Brain-controlled limb to take prosthetics a step forward, researchers hope

It had been five years since Hailey Danisewicz last thought about bending her left knee.

The 20-year-old Northwestern University sophomore was 12 when she was diagnosed with bone cancer in her left leg just above the knee.

"I had a few surgeries to try and save the leg, and I went through a year of chemo," Danisewicz said. "I was able to get rid of the cancer, but surgery never really worked out well."

After spending the next two years on crutches and barely able to walk, Danisewicz in 2005 made one of the toughest decisions of her young life. "Finally, I reached a point where I thought my quality of life would be better if I had an amputation and got around on a prosthetic," she said. "So I decided to go through with that when I was 14."

Last year, Danisewicz decided to take part in a yearlong study to help develop the world's first lower-limb prosthetic that can be controlled by thought. The preliminary findings of the study, conducted by researchers at the Rehabilitation Institute of Chicago, will be published Wednesday in the Journal of the American Medical Association.

"The findings were important, particularly in the ankle-control aspect," said Dr. Levi Hargrove, a researcher at the institute's Center for Bionic Medicine and one of the authors of the study. "We were expecting to be able to control a knee using only the muscles of the thigh, but we didn't expect to be able to control an ankle without having surgery."

Advancements in neural or brain-controlled prostheses have been made in the upper limbs for years. In 2002, research scientist Dr. Todd Kuiken of the rehabilitation institute was credited with pioneering a procedure known as targeted muscle reinnervation. The nerves of an amputated arm are surgically reconnected to a healthy muscle, which allows the amputee to send brain signals that can control the movements of a motorized prosthetic.

"Early results are that the surgery might not be required in order to control simple knee and ankle movements," Hargrove said. "Whereas with the arm, we feel we do need the surgery to provide the dexterity that is needed to control an artificial arm."

Danisewicz was among eight participants involved with the study. Each subject began by thinking about performing certain movements, such as knee and ankle flexes, with their lost limb, causing muscles in their thighs to contract.

Muscle signals from the contractions were then collected by a computer, which learned to recognize the signals, allowing the subjects to eventually move a virtual prosthesis with thought.

"It was kind of hard at first because I'm using these muscles and trying to make these movements that I haven't made in so long," Danisewicz said about the test. "With time, I kind of remembered how to do everything, and now it's really kind of natural."

Once additional testing is conducted, Hargrove said, the next step will be to test an actual prosthetic leg. The study marked the end of year two of a five-year project to develop a neural-controlled prosthetic that will be ready for clinical trials.

"I anticipate that we'll be able to be walking within the safety of our lab within the next year," Hargrove said.  "As soon as we're comfortable in our walking then we'll start going to more complex activities such as stair-climbing and stair-descent."

Studies in neural-controlled lower limb prostheses are new compared with research in upper limbs, though the vast majority of amputees in the U.S. have sustained some form of lower limb loss.

"This is a completely new area that is now being investigated," said James Kaiser, a licensed prosthetist and CEO of Oakbrook Terrace-based prosthetics provider Scheck and Siress. "Certainly the industry looks forward to this technology, and it can only benefit patients in the long run."

For Danisewicz, the prospect of being a part of research that could benefit millions was too good to pass up.

"This might sound a little weird, but I think it's really an exciting time to be an amputee just because there is so much research and development going on," she said. "Everything is just changing so rapidly, it's really exciting to be a part of that and hopefully the work that I'm doing here will be able to make a difference in other people's lives."

Copyright © 2014, Los Angeles Times
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