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To Arms

Biomedical engineer Todd Kuiken pays homage to our amazing appendages by building thought-responsive prosthetic arms and hands for amputees.

by Stephanie Yiu

Todd Kuiken is working on his computer in a Chicago campus office that overlooks Lake Michigan. His fingers tap at the keys. His wrist bends as he uses the mouse. As he speaks, his hands dance for emphasis.

"The human arms and hands are the most incredible machines in the universe," says Kuiken, a professor of biomedical engineering, a medical doctor and director of the Neural Engineering Center for Artificial Limbs at the Rehabilitation Institute of Chicago. "They're dexterous, they're efficient, and they have 70,000 built-in sensors."

And they're the inspiration for Kuiken (GMcC89, FSM90, GFSM91, 95) to build a better prosthetic arm. Touted by the media as the inventor of the world's first "bionic" arm, Kuiken, who is also an associate professor of physical medicine and rehabilitation at the Feinberg School of Medicine, has already given six amputees the ability to control a prosthetic arm with thought.

How can a prosthetic read a person's mind? Even though a person's arm may be missing, the brain can still send commands to the arm. Kuiken explains it this way: If a telephone call is unexpectedly disconnected, the caller can still speak into the phone, even if no one can hear on the other end. If the caller plugs in a new phone, the connection can be restored and the message delivered.

Kuiken's method gives the signals a destination by rewiring the nerves into an unused muscle in the body, such as a chest muscle, a process called reinnervation. This way, when a person thinks "bend elbow," the chest muscle will twitch. Electrodes can pick up these signals and communicate them to the prosthetic arm, turning "bend elbow" into "bend prosthetic elbow." It's natural and intuitive, and the brain doesn't need any retraining at all, says Kuiken.

The idea came to Kuiken in 1985 when he stumbled across an article in the Annals of Biomedical Engineering while looking for doctoral research. What started as growing nerves in rats has become a career-long endeavor.

"When you're 20-something, you don't know how long anything takes," Kuiken said. "Had I known, I might've been scared off the arm project."

This is where Jesse Sullivan, from Dayton, Tenn., comes in. A power lineman, he touched a live wire that shot 7,200 volts of electricity into his arms. Both were amputated at the shoulder. He arrived at the Rehabilitation Institute of Chicago, where Kuiken is director of amputee services, in 2001.

Kuiken originally fitted Sullivan with a conventional prosthesis, but when Sullivan needed revision surgery for painful scars, Kuiken approached him about trying an experimental surgical technique at the same time.

Sullivan's mind still remembered the arms even if they weren't there. In surgery, the four nerves that used to go to Sullivan's arms were moved to his chest muscles. Over a period of several months these nerves grew into the muscle and connected to the muscle fibers.

Five months later, Sullivan's chest muscles were wiggling — responding to his thoughts of moving his arm. They hooked him up to simple electrodes and asked him to think about closing his hand. The artificial hand closed.

It was so successful with a simple three-motor arm that Kuiken wanted to build a more complex arm with greater range of motion. He roped in longtime friend and colleague Richard Weir (GMcC89, 95), research associate professor of biomedical engineering and of physical medicine and rehabilitation at Feinberg, to help develop a six-motor arm. The two had met in 1986 when Weir came to Northwestern from Ireland to study prosthetic design.

Kuiken knew that Weir had a humeral (the humerus is the upper arm bone between the shoulder and the elbow) rotator he'd built with a Rehabilitation Engineering Research Centers grant to Northwestern's Rehabilitation Engineering Research Center and Prosthetics Research Laboratory. The rotator had never been used. So Weir stepped in to help develop the six-motor arm, which he eventually built out of parts from all over the world — a Scottish shoulder, a Bostonian elbow, a German wrist-rotator, a Chinese hand and the never-before used humeral rotator. In 2005 Sullivan was fitted with the 12-pound prosthesis. It was the first time all these components had been put together to make a complete arm.

"It worked with a little bit of coaching," Weir says, "but it was a little touch and go. The arm is a delicate thing."

