The morphology of bone mineral crystals.

This work examines two aspects of bone structure, namely the basic size and form of the bone mineral crystallites, and the three-dimensional orientation of these crystals within the whole bone. X-ray diffraction, and both bright and dark field electron microscopy of bone, strongly suggest the mineral crystals to be irregular plate-like forms, approximately 5. 0nm thick, with a variable maximum dimension; these methods also find no significant difference in the shape, size or composition of crystals in fixed and unfixed rabbit femur. The (002) diffracted beam is used to produce dark field images, the measured c-axial length distributions have mean values of 32.6nm, 36.2nm, and 32.4nm for rabbit, ox and human bones respectively. Using the x-ray method of line broadening, it is shown that c-axial measurements consistent with those of the dark field method are produced, provided that lattice strain is accounted for in the theoretical formulation. The x-ray method is used to examine crystal maturation. Results indicate that the crystals of rabbit bone increase in size and perfection from birth until a stable situation is attained after approximately seven weeks, when the crystals exhibit a mean c-axial length of approximately 34.0nm, and a maximum compressive or tensile lattice strain of 0.3% in the (002) direction. An x-ray goniometer is designed and constructed, and used to produce quantitative (002) pole figures of small samples of secondary type human, and primary type ox bones. Results show secondary bone to have a major fibre axis aligned on average with the femoral axis, and the degree of orientation shows rotational symmetry about this axis. Primary bone exhibits the same major axis, but also shows a planar orientation along the laminar direction. The results of this work, their significance, and suggestions for future developments are discussed in the final chapter