Mapping the 3D orientation of nanocrystals and nanostructures in human bone: Indications of novel structural features
Tilman A. Grünewald, Marianne Liebi, Nina Kølln Wittig, Andreas Johannes, Tanja Sikjær, Lars Rejnmark, Zirui Gao, Martin Rosenthal, Manuel Guizar‐Sicairos, Henrik Birkedal, Manfred Burghammer
Abstract
Bone is built from collagen fibrils and biomineral nanoparticles. In humans, they are organized in lamellar twisting patterns on the microscale. It has been a central tenet that the biomineral nanoparticles are co-aligned with the bone nanostructure. Here, we reconstruct the three-dimensional orientation in human lamellar bone of both the nanoscale features and the biomineral crystal lattice from small-angle x-ray scattering and wide-angle x-ray scattering, respectively. While most of the investigated regions show well-aligned nanostructure and crystal structure, consistent with current bone models, we report a localized difference in orientation distribution between the nanostructure and the biomineral crystals in specific bands. Our results show a robust and systematic, but localized, variation in the alignment of the two signals, which can be interpreted as either an additional mineral fraction in bone, a preferentially aligned extrafibrillar fraction, or the result of transverse stacking of mineral particles over several fibrils.