A Computer-simulation Model Relating Bone-cell Metabolism to Mechanical Adaptation of Trabecular Architecture

Abstract

The architecture of trabecular bone is thought to be an optimal mechanical structure in terms of maximal strength and stiffness, and minimal weight. The structural optimality seems to be maintained during growth and adulthood by adaptation of mass and structure through a relationship with actual mechanical usage. The formation and maintenance of the architecture is realized by bone-resorbing osteoclasts and bone-forming osteoblasts, the effector cells of bone metabolism. Hence, a feedback regulatory mechanism between external load and metabolism must exist. We have developed an FEA-based computer-simulation model to study explanations for the workings of such regulatory schemes (1: Huiskes et al. (2000), Nature, 404, 704-706). The model is based on a mechanosensory function of osteocytes, which are thought to react to the local strain-energy-density rate in the mineralized tissue, produced by dynamic external loading on the bone. As an effect of this signal, osteocytes are assumed to transfer an osteoblast recruitment stimulus to the surface, enhancing bone formation. Osteoclasts are assumed to resorb bone that is disused or damaged, in a spatially random manner. This model provides an explanation for the maintenance and adaptation of trabecular bone architecture as an optimal structure. In this article, the mathematical background of the model is specified.