Stress fractures in the elderly: different pathogenetic features compared with young patients.

Stress fractures mainly occur in the lower limb as a result of cyclic submaximal stresses. Most commonly affected by this specific type of fractures are young athletes, military or elderly subjects with metabolic bone diseases like osteoporosis. In consideration of the heterogeneity of affected patients is presumable that there are different pathogenic mechanisms. In young person bone tissue, although metabolically intact, is not able to withstand the stresses to which it is chronically subjected, also because of muscle fatigue. This leads to a macrostructural failure and to the development of "fatigue" fractures. Instead, in elderly patients, there are numerous physiological conditions that determine a bone metabolism alteration. This is the main reason for the structural changes in trabecular and cortical bone, which is reflected in reduced biomechanical strength. In addition, muscular situation, such as muscle fiber atrophy, is unable to correctly support bone tissue, leading to the development of insufficiency fractures.