Then the nerves began to talk back. In 2002 Sullivan noticed that when people touched the area of his chest where his nerves had regrown, he could feel someone touching his hand, with sensations of hot and cold. The nerves had not only regrown into his muscle but also his skin. This outcome led to a prosthetic arm that allowed Sullivan to "feel" how hard he was squeezing with his prosthetic hand.

This research arm stays in the lab with Kuiken, while Sullivan has a much more stable "take-home" arm made up of commercial parts, weighing approximately 6 pounds with three motors. He thinks, and it reacts — there's a 150-millisecond delay, which is imperceptible. It allows him to trim hedges, vacuum and dust better than he could with his older prosthetics. And although he can feed himself, his wife usually does it because it's quicker.

As the creator of the first "bionic arm," Kuiken has been featured in the Wall Street Journal and on countless news shows. He hears constant comparisons of his research to The Six Million Dollar Man, a 1970s television series — and one of Kuiken's high school favorites — about an astronaut injured in a plane crash who has several major body parts replaced by bionic implants.

Kuiken says that he and his fellow biomedical researchers are a long way from creating an arm that achieves the natural movement of TV character Steve Austin. If a regular prosthesis gives his patients 2 percent of normal function, his new prosthesis gives them three times that. "It's better," he says, "but it's only 6 percent. There's a lot more to be done."

It's no surprise that merging the fields of science and engineering became Kuiken's chosen profession. A self-proclaimed high school "gearhead" who loved math and science, Kuiken built his own convertible from Volkswagen parts in his teens. "It was a cool looking car," he says. "Bright orange, no doors." It made a splash in his hometown of Twin Falls, Idaho.

Born in Champaign, Ill., Kuiken moved all over the United States as a child before his family settled down in Twin Falls for his high school years. He wasn't much of a jock but somehow required stitches every year after sixth grade. Whether it was a pogo stick accident (one missing tooth), falling while ice skating and cracking his head open ("Oh, it was only six stitches") or getting run over by a car (eight months in a cast), he was in and out of the hospital throughout his teens.

"I was in the hospital for a week," he says nonchalantly of the car accident. "One surgery was due to an infection, one was to take the screws out. They were just overnight things."

And then, recalls his graduate adviser, professor emeritus Dudley Childress (GMcC67), Kuiken also broke his foot in graduate school.

"He had to use crutches, so he designed a new brace that he could use to get around campus and to carry books at the same time," Childress says. "He actually published a paper about it in a journal.

"Todd is a very inquisitive fellow," Childress adds. "While working with me, he was hard to hold down. He wanted to build a powered wheelchair that you could stand up in. I told him I thought he needed to get his graduate work done and then work on the wheelchair. He patented that chair. Even though he's a medical doctor, he's still very much an engineer."

Kuiken is now working with the Defense Advanced Research Projects Agency's Revolutionizing Prosthetics Program. Investing in multiple institutions, the Department of Defense has put $48.5 million into building a more advanced, lifelike prosthetic that could help amputees returning from war. It's probably the biggest investment in the history of the field, Kuiken says.

In early 2007 double-amputee Sullivan successfully completed clinical trials of DARPA's Proto 1. Not only could he control the force of his grip through sensory feedback, he could also walk more naturally since the prosthetic included a "free swing mode." In the trials, Sullivan took a credit card out of his pocket and stacked cups.

"Jesse was able to control the device with amazing fluidity and an ability to use that very complex arm," Kuiken says. "I was just like, `Wow.' I was jumping around saying, `This is incredible! This is history.' I love my job. Who can have a better job than giving someone a new limb?"

With the advances made by Kuiken, Weir and their peers at partner institutions, DARPA's goal is that by 2009 a prosthetic will be created that will not only look like a human arm but will also act and feel like one.

Stephanie Yiu (J08) is a Medill School of Journalism senior from Singapore.

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Todd Kuiken holds a prosthetic arm in his lab. His revolutionary six-motor arm offers a greater range of motion than a traditional prosthetic limb.Courtesy of Rehabilitation Institute of Chicago
Double amputee Jesse Sullivan demonstrates the "bionic arm," which allows him to control the force of his grip through sensory feedback.Courtesy of Rehabilitation Institute of Chicago