Scientists at Polytechnic Institute of New York University are crushing bones to study how shocks of differing speed result in varying fractures. Using a 10,000 frame-a-second camera and a scanning electron microscope they discovered that fast compressions, such as from explosions, create very small, almost invisible fractures throughout the bone. Slower compressions, such as from jogging and other more pedestrian activities, create larger, more more localized fractures.
Two years ago, Gupta attended a conference at which veterans from Iraq and Afghanistan were discussing injuries related to Improvised Explosive Devices (IEDs). At that time, more than one-third of all war casualties were due to IEDs, which cause a unique type of brain injury that is difficult to diagnose. Those “closed” brain injuries result not from a direct impact or penetration of the skull, but from the force of the compression. Similar damage may be happening to other organs and bones, as well.
Damage from blast injuries is often not visible with today’s diagnostic equipment, and soldiers may be pronounced healthy enough to return to the field. In many cases, the extent of the injury only becomes evident over time.
“I was already studying foams and body armor and developing new protective materials, but my approach changed when I learned about the nature and prevalence of IED injuries,” Gupta said. “I realized it was critical to understand how the bones themselves behaved in these circumstances in order to devise the next-generation of protection.”
Gupta set out in search of a collaborator who could bring essential medical expertise to the investigations. When colleagues introduced him to Coelho, the connection was immediate. “I had discussed the project with several physicians, but we spoke completely different languages,” Gupta said. “But because Coelho’s previous research has focused on bone surgery and we have a common background in materials science, we were able to start working very quickly.”
In addition to researching bone injuries, Coelho and Gupta also exposed protective foams to their compression machine, called a “Kolsky Bar” system. They found that much like bone, foam materials behave differently as the rate of compression changes. Foams that seem soft when slowly compressed can become much stiffer under higher compression speeds. The team plans to investigate whether this change can actually increase, instead of reduce, the risk of injuries.