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The Story Behind: Prosthetic Limbs
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Prosthetics at "Play"
Once upon a time, if a person lost a leg, he or she was relegated to a wheelchair or stuck trying to manoeuvre with a heavy, awkward artificial limb. Today, amputee athletes run, jump, bike, ski, snowboard and in many ways are hot on the heels of their two-legged counterparts. The most recent iterations of the device may even help amputee athletes run faster than those running on two biological legs.
From copper to computer chips
The earliest known leg prosthesis is the "Capua Leg," a copper and wood device found in a circa-300 BC tomb in Capua, Italy. In the fifteenth and sixteenth centuries, the same craftsmen who made suits of armour designed iron prostheses. An iron leg with an articulated knee joint was designed by French surgeon Ambroise Pare, considered a pioneer in amputation procedures.
Predictably, war has made major contributors to the development of prosthetic limbs. Advances in surgery and medicine meant that people who previously would have died from their battle wounds survived as amputees. And in many cases, it was the amputees themselves who came up with ways to improve artificial limbs.
Among the early pioneers was James Edward Hanger, who had the dubious honour of becoming the first amputee of the US Civil War after losing a leg during a land battle. After developing the Hanger limb from whittled barrel staves, he founded an orthotics company that is still in business today. In the late 1800s, Albert Winkley lost his foot in a farming accident and went on to invent a slip-socket to alleviate the uncomfortable friction between the limb's residual stump and the prosthetic device. With a partner, he started the Winkley Artificial Limb Company to market the socket to Civil War amputees.
The wars of the twentieth century inspired even more research and development into prostheses. Today, plastics and foam have made artificial legs lighter and allow for cosmetic modelling to match the user's body shape and skin colour. Computer-aid design programs have improved how sockets are fashioned to fit individual stumps. Computers have also found their way inside the prosthesis: the Otto Bock C-Leg uses microprocessors and sensors in the foot, ankle and knee components to provide a more stable and natural gait.
A leg up
It took more creativity than cosmetics to get amputee athletes back on the track or playing field, though. In 1976, Van Phillips lost his leg below the knee as a result of a water-skiing accident. At the time, prostheses were not designed for sports - they broke too easily and weren't flexible enough to withstand a runner's range of motion.
Using a carbon-fibre-based material and a keep-it-simple approach, Phillips created a sports prosthesis with a wide J-shaped blade, known as Cheetahs because of their resemblance to the fast cat's powerful hind legs. When weight is applied by landing on the heel, it is converted into energy that lets the runner literally spring forward.
The low-ankle design of Phillips' artificial leg has done more than just make it possible for amputees to run: It has made it possible for disabled athletes to hold their own against and even seriously challenge able-bodied professional runners.
The sports world doesn't know what to make of it. South African sprinter Oscar Pistorius, a double below-the-knee amputee since the age of 11 months, has become the most public face of the Cheetahs: He has set national and world records in Paralympics track events and placed second in the Senior South African National Championships against able-bodied competitors. A born athlete who also plays rugby, water polo and tennis, Pistorius has set his sights on the Olympics; he is currently appealing the International Association of Athletics Federations' ruling disqualifying him from this summer's Beijing Games on the grounds that his prostheses give him a mechanical advantage over able-bodied competitors.
Regardless of the debates on the track and field, advances in sports prostheses translate into better products for non-athlete amputees, as the technology that puts the speed in the sprint also puts a natural spring in the step.
A step forward
Even as amputees rejoice in the Cheetah's simplicity, the future of prostheses focuses on the complex. There are already myoelectric limbs, where the muscle movement in the residual stump is converted into electrical impulses that move the prosthesis. Researchers have started identifying patterns in brain signals that relate to limb movement; the hope is that amputees could one day control their artificial limbs via microchips implanted directly into the brain.
In a scenario that reads like a science fiction novel, other scientists are looking into artificial muscles powered by chemical energy found in fuel, rather than via battery-supplied electricity.
More realistic in the short term is a technique called Intraosseous Transcutaneous Amputation Prosthesis (ITAP), which eliminates the need for an external socket. With ITAP, a titanium rod is implanted into the bone. The idea is that living bone cells will attach themselves to the titanium implant, which extends from the end of the stump. In other words, the artificial limb is essentially attached directly to the stump. ITAP is already being used for small appendage prostheses such as ears, fingers and toes; its viability for sports like track and field, however, is still a long way down the road.
Read more about the inventor: Van L. Phillips (US)