Waiting For an Arm and a Leg

But these high-tech replacements can´t tell the wearer where the limb is in space. The devices act in mute isolation, unable to share information with the central nervous system, unable to grasp the user´s desires or even coordinate with the opposite limb. The only way to know whether the C-Leg has negotiated a curb is to look directly at the leg. "Your ankle talks to your other ankle-you´re distributed," says Herr, one of the Rheo´s inventors. "Amputees are not yet distributed. So if I´m using the Rheo or the C-Leg, and I´m walking along and I see steps up ahead, I have no way to tell my knee that."

Then there is the pain. Prosthetics can be heavy. If an arm socket is too tight, it pinches; too big, and the prosthetic leg feels unsteady. After six months with her C-Leg, Stockwell still moved in stages-torso, hips, legs-hating it when people stared. She decided to wear shorts, even in winter. "I'd rather they see my legs," she explains, "than wear pants and have them wondering, 'What's wrong with her?'"

Bionics: We Do Not Have the Technology . . . Yet

The higher up the arm or leg someone is amputated, the more flexibility and range of motion disappears. Losing a foot is better than losing a knee; losing a wrist beats missing an elbow. Strip away multiple joints, and the body loses pronation, supination, abduction and adduction–those lovely, complicated multi-joint moves that allow people to sip iced tea or sidestep a pothole, moves that current prosthetics cannot mimic with ease.

As an orthopedist, Roy Aaron understands this. The Brown University Medical School professor was sobered every time he read about soldiers missing arms and legs. Here were lithe, active, determined people in prime physical shape. Years of wearing current prosthetics would leave them crippled with arthritis and other overuse injuries.

Aaron had time to think about this more deeply when his own body crashed. Confined to his bed for a few months in 2004 with a bad back, he dictated notes about a multipronged prosthetics project. The effort would marry tissue engineering, electronics, metallurgy, neurology and robotics, leveraging a toolkit of techniques to create hybrid limbs-part biological, part synthetic-that would one day allow amputees to move supplely and pain-free, their minds and bodies again working together as one. If researchers could replace the lost tissue and nerves and integrate the new flesh with smart, robotic prosthetics that could sense what their wearers´ minds and bodies wanted to do, Aaron thought, these young people could once again move with ease.

Aaron´s timing couldn´t have been better-his vision helped secure some of the new VA funding for the creation of the Center for Restorative and Regenerative Medicine. There, he´s finding ways to save damaged joints and extend the residual limb, commonly called the stump. His quest is for humans to mimic the axolotl, a type of salamander and the highest animal on the evolutionary scale that can regenerate a limb. "Cut a limb off, and he'll just regenerate a whole arm or whole leg, toes and everything," he says. "I've got to figure out how to talk to these newts and find out how they do it."

But the marvelous future that this technology promises is too distant to help Halfaker, who worked with a custom-prosthetics designer at Walter Reed to fashion a limb that is light, realistic-looking-and otherwise utterly unfunctional. The designers made a translucent silicone socket liner that hugged her scar and was secured by a bra strap. Onto that they screwed an aluminum rod with tubing that could be bent into several positions. They then added urethane foam padding and, finally, stainless-steel fingers that can be bent into position. Her new arm was hand-painted by a former makeup artist with CSI: Miami to match her other arm, freckles and all. No motors, no sensors, no microprocessor. No utility except psychological: It would fill Halfaker´s sleeve and make her seem, at first glance, complete. "I want to look like I did before," she says. "Who wouldn't?"