Microarchitecture and morphology of bone tissue over a wide range of BV/TV assessed by micro-computed tomography and three different threshold backgrounds

The microarchitecture of bone both results from and in turn affects the remodelling process. Bone-specific surface, for instance, is one of these important microarchitectural parameters because remodelling is also considered to be a surface-mediated phenomenon (Berli et al.[1]). An understanding of these structural parameters across the widest possible range of porosity is essential to illuminating how bone reacts to disease, in different skeletal sites and in either its cancellous or cortical forms. 112 samples from an elephant femur were examined by micro-computed tomography (mu CT), 31 of which contained both mineralised and demineralised tissue. A critical factor in all scans is setting the correct threshold (with background the surrounding medium) and hence 3 different backgrounds were used: air, water and collagen. The effect of the 3 background thresholds on the physical characteristics of bone (BS/TV, BS/BV, TbSp, TbTh, D-mat, vs BV/TV) was then determined. The results showed that using a threshold set by the collagen background had a profound effect on the histomorphometry bone parameters when assessed by mu CT. However, the differences between air and water were not significant, suggesting that comparable data can be produced in a laboratory environment when scanning porous bone samples under either wet or dry conditions- counter to common belief. Determining which is more suitable, air or water, in laboratory and in clinical mu CT imaging is important to improve the quality and relevance of biomechanics research. The data with collagen as the threshold were illuminating as they showed that remodelling rates and the relative organic to mineral presence varied with BV/TV, concurring with some other recent studies [2,3,4].