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INTRODUCTION

OSTEOPOROSIS

Osteoporosis is defined as a reduction in bone mass [or bone mineral density (BMD)] or the presence of fragility fracture. It is defined operationally as a bone density that falls 2.5 SD below the mean for a young normal individual (a T-score of <–2.5). Those with a T-score of <1.0 (osteopenia) have low bone density and are at increased risk for osteoporosis. The most common sites for osteoporosis-related fractures are the vertebrae, hip, and distal radius.

Osteoporosis is a common condition in the elderly; women are at particularly high risk. In the United States, 8 million women and 2 million men have osteoporosis; an additional 18 million have osteopenia. The annual incidence of osteoporosis-related fractures is at least 1.5 million; almost half of them are vertebral crush fractures, followed in frequency by hip and wrist fractures. Hip fractures are associated with significant morbidity (thromboembolism) and a 5–20% mortality within a year.

Etiology

Low bone density may result from low peak bone mass or increased bone loss. Risk factors for an osteoporotic fracture are listed in Table 188-1, and diseases associated with osteoporosis are listed in Table 188-2. Certain drugs, primarily glucocorticoids, cyclosporine, cytotoxic drugs, thiazolidinediones, anticonvulsants, aluminum, heparin, excessive levothyroxine, GnRH agonists, and aromatase inhibitors also have detrimental effects on the skeleton.

TABLE 188-1RISK FACTORS FOR OSTEOPOROSIS FRACTURE
TABLE 188-2DISEASES ASSOCIATED WITH AN INCREASED RISK OF GENERALIZED OSTEOPOROSIS IN ADULTS

Clinical Features

Pts with multiple vertebral crush fractures may have height loss, kyphosis, and secondary pain from altered biomechanics of the back. Thoracic fractures can be associated with restrictive lung disease, whereas lumbar fractures are sometimes associated with abdominal symptoms or nerve compression leading to sciatica. Dual-energy x-ray absorptiometry (DEXA) has become the standard for measuring bone density. The U.S. Preventive ...

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