Oscar Pistorius (photo by David Pilbrow, distributed through Creative Commons license)
I visited London at the end of August and was exposed to the Paralympics for the first time. One of the biggest stars of the London 2012 Paralympics was Oscar Pistorius, a 200m and 400m sprinter from South Africa with double, below-knee amputations. He received a great deal of media attention because he not only competed in the Paralympics, but also competed in the able-bodied Olympics that took place a few weeks earlier in London.
The evolution of prosthetics has come a long way. As I mentioned in my first post, we have progressed a great deal from the wooden prosthetic shoe used in ancient Egypt. Today those using prosthetics can run, jump and walk faster than their able-bodied counterparts. In the case of Oscar Pistorius, he uses “Cheetah blades”, a blade-shaped carbon fibre prosthetic that allows his running motion to mimic that of a cheetah. The Cheetah blade is a breakthrough in the field of prosthetics because of its carbon fibre frame and ability to absorb and release the ground reaction force more effectively than anatomical limbs. With the blades, paralympians are able to achieve higher velocities at takeoff.
A recent publication in the British Journal of Sports Medicine discussed the fact that an energy loss of only 9 per cent with prosthetics was developed during the stance phase before a sprint, compared to a 41 per cent energy loss seen in human ankle joints, gave an unfair advantage to amputee sprinters. There is clearly a lot of gait analysis and biometric calculations done in the design and implementation of prosthetics for paralympians. However, one aspect that is not rigorously tested is the mechanical efficiency of the prosthetic brought about by the stability of the stump-socket (biomaterial) interface. The competency of the biomaterial interface to grip and provide stability for the stump ultimately affects the overall effectiveness of the prosthetic. Ways to increase the stability of the prosthetic include altering the interface texture and material itself.
The stump can also change over time, and the better equipped the prosthetic is to adapt to those changes, the more robust a product it will be. For example, the stump may be prone to swelling that may be brought about by over-use (inflammation) or humidity (moisture). It is then worthwhile to choose or even design a smart biomaterial at the interface, which can also swell to provide more cushion, or deflate (shrink) to account for the added volume of the stump. Currently the aim is to restore loss of function, not to enhance sports performance; however, as prosthetics continue to evolve towards sleeker and more efficient designs, the line between paralympians and olympians will become blurred. This is not a bad thing. It means the fields of sports medicine and regenerative medicine are working together to provide solutions to restore the loss of limbs and, in most cases, are the driving forces for innovation in biomaterials.
Roshan Yoganathan
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