Scientists from the University of Arizona's College of Medicine are working with the Department of Defence to help heal bones using 3D printers. The basic idea is to print a plastic "scaffold" filled with calcium and stem cells to replace broken or missing sections of a bone, and allow new bone to grow into it. Pilot studies already show promise, and placing sensors inside the scaffolds to gather loading/stress data is reportedly the next step, as the scientists want to see if exercise helps patients recover more quickly. Thanks to cageymaru for the tip. "Imagine an impact that causes half of a long bone to shatter so that it can't be put back together – no current surgical treatment can ensure that kind of injury will heal," explained John A. Szivek, PhD, a scientist at the UA College of Medicine – Tucson. "This is a really big problem for the military, where explosions or combat injuries can cause big bone defects." To help military personnel with these devastating injuries, Dr. Szivek, a biomedical engineer and professor of orthopedic surgery, has received a five-year, $2 million grant from the U.S. Department of Defense to launch a study to determine how to heal bone fractures using a combination of 3D printing and adult stem cells.