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October 04, 2013      

Medicine meets engineering

This time it?s a bionic leg; before that it was a bionic arm for a former power-company worker named Jesse Sullivan whose arms were destroyed to the shoulder when he accidentally touched a high-voltage line.

Both are firsts: mind-controlled prostheses that get their directions and then carry them out all from the thoughts of the wearer, similar to the way the brain controls natural limbs. Both are the products of the Rehabilitation Institute of Chicago (RIC)
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Back in 2002, RIC?s Dr. Tod Kuiken developed the TMR procedure (Targeted Muscle Reinnervation) for upper-limb amputees.

TMR is an innovative surgical procedure that reroutes brain signals from nerves severed during amputation to intact muscles, allowing patients to control their prosthetic devices by merely thinking about the action they want to perform.

In 2011, Kuiken shared the technology?s amazing capabilities and results in an equally amazing TED Talk called, A prosthetic arm that “feels”.

Back again to the Chicago bionic parts shop

This year, once again, the Rehabilitation Institute of Chicago has pulled off another bionic first.

This time a man missing his lower leg has gained precise control over a prosthetic limb, as with the aforementioned arm, just by thinking about moving it ? all because his unused nerves were preserved during the amputation and rerouted to his thigh, where they can be used to communicate with a robotic leg.

The major advance is that the man does not have to use a remote-control switch or exaggerated muscle movements to tell the robotic leg to switch between types of movements, and he does not have to reposition the leg with his hands when seated.

NATURE ?32-year-old Zac Vawter, whose knee and lower leg were amputated in 2009 after a motorcycle accident, is apparently the first person with a missing lower limb to control a robotic leg with his mind.

A team led by biomedical engineer Levi Hargrove at the Rehabilitation Institute of Chicago in Illinois reports the breakthrough today in the New England Journal of Medicine, including a video that shows the man using the bionic leg to walk up stairs and down a ramp, and to kick a football.

The major advance is that the man does not have to use a remote-control switch or exaggerated muscle movements to tell the robotic leg to switch between types of movements, and he does not have to reposition the leg with his hands when seated, Hargrove says.

Scientists had previously shown that paralyzed people could move robotic arms using their thoughts and that able-bodied people can walk using robotic legs controlled by their brains. The latest work goes a step further by using muscle signals to amplify messages sent by the brain when the person intends to move.

zac vawter

To accomplish this, surgeons redirected the nerves that previously controlled some of the man’s lower-leg muscles so that they would cause muscled in his thigh using Dr. Kuiken?s TMR technique.

They then used sensors embedded in the robotic leg to measure the electrical pulses created by both the reinnervated muscle contractions and the existing thigh muscles.

When the surgeons combined this information with additional data from the sensors, the man was able to use the leg more accurately than when attempting to control the leg with its sensors alone, the scientists report.

They hope that other people with missing limbs will be able to use the technology within the next three to five years.