Abstract
Abstract Lumbar and subcapital whole body Dual-energy X-ray absorptiometry (DXA) scans are recommended for monitoring bone mass (BMD) in boys with DMD. Complications of DMD and corticosteroids include: obesity, contractures, loss of ambulation and fractures contributing to errors in subcapital DXA accuracy and reproducibility. DXA scans in DMD boys frequently contain technical artifacts influencing BMD interpretation. We report the frequency of positioning and acquisition issues influencing subcapital DXA scan interpretation of DMD boys. Subcapital DXA scans (n = 189) of 64 DMD boys on Deflazacort were reviewed for motion artifact, contractures, obesity, suboptimal positioning, missing body segments, and orthopaedic hardware. Artifact-free scans with optimal positioning were obtained in the 64 boys when ambulatory, age 8.1 ± 2.2, BMI 16.7 ± 2.3 and 18.9 ± 3.9% subcapital body fat. 25% of the boys (16/64) when non-ambulatory, age 16.1 ± 2.1 had scans with motion artifact. 47% of the boys (30/64) developed contractures precluding optimal positioning. 14% of the boys (9/64) age 17.0 ± 2.5 when non-ambulatory, BMI 28.3 ± 4.0 and 52.8 ± 5.9% subcapital body fat had scans missing body segments; 6/9 missing digits, 1/9 both elbows, 1/9 ulna and 1/9 foot. 8% of the boys (5/64) age 17.1 ± 2.8 had hardware which increased BMD (g/cm2) from 8% to 124% (52.3 ± 50.6%) from their previous hardware-free scan. In general there are no technical issues with subcapital DXA in young ambulatory boys with DMD. As boys with DMD age, subcapital DXA scans contain a higher frequency of scan acquisition and interpretation errors from multiple sources. Attention to positioning for scan acquisition and analysis of scans in array mode may limit the potential for reproducibility and accuracy errors. Despite technical limitations DXA can identify boys with high fat mass and fracture risk. Future studies should compare the diagnostic yield of serial pQCT to DXA, to avoid the technical pitfalls of subcapital DXA.
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