Study on the mechanical properties of hard tissues using nanoindentation tests

点击翻译按钮获取中文摘要

The mechanical properties of cortical bone are a consequence of the interaction between the mineral and collagen components. Small variations in the amount of mineral present in a section of bone can have a large influence on its mechanical properties. Studies have shown the correlations between Vickers microhardness and mineral content, and Vickers microhardness and elastic modulus using three-point and four-point bending tests. However, the precise nature of statistical relationship has yet to be established. Nanoindentation, which evolved from Vickers microhardness test, allows for measurement of mechanical properties of cortical bone at the nanometer scale. The nanoindentation technique has been applied to estimate mechanical properties of bone at a microscopic length scale, overcoming the limitations of traditional mechanical tests for small specimens. In this study, mechanical properties of bovine and porcine femoral cortical bone were measured by nanoindentation. For bovine plexiform and Haversian bone specimens, the averages for the longitudinal elastic moduli were 17.3±5.7 GPa and 10.6±5.1 GPa, respectively. The average elastic modulus measured for porcine plexiform bone was 13.7±4.5 GPa, and the average for porcine Haversian bone was 8.2±3.3 GPa. The hardness showed a tendency similar to the elastic modulus among all types of bone tissues. Next, the relationships between mechanical properties measured by nanoindentation and volumetric Bone Mineral Density(vBMD) measured by peripheral Quantitative Computed Tomography(pQCT) in femoral cortical bone from a variety of ages of rats were investigated. The specimen of rat cortical bone used here was Haversian bone. Experimentally measured elastic modulus correlated with vBMD(r=0.62〜0.76). It was found that a good correlation also existed between hardness and vBMD(r=0.85〜0.90) of bone tissues.