Osteoporosis in clinical practice--bone densitometry and fracture risk.

Osteoporosis is a condition of decreased bone mass and bone density associated with an increase in fracture risk. Bone mineral density (BMD) of the lumbar spine and femur can be reliably measured by double-beam X-ray absorptiometry (DEXA), which provides a measure of bone strength. Reduction in BMD is a continuum and is associated with a progressive increase in fracture risk. The diagnosis of osteoporosis is based on BMD relative to that of healthy young adults and criteria for diagnosis are arbitrary. The original 'normal' BMD data published by some manufacturers were relatively high, leading to a relative over-diagnosis of osteoporosis. Revised normative BMD values of the spine and femur and revised criteria using degrees of severity are proposed and may provide a better basis for diagnosis and for the management of patients with osteoporosis. The indications for BMD measurement, the age at which BMD is measured, and number of measurements, depends upon the purpose of the measurement and how the result will affect the management of each patient in clinical practice.