Use of Bone Densitometry in the Clinical Management of Osteoporosis

Abstract

Osteoporosis is sometimes termed the “silent epidemic”ause early osteoporosis is asymptomatic, and significant bone loss may become evident only after a hip or vertebral fracture has occurred. Fractures, especially of the spine, hip, and wrist, are the clinical complications of osteoporosis. Initially, spine fractures tend to be asymptomatic but they are associated with significant morbidity as the severity and number of fractures increase. The most serious fractures are those of the hip, which contribute substantially to morbidity, mortality, and health care costs. Within a year of a hip fracture the mortality rate is as high as 20% with reduced functional capacity in 50% of surviving patients (1). Even the presence of clinical risk factors such as lifestyle, diet and family history of osteoporosis are relatively insensitive in predicting the presence of osteopenia (2). The pathophysiology of osteoporosis is multifactorial and complex. Fractures, the clinical manifestations of osteoporosis, depend on a variety of factors including the propensity to fall, visual acuity, response to falling, and bone strength (3,4). However, bone mass is the most important determinant of bone strength and accounts for up to 80% of its variance (5,6). Thus reduced bone mass should be a useful predictor of increased fracture risk (7). In fact, many prospective studies of older subjects have shown that levels of bone density at the spine or hip that are one standard deviation below the population mean increases the risk by a factor of two to three (8–11). Methods of measuring bone mineral density are pertinent to the assessment of osteopenia, identification of those individuals at risk of fracture, and identification of candidates for prevention or treatment strategies.