3D parametric finite element models to assess the mechanical role of the bone-lesion interface in human metastatic vertebrae

Vertebral bone metastases are frequent in oncological patients and lead to a significant risk of vertebral fractures. Computational modelling offers a valuable tool for investigating how metastatic lesions affect the mechanical stability and integrity of the spine. This study presents the development of a Python-based algorithm for a 3D subject-specific parametric finite element model (SS-parFEM) designed to semi-automatically generate simplified spine segments that reproduce deformation patterns similar to those observed experimentally. The model represents a metastatic vertebra including the lesion and an adjacent healthy vertebra separated by an intervertebral disc, with geometry and mean trabecular and cortical bone material properties derived from computed tomography (CT) images. By applying the experimentally measured axial compressive failure loads, predicted principal strain fields were compared with full-field experimental data obtained from Digital Volume Correlation (DVC). Good agreement in spatial strain patterns was observed, suggesting the model's ability to capture the main features of the mechanical response of metastatic vertebrae, although peak strain magnitudes were not fully reproduced. The framework was further applied to investigate the mechanical influence of lesion type and the bone-metastasis interface. The preliminary findings suggest that interface bonding conditions can affect load transfer and stress distributions in blastic lesions, whereas lytic lesions exhibited a mechanical behaviour largely independent of interface integrity. This adaptable parametric approach provides a foundation for future subject-specific investigations and offers a useful tool for biomechanical studies of metastatic spine stability.