【摘要】 背景:目前评估骨折风险仍依靠骨密度测试,然而,骨密度检测忽略了影响骨折的其他机制,包括多个尺度上的骨三维结构和材料特性。尽管骨密度提供了有用的信息,但其在预测骨折风险方面的价值有限。目的:通过构建不同松质骨体积分数股骨近端三维有限元模型,探究微观参数松质骨体积分数对股骨近端表观力学响应的影响。方法:收集1例健康志愿者股骨近端CT数据,以DICOM格式导入Mimics重建三维模型,并赋予骨质疏松皮质骨、松质骨相应材料参数,导入Abaqus中通过单元均匀删除脚本,构建35%,30%,25%,20%,15%松质骨体积分数的有限元模型。在股骨头上方建立参考点并施加载荷于股骨头上方与髋臼接触区域,分析股骨近端在生理站立位应力下的力学响应差异。结果与结论:(1)站立位载荷条件下,股骨颈外上侧所受张应力始终大于颈内下侧压应力值,随着松质骨体积分数降低,股骨近端所受张应力、压应力均逐渐增大,15%模型最大张应力、最大压应力分别是35%模型的1.91倍和1.42倍,最大主应变增加4.76倍,股骨整体刚度下降58%;(2)单足站立状态下,股骨皮质骨较松质骨相比承担了更多的应力,而松质骨在股骨整体弹性响应中承担不可或缺的作用;(3)随着松质骨体积分数的下降,股骨颈外上侧张应力增加幅度更大,结合颈外上侧区域作为骨量丢失最为显著的区域,在跌倒载荷下同样处于应力集中区域,在临床中常常为骨折断裂的起点,这提示着颈外上侧的相关参数(如骨密度和体积分数)是否可能成为预测脆性股骨颈骨折更为敏感的指标,值得进一步探究。更多还原

【Abstract】 BACKGROUND: The assessment of fracture risk still depends on bone mineral density testing. However, it ignores other mechanisms that affect fractures, including three-dimensional bone structures and material properties on multiple scales. Although bone mineral density provides useful information, its value in predicting fracture risk is limited. OBJECTIVE: A three-dimensional finite element model of proximal femur with different cancellous bone volume fractions was constructed to explore the effect of bone volume fraction on the apparent mechanical response of proximal femur.METHODS: The CT data of a volunteer’s proximal femur were collected and imported into Mimics to reconstruct the three-dimensional model in DICOM format. The osteoporotic cortical bone and cancellous bone were given corresponding material parameters. Then, the model was imported into Abaqus and the finite element model with 35%, 30%, 25%, 20% and 15% cancellous bone volume fractions was constructed by uniform deletion of the script. A reference point was established above the femoral head and a concentrated load was applied to the area of contact with the acetabulum above the femoral head to analyze the difference of mechanical response of the proximal femur under orthostatic stress. RESULTS AND CONCLUSION:(1) Under the condition of standing load, the tensile stress on the upper and outer side of the femoral neck was always greater than the compressive stress on the medial and inferior side of the neck. With the decrease of cancellous bone volume fraction, the tensile stress and compressive stress of proximal femur increased gradually, and the maximum tensile stress and maximum compressive stress of 15% model were 1.91 times and 1.42 times of 35% model, respectively. The maximum principal strain increased by 4.76 times, and the overall stiffness of the femur decreased by 58%.(2) Under the condition of standing on one foot, the cortical bone of the femur bore more stress than the cancellous bone, and the cancellous bone played an indispensable role in the overall elastic response of the femur.(3) With the decrease of the volume fraction of cancellous bone, the tensile stress of the lateral superior side of the femoral neck increased greatly. The region of the lateral superior side of the neck is the most significant area of bone mass loss, and it is also in the area of stress concentration under the fall load. This suggests whether the relevant parameters of the lateral superior side of the neck(such as bone mineral density and volume fraction) may become a more sensitive index for predicting brittle femoral neck fracture, which is worth further exploring.更多还原