BACKGROUND: When Virginia Tech's star running back fractured his ulna (an arm bone) three weeks before a big game, students in the engineering department worked with their professor to develop a better bracing system to provide better support for the athlete. They used a polypropylene/carbon fiber composite to mold a prototype, and found that the prototype was stiffer and stronger than the current braces that are commercially available.
WHAT ARE COMPOSITES? A composite material combines two or more separate materials to build a single construct that combines the best properties of both, such as the silicon-germanium-arsenide composites used to build ultra-fast semiconductor chips. More common materials, such as concrete, paper, cardboard, plywood, fiberglass and bricks are all composites. The first manmade composite was probably the adobe brick. Mud or clay can be shaped and dried into a hard block, but it has little load-bearing strength. Mixing in dried grass or straw makes the bricks tougher. Reinforced concrete, in which steel rods are encased in a matrix of concrete to improve strength and load-bearing properties, is used in bridges and buildings. Tiny carbon nanotubes are beginning to serve the same purpose in building structures.
ABOUT FRACTURES: A fractured bone is the same thing as a broken bone. They occur because a bone area is unable to support the energy placed on it. That energy can be acute, as from a car crash or a two-story fall, or chronic and low-energy repetitive activity. The latter is responsible for stress fractures, an overuse injury commonly seen in athletes. The increased demand places on the bone causes it to remodel and become stronger in areas of higher stress, but if the repetitive demands become too great, a stress fracture can result.
HOW BONES HEAL: The 206 bones in the body renew themselves continually through a process known as remodeling, which is also how fractures heal. Complex chemical signals prompt cells called osteoclasts to break down and remove (by absorbing it) old bone. Other cells called osteoblasts deposit new bone. When a bone breaks, inflammatory cells rush to destroy invaders and isolate injured tissue, causing pain, swelling and heat at the breakage site for a few days. Tiny new blood vessels (capillaries) begin growing into the site, and new cells grow, too. New connective tissue bonds fractured bone ends and the remodeling process begins.
DON'T SMOKE! Research has shown that smoking cigarettes can significantly slow down healing time for bone fractures -- it can take more than two months longer. Bones are nourished by blood carrying nutrients, minerals and oxygen. Smoking elevates the levels of nicotine in the blood, causing the vessels to constrict by as much as 25 percent, decreasing blood flow and therefore the levels of nutrients supplied to the bones.