Bionic Limbs: Examining The Promise and Pitfalls of Powered Prosthetics

From wireless prosthetics that can grip and move, to advanced prosthetic limbs that can mimic the sensation of human touch, the research into high-tech prosthetics has really taken off in the past few years. Lately, much of the focus has been centered around powered prosthetics, and a recent study that examines the technology has revealed not only the promising future of bionic limbs, but the potential dangers as well.

A recent study from North Carolina State University examined what happens when powered prosthetics fail, specifically when errors in the technology cause users to stumble or fall. Helen Huang, senior author of the paper on the work and a biomedical engineering professor at the university, spoke to NC State University news about the focus of the study and how they intend to identify the lingering issues of the technology.

"My work has focused on developing technology that translates electrical signals in human muscle into signals that control powered prosthetic limbs," she said. "Decoding muscle signals to tell a prosthetic leg that it needs to walk forward or step up onto a staircase."

The unfortunate reality is that sometimes this "decoding" technology makes mistakes, such as thinking someone wants to climb a step, when they really don't. This problem is not only an issue because it can be potentially dangerous to users who are unexpectedly forced into an action with their prosthetic, but it also makes it hard for users to trust in the reliability of a seemingly unpredictable limb.

Of course Huang's team isn't the first to venture into cutting-edge bionic limb technology. BiOM, a company based out of Bedford, MA has also been working on an advanced bionic ankle system that replaces the function of lost muscle and tendons in amputee patients. The artificial ankle is unlike any other device currently available, as researchers continue to look toward bionic prosthetic technology to provide the ideal replacement limb for amputee patients. Doctors have even extended the work into the realm of bionic hands that can provide a rudimentary sense of touch.

It was with this shift to powered prosthetics in mind, that Huang and her team decided to look into what exactly is happening when users experience an error in the decoding technology that causes the prosthetic to react incorrectly. Their aim was to not only improve the accuracy of the decoding process, but determine which errors are more significant, and which errors have little or no impact on the user at all.

To address the issue, researchers made study subjects use a custom prosthetic device that was programmed to make errors, all while in a lab setting that enabled the team to monitor each user's balance and biomechanics. They also had each user describe how stable they felt during different moments of the trial. The research showed that some errors were so insignificant that the users didn't even notice them, while other errors lasted longer and were more noticeable. Researchers also noticed critical errors occurred most often when the prosthetic limb thought it had to do significantly more or less work than the user intended.

Going forward, Huang says that the goal of the work is to seek ways to limit the mechanical work change, as the group looks to find ways to make the critical errors effectively insignificant. Huang notes that a system that involves human interface will always have occasional errors, but the idea is to limit them as best as possible. The hope is that the work being done by Huang and her group could provide data that leads to a whole new generation of cutting-edge prosthetics that restore full functionality to amputee patients around the world.

Kristopher Sturgis is a contributor to Qmed and MPMN.

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