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Prosthetic limb brain interface could enable finger movement for amputees

Image credit: pa

‘Nerve interface’ technology has been developed that could allow amputees to move individual fingers at the end of prosthetic limbs using their mind.

A team at the University of Michigan used a combination of muscle grafts, electrodes and machine learning algorithms to amplify the faint nerve signals coming from the amputee’s residual limb so the bionic hand can receive these signals in real time.

They said the prosthetic should function normally for nearly a year without any adjustment from medical practitioners.

“This is the biggest advance in motor control for people with amputations in many years,” said Dr Robert Oneal, plastic surgery professor at the University of Michigan.

“We have developed a technique to provide individual finger control of prosthetic devices using the nerves in a patient’s residual limb.

“With it, we have been able to provide some of the most advanced prosthetic control that the world has seen.”

prosthetic limb

Image credit: pa

As the peripheral nerve signals in an amputated limb are too faint to be picked up by the electrodes, the researchers found a way to amplify these signals wrapping the nerves in tiny muscle grafts.

These muscle grafts then regenerated and developed nerves and blood vessels over three months, which prevented the growth of nerve masses that lead to phantom limb pain.

Electrodes implanted in the muscle grafts were able to record the peripheral nerve signals and pass them on to a prosthetic hand in real time.

Dr Oneal said: “We designed a way to connect up the peripheral nerves with a piece of muscle.

“When a tiny peripheral signal comes down the nerve it goes down to the muscle and becomes a huge muscle signal.”

In the lab, the participants were able to pick up blocks with a pincer grasp and move their thumb in a continuous motion using their thought.

In addition, they were able to lift round objects and even play a version of the 'rock, paper, scissors' game.

prosthetic limb

Image credit: pa

Associate professor Dr Cindy Chestek said: “Now we can access the signals associated with individual thumb movement, multi-degree of freedom thumb movement, individual fingers.

“This opens up a whole new world for people who are upper-limb prosthesis users.”

The researchers said their nerve interface worked for up to 300 days without requiring readjustments.

Study participant Joe Hamilton, who lost his arm in a fireworks accident in 2013, said, “It’s like you have a hand again. You can pretty much do anything you can do with a real hand with that hand. It brings you back to a sense of normalcy.”

The researchers are now looking for new participants as part of an ongoing clinical trial.

E&T recently looked at the rise of the custom prosthetics market, where amputees are able to make aesthetic decisions about the appendages they use.

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