Materials in sport – Prosthetic limbs
Intro
Competition amongst paralympians is no less fierce than that experienced by their able bodied compatriots, with competitors producing athletic performances that are truly inspiring. The current world record for the 100 metre sprint by an amputee athlete is 11.03 seconds, only about a second slower than the fastest Olympic sprinters. What makes this possible?
A brief history of the ‘non-intelligent’ artificial leg:
Before intelligent prosthetics had been developed, and all that was available was the original artificial leg, the material being used for the leg frame was mainly wood with the socket made from reinforced leather. In the 1950’s and 60’s laminated and reinforced plastics were used for sockets with fibre glass materials for the rest of the leg. These rigid plastic sockets however are generally no longer in use as they are uncomfortable and do not respond to each specific need of the patient. Researchers such as Tom Guth, chief research prosthetist at the RGP Prosthetic Research Centre, in San Diego, California, therefore tried to develop semi-flexible thermoplastic sockets as well as rubber and silicone ones, instead of the older rock hard laminated material, for patients with above the knee amputation. These newer materials are lighter, more easily moulded and fit more comfortably to the skin than older designs. Using this and a carbon graphite frame, sprinters who have below the knee amputation with some residual limb, are able to run more easily as the artificial leg has openings promoting the runners’ residual muscle to expand and grow. This means that instead of letting the muscles atrophy, they can provide the energy to propel their knee forwards. With the softer materials, instead of tensing the muscles to absorb the impact of the heel when running or walking, patients whether athletes or not, naturally take the impact allowing for more comfort with the weight of the residual limb equally distributed over the prosthesis. The new designs also keep the leg in line with the residual limb and is held on by suction instead of using straps, allowing more control over the leg for a more natural motion of running
