A 31-year-old amputee has made medical history by climbing
103 storeys to the Skydeck of Chicago's Willis Tower with his
state-of-the-art bionic leg.
Researchers at the Rehabilitation Institute of Chicago
equipped Zac Vawter with the prosthetic limb after he lost
his right leg in a 2009 motorcycle accident.
Their design allows him to control the leg with his thoughts,
a groundbreaking medical achievement that's been years in the
"The first time that we went up and down stairs was a little
clunky and not particularly smooth," said Vawter, a software
engineer from Yelm, Wash. "Now I'm comfortable taking a hand
off of the railing."
The climb, called SkyRise Chicago, was the bionic limb's
first public appearance and its most gruelling test yet, said
lead researcher Levi Hargrove.
About 2700 people were registered to climb alongside him
during the event, which doubled as a fundraiser for the
Hargrove said the leg responds to electrical impulses from
the muscles in Vawter's upper leg, including his rewired
hamstring. That's where the surgeon who amputated his leg
reattached the dangling nerves that previously carried
signals past his knee.
The procedure, known as targeted muscle reinnervation,
allowed Hargrove and his team at the institute's Center for
Bionic Medicine to tap into the preserved neural signals to
control the prosthetic limb.
"He just thinks about moving his ankle," Hargrove said as an
example. "He thinks about doing those movements, and the
signals travel down the nerves and are redirected on to
hamstring muscle. The body doesn't know that the ankle is not
contracting. It is very intuitive for him."
That the US Department of Defense is funding the five-year,
$8-million research project hints at the bionic leg's
potential. Hargrove said injured veterans who lost legs in
combat have much to gain from the new technology.
Although bionic arms have been available for several years,
their lower-limb equivalents won't be on the market for at
least a few more. Having finished the climb, Vawter now has
to return the leg to researchers, who will work to fine-tune
Hargrove said safety was his top concern and the largest
hurdle to overcome before the leg coul be sold commercially.
A malfunctioning leg could cause its wearer to stumble, or
worse -- fall down a flight of stairs.
"We have to make sure our system is really safe and robust to
prevent those sorts of injuries," Hargrove said. "It'll be a