Shortcomings of DXA to assess changes in bone tissue density and microstructure induced by metabolic bone diseases in rat models.
The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative computed tomography, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.


BACKGROUND
The aim of this study is to demonstrate the deficiencies of dual-energy X-ray absorptiometry (DXA), compared with quantitative CT, to reflect and differentiate between changes in bone mineral density and microstructure that contribute to a well-defined finding of altered skeletal state for both osteoporosis and renal osteodystrophy induced by chronic renal insufficiency.


METHODS
Forty-five female Sprague-Dawley rats were divided into three equal groups: control, ovariectomy, and nephrectomy. Following euthanasia, femurs were excised, divided into diaphyseal and distal metaphyseal sections, and subjected to DXA and micro-CT imaging and mechanical testing.


RESULTS
Ovariectomy does not affect the structural and mechanical properties of cortical bone material, but partial nephrectomy does adversely affect these properties. Both are verified by DXA and micro-CT imaging and mechanical testing. Meanwhile, nephrectomy does not affect trabecular bone microstructure or equivalent density, yet ovariectomy affects the trabecular microstructure. DXA is unable to detect changes in trabecular bone microstructure in relation to changes in their mechanical properties.


CONCLUSIONS
Dual energy X-ray absorptiometry measures the average bone mineral content in a 2D projected area and cannot differentiate whether the changes occur in the bone microstructure or equivalent bone tissue density. In contrast, micro-CT provides an accurate measurement of the changes in both equivalent bone tissue mineral density and microstructure for cancellous and cortical bone.
Orthopedic Biomechanics Laboratory, Beth Israel Deaconess Medical Center and Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA.
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A
Nazarian
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Cory
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R
Müller
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Snyder
D015502:Absorptiometry, Photon / Q000592:standards*; D000818:Animals; D015519:Bone Density; D001851:Bone Diseases, Metabolic / Q000000981:diagnostic imaging / Q000503:physiopathology*; D001842:Bone and Bones / Q000000981:diagnostic imaging; D005260:Female; D023421:Models, Animal; D009392:Nephrectomy; D010024:Osteoporosis / Q000000981:diagnostic imaging / Q000503:physiopathology; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D051437:Renal Insufficiency / Q000000981:diagnostic imaging / Q000503:physiopathology; D014057:Tomography, X-Ray Computed / Q000592:standards*