LA Times, Sept. 25: Bionic leg is controlled by brain power
A team of specialists has designed a bionic prosthetic leg that can reproduce a full range of ambulatory movements by communicating with the brain of the person wearing it.
The act of walking may not seem like a feat of agility, balance, strength and brainpower. But lose a leg, as Zac Vawter did after a motorcycle accident in 2009, and you will appreciate the myriad calculations that go into putting one foot in front of the other.
Taking on the challenge, a team of software and biomedical engineers, neuroscientists, surgeons and prosthetists has designed a prosthetic limb that can reproduce a full repertoire of ambulatory tricks by communicating seamlessly with Vawter's brain.
Given surgical practices still in wide use, the prospects for such a connection between a patient's prosthetic and his or her peripheral nerves are generally dim. In most amputations, the nerves in the thigh are left to languish or die.
Dr. Todd Kuiken, a neurosurgeon at the rehabilitation institute, pioneered a practice called "reinervation" of nerves severed by amputation, and Vawter's orthopedic surgeon at the University of Washington Medical Center was trained to conduct the delicate operation. Dr. Douglas Smith rewired the severed nerves to control some of the muscles in Vawter's thigh that would be used less frequently in the absence of his lower leg.
Within a few months of the amputation, those nerves had recovered from the shock of the injury and begun to regenerate and carry electrical impulses. When Vawter thought about flexing his right foot in a particular way, the rerouted nerve endings would consistently cause a distinctive contraction in his hamstring. When he pondered how he would position his foot on a stair step and ready it for the weight of his body, the muscle contraction would be elsewhere — but equally consistent.
Compared with prosthetics that were not able to "read" the intent of their wearers, the robotic leg programmed to follow Vawter's commands reduced the kinds of errors that cause unnatural movements, discomfort and falls by as much as 44%, according to the New England Journal of Medicine report.