Engineer says new study forces researchers to rethink how elderly break their bones

To better understand why many elderly people are prone to break a bone in a fall (known as bone fragility fractures), perhaps doctors and researchers should look at the human skeleton in much the same way civil engineers analyze buildings and bridges, according to a new study from a University of Utah mechanical engineering professor. A team of researchers led by U mechanical engineering assistant professor Claire Acevedo believes the bones of an older person, say above the age of 50, become more susceptible to a break due to repeated stress from everyday activities such as walking, creating microdamage that affects the quality of the bone. That is in contrast to the common-held belief that bone breaks in the elderly are largely due to one massive impact or force on the bone, such as a fall. "It really starts with a small microcrack that grows over time under repeated loading," says Claire Acevedo, who has just joined the University of Utah College of Engineering faculty. "You need to be doing something like just walking or moving, and the crack is slowly propagating. At some point, the remaining cross-section of the bone that is still connected is too small and will break suddenly." In that case, such fractures in the elderly would be the cause of a fall rather than the result of a fall. The study, "Fatigue as the missing link between bone fragility and fracture," was published online this week in the latest issue of Nature Biomedical Engineering. Acevedo says this theory that "cyclic loading" (repeated and fluctuating loads) might be a bigger contributor to bone breaks is similar to the study of structures and engineered materials. This type of stress in structures and materials resulted in a rise of catastrophic accidents near the turn of the 20th Century and has led to the development of "fracture mechanics."