The incidence of vertebral fragility fracture is increased by the presence of preexisting pathologies such as metastatic disease. Computational tools could support the fracture prediction and consequently the decision of the best medical treatment. Anyway, validation is required to use these tools in clinical practice. To address this necessity, in this study subject-specific homogenized finite element models of single vertebrae were generated from micro CT images for both healthy and metastatic vertebrae and validated against experimental data. More in detail, spine segments were tested under compression and imaged with micro CT. The displacements field could be extracted for each vertebra singularly using the digital volume correlation full-field technique. Homogenized finite element models of each vertebra could hence be built from the micro CT images, applying boundary conditions consistent with the experimental displacements at the endplates. Numerical and experimental displacements and strains fields were eventually compared. In addition, the outcomes of a micro CT based homogenized model were compared to the ones of a clinical-CT based model. Good agreement between experimental and computational displacement fields, both for healthy and metastatic vertebrae, was found. Comparison between micro CT based and clinical-CT based outcomes showed strong correlations. Furthermore, models were able to qualitatively identify the regions which experimentally showed the highest strain concentration. In conclusion, the combination of experimental full-field technique and the in-silico modelling allowed the development of a promising pipeline for validation of fracture risk predictors, although further improvements in both fields are needed to better analyse quantitatively the post-yield behaviour of the vertebra.

翻译：椎体脆性骨折的发生率因转移性病变等既有病理的存在而增加。计算工具可支持骨折预测，进而辅助最佳治疗方案决策。然而，这些工具需经验证方能应用于临床实践。为应对这一需求，本研究基于显微CT图像分别构建了个体特异性均质化有限元模型（涵盖健康与转移椎体），并通过实验数据进行验证。具体而言，对脊柱节段施加压缩载荷并进行显微CT成像，利用数字体相关全场技术逐椎提取位移场。基于显微CT图像建立各椎体的均质化有限元模型，在终板处施加与实验位移一致的边界条件，最终比较数值与实验的位移场及应变场。此外，还将基于显微CT的均质化模型结果与基于临床CT的模型结果进行了对比。结果显示：健康与转移椎体的实验与计算位移场均具有良好一致性；基于显微CT与临床CT的模型结果呈现强相关性；模型能定性识别实验中应变高度集中的区域。综上所述，实验全场技术与数值模拟的结合为验证骨折风险预测因子提供了可行方案，但需进一步改进两方面技术，以更定量地分析椎体屈服后行为。