Validation of Homogenized Finite Element Models of Human Metastatic Vertebrae Using Digital Volume Correlation

The incidence of vertebral fragility fracture is increased by the presence ofpreexisting pathologies such as metastatic disease. Computational tools couldsupport the fracture prediction and consequently the decision of the bestmedical treatment. Anyway, validation is required to use these tools inclinical practice. To address this necessity, in this study subject-specifichomogenized finite element models of single vertebrae were generated from microCT images for both healthy and metastatic vertebrae and validated againstexperimental data. More in detail, spine segments were tested under compressionand imaged with micro CT. The displacements field could be extracted for eachvertebra singularly using the digital volume correlation full-field technique.Homogenized finite element models of each vertebra could hence be built fromthe micro CT images, applying boundary conditions consistent with theexperimental displacements at the endplates. Numerical and experimentaldisplacements and strains fields were eventually compared. In addition, theoutcomes of a micro CT based homogenized model were compared to the ones of aclinical-CT based model. Good agreement between experimental and computationaldisplacement fields, both for healthy and metastatic vertebrae, was found.Comparison between micro CT based and clinical-CT based outcomes showed strongcorrelations. Furthermore, models were able to qualitatively identify theregions which experimentally showed the highest strain concentration. Inconclusion, the combination of experimental full-field technique and thein-silico modelling allowed the development of a promising pipeline forvalidation of fracture risk predictors, although further improvements in bothfields are needed to better analyse quantitatively the post-yield behaviour ofthe vertebra.