These big questions seem far away when I first see engineers working on the Bionic Man. It is still a faceless collection of unassembled parts. Yet the arms and legs laid out on a long black table clearly evoke the human form.
Meyer himself speaks to that quality, describing his i-limb as the first prosthetic he has used in which the aesthetics match the engineering. It truly feels like part of him, he says.
David Gow, a Scottish engineer who created the i-limb, says one of the most significant accomplishments in the field of prosthetics has been making amputees feel whole again, and no longer embarrassed to be seen wearing an artificial limb. “Patients actually want to shake people’s hands with it,” he says.
Gow, 56, has long been fascinated by the challenge of designing prosthetics. After briefly working in the defense industry he became an engineer at a government research hospital attempting to develop electrically powered prosthetics. He had one of his first breakthroughs while trying to figure out how to design a hand small enough for children. Instead of employing one central motor, the standard approach, he incorporated smaller motors into the thumb and fingers. The innovation both reduced the size of the hand and paved the way for articulated digits.
That modular design later became the basis for the i-limb: Each finger is powered by a 0.4-inch motor that automatically shuts down when sensors indicate sufficient pressure is applied to whatever is being held. Not only does that prevent the hand from crushing, say, a foam cup, it allows for a variety of grips. When the fingers and thumb are lowered together, they create a “power grip” for carrying large objects. Another grip is formed by closing the thumb on the side of the index finger, allowing the user to hold a plate or (rotating the wrist) turn a key in a lock. A technician or user can program the i-limb’s small computer with a menu of preset grip configurations, each of which is triggered by a specific muscle movement that requires extensive training and practice to learn. The latest iteration of the i-limb, released this past April, goes a step farther: An app loaded onto an iPhone gives users access to a menu of 24 different preset grips with the touch of a button.
To Hugh Herr, a biophysicist and engineer who is the director of the biomechatronics group at the Massachusetts Institute of Technology’s Media Lab, prosthetics are improving so quickly that he predicts disabilities will be largely eliminated by the end of the 21st century. If so, it will be in no small part thanks to Herr himself. He was 17 years old when he was caught in a blizzard while climbing New Hampshire’s Mount Washington in 1982. He was rescued after three-and-a-half days, but by then frostbite had taken its toll, and surgeons had to amputate both his legs below the knees. He was determined to go mountain climbing again, but the rudimentary prosthetic legs he had been fitted with were only capable of slow walking. So Herr designed his own legs, optimizing them to maintain balance on mountain ledges as narrow as a dime. More than 30 years later, he holds or co-holds more than a dozen patents related to prosthetic technologies, including a computer-controlled artificial knee that automatically adapts to different walking speeds.
Herr personally uses eight different kinds of specialized prosthetic legs, designed for activities that include running, ice climbing and swimming. It’s extremely difficult, he says, to design a single prosthetic limb “to do many tasks as well as the human body.” But he believes that a prosthesis capable of “both walking and running that performs at the level of the human leg” is just one or two decades away.
The oldest known prosthetics were used some 3,000 years ago in Egypt, where archaeologists have unearthed a carved wooden toe attached to a piece of leather that could be fitted onto a foot. Functional mechanical limbs didn’t come along until the 16th century, when a French battlefield surgeon named Ambroise Paré invented a hand with flexible fingers operated by catches and springs. He also built a leg with a mechanical knee that the user could lock into place while standing. But such advances were the exception. Throughout most of human history, a person who lost a limb was likely to succumb to infection and die. A person born without a limb was typically shunned.
In the United States, it was the Civil War that first put prosthetics into widespread use. Amputating a shattered arm or leg was the best way to prevent gangrene, and it took a practiced surgeon just minutes to administer chloroform, lop off the limb and sew the flap shut. Around 60,000 amputations were performed by both North and South, with a 75 percent survival rate. After the war, when the demand for prosthetics skyrocketed, the government stepped in, providing veterans with money to pay for new limbs. Subsequent wars led to more advances. In World War I, 67,000 amputations took place in Germany alone, and doctors there developed new arms that could enable veterans to return to manual labor and factory work. Following World War II, new materials such as plastics and titanium made their way into artificial limbs. “You can find major innovations after every period of war and conflict,” says Herr.
The wars in Iraq and Afghanistan are no exception. Since 2006, the Defense Advanced Research Projects Agency has put some $144 million into prosthetic research to help the estimated 1,800 U.S. soldiers who have suffered traumatic limb loss.