Bone biomechanics and the determinants of skeletal fragility

Abstract

Fractures are among the most dramatic and devastating sequelae of aging of the human skeleton. In the USA alone, there are over 1.5 million fractures each year, including 280,000 hip fractures and 500,000 vertebral fractures. Of greater importance, however, is the fact that based on current demographic trends predicting a "graying" of the population worldwide, the number of fractures is projected to double or triple in the next 30-50 years. Whereas low BMD is among the strongest risk factors for fracture, a number of clinical studies have demonstrated the limitations of BMD measurements in assessing fracture risk and monitoring the response to therapy. These observations have brought renewed attention to the broader array of factors that influence fracture risk, including those that are directly related to skeletal fragility as well as those related to skeletal loading. This chapter reviews the etiology of age-related fractures from a biomechanics viewpoint, by introducing a standard engineering concept used to evaluate structural failures and considering the various components that influence whole bone strength, with discussion of how key dietary factors may influence the determinants of bone strength.