Micromechanical testing of bone trabeculae-potentials and limitations

The mechanical properties of bone are studied mostly for reasons related to skeletal pathology. However, bone is also very interesting from a material science perspective because it is a natural hierarchical composite material. The mechanical properties of bone depend on both the structural arrangement and the properties of the constituting materials, namely the organic polymer collagen and the inorganic salt apatite. While the mechanical properties of bone samples at the macroscopic scale are measured routinely, mechanical tests on micrometer-sized specimens are still at development stage. In this paper, protocols for measuring the elasticity of cancellous bone trabeculae are reviewed. The published values for the elastic modulus of trabeculae vary between 1 GPa and 15 GPa. Reasons for this broad range of values may be located in the intrinsic difficulties of preparing, handling, and testing inhomogeneous, anisotropic and asymmetric micro-samples. We discuss the major error sources in existing testing procedures and suggest potential strategies to enhance their performance.