New Technique for Evaluation of Preferential Alignment of Biological Apatite (BAp) Crystallites in Bone Using Transmission X-ray Diffractometry

Two-dimensional quantitative analysis of point focus X-ray beam diffraction (XRD) was performed using a transmission optics system to examine the biological apatite (BAp) orientation in the femurs of an osteopetrotic (op/op) mouse and a normal mouse.The Mo K (wavelength: 0.07107 nm) was used as characteristic X-ray radiation as a substitute for conventional Cu K (wavelength: 0.15418 nm) radiation.At first a theoretical calculation concerning with X-ray absorption and peak resolution was performed, and subsequently X-ray diffraction measurements were carried out to confirm the usefulness of the transmission X-ray method by Mo K radiation.The distribution of the preferential orientation of the BAp c-axis was finally measured and calculated as an integrated intensity ratio of ( 002)/(310) in a plane roughly containing the bone longitudinal axis.The result resembled analysis from a conventional reflection X-ray diffraction method by Cu K radiation but this transmission optics system was more convenient for the screening of BAp orientation in bones without sectioning.The distribution of the preferential alignment of the BAp c-axis was measured as a function of the longitudinal axis in the femurs of a 12week mutant osteopetrotic (op/op) mouse and a littermate control mouse.The preferential alignment of the BAp c-axis along the longitudinal direction is much lower in the op/op mouse than in the control mouse in all analytical positions.The transmission optics system using Mo K radiation in this study provides a fuss-free method for analyzing BAp orientation as a bone quality parameter.