Osteoporosis is a systemic skeletal disease characterized by low bone mass and microarchitectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture.1 The disease represents a major world-wide public health problem.2,3 Low bone density is an important determinant in the risk assessment of hip fractures, and recent studies have shown that a decrease in femoral bone density of one standard deviation increases the risk by a factor of two to three.4,5 However, for a given bone density, the risk of hip fracture still increases with age, and there is an overlap of bone density between women with and without fractures.4 This may be variously related to additional skeletal and extraskeletal factors. Extra skeletal factors include falls and the response to trauma. Skeletal factors in addition to bone mineral density (BMD) include accumulated fatigue and changes in trabecular or cortical architecture.
In the last 25 years, several noninvasive techniques based on the attenuation of ionizing radiation have been developed to quantify BMD in the axial and peripheral skeleton. These include single photon absorptiometry (SPA), single X-ray absorptiometry (SXA), dual X-ray absorptiometry (DXA), and quantitative computed tomography (QCT).6 They represent valid methods for the determination of BMD and explain about 60–80% of the variation in bone strength.7,8 However, they provide only limited information on bone structure and bone material properties. Consequently, researchers and clinicians are looking for new methods that may have a role in assessing skeletal status. An ideal screening tool should be inexpensive, the patient should be exposed to little if any risk or discomfort, and it should detect fragility, whatever its basis, and not just decreased BMD. It is possible that a combination of elasticity, structure, and density information will provide a more sensitive indicator of fracture risk than techniques that reflect bone density alone.
Quantitative ultrasound (QUS) methods have been developed and introduced in recent years for the assessment of skeletal status.9–12 Researchers investigating osteoporosis by means of QUS have reported favorable results, and most recently, manufacturers have released a great variety of commercial devices for QUS assessment at peripheral measurement sites.13–18 Appreciating the substantial potential of this new technology but recognizing the limited experience that has been gathered during this relatively short time period,19 both researchers and clinicians have expressed the need for a consensus statement on ultrasound applications in osteoporosis. The goals of this statement are to review existing knowledge and to aid and guide further development and clinical introduction of QUS technologies. An international expert panel with members from Asia, Australia, Europe, and North and South America held two meetings, one in Amsterdam, The Netherlands, on May 21, 1996 and another in Seattle, WA, U.S.A., on September 10, 1996 and formulated the following consensus. It has been endorsed by several major international osteoporosis societies.11