Fig. 4. Pairwise comparison of three situations, viz. normal vertebrae with normal eccentricity (normal, blue), normal vertebrae with doubled eccentricity (double, grey) and lordotic vertebrae with their characteristic high eccentricity (lordotic, red) (see top row). Box plot comparison of mean between (A) normal vertebrae and normal vertebrae with double eccentricity, (C) normal and lordotic vertebrae and (E) lordotic and normal vertebrae with double eccentricity. As the volumes of all finite elements in the models are approximately equal, the mean dimensionless strain energy density, , is approximately equal to the total dimensionless strain energy in each vertebra. Subplots B, D and F show a histogram of the percentage of the total number of elements in a number of categories. Comparisons are equal to those in subplots A, C and E, respectively. The last category includes all elements with >2000. Standard deviation is indicated by boxes around the solid line. Colour of the boxes indicates the loading situation. Grey shading indicates significant (P<0.05 in a one-tailed non-parametric Wilcoxon test) differences between the respective groups.