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Overview of dual-energy x-ray absorptiometry

E Michael Lewiecki, MD
Section Editor
Clifford J Rosen, MD
Deputy Editor
Jean E Mulder, MD


Osteoporosis or low bone mass (osteopenia) occurs in about 53 million American men and women, accounting for 55 percent of the population age 50 years and over [1]. Osteoporosis has been defined as “a skeletal disease characterized by compromised bone strength predisposing a person to an increased risk of fracture” [2].

There are approximately two million fragility fractures in the United States each year: 547,000 vertebral fractures (VFs), 297,000 hip fractures, 397,000 wrist fractures, and 675,000 at other skeletal sites [3]. Fractures of the spine and hip are associated with chronic pain, deformity, depression, disability, and death. About 50 percent of patients with hip fractures will never be able to walk without assistance and 25 percent will require long-term care [4]. The mortality rate five years after a fracture of the hip or a clinical VF is about 20 percent greater than expected [5]. The direct cost of incident osteoporotic fractures in the United States was about $17 billion per year in 2005 [3].

This topic review will discuss the clinical applications and interpretation of dual-energy x-ray absorptiometry (DXA) in evaluating osteoporosis. Other aspects of screening for osteoporosis are reviewed elsewhere. (See "Screening for osteoporosis".)


Bone strength is determined by bone mineral density (BMD) and other properties of bone that are often collectively called “bone quality” [6]. Non-BMD determinants of bone strength include bone turnover, architecture (size and shape, or bone geometry), microarchitecture (eg, trabecular thickness, trabecular connectivity, trabecular perforation, cortical thickness, and cortical porosity), damage accumulation, matrix properties, mineralization, and mineral properties (eg, crystal size and orientation).

Investigation of bone quality has provided insight into the pathogenesis of osteoporosis and a better understanding of the mechanism of action of medications used to treat osteoporosis, but with the exception of bone turnover markers it is not yet possible to measure these routinely in clinical practice. Technologies such as high resolution peripheral quantitative computed tomography (HR-pQCT) and micro-magnetic resonance imaging (micro-MRI) can be used to assess trabecular microarchitecture, but at the present time these are largely used for research, with no established clinical applications. For now, in the absence of a fragility fracture, bone density is the best predictor of fracture risk.

