A refined Mechanostat Model of Bone Transformation

Abstract

Bone is a living tissue that shows adaptation in shape and structure, if the prevailing load conditions are significantly changing. One example is the loss of bone mass of astronauts under microgravity, which can already be measured after missions of medium duration. Transformation laws derived from experimental data have been able to explain morphologic adaptation of the microstructure of trabecular bone to external loads. In the present work the focus is on the hypothesis, that the same transformation law is able to govern shape adaptation and adaptation of microstructure depending only on the different load pattern. This work is an effort to concile the famous phenomenologic mechanostat model of Frost [Frost 2000] with a mechanistic approach of Huiskes and his co-workers [Huiskes, 2000]. The present in-silico study has shown that the mechanostat scheme based on basic mechanistic principles can engender diverse load bearing structure depending on the different needs: the epiphysis collecting loads from different directions prefers trussy structure, the torsion and axial load bearing shaft prefers tubular structure. That is similar to the findings in bone with the difference, that the “trussy” structure in epiphysis is much finer, namely spongy. That seems to be a scaling problem to be analysed in the future.