Effect Of Microstructure And Bone Mineral Density On Mechanical Properties Of Cortical Bone

MicroCT has been widely used in bone studies with high resolution and the ability to observe the microstructure of a material without damage to the sample.The trabecular bone structure of cancellous bone is considered to be significantly correlated with the mechanical properties of cancellous bone,while the cortical bone structure is more compact,and the relationship between its microstructure and mechanical properties is not yet clear.The high-resolution microCT can accurately obtain the internal microstructure parameters of the cortical bone.Therefore,this technique can be used to study the influence of the microstructure parameters of cortical bone on its mechanical properties.In this study,10 bovine specimens with the size of 12mm×2mm×0.5mm are prepared from the anterior position of the middle of 10 bovine femurs from different individuals.The microCT scan is performed with a scanning resolution of 5?m.The analysis was performed using Skyscan CT-analyser software.The cortical porosity,canal diameter,canal separation,number of canal,and degree of anisotropy for each sample.The scanned images of each sample were calibrated using bone mineral density calibration models at two densities of 0.25 g/cm~3 and 0.75 g/cm~3 and bone mineral density parameters were obtained.All samples underwent quasi-static three-point bending test with a rate of 0.02 mm/s,the loading force-displacement curve was thereby obtained.Using the optimization method combined with specimen-specific finite element(FE)models to acquire the following constitutive parameters:elastic modulus,tangent modulus,yield stress,effective plastic strain,yield strain,ultimate stress,pre-yield toughness,post-yield toughness,toughness.Taking the cortical bone microstructural parameters and bone min eral density as independent variables,and the material parameters obtained by the optimization method as dependent variables,the effect of bone micro-structure and bone mineral density on the mechanical properties of bone was investigated using multiple linear regression analysisThe statistical results showed that the positive correlation between canal separation and yield stress(R~2=57.1%)and ultimate stress(R~2=61.2%),showed a positive correlation with elastic absorption(R~2=44.9%).The cortical porosity and post-yield toughness showed a negative correlation(R~2=42.3%).The number of canals showed a strong negative correlation with the tangent modulus(R~2=53.6%).In addition,the regression model of canal separation and bone mineral density showed a positive correlation trend with strong elastic modulus(R~2=82.9%,p=0.106),but more statistical analysis results were needed to prove it.Above all,cortical bone between micro structure parameters such as porosity of the cortex,pipe,pipe number show material parameters have strong correlation with bone,so can consider when building material parameters of regression model microstructure parameters on the influence of material parameters.