Bone Abstracts

Vertebral fractures (VF) in adults are the most common osteoporotic fracture, are powerful predictors of future fracture risk (hip X2; spine X5) and their prevalence increases as bone mineral density (BMD) declines. The most common imaging method for diagnosis is spinal radiography, but they can be identified fortuitously also on other imaging techniques performed for various clinical indications.¹ Midline reformations of multi-detector CT (MDCT) scans of thorax and abdomen are particularly sensitive to identify VF.^1,2 There is underreporting of VF in adults^3,4 which stimulated the Vertebral Fracture Initiative of the International Osteoporosis Foundation (http://www.iofbonehealth.org/vertebral-fracture-teaching-program). For assessment of VF grading the semi-quantitative method (SQ) method is most widely applied.⁵ Vertebral fracture assessment (VFA) from DXA images is being used increasingly in adults with improvement in spatial resolution to 0.35 mm (6).

In children the epidemiological study of VF is much less extensive and relation to low BMD less clearly defined.⁷ VF may occur in children in relation to trauma⁸ and in various diseases and therapies which compromise bone strength. Spinal radiographs are the most common imaging technique used to identify VF in children and studies applying the SQ method of grading have indicated the prevalence is higher than previously perceived.⁹ This might in part be that clinicians have been reluctant to perform spinal radiographs because of the high dose of ionising radiation involved (500–600 microSv for lateral projection).¹⁰ DXA VFA has several advantages with the entire spine being depicted on a single image, the X-ray beam being parallel to the vertebral endplates, so avoiding the biconcavity of endplates (‘bean can’ effect) caused by the divergent X-ray beam in radiographs and most importantly a low radiation dose (3–10 microSv).¹⁰ Single (SE) and dual-energy (DE) VFA images are obtained, but differently between scanner manufacturers; simultaneously in a single pass with Lunar General Electric (Madison, MI, USA) and separately by Hologic (Bedford, MA, USA). Former has advantages in children with DE images obtained more rapidly. In adults DE images are superior to SE images to visualize the thoracic vertebrae. An initial report in 2007 of DXA VFA in children was disappointing,¹¹ but further improvements in image quality give VFA the potential for routine application to identify VF in children.

References: 1. Link TM et al. Eur Radiol 200 15 (8) 1521–1532.

2. Williams AL et al. Eur J Radiol 2009 69 (1) 179–183.

3. Gehlbach S et al. Osteoporos Int 2000 11 577–582.

4. Delmas PD et al. J Bone Miner Res 2005 20 (4) 557–563.

5. Genant HK et al. J Bone Miner Res 1993 8 (9) 1137–1148.

6. Diacinti D et al. Calcif Tissue Int 2012 91 (5) 335–342.

7. Rauch F et al. ISCD 2007 Pediatric Official Positions. J Clin Densitom 2008 11 (1) 22–28.

8. Roche C & Carty H. Pediatr Radiol 2001 31 (10) 677–700.

9. Halton et al. of Canadian STOPP Consortium. J Bone Miner Res 2009 24 (7) 1326–1334.

10. Damilakis J et al. Eur Radiol 2010 20 (11) 2707–2714.

11. Mäyränpää MK et al. Bone 2007 41 (3) 353–359.