Peripheral bone mass measurements: current and future perspectives on quantitative ultrasound and peripheral DXA

Although peripheral bone mass measurements have been available for more than a quarter of a century to predict osteoporotic fractures, these studies fell out of favor in the late 1980s and early 1990s as axial measurements replaced appendicular determinations for risk assessment and therapeutic responsiveness. Within the last half decade there has been a resurgence in utilization of peripheral measurements, primarily because of improved technology, enhanced precision, and greater accessibility. There are now nearly 11,000 peripheral densitometers in use around the world with quantitative ultrasound (QUS) of the calcaneus and peripheral densitometry (pDXA) of the wrist or calcaneus the most popular. Three recent prospective studies involving more than 20,000 postmenopausal women have demonstrated that QUS of the calcaneus can predict future fractures as accurately as central measurements of the spine or femur. This has raised the possibility that widespread screening with QUS or pDXA will soon become a reality. In this articles we hypothesize that global utilization of peripheral technology by primary care physicians is an absolutely necessity for the successful identification and treatment of all osteoporotic patients. But despite improvements in the accuracy and precision of these machines, several critical questions remain. In particular the issues which demand further study include: 1. The rate of false negative tests by peripheral instruments; 2. The utilization of appendicular sites to measure therapeutic efficacy of various antiosteoporotic drugs; 3. The timing of follow-up measurements to assess responsiveness; 4. The relationship between fracture risk education and incremental changes in bone mass; 5. The interrelationship between bone density and bone architecture and 6. cost effectiveness of peripheral vs central measurements. Notwithstanding these issues, peripheral scanning by one of several techniques is likely to be at the forefront of screening for osteoporosis risk, not only in specialized clinics but at the "point of care" in primary care offices.