Thought-controlled prosthetic makes for smart bionic leg

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A giant step forward for leg amputees. A thought-controlled prosthetic so smart it’s carrying users to new heights with little effort.

Mike Gilbert, bionic leg user: “I’ve tried every leg made by man.”

But this one trumps them all -- a prosthetic that combines a knee and ankle joint with thought-controlled bionics.

Dr Levi Hargrove, RIC research scientist: “In order to do that we leverage the neuro signals, the muscle signals, because they contract naturally. You can see we have sensors on the inside of the socket, and that’s what Mike wears. And these sensors pick up his muscle signals, and the wires send it to the computer that’s on the leg.”

The smart technology developed at the Rehabilitation Institute of Chicago continues the chain of communication down the motorized device – just as nerves would in a natural leg.

Dr Hargrove: “It decodes it in real time and instantly sends the command to the motors in the knee and ankle, and then they move. Our algorithms are very smart, and they can figure out what the person is trying to tell the leg to do.”

The idea is to mimic the user’s natural movement – something Mike’s tried to master since losing his leg after being struck by a car at age 12. Now, with each step a computer learns his gait, memorizes it then predicts his knee bend, ankle flexion and foot strike. As he practices walking, research engineers monitor his movement – making tweaks on the fly.

Kim Ingraham, RIC research engineer: “We can adjust the timing, we can adjust the speed, we can adjust how much it bends, how much resistance it has.”

Climbing stairs and ramps are where the device offers the greatest advantage. On the left, Mike navigates steps with the prosthetic he typically wears. On the right -- a much smoother ascent and descent with the bionic leg.

Mike Gilbert: “When you walk and you’re self-conscious, you think, you use a little energy. But with this leg you don’t have to do anything. Everything gets easier, smoother, stronger, lighter.”

Study results just published show the bionic technology outperformed a standard control system.

Dr Hargrove: “We found the one that used the neuro signals, or EMG signals, behaved better. It was more reliable, more robust and every patient who used it noticed it and said they would prefer to walk with a system like that that made fewer mistakes, allowed them to move around intuitively without thinking too much about it.”

Mike Gilbert: “I wish they’d hurry up and get it. I want it to be ready.”

The bionic leg isn’t ready for daily use just yet, but researchers at RIC are recruiting participants to test the device at-home – a study supported by the US Army and NIH. They hope to have the bionic leg ready for the general public within four to five years.

To learn more about the bionic limb program at RIC, go to http://www.ric.org/research/centers/bionic-medicine/

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