In this study, based on the measurements of intracortical vascular canal structure, we investigated the disuse effect on local O2 supply in the cortical bones of growing rats. Hindlimb disuse was produced by unilateral sciatic neurectomy (SN) at 4 weeks age. The canal network structures within tibial cortical bone were evaluated in 8- and 12-week-old rats undergoing SN or no treatment (control) by synchrotron radiation micro-CT. Additionally, we developed an intracortical network model by combining the imaged-based canal network with a bone matrix containing theoretical lacunar-canalicular network, and determined the distribution of O2 concentration in bone tissue numerically. In the control bone, canal network was reduced with growth, resulting in decreased blood flow and averaged O2 concentration and increased spatial heterogeneity in tissue O2 concentration. Disuse reduced the canal network, leading to a lower flow rate, lower average O2 concentration and higher heterogeneity of O2 concentrations. However, the rarefaction of the canal network with growth was smaller under the disuse condition, and accordingly, the flow rate, the average O2 concentration and the heterogeneity of O2 concentrations remained stable. In particular, although the fraction of the canal volume was smaller, the densities of canal segments and bifurcation points under disuse condition tended to be higher than those of the control bone. The heterogeneity of O2 concentration was lower. Our results indicated that the disuse may lead to more uniformity in the canal network structure and thereby uniform O2, possibly contributing to O2 supply efficiency.
Keywords: Cortical bone; Disuse; Lacunar–canalicular network; Numerical simulation; O2 supply; Vascular canal network.