Diamant I, Shahar R, Masharawi Y, Gefen A
Department of Biomedical Engineering, Faculty of Engineering, Tel Aviv University, Tel Aviv 69978, Israel.
Clin Biomech (Bristol). 2007 Mar;22(3):282-91. doi: 10.1016/j.clinbiomech.2006.10.005. Epub 2006 Nov 28.
In the context of osteoporosis, important determinants of the fracture risk are the apparent strength and stiffness of cancellous bone, as well as its brittleness and energy absorption capacity. Standard medical imaging, however, cannot measure these mechanical properties directly. Consequently, an estimation of the risk for fracture is made by correlating relative density or mineral density at a skeletal site with statistics of fracture occurrence, which provides limited and partial indications on fracture risks. A better method for evaluating the patient-specific mechanical properties of cancellous bone is therefore required.
In order to asses the mechanical properties of vertebral cancellous bone, we developed a finite element parametric model of lattice trabecular architecture that, in the future, will be suitable for use with bone imaging modalities. The model inputs are apparent morphological parameters (trabecular thickness and trabecular separation) and the bone mineral density. We conducted uniaxial compression tests on 36 canine vertebral cancellous bone specimens (C7 and L1) to validate model predictions of strength and stiffness in vitro.
Predictions of strength and stiffness matched the experimental results within relative absolute errors of 17.7% and 12.8%, respectively (average of differences between model-predicted and measured values, divided by the average of measured values). We also employed the model for evaluation of strength and stiffness of human L1 and L5 vertebrae and found mean strength of 1.67 MPa (confidence interval 0.42 MPa) and mean elastic modulus of 190 MPa (confidence interval 50 MPa), which are well within the range of previously reported apparent strength and stiffness properties.
The present model can be used to improve medical imaging-based evaluation of the spine in osteoporotic individuals by providing more specific information on the individual bone's susceptibility to fracture once clinical bone scans will be able to provide more reliable measures of trabecular thickness and separation.
在骨质疏松的背景下，松质骨的表观强度、刚度以及脆性和能量吸收能力是骨折风险的重要决定因素。然而，标准医学成像无法直接测量这些力学性能。因此，通过将骨骼部位的相对密度或矿物质密度与骨折发生率的统计数据相关联来估算骨折风险，这只能提供有限且不全面的骨折风险指示。因此，需要一种更好的方法来评估患者特异性的松质骨力学性能。
为了评估椎体松质骨的力学性能，我们开发了一种晶格小梁结构的有限元参数模型，该模型未来将适用于骨成像模态。模型输入为表观形态参数（小梁厚度和小梁间距）以及骨矿物质密度。我们对36个犬类椎体松质骨标本（C7和L1）进行了单轴压缩试验，以在体外验证模型对强度和刚度的预测。
强度和刚度的预测与实验结果相匹配，相对绝对误差分别为17.7%和12.8%（模型预测值与测量值之间差异的平均值除以测量值的平均值）。我们还使用该模型评估了人类L1和L5椎体的强度和刚度，发现平均强度为1.67MPa（置信区间0.42MPa），平均弹性模量为190MPa（置信区间50MPa），均在先前报道的表观强度和刚度特性范围内。
一旦临床骨扫描能够提供更可靠的小梁厚度和间距测量值，本模型可通过提供关于个体骨骼骨折易感性的更具体信息，用于改善基于医学成像的骨质疏松个体脊柱评估。
