Morphologic detail of aging bone in human vertebrae.

To investigate aging bone structure of humans--here, in the lumbar vertebral bodies-requires methodologies that have sufficiently high resolving power yet still have sufficient width and depth of field. No clinical imaging method can come close to meeting the first requirement, leading to the disadvantage of being limited to postmortem studies. Few microscopic methods meet the second and third requisites. The three-dimensional (3D) images of bone in this article were obtained using deep-field 3D optical imaging, X-ray imaging, and scanning electron microscopy (SEM) of macerated plane parallel slices. The study of bone as a 3D object provides a different perspective from conventional two-dimensional images, and enriches our understanding of how modeling and remodeling processes regulate bone structure and connectivity. The study of ultraflat block surfaces by quantitative back-scattered electron imaging permits acquisition of data on mineral distributions and densities within a very thin layer (a continuous and perfect very thin section) in the block face. With this information, bone can be viewed as a spectrum of tissue types varying in degree of mineralization.