A technique used to pinpoint the origin of an earthquake could be adapted to warn of an impending injury to dancers, athletes and even racehorses.
Just as earthquakes produce detectable seismic waves at the Earth鈥檚 surface, the tiny cracks that appear in stressed bones emit ultrasound. So Ozan Akkus, a biomedical engineer at Purdue University in West Lafayette, Indiana, has built a wearable device that detects this telltale ultrasound and warns athletes before a series of small cracks turns into a full-blown fracture.
X-rays can capture the hairline fractures that occur when tiny cracks in bones build up due to repeated stress, but not the cracks themselves. So athletes often do not stop exercising until it is too late. 鈥淭here is some pain,鈥� says Akkus, 鈥渂ut people who get stress fissures are likely to be tough and competitive. They keep pushing themselves.鈥�
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To see if he could detect the small cracks, Akkus applied stress to human cadaver bones and recorded the ultrasound waves using a piezoelectric sensor that converts bone vibration into an electrical signal. He found that the rate of high-frequency sound waves 鈥渟kyrockets鈥� shortly before a fracture occurs. Now he wants to use this to predict a fracture in athletes.
鈥淲e now need to identify the signal that actually indicates impending catastrophic failure,鈥� he says. Early next year, he will equip student sports teams with his piezoelectric patches and look for signature patterns in the rate, frequency and size of vibrations that suggest a fracture isn鈥檛 far-off.
