基于微结构MR成像的有限元模型定量分析老年髋部脆性骨折风险

Hip fractures in the elderly are often referred to as "The last Fracture of life", with a high degree of morbidity, mortality, and disability. Therefore, it is important to identify subjects with risk factors of bone brittleness for hip fracture prediction and treatment. The trabecular bone structure of proximal femur is essential for hip bone strength. However, it is not clear which structural characteristics and mechanical properties are related to hip fractures. Our previous studies indicated that the spatial distribution of trabecular vBMD and bone shape changes play a significant role in hip fracture. In view of this, we put forward the hypothesis that the microstructure and mechanical properties in specific areas of trabecular bone of the proximal femur increase the risk of hip fracture. In this study, high-resolution 3T MR imaging will be performed on the proximal femoral specimen and hip fracture and non-fractured population, and the finite element analysis(FEA) will be constructed based on MR images of bone microarchitecture, with the goal of visualizing the mechanical strength under virtual stress testing of bone in the sub-anatomical region, and accurately characterizing the spatial distribution of structure, thickness and shape of trabecular plates in a quantitative and non-invasive way. The aim of our study is to evaluate potential bone strength risk factors for hip fractures in the elderly, to find sensitive and specific FEA features to hip fractures and related high-risk factors (gender, age), and to supply a new method for appropriately predicting and assessing subjects at risk for hip fracture.

老年髋部骨折常被称为“人生最后一次骨折”，具有发病率高、死亡率及致残率极高的特点，研究其骨脆性风险因素对老年髋部骨折的防治有重要意义。股骨近段骨小梁结构是影响髋部骨强度的重要因素，但哪些结构特点和力学形变特性影响髋部骨折尚不清楚。我们研究发现：股骨松质骨密度空间分布及形态变化是影响髋部骨脆性增加的因素。据此我们提出假说：股骨近段特定区域骨小梁微结构及力学特性改变增加髋部骨折风险。本研究通过对离体股骨近段标本和髋部骨折与非骨折人群进行3T MR高分辨成像，利用基于微结构MR的骨小梁成像构建基于MRI的有限元模型，从而直观显示亚解剖区域骨骼压力测试下力学强度，准确、无创、定量的分析股骨近段骨小梁空间分布上的结构、厚度、形态特点，评价老年髋部骨折的潜在骨强度风险因素,寻找和发现对髋部骨折及其高危因素（性别、年龄）相对敏感和特异的有限元特征，为合理预测和评价高危人群髋部骨折风险提供新的评估方法。

股骨近段骨小梁结构是影响髋部骨强度的重要因素，但哪些结构特点和力学形变特性影响髋部骨折尚不清楚。通过实现高分辨（μ）MRI和QCT图像的处理及有限元建模（FEA），并建立配准计算，分析股骨颈和大转子感兴趣区的刚度、拉压应力/应变对比等，我们发现人体自然站立姿态下，股骨颈上、下侧皮质骨分别出现拉、压应力集中现象，发现不同年龄和不同姿态下股骨近端表面刚度和应变的差异；发现模拟侧向跌倒和站立姿态下，μMRI 和 QCT 模型股骨近端高风险拉压应力均观察到有极高的相关性，（R2=0.70-0.80）；发现自然站立时股骨颈皮质骨和松质骨所受应力和应变较大，提示股骨颈是易发生骨折的高危区域，与临床观察一致。本研究探索建立基于高分辨MR的股骨近段有限元分析的无创评估手段，并与BMD和骨结构参数结合，分析不同组织层次下股骨近端多尺度生物力学行为。为μMRI-FEA 在临床前研究中探究微观股骨力学行为的应用提供部分新的理论基础。