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Literature review current through: Sep 2017. | This topic last updated: Mar 10, 2017.
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  1. Cosman F, de Beur SJ, LeBoff MS, et al. Clinician's Guide to Prevention and Treatment of Osteoporosis. Osteoporos Int 2014; 25:2359.
  2. NIH Consensus Development Panel on Osteoporosis Prevention, Diagnosis, and Therapy. Osteoporosis prevention, diagnosis, and therapy. JAMA 2001; 285:785.
  3. Burge R, Dawson-Hughes B, Solomon DH, et al. Incidence and economic burden of osteoporosis-related fractures in the United States, 2005-2025. J Bone Miner Res 2007; 22:465.
  4. Riggs BL, Melton LJ 3rd. The worldwide problem of osteoporosis: insights afforded by epidemiology. Bone 1995; 17:505S.
  5. Cooper C, Atkinson EJ, Jacobsen SJ, et al. Population-based study of survival after osteoporotic fractures. Am J Epidemiol 1993; 137:1001.
  6. Watts NB. Bone quality: getting closer to a definition. J Bone Miner Res 2002; 17:1148.
  7. Marshall D, Johnell O, Wedel H. Meta-analysis of how well measures of bone mineral density predict occurrence of osteoporotic fractures. BMJ 1996; 312:1254.
  8. El Maghraoui A, Roux C. DXA scanning in clinical practice. QJM 2008; 101:605.
  9. The International Society for Densitometry. 2013 ISCD Official Positions – Adult. Middletown, CT: The International Society for Densitometry, 2013. http://www.iscd.org/official-positions/2013-iscd-official-positions-adult/ (Accessed on September 21, 2013).
  10. Lotz JC, Cheal EJ, Hayes WC. Fracture prediction for the proximal femur using finite element models: Part I--Linear analysis. J Biomech Eng 1991; 113:353.
  11. Kanis, JA, on behalf of the World Health Organization Scientific Group (2007). Assessment of osteoporosis at the primary health-care level. Technical Report. World Health Organization Collaborating Centre for Metabolic Bone Diseases, University of Sheffield, UK. 2007: Printed by the University of Sheffield. http://www.shef.ac.uk/FRAX/pdfs/WHO_Technical_Report.pdf (Accessed on November 02, 2010).
  12. Cranney A, Guyatt G, Griffith L, et al. Meta-analyses of therapies for postmenopausal osteoporosis. IX: Summary of meta-analyses of therapies for postmenopausal osteoporosis. Endocr Rev 2002; 23:570.
  13. Wasnich RD, Miller PD. Antifracture efficacy of antiresorptive agents are related to changes in bone density. J Clin Endocrinol Metab 2000; 85:231.
  14. Mazess R, Chesnut CH 3rd, McClung M, Genant H. Enhanced precision with dual-energy X-ray absorptiometry. Calcif Tissue Int 1992; 51:14.
  15. Njeh CF, Fuerst T, Hans D, et al. Radiation exposure in bone mineral density assessment. Appl Radiat Isot 1999; 50:215.
  16. Kanis JA, McCloskey EV, Johansson H, et al. A reference standard for the description of osteoporosis. Bone 2008; 42:467.
  17. Kanis JA, Oden A, Johnell O, et al. The burden of osteoporotic fractures: a method for setting intervention thresholds. Osteoporos Int 2001; 12:417.
  18. Siris ES, Adler R, Bilezikian J, et al. The clinical diagnosis of osteoporosis: a position statement from the National Bone Health Alliance Working Group. Osteoporos Int 2014; 25:1439.
  19. Melton LJ 3rd, Chrischilles EA, Cooper C, et al. Perspective. How many women have osteoporosis? J Bone Miner Res 1992; 7:1005.
  20. Baim S, Leonard MB, Bianchi ML, et al. Official Positions of the International Society for Clinical Densitometry and executive summary of the 2007 ISCD Pediatric Position Development Conference. J Clin Densitom 2008; 11:6.
  21. Writing Group for the ISCD Position Development Conference. Diagnosis of osteoporosis in men, premenopausal women, and children. J Clin Densitom 2004; 7:17.
  22. Binkley N, Kiebzak GM, Lewiecki EM, et al. Recalculation of the NHANES database SD improves T-score agreement and reduces osteoporosis prevalence. J Bone Miner Res 2005; 20:195.
  23. Hochberg MC, Ross PD, Black D, et al. Larger increases in bone mineral density during alendronate therapy are associated with a lower risk of new vertebral fractures in women with postmenopausal osteoporosis. Fracture Intervention Trial Research Group. Arthritis Rheum 1999; 42:1246.
  24. Miller NH. Compliance with treatment regimens in chronic asymptomatic diseases. Am J Med 1997; 102:43.
  25. Ravnikar VA. Compliance with hormone therapy. Am J Obstet Gynecol 1987; 156:1332.
  26. McCombs JS, Thiebaud P, McLaughlin-Miley C, Shi J. Compliance with drug therapies for the treatment and prevention of osteoporosis. Maturitas 2004; 48:271.
  27. Caro JJ, Ishak KJ, Huybrechts KF, et al. The impact of compliance with osteoporosis therapy on fracture rates in actual practice. Osteoporos Int 2004; 15:1003.
  28. Lewiecki EM. Nonresponders to osteoporosis therapy. J Clin Densitom 2003; 6:307.
  29. Klotzbuecher CM, Ross PD, Landsman PB, et al. Patients with prior fractures have an increased risk of future fractures: a summary of the literature and statistical synthesis. J Bone Miner Res 2000; 15:721.
  30. Cooper C, Atkinson EJ, O'Fallon WM, Melton LJ 3rd. Incidence of clinically diagnosed vertebral fractures: a population-based study in Rochester, Minnesota, 1985-1989. J Bone Miner Res 1992; 7:221.
  31. Ferrar L, Jiang G, Adams J, Eastell R. Identification of vertebral fractures: an update. Osteoporos Int 2005; 16:717.
  32. Lewiecki EM, Laster AJ. Clinical review: Clinical applications of vertebral fracture assessment by dual-energy x-ray absorptiometry. J Clin Endocrinol Metab 2006; 91:4215.
  33. Schousboe JT, Debold CR. Reliability and accuracy of vertebral fracture assessment with densitometry compared to radiography in clinical practice. Osteoporos Int 2006; 17:281.
  34. Hospers IC, van der Laan JG, Zeebregts CJ, et al. Vertebral fracture assessment in supine position: comparison by using conventional semiquantitative radiography and visual radiography. Radiology 2009; 251:822.
  35. Rosen HN, Vokes TJ, Malabanan AO, et al. The Official Positions of the International Society for Clinical Densitometry: vertebral fracture assessment. J Clin Densitom 2013; 16:482.
  36. Baim S, Binkley N, Bilezikian JP, et al. Official Positions of the International Society for Clinical Densitometry and executive summary of the 2007 ISCD Position Development Conference. J Clin Densitom 2008; 11:75.
  37. Writing Group for the ISCD Position Development Conference. Nomenclature and decimal places in bone densitometry. J Clin Densitom 2004; 7:45.