Longitudinal Changes in Apparent Young Modulus and Bone Volume by Denervation: Subject-Specific Finite Element Analysis Considering Heterogeneous Tissue Properties

This study aimed to predict bone fracture risk during skeletal unloading through a subject-specific finite element (FE) analysis considering heterogeneous tissue modulus. Twelve male and 14 female Institute of Cancer Research (ICR) mice (6 weeks old) were allocated into skeletal unloading and normal groups (each gender in both groups). The right hind tibia of each mouse in the skeletal unloading groups was subjected to sciatic neurectomy (denervation) and was scanned before and at 2 week after denervation using µCT. Bone volume (BV) and the distribution of Young's moduli (E) were measured from µCT images. The apparent modulus (Eapp) was calculated using the subject-specific (FE) analysis considering the heterogeneous tissue modulus derived by Hounsfield unit. At 2 weeks after denervation, the Eapp was significantly decreased in both genders (p < 0.05), and the distributions of E differed between the skeletal unloading and normal groups. However, the BV in females was significantly decreased (p < 0.05), while that in male was unchanged (p > 0.05). These results indicated that skeletal unloading reduced bone strength, leading to increased bone fracture risk.