Simultaneous Presence of Growth and Remodeling in the Bone Adaptation Theory

Ahmedi Ahmedi

doi:10.3844/ajassp.2009.352.360

Abstract

Mechanical forces acting on bone during growth affect their final shape and strength. Mechanoregulation of bone growth is maybe recognized in embryogenesis, and also in the adaptation of the adult skeleton to changes in mechanical loading. By combining equations describing bone remodeling and growth with an iterative finite element analysis, a computational model to simulate the simultaneous effects of bone remodeling and bone growth was proposed in this study. Strain-energy density was assumed as mechanical stimulus of bone adaptation process. Negative exponential decay function over time was considered as metabolic growth rate. Based upon numeric results, the model shows an acceptable behavior under various modes of loading, e.g. altering in trabecula’s orientation or its thickness. This model also shows that by neglecting growth part in the adaptation model, a considerable error would result in both final density distribution and microstructural pattern of spongy bone.

Highlights

The development, growth, and remodeling of skeletal structures is a highly regulated process beginning with mesenchymal stem cells condensations in the early embryo and finishing with the homeostatic skeleton of the adult
It is widely accepted that both genetic and epigenetic factors determine the final shape and strength of the skeleton, and many authors have proposed an epigenetic role for mechanical forces[1,2,3]
In the adaptive elasticity theory, it is assumed that the rate of change in bone mass is correlated with the history of mechanical strain[5]

Summary

INTRODUCTION

The development, growth, and remodeling of skeletal structures is a highly regulated process beginning with mesenchymal stem cells condensations in the early embryo and finishing with the homeostatic skeleton of the adult. In a very recent effort, Vahdati and Rouhi proposed another modification on the Huiskes et al’s model[13] They included the effects of both microcracks and disuse on activation of resorption in one unifying formulation based on latest experimental findings besides considering cellular accommodation effect. Applied Sci., 6 (2): 352-360, 2009 on the adaptive elasticity theory by replacing volume fraction with free surface density in the constitutive equations[14] In another attempt, Rouhi et al incorporated a microcrack factor in their first model and showed that mechanical stimuli, and their rate and history are effective and at play in the bone remodeling process[15]. This positive slope represents modeling process (Fig. 1)[18]

MATERIALS AND METHODS

CONCLUSIONS

Findings

Redefining