Scaling relations between trabecular bone volume fraction and microstructure at different skeletal sites

In this study, we investigated the scaling relations between trabecular bone volume fraction (BV/ TV) and parameters of the trabecular microstructure at different skeletal sites.Cylindrical bone samples with a diameter of 8. mm were harvested from different skeletal sites of 154 human donors in vitro: 87 from the distal radius, 59/69 from the thoracic/lumbar spine, 51 from the femoral neck, and 83 from the greater trochanter. μCT images were obtained with an isotropic spatial resolution of 26. μm. BV/. TV and trabecular microstructure parameters (TbN, TbTh, TbSp, scaling indices (< > and σ; of α and α_z), and Minkowski Functionals (Surface, Curvature, Euler)) were computed for each sample. The regression coefficient β was determined for each skeletal site as the slope of a linear fit in the double-logarithmic representations of the correlations of BV/. TV versus the respective microstructure parameter.Statistically significant correlation coefficients ranging from r= 0.36 to r= 0.97 were observed for BV/ TV versus microstructure parameters, except for Curvature and Euler. The regression coefficients β were 0.19 to 0.23 (TbN), 0.21 to 0.30 (TbTh), - 0.28 to - 0.24 (TbSp), 0.58 to 0.71 (Surface) and 0.12 to 0.16 (< α>), 0.07 to 0.11 (<. α_z>), - 0.44 to - 0.30 (σ;(α)), and - 0.39 to - 0.14 (σ;(α_z)) at the different skeletal sites. The 95% confidence intervals of β overlapped for almost all microstructure parameters at the different skeletal sites. The scaling relations were independent of vertebral fracture status and similar for subjects aged 60-69, 70-79, and >. 79. years.In conclusion, the bone volume fraction-microstructure scaling relations showed a rather universal character.