing the device which uses neurosignals from his upper leg muscles to control the prosthetic knee and ankle.
The robotic leg senses the unconscious muscle movements and translates them into movements for the knee and ankle of the device.
Mr Vawter, who lost his leg four years ago, said the artificial limb "is a big improvement compared to my regular prosthetic leg" because it "responds quickly and more appropriately, allowing me to interact with my environment in a way that is similar to how I moved before my amputation".
Seattle-based Mr Vawter is the subject of a case report by Levi Hargrove and his Rehabilitation Institute of Chicago colleagues in the New England Journal of Medicine.
"This technology offers a seamless transition to walking around, climbing stairs and descending stairs and moving around on slopes and even repositioning the prosthesis without thinking about it. That's something no other device offers now," Mr Hargrove said.
The mind-controlled bionic leg is one of many ongoing attempts to develop powered artificial limbs that reproduce the complex process of walking - both to help restore motion to amputees or for people with other problems such as spinal cord injuries.
But the 4.5kg (10-pound) leg does have limitations, Mr Hargrove said.
"We need to make it lighter, quieter, have the battery life that lasts a bit longer" and reduce the movement error rate.
The robotic leg is being developed with an $8m (£5m) grant from the US Army hoping to improve the lives of soldiers who have lost a lower limb.
There are more than one million lower leg amputees in the US.
The current model is good for about 5,000 steps and the Army's goal is 10,000 steps.
Troy Turner, a member of the scientific advisory panel of The Amputee Coalition in Manassas, Virginia, said the project "represents the first true effort at letting someone control their prosthetic leg in a way that's very similar to biologic control".
A similar system has been used in robotic arms for years. But the challenge is greater in developing a robotic leg, according to Mr Hargrove, because users of a robotic arm do not face a serious risk of falling if the signals are misread.
"If you're using a bionic arm and it misbehaves, the elbow may move slightly. If the prosthetic leg misbehaves ? that could be quite a safety issue," Mr Hargrove said.