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Powerful Thoughts on Prosthetics

By: Katelyn Six, Section Editor for Block Beat (

Many of us take for granted all the things our legs allow us to do, such as walking, running, and even traveling up and down a flight of stairs.  However, thousands of people living with amputations know the important role mobility plays in terms of the quality of life.  While most people do not think twice about moving their legs to walk, run or jump, 32-year-old Zac Vawter puts a great deal of thought into every single step he takes.  According to the Wall Street Journal, Vawter effectively controls motorized movements of a prosthetic leg using only his thoughts. 

Although this technological development will not be strong enough to be sent home with patients to try for another three to five years, Vawter had the opportunity to give this bionic leg a thorough test-run. A software engineer from Yelm, Washington who lost his right leg in a 2009 motorcycle accident, he is currently testing out the capabilities of the bionic leg in weekly sessions at the center in Chicago.

Vawter said one of the reasons this technology is so “groundbreaking” lies in the fact that there is no specific training necessary to operate the bionic leg.  Instead, he explained, “The control system is very intuitive. There isn’t anything special I have to do to make it work right.”

What makes this advancement unique is that, unlike previous prosthetics, it does not involve the physical turn of a key or press of a button to transition from one movement to the next.  According to Levi J. Hargrove, a researcher at the Center for Bionic Medicine, Rehabilitation Institute of Chicago, existing prosthetics that encompass both knee and ankle mobility require pressing a button controlled by a remote when attempting to climb a flight of stairs.  By pressing this button, patients can trigger rocking and kicking of the leg backward to clear the step upward.

However, this new technology works by allowing Vawter’s brain to transmit signals to his prosthetic limb, resulting in controlled movements.  The bionic leg uses sensors that rely on re-innervated nerves, which Alexandra Sifferlin reported in Time Magazine to be “nerves that were formerly used to control Vawter’s leg muscles, but are surgically rewired to control his limb.”  Where former prosthetics needed to be quite strong, the new robotic prosthetic needs to be “smart” in order to decode the contractions from the re-innervated nerves and muscles that control the movements of the knee and ankle.

Vawter said the most significant and beneficial aspect of the bionic leg is the change in his stair-climbing experience.  “Going upstairs with my normal prosthetic, my sound leg goes up first for every step,” said Vawter.  He added, “With this I go foot-over-foot up the stairs and down the stairs.”  One of the complaints from amputee patients living with prosthetic limbs is that the ability to have a normal gait is compromised when ascending or descending a flight of stairs.  To combat this, specialists designed the robotic prosthetic so that patients are able to place one foot in front of the other when going up each stair step, rather than dragging their prosthetic.

Sean Gallagher wrote in Aus Technica that this brain-powered leg is the product of the work done under an $8 million research grant from the Department of Defense.  He explained that the artificial leg “uses sensors to pick up electromyographic (EMG) impulses from nerves in the remaining thigh muscle tissue in the patient’s leg.”  The people that may benefit from this advancement will be those with above-knee amputations.

One suggestion for improving the prosthetic is to give the semblance of touch or pressure so that the wearer will be able to “feel” their feet as they place one foot in front of the other.  Since Vawter only wears the leg for one-week periods every few months when visiting the researchers in Chicago, he must still use his normal prosthetic in his everyday activities.  While progress continues to be made in prosthetics technology, there is still a long way to go before people living with amputations will be able to use their thoughts to control movement in every day life.

For more information on bionic leg prosthetics, visit:

For further news on Zac Vawter’s experience with his brain-powered prosthetic, visit:


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