HOMOGENIZATION THEORY AND DIGITAL IMAGING - A BASIS FOR STUDYING THE MECHANICS AND DESIGN PRINCIPLES OF BONE TISSUE

Bone tissue is a complex multilevel composite which has the ability to sense and respond to its mechanical environment. It is believed that bone cells called osteocytes within the bone matrix sense the mechanic al environment and determine whether structural alterations are needed . At present it is not known, however, how loads are transferred from the whole bone level to cells. A computational procedure combining rep resentative volume element (RVE) based homogenization theory with digi tal imaging is proposed to estimate strains at various levels of bone structure. Bone tissue structural organization and RVE based analysis are briefly reviewed. The digital image based computational procedure was applied to estimate strains in individual trabeculae (first-level microstructure). Homogenization analysis of an idealized model was use d to estimate strains at one level of bone structure around osteocyte lacunae (second-level trabecular microstructure). The results showed t hat strain at one level of bone structure is amplified to a broad rang e at the next microstructural level. In one case, a zero-level tensile principal strain of 495 mu E engendered strains ranging between -1000 and 7000 mu E in individual trabeculae (first-level microstructure). Subsequently, a first-level tensile principal strain of 1325 mu E with in an individual trabecula engendered strains ranging between 782 and 2530 mu E around osteocyte lacunae. Lacunar orientation was found to i nfluence strains around osteocyte lacunae much more than lacunar ellip ticity. In conclusion, the computational procedure combining homogeniz ation theory with digital imaging can provide estimates of cell level strains within whole bones. Such results may be used to bridge experim ental studies of bone adaptation at the whole bone and cell culture le vel. (C) 1994 John Wiley and Sons, Inc.