To Arms

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.

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