Osteoporosis

Osteoporosis is a disease of bone in which bone mineral density is reduced and bone microarchitecture is disrupted. Osteoporotic bones are susceptible to fracture. It is defined according to the bone mineral density (BMD) as measured by DEXA: a BMD of 2.5 standard deviations below the peak bone mass (20-year-old person standard) is considered osteoporosis. While treatment modalities are becoming available, prevention is still the most important way to reduce fracture. Due to its hormonal component, more women suffer from osteoporosis than men.

Natural history

Today, most cases of osteoporosis are diagnosed before symptoms develop. This is due to widespread screening for osteoporosis using the DEXA scan. With treatment, bone mineral density increases, and fracture risk decreases.

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In the absence of treatment, overt osteoporosis is heralded by a fracture. Some fractures, like vertebral compression fractures or sacral insufficiency fractures, may not be apparent at first, appearing to patient and physician as a very bad back ache or completely without symptoms. Hip fractures and wrist fractures are more obvious.

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Hip fractures are responsible for the most serious consequences of osteoporosis. In the United States, osteoporosis causes a predisposition to more than 250,000 hip fractures yearly. It is estimated that a 50-year-old white woman has a 17.5% lifetime risk of fracture of the proximal femur. The incidence of hip fractures increases each decade from the sixth through the ninth for both women and men for all populations. The highest incidence is found among those men and women ages 80 or older.

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An estimated 700,000 women have a first vertebral fracture each year. The lifetime risk of a clinically detected symptomatic vertebral fracture is about 15% in a 50-year-old white woman.

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Distal radius fractures, usually of the ' type, are the third most common type of osteoporotic fractures. In the United States, the total annual number of Colles' fractures is about 250,000. The lifetime risk of sustaining a Colles' fracture is about 16% for white women. By the time women reach age 70, about 20% have had at least one wrist fracture.

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