Researchers at Purdue University and the University of Toledo have developed a prototype device to monitor the formation of "microcracks" in bones that can lead to hairline stress fractures that can develop if they are not detected in time. Seismologists use a similar technique to gauge the size of earthquakes. The prototype can be applied in this way because the crack formations generate waves similar to those created by earthquakes.

"The goal is to create a wearable device that would alert the person when a stress fracture was imminent so that they could stop rigorous physical activity long enough for the bone to heal," said Ozan Akkus, associate professor, Weldon School of Biomedical Engineering, Purdue University.

The system records "acoustic emission data," or sound waves created by the tiny bone fissures. Conventional imaging technologies have difficulty seeing hairline fractures because they are caused by the gradual accumulation of microscopic cracks, according to the researchers.