Dr. Richard Weir is holding a pair of metal hooks. Designed during World War II, the devices open and close using the same coil found in bike breaks. The coils are extremely impersonal.
Yet for those who have lost their hands, this basic, mechanical instrument is still the most effective prosthetic on the market.
As a research professor at the Department of Physical Medicine and Rehabilitation at Northwestern’s Feinberg School of Medicine, Weir has spent a career engineering prostheses. He is three years into a project to design a new prototype that one day might simulate the full range of motion of the human hand. He calls it his “grand vision” and the hardest thing he has ever attempted.
Weir came to the United States from his native Ireland in 1986 with a singular focus.
“There was no question that I was – going to study artificial limbs,” he said.
In some ways, it was as if his whole life had been leading up to it. Born into a family of doctors and engineers, Weir had been a tinkerer from childhood, an “airplane nut” who built and flew his own models. And when he was five years old, his twin sister lost her hand in a lawn-mower accident.
“I’m sure those are all the subconscious factors that went into this thing,” he said. “I’m an engineer who makes things and probably always wanted to make hands.”
Upper-body prostheses lag far behind most other medical technology. The options available to a hand or arm amputee are more limited than those for an individual missing a leg. Half choose not to wear a prosthesis at all. For those who do, they can choose between the hooks or an aesthetically attractive, but functionally limited “myoelectric” model.
The myoelectric model, designed in the 1970s, uses electrodes on the skin to read electrical impulses from two of the 33 muscles that help move the hand and wrist. The model opens, closes and looks like a real hand, but can do nothing else; lost are the motion and expressiveness that make a hand so personal and distinctive.
Weir is looking to improve upon that model. He said he wants to create a prosthetic that will measure the impulses from a greater number of muscles, using sensors inside the tissue. It is a difficult project that requires complicated, compact designs, and he said he expects only gradual success.
“If we got eight muscles, we’d be euphoric,” he said.
Prof. Philip Troyk of the Illinois Institute of Technology is collaborating with Weir, designing the electronic sensors to measure muscle signals. The sensors will receive power from a magnetic coil in the prosthesis, and are small enough to be injected using a large hypodermic needle. He likens them to a “miniature cell-phone network in your arm.”
The project will take years to complete. Soon, Weir and Troyk will test their electronics to see if the magnetic coil can deliver power through living tissue.
“We hope to be testing in steak first,” Weir said. “You can’t go willy nilly sticking them into animals.”
In the meantime, Weir will continue working on simpler projects – a prosthesis for blast victims who have a wrist but no fingers, for instance. That, he said, will be his most commercially viable invention.
“I think most people who are involved in this area are people who want to make a difference,” he said. When students ask to work with him, he makes sure to scrutinize their motives. “I want them to be very sure that this is what they want to do, because there’s no money in this field.”
Later, while making adjustments to an old prototype, he mentions that the Iraq war has renewed the government’s interest in prosthetics. Because soldiers’ body armor only covers their torsos, record numbers of veterans are returning home without limbs.
“We’ve become very fashionable since Iraq.” he said. “That’s pretty much the dark side of our field. You look at major prosthetic advances through history and they’re pretty much always tied to some major conflict.”
Reach Jordan Weissmann at [email protected].
