Fig 1.
Specimen mounted on the testing machine with the set up in the compression-flexion configuration.
Fig 2.
Workflow used to compare predicted and experimental local displacements.
a) Registration of the DIC points (red surfaces) to the segmentation obtained from the CT data. By aligning the surfaces, it was possible to perform the comparison between the displacements predicted by the FE model and the ones measured using the DIC. b) Boundary conditions applied to the FE model: the inferior surface of the lower vertebral body was fixed while translations (TSP) and rotations (RSP) are applied through a pilot node SP to the superior surface of the upper vertebral body. c) Illustration of the tool used for the local displacement comparison.
Fig 3.
Graphical representation of spatial distribution of the registration error.
Spatial distribution of the registration error of DIC points on the vertebral surfaces of the FE model.
Fig 4.
Linear regressions plots between predicted and experimental local displacements.
Comparison between the displacements measured using DIC and the ones predicted by the FE model for L2 (yellow) and L3 (blue) vertebral surfaces. The Euclidean norms of the displacements, referred as Intensity, and the three displacement components defined in the FE model coordinate reference system are plotted. Linear regression and coefficient of determination are also reported for the correlation plots. It is important to notice that the SI component is plotted with the sign changed to allow comparison with the other subplots.
Fig 5.
Residual analysis estimated between FE and DIC displacements.
Bland-Altman plots showing the dependence of the vector sum magnitude (Diff) on the average value between measured and predicted local displacement.
Fig 6.
Representation of comparison error spatial distribution.
Spatial distribution of the vector resultant (Diff) on the vertebral surfaces of the FE model.
Fig 7.
Displacement field of the two vertebral surfaces.
Comparison between computational and experimental displacement fields in the three directional components X, Y and Z for each vertebra (L2 left, L3 right). To help the reader in appreciating the comparison, both experimental and computational displacements have been interpolated over the same mesh.
Table 1.
Summary of the validation metrics values for local displacement comparisons between DIC and FE results.