Correlation between strain maps and microstructural properties of the endplates in metastatic vertebrae

The presence of vertebral bone metastasis is frequent in patients affected by tumors. Metastasis can compromise the bone microstructure by modifying its natural optimization that could lead to a decrease in the load-bearing capacity and an increase of the risk of fracture. The endplates, a 2mm thin layer of bone tissue placed in the most superior and inferior region of the vertebral body, play a crucial role in the mechanism of fracture. In this work, 15 specimens consisting of a healthy and a metastatic vertebra were analyzed to evaluate the mechanical behaviour under axial compression in a micro-computed tomography (CT). Subsequently the deformations were identified through a Digital Volume Correlation (DVC) using a global algorithm. In this study we first analyzed the microstructure of the endplates, both healthy and affected by lytic, blastic and mixed metastasis. In blastic vertebrae, higher values of bone density, number of trabeculae and trabecular pattern factor were identified than in healthy or lytic vertebrae. On the contrary the space between the trabeculae was smaller. Afterwards, the microstructure of the endplates was evaluated by dividing each endplate into 9 sub-regions to verify a possible qualitative correlation between the deformation maps obtained using the DVC and the microstructural properties. The result showed that in subROIs with low trabecular number and high trabecular separation, the endplates were more likely to deform and at risk of fracture.