Waiting For an Arm and a Leg

by John B. Carnett At the Massachusetts Institute of Technology's Media Laboratory, engineers in the biomechatronics group are developing a motorized ankle that automatically adds or dissipates energy while the user is walking to maintain stride and balance John B. Carnett

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Launch the slideshow to see the tech behind today's–and tomorrow's–advanced prosthetics. Also, click here to learn how high-tech prosthetics help disabled athletes stay on top of their game.

There's always a Plan C-West Point teaches you that. If the road is mined, the bridge in splinters, and your opponent's brigade massing on your left, you find a new road, build a new bridge. That´s Army DNA, the building blocks of a successful warrior, and it has been flush through Capt. Dawn Halfaker´s cells since her first weeks at the elite military college and as a guard on its women´s basketball team. Keep moving. There´s always another way.

Then you graduate and, because you´re an action junkie thrilled by weapons and foreign cultures, you´re assigned to run a military police station outside Baghdad. One morning before sunrise in June 2004, you´re bumping along in a Humvee on a routine patrol when someone aims a rocket-propelled grenade your way. It´s a lucky shot. The bomb tunnels into the carriage, shears off your buddy´s arm, and blasts through your own, making spaghetti out of tendons and muscle. What the insurgents don´t get, the surgeons finish off, leaving you with nothing below your shattered right scapula but expectations.

You're 24, a child of the computer age. When you wake up and learn there is no more right arm to write and eat and shoot jumpers with, you just know that the country that invented supercomputing and reconstructive surgery can give you something gleaming and spectacular. An arm to rival Will Smith´s appendage in I, Robot.

Since the invasions of Iraq and Afghanistan, more than 370 U.S. soldiers have had amputations. Indeed, there are wheelchair traffic jams on the third floor of Walter Reed Army Medical Center in Washington, D.C. That´s where Halfaker befriended Melissa Stockwell, a former gymnast and rock climber who was in Baghdad for only a few weeks before she lost her left leg to a roadside bomb in April 2004.

The two women bonded in frustration. Stockwell, 26, received the microprocessor-enhanced C-Leg but struggled for months to walk free of pain, wishing that the large silicone socket holding what she calls her "little leg" wouldn't chafe or thrust to the side, broadcasting her limp. Halfaker was the lone female soldier with what's bloodlessly called a shoulder disarticulation, her right side barren like a sheer cliff. Prosthetists fit her at first with a partly mechanical, partly battery-powered arm held on with a thick plastic socket that fit like a shield and was Velcroed around her body. The device worked with muscle power; when she shrugged, pulleys and cables would trigger the motorized arm to open a blocky claw. It was a prosthetic born out of a previous war, uncomfortable and clumsy, and made her feel like a Playskool toy-and she let the prosthetists know her displeasure. "I don't want an arm that weighs 20 pounds. I want an arm that weighs three pounds," she told them. Something that wouldn't slow her down. She was offered a hand that was a hook, a device straight out of the post-World War II weepie The Best Years of Our Lives. Absolutely not. "Because," Halfaker said, "it looks like a hook."

And that was it. There was no Plan C. For Stockwell, there was no leg and socket that would allow her to stride quickly and pain-free, that didn't leave raw, angry marks on her pale thigh. For Halfaker, there was no arm that was strong and nimble and light enough that she could slip it under a silk blouse. Stockwell persisted, learning to walk in her new mechanical leg, though with a noticeable limp. She adapted. Halfaker rebelled, left her arm in a heap in her room. She learned to wash, dress, drive, and run with one arm, her empty sleeve dangling by her side. She adapted too.

But one day soon, in part because of the experiences of Iraq veterans like Stockwell and Halfaker, prosthetics wearers won´t have to do so much adapting. It´s the prosthetics that will be doing the adapting.