Bone Abstracts

Additionally to the standard histomorphometric and pathohistologic evaluation, the transiliac bone biopsy sample from a patient can be further analyzed for additional information on structural and material characteristics. Under the term ‘new histology’, several non-destructive techniques and combinations thereof providing high spatial resolution have been introduced. In contrast to conventional histology, these techniques allow the characterization of structural, compositional as well as mechanical properties of the bone material. At its lowest level of hierarchical structure, bone is a nano-composite consisting of stiff mineral particles embedded in a soft organic matrix. The mineralized collagen fibril represents the basic building block. This level can be accessed by vibrational spectroscopic methods (Fourier Transform Infrared and Raman microspectroscopy). A level of hierarchy higher, these collagen fibrils form fibers in a more or less ordered arrangement (in lamellar or woven bone respectively), which can be described by polarized light microscopy, Raman microspectroscopy and scattering techniques like small-angle X-ray scattering (SAXS). At the microscopic scale of a sectioned sample, the bone structural units with their different mineral content can be visualized and quantified by backscattered electron imaging. The micro-porosity formed by the osteocyte–lacunar–canalicular network can be characterized in 3D by confocal laser scanning microscopy using rhodamine fluorescent stained bone tissue. The characteristics at all these hierarchical levels and their interplay are determinants of the mechanical properties as well as of the intrinsic resistance to fractures. The mechanical material properties can be measured by nano-indentation and acoustic microscopy. All these characteristics of bone provide information for fracture risk assessment and reflect the history of the bone turnover and mineralization processes. The deviations from normal in pathological conditions might contribute to differential diagnosis and support the understanding of pathophysiological mechanisms and the effects of treatment.

The power of these techniques for histologic analysis, which can be complemented by micro-CT regarding architectural quality, will be demonstrated by examples of specific diseases, including osteogenesis imperfecta and chronic kidney disease among others.

Disclosure: The author declared no competing interests.