Figure 3. Whole bone structural and mechanical properties.
(A) Structural parameters of wild-type (+/+) and homozygous (−/−) femora at 8 weeks of age characterize reduced bone formation in CyPB-deficient mice (n = 9/genotype). Left, 3D reconstructions illustrate reduced trabecular and cortical bone volumes. Right, Trabecular parameters are decreased in homozygous (−/−) femora, including reduced bone volume (Tb BV/TV, p = 0.01), thickness (Tb Th, p = 0.04) and number (Tb N, p = 0.01). Cortical bone parameters of CyPB-deficient mice are also reduced, with reductions in cortical thickness (Ct Th, p = 0.003) and area (Ct Ar, p = 0.02). (B) Left, Representative load-displacement curve demonstrating differences between samples selected for median post-yield displacement. Right, CyPB-deficient femora are weaker in yield (Yd Load, p = 1.9×10−6), ultimate (Ult Load, p = 8.9×10−7) and failure loads (p = 2.1×10−5), with reduced stiffness (p = 0.001). Ppib −/− femora are also more brittle than wild-type femora, as demonstrated by decreased post-yield displacement (PYD, p = 0.001). Reduced toughness of Ppib −/− femora is evident by decreases in the elastic and plastic energy (E) values (p = 0.001 and 0.0003, respectively).