[Increase in bone mineral density and its effect on fracture risk]

Over the past 10 years a number of clinical trials have evaluated several agents for treatment and prevention of osteoporosis, and demonstrated that these agents can increase bone mineral density (BMD) and reduce the incidence of fracture. Although the relationship between antifracture efficacy and changes in BMD varies greatly among reports, all of them suggest the presence of antifracture effect that is mediated by factors other than BMD. Fracture risk is associated with bone strength and nonskeletal risk factors such as the propensity to fall. Bone strength is primarily determined by BMD, but bone quality such as bone remodeling, structural and material properties is also an important determinant of bone strength. Some of the agents for osteoporosis treatment might provide the atifracture effect mainly through the improvement of bone quality. The mechanism how the reduction in fracture risk is achieved deserves further studies.