Institute of Lightweight Design and Structural Biomechanics, Vienna University of Technology, Austria.
Bone. 2013 Jan;52(1):27-38. doi: 10.1016/j.bone.2012.09.006. Epub 2012 Sep 14.
Femoral fracture is a common medical problem in osteoporotic individuals. Bone mineral density (BMD) is the gold standard measure to evaluate fracture risk in vivo. Quantitative computed tomography (QCT)-based homogenized voxel finite element (hvFE) models have been proved to be more accurate predictors of femoral strength than BMD by adding geometrical and material properties. The aim of this study was to evaluate the ability of hvFE models in predicting femoral stiffness, strength and failure location for a large number of pairs of human femora tested in two different loading scenarios.
Thirty-six pairs of femora were scanned with QCT and total proximal BMD and BMC were evaluated. For each pair, one femur was positioned in one-legged stance configuration (STANCE) and the other in a sideways configuration (SIDE). Nonlinear hvFE models were generated from QCT images by reproducing the same loading configurations imposed in the experiments. For experiments and models, the structural properties (stiffness and ultimate load), the failure location and the motion of the femoral head were computed and compared.
In both configurations, hvFE models predicted both stiffness (R(2)=0.82 for STANCE and R(2)=0.74 for SIDE) and femoral ultimate load (R(2)=0.80 for STANCE and R(2)=0.85 for SIDE) better than BMD and BMC. Moreover, the models predicted qualitatively well the failure location (66% of cases) and the motion of the femoral head.
The subject specific QCT-based nonlinear hvFE model cannot only predict femoral apparent mechanical properties better than densitometric measures, but can additionally provide useful qualitative information about failure location.
股骨骨折是骨质疏松个体中常见的医学问题。骨密度（BMD）是评估体内骨折风险的金标准。基于定量计算机断层扫描（QCT）的均匀体素有限元（hvFE）模型通过增加几何和材料特性，已被证明比 BMD 更能准确预测股骨强度。本研究旨在评估大量人体股骨在两种不同加载情况下进行测试时，hvFE 模型预测股骨刚度、强度和失效位置的能力。
36 对股骨用 QCT 进行扫描，评估总近端 BMD 和 BMC。对于每一对股骨，其中一根股骨置于单腿站立（STANCE）配置，另一根置于侧向配置（SIDE）。通过再现实验中施加的相同加载配置，从 QCT 图像生成非线性 hvFE 模型。对于实验和模型，计算并比较了结构特性（刚度和极限载荷）、失效位置和股骨头的运动。
在两种配置下，hvFE 模型均比 BMD 和 BMC 更好地预测了刚度（STANCE 的 R(2)=0.82，SIDE 的 R(2)=0.74）和股骨极限载荷（STANCE 的 R(2)=0.80，SIDE 的 R(2)=0.85）。此外，模型还能定性地很好地预测失效位置（66%的情况）和股骨头的运动。
基于 QCT 的非线性、个体特异性 hvFE 模型不仅可以比密度测量更好地预测股骨的表观力学特性，而且可以提供关于失效位置的有用定性信息。
