Researchers at the Rehabilitation Institute of Chicago recently announced that they had developed the first thought-controlled bionic leg. Zac Vawter, a 32-year-old software engineer who lost his right leg just above the knee in a 2009 motorcycle accident, was equipped with an artificial leg that uses neurosignals from upper leg muscles to control the knee and ankle. While some existing prosthetic legs incorporate sensors and motorized components, none allow for the natural rhythm and adjustments that Vawter’s new limb does. Given the nature of the leg and the importance of protecting the wearer, flawless code design for the limb’s software was imperative, researchers said.
Vawter contacted the research institute after reading about its work on bionic arms, NBC News reported. While his previous leg, like others on the market, was robotic, the current one connects to hamstring muscles via electrodes to sense and fulfill natural muscle movements. The result is a smoother gait regardless of the incline, particularly when walking up stairs. While the mechanical model required Vawter to go up steps with his sound leg first and drag the prosthetic one behind, the new one makes it possible to climb stairs leg over leg.
“In my mind, it’s still the same thing in terms of moving my ankle down or up, or extending my leg forward or back,” Vawter told Bloomberg. “It’s just walk like I would normally walk. It’s not special training or buttons or tricks. That’s a big piece of what I think is groundbreaking and phenomenal about this work.”
Achieving a flawless design
The research, funded in part by an $8 million grant from the U.S. Army’s Telemedicine and Advanced Technology Research Center, was the product of three years of periodic visits by Vawter to Chicago, ending in 2012. Perfecting the design took two major mechanical redesigns and multiple software revisions, NBC News reported. Building a bionic leg is more challenging than a bionic arm because the motors must be more powerful while remaining small. Similarly, the stakes for the computer control system are higher, as a person’s balance may be in question.
“If there is a mistake or error that could cause someone to fall, that could be potentially catastrophic, and we want to avoid that at all costs,” Levi Hargrove, lead author of the study and a research scientist at RIC, told NBC News.
As software increasingly enters medicine through the use of bionic limbs, robotic surgery and avatar-based therapy, preventing errors is an ongoing concern. For developers behind such applications, that may mean using technologies such as static analysis software and peer code review platforms to ensure their code does not contain potentially harmful flaws.
With such hurdles cleared, these technologies can be safely brought onto the market. Currently, software error rates are too high for the product to be offered commercially, Hargrove told NBC News, and the mechanical components need to be made quieter and lighter. As a result, leveraging solutions to reduce error rates is essential. However, it’s possible that the new bionic leg technology could be on the market in as few as three to five years, offering a solution for the more than one million Americans with lower leg amputations.
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