Prosthesis

FACTS ABOUT PROSTHETIC LIMBS
by Molly

• A prosthesis is an artificial limb that replaces an amputated or missing arm or leg. It can be transhumeral (above the elbow); transradial (below the elbow); transtibial (below the knee); or transfemoral (above the knee).
• Most prostheses are custom designed using a plaster mold and/or computer to create a socket that fits a specific individual’s stump or residual limb. The socket is then attached to the stump using suction, belts or cuffs.
• An amputee requires several months of physical therapy to master the use of the prosthesis: performing daily activities; maintaining balance, positioning and strength; and handling problems such as falling down and getting up.
• Ideally, prostheses should be comfortable, lightweight, durable, well-functioning, and easy to put on and take off. Ill-fitting prostheses can cause skin problems, scar tissue irritation, muscle strain, posture problems, causalgia (burning pain from peripheral nerve injury), and phantom pain (shooting, stabbing, or throbbing that feels like it comes from a missing body part).
• New plastics and carbon fiber are making artificial limbs stronger, lighter, and more energy-efficient. High-tech prosthetics can use myoelectric signaling (with impulses sent from voluntary muscle contractions); targeted muscle reinnervation (with impulses sent from surgically-rerouted motor nerves); targeted sensory reinnervation (with sensory and not motor nerves surgically rerouted); and direct bone attachment (with a titanium bolt inserted into bone at the end of the stump).
• Prostheses last an average of three years, but must be replaced more often when the amputee is a growing child.
• Two amputees, both South African, competed in the 2008 Beijing Olympics: Oscar Pistorius, a sprinter who wore carbon-fiber prostheses on both legs, and Natalie du Toit, a swimmer who removed her prosthesis while competing.
• The oldest-known functioning artificial limb is a Roman copper-and-wood leg dating from 300 B.C. The newest available model is the 2007 Scottish i-Limb hand, which features four individually powered fingers and a rotatable thumb.
• Depending on their location, size and technical capabilities, prosthetic limbs usually range in price from $6,000 to $35,000 (USD). The least expensive may be India’s Jaipur foot ($40), while the most expensive may be a high-tech U.S. prosthetic arm that is still in development ($90,000).

A Personal Call to a Prosthetic Invention
New York Times, July 2, 2008

While working at the Center for Biomedical Design at the University of Utah, Van Phillips (an amputee) worked on weekends to create an everyday prosthetic that would allow him to run. He used carbon graphite, which is stronger than steel and lighter than aluminum...the result was Flex-Foot Inc, which designed many prosthetics for a range of people including the Cheetah for elite athletes.