Fig. 11

Mean tensile (ε1, left plots) and compressive (ε2, right plots) strains on the L2-L3, L3-L4, L4-L5 and L5-S1 intervertebral discs, in flexion, extension, and lateral bending after the two-level laminectomy, and after posterior fixation. All the data were normalized with respect to the intact condition (dashed green line), and averaged between all the specimens. A value larger than 1.0 indicates an increase of strain magnitude with respect to the intact condition. As data for the intact condition were lost for the first six specimens, the box plot summarizes the distribution of the remaining six specimens. The bottom of the box represents the first quartile (25th percentile) of the data; the horizontal line inside the box represents the median of the data and the top of the box represents the third quartile (75th percentile). The “X” cross represents the mean of the data. The top and bottom whiskers include the maximum and the minimum data, excluding the outliers which are shown as dots. The asterisks * above the box indicate a statistically significant differences (post-hoc) with respect to the intact condition (p < 0.05). The asterisks * above the squared brackets indicate a significant difference between the laminectomy and fixation conditions. The results of the Repeated Measures Two-Way ANOVA are reported in Table 2.