Department of Radiology, University of Pennsylvania, United States of America; Department of Orthopaedic Surgery, University of Pennsylvania, United States of America.
Department of Radiology, University of Pennsylvania, United States of America.
Bone. 2020 Apr;133:115227. doi: 10.1016/j.bone.2020.115227. Epub 2020 Jan 9.
Half of the women who sustain a hip fracture would not qualify for osteoporosis treatment based on current DXA-estimated bone mineral density criteria. Therefore, a better approach is needed to determine if an individual is at risk of hip fracture from a fall. The objective of this study was to determine the association between radiation-free MRI-derived bone strength and strain simulations compared to results from direct mechanical testing of cadaveric femora. Imaging was conducted on a 3-Tesla MRI scanner using two sequences: one balanced steady-state free precession sequence with 300 μm isotropic voxel size and one spoiled gradient echo with anisotropic voxel size of 234 × 234 × 1500 μm. Femora were dissected free of soft-tissue and 4350-ohm strain-gauges were securely applied to surfaces at the femoral shaft, inferior neck, greater trochanter, and superior neck. Cadavers were mechanically tested with a hydraulic universal test frame to simulate loading in a sideways fall orientation. Sideways fall forces were simulated on MRI-based finite element meshes and bone stiffness, failure force, and force for plastic deformation were computed. Simulated bone strength metrics from the 300 μm isotropic sequence showed strong agreement with experimentally obtained values of bone strength, with stiffness (r = 0.88, p = 0.0002), plastic deformation point (r = 0.89, p < 0.0001), and failure force (r = 0.92, p < 0.0001). The anisotropic sequence showed similar trends for stiffness, plastic deformation point, and failure force (r = 0.68, 0.70, 0.84; p = 0.02, 0.01, 0.0006, respectively). Surface strain-gauge measurements showed moderate to strong agreement with simulated magnitude strain values at the greater trochanter, superior neck, and inferior neck (r = -0.97, -0.86, 0.80; p ≤0.0001, 0.003, 0.03, respectively). The findings from this study support the use of MRI-based FE analysis of the hip to reliably predict the mechanical competence of the human femur in clinical settings.
有一半的髋部骨折女性不符合当前基于 DXA 估计骨密度标准的骨质疏松症治疗标准。因此,需要一种更好的方法来确定个体是否有因跌倒而髋部骨折的风险。本研究的目的是确定与直接机械测试尸体股骨相比,无辐射 MRI 衍生骨强度和应变模拟之间的关联。在 3T MRI 扫描仪上使用两种序列进行成像:一种平衡稳态自由进动序列,具有 300μm 的各向同性体素大小,另一种是各向异性体素大小为 234×234×1500μm 的扰相梯度回波序列。股骨从软组织中解剖出来,并将 4350 欧姆的应变计牢固地应用于股骨干、下颈、大转子和上颈的表面。将尸体用液压万能试验机进行机械测试,以模拟侧向跌倒方向的加载。在基于 MRI 的有限元网格上模拟侧向跌倒力,并计算骨刚度、失效力和塑性变形力。来自 300μm 各向同性序列的模拟骨强度指标与通过实验获得的骨强度值具有很强的一致性,其中刚度(r=0.88,p=0.0002)、塑性变形点(r=0.89,p<0.0001)和失效力(r=0.92,p<0.0001)。各向异性序列在刚度、塑性变形点和失效力方面也表现出相似的趋势(r=0.68、0.70、0.84;p=0.02、0.01、0.0006,分别)。表面应变计测量结果与大转子、上颈和下颈的模拟大应变值具有中度到高度一致性(r=-0.97、-0.86、0.80;p≤0.0001、0.003、0.03,分别)。本研究的结果支持在临床环境中使用基于 MRI 的髋关节有限元分析来可靠地预测人类股骨的机械性能。
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