Finite element models of intact and lesion-affected human vertebrae based on clinical CT and high resolution imaging: validation against displacements and strains from an innovative and controlled experimental setup

The aim of this thesis is to validate a finite element model (FEM) of the human vertebral body, with the long-term goal of applying it in clinical settings for the assessment of lytic lesions, particularly those of metastatic origin. A FEM model of a T9 vertebra affected by an anterior cortical lesion was developed from clinical CT imaging. To serve as a high-resolution reference, an additional FEM model was created using HR-pQCT imaging. Loading conditions, both in the experimental and numerical setups, consisted of axial compression applied to the caudal endplate, within a novel experimental setup that permitted endplate deflection under controlled load by distributing pressure on the whole endplate by pressurization of a confined gel. Strain and displacement fields were experimentally acquired using Digital Image Correlation (DIC) on selected patches of the vertebral body and were used to validate the mechanical behavior predicted by the FEM simulations. The comparison between numerical and experimental results showed good agreement, indicating that the proposed protocol is capable of accurately reproducing the mechanical response of the vertebra under axial loading. The present work extends the validation of CT-based models of human vertebrae to the case of lesions affecting the vertebral cortical wall, and although it would need to be confirmed and supported by larger studies, represents a step forward to the definition of a clinically applicable finite element model.