Man with Bionic Leg Climbs Willis Tower
Zac Vawter hiked 103 floors with a prosthesis controlled by his thoughts
On Sunday, a trailblazing prosthetic leg was put to the test when the device’s self-proclaimed “test pilot,” Zac Vawter, climbed 103 flights of stairs to the top of Chicago’s Willis Tower. The accomplishment signaled a major advance in the field of thought-controlled prosthetics—an area that, until now, only covered hands and arms.
The 10-pound prosthetic is a breakthrough in its ability to respond to electrical impulses caused by thought, just as normal muscles respond to electrical impulses from the brain. At best, other lower-limb models have motorized or mechanical components. This device's electrodes were connected to nerve endings in Vawter's hamstring muscles.
After Vawter, 31, lost his right leg in a motorcycle accident in 2009, he signed up to be a research subject for the new technology. Doctors prepared his leg for the device through a surgical procedure in which the nerves that would normally carry signals to the lower part of his leg were sewn onto new spots on Vawter’s hamstring. The nerves grew into the muscle and provide signals that can be processed by the bionic limb’s built in microcomputer. Therefore, during the cimb when Vawter thought about moving his ankle, his hamstring would move and cause the prosthesis to work. When Vawter thought climbing stairs, the motors, belts and chains in the prosthetic synchronized the movements of its ankle and knee.
To make sure Vawter and the bionic leg were ready for the climb, Vawter and the scientists spent hours adjusting the leg's movements. In one instance, 11 electrodes attached to Vawter’s thigh fed data to the bionic leg’s microcomputer. With the new technology, Vawter was able to kick a soccer ball, walk around the room and climb stairs.
The Willis Tower, formerly known as the Sear’s Tower, is the tallest building in the United States at 1,451-feet. Vawter went alongside nearly 3,000 others in an event called “SkyRise Chicago,” a fundraiser for the Rehabilitation Institute of Chicago. The trip took Vawter 53 minutes and 9 seconds.
When Vawter returns to his family in Yelm, WA., the experimental leg will stay in Chicago, where researchers will continue to refine the model. Safety and rigorous testing are particularly important with prosthetic legs because malfunctions could result in serious falls.
The $8 million project is a collaboration between Vanderbilt University, the Massachusetts Institute of Technology, the University of Rhode Island and the University of New Brunswick, and is funded by the U.S. Department of Defense. Researchers will continue to work on the device, and do not expect the new prosthetic to be on the market for at least several more years.