Abstract:
Intracortical canals are a major contributor to cortical bone porosity and influence its mechanical response. Canal
networks act as stress concentrators and the magnitude of which depends on the size and spatial distribution of
canals. In the present study, we investigated site-dependent variation in intracortical canal network morphological indices and their effect on the mechanical response of bone. For this, mid-diaphysis of rat tibia bones were
scanned using high-resolution micro-CT and morphological indices were measured for four main anatomical
sites-anterior, posterior, medial and lateral. Further, a micro-finite element (μFE) model was developed to
quantify the stress concentration regions in different cortices. The fracture risk was assessed using an effective
strain approach. Results show that canal porosity, canal orientation and canal length are site-dependent whereas
canal diameter and canal number density are independent of the site. The lateral cortex has significantly higher
porosity compared to the posterior cortex (p < 0.05). The orientation of canals is found significantly different
between endosteal and periosteal regions for anterior and medial quadrants. Canals are inclined at higher angles
with bone axis in the endosteal region as compare to the periosteal region. The μ-FE results show that the regions
with higher effective strain are concentrated around the canals. Further, failed element volume per unit bone
volume is found highest for medial cortex whereas lowest for posterior cortex. The higher failed volume is
associated with more radial canals in the medial cortex as compare to other cortices. The linear regression
analysis shows that the volume of overstrained elements strongly depends on canal orientation (R2 = 0.73, p <
0.0001) and canal porosity (R2 = 0.61, p < 0.0001). The findings from this study suggest that along with vascular
canal porosity, canal orientation and canal diameter can further improve the bone fracture risk assessment
