Investigators at Purdue University and the University of Toledo, utilizing an already existing technology that monitors the state of materials under stress, are developing a monitor that might warn patients and prevent bone stress fractures:
“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 (pronounced Ah-Koosh), an associate professor in Purdue’s Weldon School of Biomedical Engineering.
The system records “acoustic emission data,” or sound waves created by the tiny bone fissures. The same sorts of acoustic emissions are used to monitor the integrity of bridges, other structures and mechanical parts like helicopter turbine blades…
Akkus is working with researchers at the University of Toledo to develop a wearable prototype that will record crack-formation data, which could be downloaded to a portable digital assistant, or PDA, for review by medical professionals. Such a device could immediately alert the person by sounding an alarm, and the data could then be scrutinized by a doctor.
“All of the technology is available, and the sensors exist off the shelf,” he said. “We just have to modify them to work with our system.”
Sensors made of a “piezoceramic” material generate electricity when compressed by a force, such as the vibration created by seismic waves resulting from crack formation.
“Recently, flexible polymer-based sensors have appeared on the market, and these could be incorporated into athletic apparel, such as running shoes and exercise tights to monitor areas most susceptible to fractures,” Akkus said. “Ultimately, we would like to do real-time monitoring of damage activity and learn how to distinguish between a small crack and a more structurally threatening defect.
“There are different types of cracks that occur, and it’s important to be able to distinguish among them so that we can determine how serious the damage is.”
To distinguish the difference between the various types of cracks, researchers are integrating “pattern recognition” software and earthquake models, working with Robert Nowak, a Purdue professor of earth and atmospheric sciences. The multidisciplinary research involves biomedical and electrical engineering, veterinary medicine, and earth and atmospheric sciences.
“One challenge will be to learn when damage is serious enough that you should stop exercising,” Akkus said. “You don’t want to give a professional athlete a premature warning.”