Osteoporosis, a systemic metabolic disease of bone, is characterized by low bone mass and altered trabecular pattern, leading to increased risk of fractures. It increases in prevalence with age, especially in postmenopausal women, and can have other secondary causes. Radiologic evaluation of osteoporosis has historically used conventional radiography, which demonstrates cortical thinning, increased radiolucency, and altered trabecular patterns, and also aids in assessing vertebral fractures. Many indexes have been devised, such as the Saville index for the degree of radiolucency, and the Genant grading system for vertebral fractures. Other grading systems have been produced to assess the change in trabecular patterns in the proximal femur and the calcaneus. Differentiating osteoporosis from other bone disorders, such as malignancy, endocrinologic or metabolic diseases, and other causes is also important. Bone scintigraphy, although useful in excluding other metabolic bone diseases and determining the age of vertebral fractures, is less useful for diagnosis of osteoporosis. More recently, the measurement of Hounsfield units on multidetector computed tomography has emerged as a possible modality for opportunistic screening of osteoporosis when being performed for other indications.
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