Site Specificity of Bone Architecture Between the Distal Radius and Distal Tibia in Children and Adolescents: An HR-pQCT Study

High-resolution quantitative computerized tomography permits evaluation of site specific differences in bone architecture. The purpose of this study was to compare bone architecture between distal radius and distal tibia. We present bone architecture at the distal radius and distal tibia in 151 male and 172 female participants, as follows: total bone area (mm(2)), total bone density (mg HA/cm(3)), trabecular bone density (mg HA/cm(3)), cortical bone density (mg HA/cm(3)), cortical thickness (μm), trabecular number (1/mm), trabecular thickness (μm), and trabecular separation (μm). We evaluated differences in and correlations between bone variables (absolute values) across sites. We calculated individual z scores and used regression to assess discordance between sites. In pubertal and postpubertal male and female participants, absolute values of total bone area, cortical bone density, cortical thickness, and trabecular thickness were significantly lower at the radius compared with the tibia (P < 0.01). Absolute values for trabecular bone density were significantly lower at the radius compared with the tibia in postpubertal male and female participants (P < 0.01). Absolute values for trabecular separation was significantly lower at the radius compared with the tibia in pubertal female participants (P < 0.01). Bone architecture was moderately to highly correlated between sites (r = 0.34-0.85). There was discordance between z scores at the radius and tibia within male participants (pubertal R (2) between 36 and 64%; postpubertal R (2) between 22 and 77%) and female participants (pubertal R (2) between 10 and 44%; postpubertal R (2) between 25 and 62%). In conclusion, it is vital to evaluate bone architecture at the specific skeletal site of interest.