Potential and limitations of 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. The underlying remodeling processes are still under investigation. Remodeling laws derived from experimental data are able to explain morphologic adaptation of the microstructure of trabecular bone to external loads. However, the question whether such mechanistic algorithms can be transferable to the bone shape level is yet unaddressed. Clinical practice is full of bone morphing examples after surgery. The present paper uses the problem of ‘flexure neutralization’ to scrutinize if this transformation law as inherent part of a Frost-type mechanostat [Frost, 1987] could explain whole-bone adaptation. The present in-silico study has shown that a mechanostat scheme based on basic mechanistic principles can engender a shaft-like geometry in response to a loading regime that is typical for a long bone shaft. The Huiskes mechanostat mechanism seems to explain flexure neutralization more elegant than the phenomenologic approach in the work of Frost [Frost, 1990]. On the other hand it remains unclear under what assumptions mechanostat-like transformation could generate smooth periosteal surfaces.