Bone density

Bone density, or bone mineral density (BMD), is the amount of bone mineral in bone tissue, measured as mass of mineral per volume of bone (relating to density). Clinically it is measured by proxy according to optical density per square centimetre of bone surface upon imaging. Bone density measurement is used in clinical medicine as an indirect indicator of osteoporosis and fracture risk. It is measured by a procedure called densitometry, often performed in the radiology or nuclear medicine departments of a hospital or clinic. The measurement is painless and non-invasive with low radiation exposure. Measurements are usually made over the lumbar spine and the upper part of the hip. The forearm may be scanned if the hip and lumbar spine are not accessible. There is a statistical association between poor bone density and a higher probability of fracture. Fractures of the legs and pelvis due to falls are a significant public health problem, especially in elderly women, leading to substantial medical costs, inability to live independently, and even risk of death. Bone density measurements are used to screen people for osteoporosis risk and to identify those who might benefit from measures to improve bone strength. Volumetrically, women have greater bone density than men, as their bones are often not as long as men's bones.