Up to now, due to cortical thickness and imaging resolution, it is not possible to derive subject-specific mechanical properties on the 'vertebral shell' from imaging modalities applicable in vivo. As a first step, the goal of this study was to assess the apparent Young's modulus of vertebral cortico-cancellous bone specimens using an inverse method. A total of 22 cortico-cancellous specimens were harvested from 22 vertebral bodies. All specimens were tested in compression until failure. To compute the apparent Young's modulus of the specimen from the inverse method, the boundary conditions of the biomechanical experiments were faithfully reproduced in a finite element model (FEM), and an optimisation routine was used. The results showed a mean of the apparent Young's modulus of 374 ± 208 MPa, ranging from 87 to 791 MPa. By computing an apparent Young's modulus of a cortico-cancellous medium, this study gives mechanical data for an FEM of an entire vertebra including an external shell combining both bone tissues.

This work underlines the potential of low-dose biplanar x-ray devices to make subject-specific FEMs for prediction of vertebral strength.

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