Determination of Variation in Natural Frequencies of a Femur Bone

The elderly population is on the rise and this trend is expected to persist. Age-related bone loss and osteoporosis in the elderly increase the risk of fractures and morbidity in this population. It is important to identify the possible pathologic mechanisms underlying bone fragility in old age. We have selected femur bone as the bone for our study as it the longest and the heaviest bone in the human body. The bone mechanical properties such as young's modulus, Poisson's ratio, shear modulus, density and porosity vary with age. All these mechanical properties follow a decreasing trend with age. Different methods have been used to find out these variations of mechanical properties with age. The FEA model of the femur bone was imported, and static analysis was performed on that and compared with the experimental data to verify if the femur model was accurate or not. Since the femur bone is a complex structure the material properties cannot be isotropic, but they are anisotropic. Orthotropic variation of the bone mechanical properties of a human female bone were considered. Using these material properties, modal analysis was performed to determine the natural frequencies of bones for different ages. First six modes of natural frequencies for different age groups are considered. A decreasing trend has been observed in natural frequency against age. After literature survey, the variation of porosity with age has been found out. The graph between natural frequency and porosity is drawn out. Further, this graph can be used to find out the porosity in different people by finding out the intermediate parameter i.e., natural frequencies of the bone.