Nanoindentation Testing of Porcine Bone

Nanoindentation testing is a technique that is used to measure mechanical properties of materials at the nano-scale. The method has been used to measure properties of metals, ceramics and also biological materials. In this study nanoindentation testing was used to measure the reduced modulus and hardness in the porcine tibia and femur. Testing was done to measure the properties in different directions and also in the anterior and posterior regions of the bone. Two bone samples were analyzed in this study. Bone samples were obtained and cleaned and polished in the area of interest. Samples were tested after air drying for 48 hours. Digital microscopy was used to locate osteon bone in the region of interest. The bone was testing in the axial (x) direction, sagittal plane (y) direction and the frontal plane (z) direction. A loading function with a 5 s rise time, 5 s holding time and 5 s unloading time with a peak value of 4000 μN was used. Statistical analysis of the data was done using a one-way Anova, Tukey test and a linear mixed model.\ud In the first sample, mechanical properties did not vary in different areas tested within a region while in the second sample properties did vary between areas in some regions. Differences in mechanical properties between anterior and posterior regions were found in both femur and tibia of the first sample and the femur of the second sample. Besides, differences in mechanical properties in the different directions were found in both the tibia and femur with most of the axial direction being highest and those in the sagittal plane being the lowest. In general the properties in the femur were greater than that of the tibia.\ud Greater loading in certain bone regions may induce higher hardness and elastic modulus. The different properties in the different directions may suggest a plywood-like composite structure with most fibers orthogonal to the laminate direction. The evaluation of bone mechanical properties can contribute to the knowledge of the effects of location, disease or other factors on the tissue. \u