Biomechanical etiology of femoral neck fracture in osteoporosis and the development of hip screw for fixation of osteoporotic fracture

在这项研究中，研究了人类股骨近端骨质疏松松质骨的强度，或骨的结构脆弱性;并提出了脆性评价方法。另一个目的是研制一种能更稳定、更长时间固定骨折的羟基磷灰石涂层骨内固定系统。本文介绍了利用μCT扫描仪对人体骨骼进行三维动态观察的方法，以及在进行μCT扫描的同时观察骨骼动态变形和断裂行为的方法，并比较了人体正常骨和骨质疏松骨动态行为的差异。通过对骨小梁断裂模式和裂纹扩展的分类，研究了骨小梁结构脆性与断裂模式的关系。松质骨的表观抗剪强度较正常松质骨的表观抗剪强度低，约为正常松质骨的30%。在骨质疏松骨中，虽然剪切强度取决于骨折模式。在骨螺钉的研制过程中，采用非线性有限元方法研究了螺纹与骨的固定情况，分析了5种螺纹形状在骨中的应力和应变分布，以获得最佳螺纹形状。建立了表面羟基磷灰石涂层的有限元模型，采用非线性有限元法分析了涂层表面的应力应变分布。羟基磷灰石涂层螺钉防止了螺纹与骨界面应力集中的扩大。已知涂层螺钉在边界区域中形成均匀的应力和应变分布。

In this study, strength of osteoporotic cancellous bone in human proximal femur, or structural fragility of the bone is studied; and the evaluation method of the fragility has been developed Also, another aim is that a bone fixation system with the hydroxyapatite coating in which to fix the fracture with the more stability and longer period is developed.Not only the trabecula architecture and bone morphologic property were examined three-dimensionally by μCT scanner, but also the method which observed the dynamic deformation and fracture behavior in the bone, while doing μCT was developed.The difference between both dynamic behavior of human normal and osteoporotic bones was comparatively examined Also, the relationship between structural fragility and fracture mode of the trabecula was studied by the classification of fracture modes and crack propagation in the trabecula in 3 types such as the Shear and Crack type, Apparent shear strength of osteoporotic bone was small with about 30%, when comparing with it of normal cancellous bone. In the osteoporotic bones, though the shearing strength is dependent on the fracture mode. The fracture mode changed by direction of applied force, and the cause depended on the morphological change of trabecular architecture with bone atrophy.In the development of bone screw, the fixture condition between threads and bone was examined by non linear FE method Stress and strain distributions for 5 kinds of screw thread shape in the bone were analyzed in order to obtain the optimum thread shape. The finite element model in which the surface was coated by hydroxyapatite film was constructed, and stress and strain distribution was analyzed through non-linear FEM. T The hydroxyapatite coated screw prevented the enlargement of the concentrated stress in the boundary between thread and bone. It is known that the coated screw develop a uniform stress and strain distribution in the boundary zone.