Experimental and Finite Element Strain Analysis of the Rat Ulnar Loading Model –correlations with Woven Bone Formation

INTRODUCTION: The biological response of bones to a mechanical stimulus depends on signal transduction pathways that are not fully elucidated. A wide variety of animal models have been developed in order to examine these signal transduction pathways, one of which is the ulnar compression model. We have used the rat ulna model to study woven bone formation (bone adaptation) in response to fatigue loading (mechanical stimuli). On application of compressive loads, bending of the ulna due to its inherent curvature results in peak compressive and tensile strains on the bone surfaces, next to the periosteum. As the periosteal cells can directly induce bone formation, we hypothesized that the periosteal bone formation and increased bone mineral content would be related to the peak strains on the bone surfaces. In this study, we use finite element analysis validated with strain gage studies to relate ulnar surface strains to the pattern of bone formation.