Mechanical Properties of Individual Trabeculae in a Physiological Environment

Martin Frank, Dorothee Marx, Dieter H. Pahr, and Philipp J. Thurner

Keywords

tensile test, hydration, bone fracture risk assessment, postyield behaviour, local strain, structural influence

Abstract

Reliable mechanical properties of trabecuale are needed at the tissue-level for prediction of mechanical behavior of the overall trabecular structure using Finite element analysis (FEA). The aim of this study was to develop a set-up to test trabeculae in tension in a close to physiological environment, and to determine reliable tissue-level properties.Ten bovine trabeculae were tested until failure. Tissue-stress can only be indirectly determined, since it is based on a defined cross-sectional area. Different geometrical assumptions for the cross-section were compared. The mean tissue Youngs modulus, based on the assumption of an elliptical cross-sectional area, was 9.9 ± 3.4GPa, the mean tissue ultimate tissue strain 9.8 ± 3.9%. Back-calculation of the tissue Youngs modulus by means of FEA illustrated a significant reduction to 8.2 ± 2.4GPa (p < 0.001). However, with simple geometric assumptions, it is possible to estimate a reasonable upper and lower boundary for the tissue Young’s modulus. Full-field strain measurements were done to detect localization of strain. It was shown that local strain peaks occur already early after yielding, with a local strain at fracture of 19.7 ± 6.6%. These findings clearly show that individual trabeculae can withstand much higher tissue strains as previously reported.

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