A comprehensive methodology to assess human bone transversal toughness based on macroscopic specimens, the compliance method, and 3D bio-faithful numerical simulations

This study proposes a method for assessing the transverse toughness of human long-bone cortical tissue. The method is based on a three-point bending test of pre-notched femur diaphysis segments, post-processed using the compliance method coupled with numerical simulations. Given the cracking nature of bone and if cracking processes remain confined to the crack tip, it is assumed that the compliance method can be used. Numerical simulations are based on a bio-faithful 3D reconstruction of the bones tested and a detailed consideration of the boundary and loading conditions of the mechanical test. The resulting toughness values obtained on embalmed bones range from G_c=4.3 to 7.1 N/mm. The assumptions made, the biofidelity of the simulations, and the ability of the method to determine an intrinsic toughness value of cortical bone, considered a heterogeneous material, are discussed. Although related to embalmed bones, and considering the limitations this state can induce, the toughness values obtained are consistent with data from the literature. Due to the larger specimen size, they are also more realistic, ensuring a complete description of the material's crack extension resistance curve. They mainly characterize the medial and lateral quadrants of the bone transversal section. The study concludes that the proposed method provides a robust approach for assessing bone transversal toughness.