ASSESSMENT OF MECHANICAL PROPERTIES OF HUMAN OSTEON LAMELLAE EXHIBITING VARIOUS DEGREES OF MINERALIZATION BY NANOINDENTATION
Résumé
Background: Cortical bone analysis has been investigated at the macroscopic level with mechanical tests and imaging techniques, but few studies have been done at the microscopic level (osteons). The purpose of this study is to measure the elastic modulus of thick lamellae of osteons exhibiting different degrees of mineralization. This study aims to provide clinicians with a better understanding of bone remodeling and help in assessing the different stages of bone healing. Methods: Six femoral human samples (5 mm × 5 mm × 5 mm) were cut transversally along the length of a human femur. Scanning electron micrographs were produced to reflect the composition of the microstructure. Three types of osteons were selected: white (high mineralization), gray (intermediate mineralization), and dark (low mineralization) osteons. Nanoindentation tests were performed on three locations of the thick lamella located in the middle of each osteon. The mechanical test induced three holdings and unloadings with a constant holding of 10 s. The maximal force was 2500 μN, which induced a maximal depth of about 400 nm. Results: Elastic modulus (E) and hardness (H) for the white (N = 61), gray (N = 17), and dark (N = 39) osteons were E white = 21.30 GPa ± 3.00 GPa and H white = 0.55 GPa ± 0.15 GPa, E gray = 19.27 GPa ± 1.78 GPa and H gray = 0.41 GPa ± 0.09 GPa, and E dark = 12.95 GPa × 2.66 GPa and H dark = 0.30 GPa ± 0.10 GPa, respectively. The variation of elastic properties within a lamella was approximately 2.6 GPa, depending on the level of mineralization. Conclusions: These results demonstrate the inhomogeneity of the lamella, suggesting that both the orientation of collagen fibers and the degree of mineralization may vary within the lamella. Our study shows a large range of elastic properties and hardness, reflecting different degrees of osteon mineralization.
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