X-RAY-DIFFRACTION AND POLARIZING OPTICAL MICROSCOPY INVESTIGATION OF THE STRUCTURAL ORGANIZATION OF RABBIT TIBIA

X-ray diffraction and polarized optical microscopy investigations were carried out on thin sections of rabbit tibia in order to study the mo rphological. organization of the structural components of this tissue, which often is utilized to test bone response to implants. In the opt ical microscope, the lateral face as well as the lateral portion of th e caudal face exhibit a lamellar structure with an alternation of dark and bright lamellae running parallel to the long axis of the tibia. I n contrast, both in the medial face and in the medial portion of the c audal face there are numerous osteonic structures. In spite of the com plexity of this morphological organization, the results of small- and high-angle X-ray diffraction analyses indicate that the structural rel ationship between collagen fibrils and inorganic crystals is quite sim ilar to that observed in single osteons and allows evaluation of the o rientation of the two main structural components. Both collagen fibril s and apatitic crystallites are preferentially oriented parallel to th e long axis of the tibia. The degree of orientation is greater in the thickness than in the plane of the lamellae, suggesting that collagen fibrils and inorganic crystallites lie preferentially in the plane of the lamellae, where they follow an oblique course. The degree of orien tation of the apatitic crystallites is higher in the lateral face than in the medial and caudal faces, in agreement with the optical microsc opic images. The results provide information that must be taken into a ccount when evaluating the structural modifications of bone due to the insertion of a prosthetic device. (C) 1998 John Wiley & Sons, Inc.