Assessment of spine bone mineral density in juvenile idiopathic arthritis: impact of scan projection.
Although children with juvenile idiopathic arthritis (JIA) are at risk for vertebral fractures, recent conventional posterior-anterior (PA) spine dual-energy X-ray absorptiometry studies reported minimal areal bone mineral density (aBMD, g/cm2) deficits. Width-adjusted BMD (WA-BMD, g/cm3) represents the bone mineral content (BMC) from the lateral projection, excluding the dense cortical spinous processes, divided by the estimated vertebral body volume based on paired PA-lateral bone dimensions. Therefore, WA-BMD may be more sensitive to JIA effects on the predominantly trabecular vertebral body. Age- and sex-specific Z-scores for spine aBMD and WA-BMD were generated in 84 JIA subjects compared with healthy controls, aged 5-21 yr. JIA was associated with lower mean WA-BMD Z-scores (-0.78, 95% CI: -1.03, -0.53; p<0.001) and aBMD Z-scores (-0.26, 95% CI: -0.49, -0.02; p<0.05), compared with controls. WA-BMD Z-scores were significantly lower than aBMD Z-scores in JIA (p<0.001). A significant JIA by age interaction (p<0.001) indicated that the magnitude of the difference between WA-BMD and aBMD Z-scores was greater in younger subjects. In conclusion, WA-BMD may be more sensitive to disease effects in children because it selectively measures the trabecular-rich vertebral body and is independent of growth-related changes in BMC of the dense spinous processes.
Dubner
Sarah E
SE
University of Pennsylvania School of Medicine, Philadelphia, PA, USA.
Shults
Justine
J
Leonard
Mary B
MB
Zemel
Babette S
BS
Sembhi
Harjeet
H
Burnham
Jon M
JM
D015502:Absorptiometry, Photon / Q000379:methods*; D000293:Adolescent; D000328:Adult; D001171:Arthritis, Juvenile / Q000000981:diagnostic imaging*; D015519:Bone Density; D016022:Case-Control Studies; D016009:Chi-Square Distribution; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D008159:Lumbar Vertebrae / Q000000981:diagnostic imaging*; D008297:Male