New ‘bionic leg’ that helps amputees walk 41% faster than prosthetics is so good its inventor wants two fitted
Electrodes allow the wearer to control the foot without thinking
AMPUTEES could walk normally again with “miraculous” bionic legs that are so good the inventor plans to fit them to his own body.
Dr Hugh Herr, from the Massachusetts Institute of Technology, lost both feet after a horror rock climbing accident in 1982.
He has now developed what he believes is the best ever “neuroprosthetic interface” that allows patients to control a prosthetic leg with nerve signals from their remaining leg muscle.
It fits below the knee and moves like a foot to make walking faster and easier.
A study found patients strolled up to 41 per cent faster than with standard prosthetics – equal to a normal walking speed.
It also significantly improved their technique walking on slopes, stairs and past obstacles.
The limb feels natural and moves naturally without conscious thought
Dr Hugh Herr
Dr Herr said: “The brain is so adaptive and so smart it can figure out how to control a very complex prosthesis with just a small amount of information.
“When the participants think, those actions are recorded from the muscles and that’s reflected in the movements in the prosthesis.
“Then when the prosthesis moves the people feel the movement as a natural sensation.
“Here, with just a small fraction of perception, a person is able to walk at normal speeds.
“It is quite miraculous.
“The patients with this interface are able to move really without thinking about it.
“Even though their limb is made of titanium and silicone, it feels natural and moves naturally without conscious thought.”
Walking speed equal to non-amputee
The study, in the journal Nature Medicine, tested the prosthetic in a group of 14 amputees.
Half had surgery to connect their leg muscles in a certain way to transmit nerve signals to special electrodes in the bionic lower leg, and half were not.
High-tech sensors helped them to control the exact position of the foot and also improved spatial awareness so they knew where it would land.
Patients with the bionic leg had a top walking speed 41 per cent faster, on average, and managed a “normal gait”.
Dr Herr said the procedure could be done when a person first loses their limb or many years or even decades later.
He said: “My legs were amputated in 1982 from frostbite damage in a mountain climbing accident.
“So I’ve been a person with amputation for many many decades and I could go and get this procedure as a revision technique.
“I absolutely am thinking of doing that for both of my legs in the coming years.”
He said the new study showed patients reduced their pain and also improved their leg control with the prosthetics.
Dr Herr added: “For me personally it’s a very easy decision to undergo this procedure.”
HOW DOES THE BIONIC LEG WORK?
THE bionic leg is a prosthetic limb that connects to the brain via special sensors.
- The amputee has an operation to connect muscles in the stump of their amputated leg in a particular way.
- These “muscle pairs” then transmit nerve signals from the brain to electrodes inside the bionic leg.
- When the person tries to move their phantom foot, signals travel down the leg and, instead of stopping at the amputation site, continue down into the bionic leg.
- The prosthesis then has technology that can interpret these signals and turn them into the movement the brain was trying to achieve.
- The bionic leg then sends signals back up to the brain to tell it the leg and foot have moved, as well as information about where and how it has moved.
- The signals are much weaker than if someone had a fully functioning natural leg, but the brain can adapt to turn it into a natural-feeling limb.