Zac Vawter imagines movements that his leg mimics just like everyone else. When going up an incline, he visualizes his ankle moving as needed, and it does. But there's something remarkable about that moment: It's actually "a marvel of 21st century engineering," reports the Los Angeles Times. Vawter, 32, is the "test pilot" for a new bionic leg—the first of its kind to communicate with the brain (though the technology has been used with arm prostheses). It uses sensors to harness "reinnervated" nerves; they're essentially nerves that, rather than being allowed to die, are surgically "rewired" to control his right thigh muscles; the bionic leg is then programmed to read the contractions of those muscles.
The comparison to his other prosthesis is "night and day," Vawter tells the Wall Street Journal. The error rate (that includes things like the risk of falling) is shaved, from 12.9% with a robotic leg, down to just 1.8%, Bloomberg reports via a New England Journal of Medicine report. Weighing about 10 pounds, the bionic leg is the work of the Rehabilitation Institute of Chicago, which saw an $8 million boost from the US Army. The latter hopes the leg can one day benefit some 1,200 Iraq and Afghanistan vets who could use it. But there's much broader appeal: About 1 million Americans are without lower limbs and the device could be available to them in three to five years, Bloomberg reports. "The value it will provide to the people who use it will be enormous," the study's lead author said. "We are making fantastic progress." (Read more prosthesis stories.)