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，骨质疏松松质骨在人类股骨近端，或结构脆性骨的强度进行了研究；研究了羟基磷灰石涂层的骨固定系统，使其具有更大的稳定性和更长的固定时间。利用μCT对骨小梁结构和骨形态特性进行了三维检测，并建立了在进行μCT扫描时观察骨内部动态变形和断裂行为的方法。对比分析了人体正常骨与骨质疏松骨的动力行为差异。通过对骨小梁断裂模式和裂纹扩展类型（剪切型和裂纹型）的分类，研究了骨小梁结构脆性与断裂模式的关系。骨质疏松骨的表观抗剪强度与正常松质骨相比较小，约为30%。在骨质疏松的骨骼中，虽然剪切强度与断裂方式有关。骨折方式随受力方向改变，骨折原因与骨小梁结构形态改变有关。在骨螺钉的研制过程中，采用非线性有限元法考察了螺纹与骨之间的固定状态，分析了5种螺纹形状在骨内的应力应变分布，得到了最佳螺纹形状。建立了表面涂覆羟基磷灰石膜的有限元模型，并采用非线性有限元法分析了其应力应变分布。羟基磷灰石包覆螺钉可防止螺纹与骨交界集中应力的扩大。已知涂覆螺杆在边界区形成均匀的应力应变分布。

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.