Mechanical properties of individual trabeculae in a physiological environment

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.