  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.
