Biological and Micromechanical Approaches to Single Osteon of Equine Tibia

Abstract

In the previous paper, the relationship between the biological characteristics in micrometer sizes at cross section and the mechanical ones in millimeter sizes to long axis for equine tibial diaphyses were investigated. In equine tibial diaphyses, there were resultingly verified the distributions of osteons that were reinforced multilayered microstructures adapting to compressive load support dependent on both the placement of osteocytes and the orientation of collagen fibers in micrometer sizes or under. Therefore, in the present paper, the relationship between the biological characteristics at cross section and the mechanical ones to long axis for equine tibial diaphyses were investigated in micrometer sizes. Bone blocks in 10mm thick were cut off from front and rear parts in cross section of right tibial diaphysis of 4 grown-up thoroughbred equines. Each single osteon column, so as to be 200μm in diameter and 100μm in height, was dug up out of the bone blocks by micromechanical processes using a microscope. Static microcompression test was carried out and initial stiffness from the origin to strain 2% and maximal stress occurring at strain 10% were calculated from stress-strain curve for each single osteon. Furthermore, single osteons after testing was observed by microscopes. Consequently, both results of initial stiffness and maximal stress for single osteon were much greater in rear part than in front part in cross section of equine tibial diaphysis. So, it was proved that the reinforced structure by collagen fibers for compressive load support were formed at least single osteon level.