We have the technology to rebuild ourselves

We have the technology to rebuild ourselves
07 January 2009 by Julian Smith

Double arm amputee Christian Kandlbauer shows how realistic prostheses can be (Image: Waltraud Grubitzsch/epa/Corbis)
FIVE years after he lost a leg to a landmine in Afghanistan, American war veteran Mike McNaughton can run well enough to coach his 11-year-old son's soccer team. This amazing comeback comes partly from his determination to get back on two feet, but also from a piece of high-tech hardware: a computerised, hydraulic knee that monitors and adjusts every step, with a response time in milliseconds. "Now I can run with the kids full blast and kick the ball around with them," he says.
After decades of amputees having to make do with designs that had changed little since the second world war, artificial limbs that predict their user's every movement and look like the real thing are finally breaking out of the lab. Yet convincing and comfortable synthetic limbs like McNaughton's are only the beginning of the bionic age.
Emerging prosthetic technologies promise not only greater power and flexibility but also pressure-sensitive artificial skin, and even limbs that are bonded to the body and controlled by the mind - and much of this within five years. Rebuilding amputees to be faster and stronger than before is rapidly becoming a realistic possibility. With experimental prosthetics increasingly able to integrate with flesh, bone and the nervous system, the very idea of "losing a limb" may one day become obsolete.
"This is perhaps the most exciting time ever to be involved in advanced prosthetics," says John Bigelow of the applied physics laboratory at Johns Hopkins University in Baltimore, Maryland, who works on brain-controlled robotic arms.
There are many reasons for this bionic gold rush, says Bigelow. Smaller, better components have made it possible to pack more hardware into a limb than ever before. There are also more and more amputees in the US because of soaring rates of diabetes - which can cause nerve and vascular damage - and injuries suffered by soldiers in the Middle East. These factors have encouraged more investment in bionic technologies than ever before.
The early results of this boom are now reaching the open market. For up to $30,000, a person who has lost a leg to illness or injury can obtain a prosthetic like McNaughton's, complete with "intelligent" software that learns a user's gait and can adapt to changing terrain. Examples include the C-Leg from German orthopaedic company Otto Block and the Rheo Knee, which McNaughton uses, from the Icelandic company Össur. These use a combination of hydraulics and motors to make carrying the leg less tiring, plus carbon fibre to mimic the elastic properties of bones and tendons.
Prosthetic feet have always been particularly tricky to design. The muscles in natural feet and ankles constantly add or damp forces as necessary, and the elasticity of our tendons lets us walk using relatively little energy. Lower-limb amputees, though, "walk slower, use more metabolic energy and are less stable - even on flat ground", says Hugh Herr, director of the Biomechatronics Group at the Massachusetts Institute of Technology and himself a double lower-limb amputee. To tackle this problem Herr's group has designed a prosthetic foot, the iWalk PowerFoot One, which uses an electric motor and tendon-like springs to propel the user forward or slow them down, controlled by two microprocessors and six sensors that measure the ankle's position and the forces it is experiencing.