전체 척추 몸통 뼈의 내적 물성과 외적 물성에 관한 유한 요소 시뮬레이션

Abstract

Mechanical bone properties which characterized by bone strength, brittleness, work to failure are important parameters to diagnosis and investigate the osteoporosis, because Bone fragility depends on mechanical bone properties and it is distinguished extrinsic property which depends on bone mass and bone morphology and intrinsic property which depends on bone matrix property. Extrinsic property is characterized by stiffness and yield force from the biomechanical test and intrinsic property is characterized by young’s modulus and hardness from the nanoindentaion. These properties cannot directly compare because of incoincidence of measurement parameters. Furthermore the inherent difference due to different measurement length scale between extrinsic and intrinsic bone properties has been poorly understood. In this study we simulated both extrinsic and intrinsic bone property for directly comparison. The intrinsic tensile properties were simulated from nanoindentation curve to directly comparison with extrinsic properties. To quantify the effects of microarchitecture and microporosity on intrinsic properties, synchrotron x-ray micro-CT-based multiscale micro-FE system which included microarchitecture and microporosity was successfully developed. We revealed that intrinsic yield strength is one-third times of nanoindentation hardness as same as non-work hardening material case. And higher stiffness and yield force of intrinsic properties than extrinsic properties were measured by 93% and 43% respectively. We quantified that the effects of microarchitecture and porosity on intrinsic properties explained 82% portion of the discrepancy of stiffness. And it is fully explained the discrepancy of yield force. These finding demonstrated that microarchitecture and microporosity are main factors of the difference between extrinsic and intrinsic bone properties.