This article is based on review of international publications collected by the author during his time working in the specialty.
SeriesDiagnosis of osteoporosis and assessment of fracture risk
Introduction
As prevalence and awareness of osteoporosis increases, and treatments of proven efficacy become available, the demand for management of patients with the disease will also rise. Such demand will, in turn, require widespread development of facilities for the diagnosis and assessment of osteoporosis. Measurement of bone mineral density (BMD) is the central component of any provision that arises from the internationally agreed definition of osteoporosis: a systemic skeletal disease characterised by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture.1 The diagnosis of osteoporosis thus centres on assessment of bone mass and quality. There are no satisfactory clinical means to assess bone quality. Diagnosis of osteoporosis, therefore, depends on the measurement of skeletal mass.
The clinical significance of osteoporosis rests with the fractures that arise as a consequence of the condition, and their attendant morbidity and mortality. Low bone mass is an important component of the risk of fracture, but other abnormalities arise in the skeleton that contribute to skeletal fragility. Furthermore, various non-skeletal factors, such as the liability to fall, contribute to fracture risk. Thus, ideally, assessment of fracture risk should encompass all these aspects. There is, therefore, a distinction to be made between diagnosis of osteoporosis and assessment of risk, which in turn implies a distinction between diagnostic and intervention thresholds.
Section snippets
Single and dual X-ray absorptiometry
Single and dual X-ray absorptiometry (DXA) are used to assess mineral content of the entire skeleton and that of specific sites, including those most vulnerable to fracture.2 Bone mineral content is the amount of mineral in the specific site scanned and, when divided by the area measured, can be used to derive a value for BMD. Both techniques provide a two-dimensional, areal picture, rather than a true volumetric density. Thus, the size of the bone affects the apparent density, since the
Ultrasonic measurement of bone
Skeletal status in osteoporosis can be measured with quantitative ultrasound methods. The most widely assessed methods are broad-band ultrasound attenuation and speed of sound (or ultrasound velocity) at the heel. Because these techniques do not involve ionising radiation and could provide some information with respect to the structural organisation of bone in addition to bone mass, there is much interest in their use. For reasons outlined below, these techniques cannot be used to diagnose
Computed tomography
Quantitative computed tomography has been applied both to the appendicular skeleton and to the spine.9, 10, 11 Conventional whole body computed tomography scanners need calibration to convert their results into units relevant to BMD. Quantitative computed tomography is most useful in the assessment of cancellous bone density because it provides a measure of true volumetric density, rather than an area-adjusted result (as is the case with DXA). Cancellous bone is more responsive than cortical
Radiography
Osteoporosis can often be diagnosed by looking at simple radiographs, albeit with low sensitivity. Furthermore, there are several characteristic features of osteoporosis that can be seen with this technique, which help in diagnosis or in differential diagnosis. Subclinical vertebral fracture is a strong risk factor for subsequent fractures, for example, both at new vertebral sites and at other sites susceptible to osteoporosis. There is, therefore, great interest in the identification of
Conclusions
The diagnosis of osteoporosis is generally based on assessment of BMD at the proximal femur by DXA. By contrast, intervention thresholds should be based on fracture probability. Several clinical risk factors for fracture with and without BMD allow the more accurate stratification of risk than the use of BMD alone. In the absence of validated screening strategies, a case-finding approach is advocated for individuals with strong risk factors who are referred for BMD assessment. Intervention is
Search strategy
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