Anatomical Variation of Human Bone Bioapatite Crystallography and Comparison to Hydroxyapatite

This systematic investigation of bioapatite, the mineral component of human bone, aims to characterize its crystallographic state, including lattice parameters and average crystallite size, and correlate these values with respect to anatomical position (bone function), physicality, and age. In bone sample sets from three different human adults, anatomical variation of crystallographic lattice parameters and average crystallite size were observed.In general, the observed bioapatite lattice parameters among all analyzed human bones in this study are larger compared to those of stoichiometric hydroxyapatite (HAP) lattice parameters. Across all analyzed samples, the relative standard deviation of the mean a(=b) cell lattice parameter (unit cell edge-length) varies more (0.032%) than it does for the c lattice parameter (0.018%). Average crystallite size (average coherent diffracting domain size) in the c-direction was equal to approximately 25 nm, ranging among the analyzed 18 bone samples from about 20-32 nm, varying more than crystallite size in the a,b-direction (~8-10 nm). Neither lattice parameters nor average bioapatite crystallite sizes appeared to be correlated with bone function and the associated mechanical stresses but may be correlated to age. The results of this study prompt the need for large-scale systematic study of human bone mineral structure with consideration of different influencing bone traits, including but not limited to anatomical position, individual physical constitution, and age.