Haversian system of compact bone and comparison between endosteal and periostealsides using three-dimensional reconstructionin rat

The current model of compact bone is that of a system of Haversian (longitudinal) canals connected by Volkmann's (transverse) canals. Models based on either histology or microcomputed tomography do not accurately represent the morphologic detail and microstructure of this system, especially that of the canal networks and their spatial relationships. The aim of the present study was to demonstrate the morphologic pattern and network of the Haversian system and to compare endosteal and periosteal sides in rats using three-dimensional (3D) reconstruction. Ten Sprague-Dawley rats aged 8-10 weeks were used. The femurs were harvested from each rat and fixed, decalcified with 10% EDTA-2Na, serially sectioned at a thickness of 5 mm, and then stained with hematoxylin and eosin. The serial sections were reconstructed three-dimensionally using Reconstruct software. The Haversian canals in the endosteal region were found to be large, highly interconnected, irregular, and close to neighboring canals. In contrast, the canals in the periosteal region were straight and small. This combined application of 3D reconstruction and histology examinations to the Haversian system has confirmed its microstructure, showing a branched network pattern on the endosteal side but not on the periosteal side.