Bone tissue is a composite material composed of hydroxyapatite (HAp) and collagen fiber. The interplanar spacing of HAp crystals can be measured using the X-ray diffraction method, and HAp crystal strain is calculated from the deformation of the interplanar spacing. Previous studies have shown that HAp crystal strain in cortical bone is almost proportional to the tissue strain in the bone axial and circumferential directions. The aim of this study is to measure the HAp crystal strain under tensile loading and the orientation of c-axis of HAp crystals in femoral trabeculae. The experiments in the study used the trabeculae specimens taken from the cancellous bone in a bovine femur. As a result, the c-axis of HAp crystals oriented to the longitudinal direction in the trabeculae. Furthermore, the HAp crystal strain increased with the tissue strain under tensile loading, and the HAp crystal strains were not uniform between the specimens.
