Fig. 3

Sspo-deficiency has a mild impact on spinal curvature in the thoracic level. A Principle of the biplanar annotation approach used to measure three-dimensional spinal trajectories. A spline approximation of the spinal midline was first obtained on a horizontal projection image (right image in left panel); reference points (yellow dots) were then placed at the ventral aspect of intervertebral spaces on a lateral projection image computed from a stripe of voxels along the spline (middle); their medio-lateral position was interpolated using the spline, yielding a set of Cartesian coordinates describing the three-dimensional trajectory of the spine (right). The example mouse shown here was slightly tilted to the left, as shown by the coronal projection (left image in the left panel), resulting in an apparent deviation of the spine in the horizontal projection (right image in left panel); this apparent deviation disappeared after applying the corrective rotation computed using the three-dimensional trajectory (horizontal projection in right panel). A: anterior; D: dorsal; P: posterior; V: ventral. B Optimal alignments of individual spinal trajectories for wild type (Sspo^+/+) and Sspo^−/− mice grouped by gender and age (6 and 12 weeks). In each case, top and lateral views are shown (top and bottom curves, respectively). C Sketch detailing the calculation of local curvature angles. D Average curvature angle (± S.D., shaded area) at each vertebral position computed across mice grouped by gender, age (6 and 12 weeks) and genotype. Vertebral levels at which significant differences between Sspo^−/− and Sspo^+/+ mice were found using linear mixed-effects models followed by post hoc pairwise comparisons are indicated (*: p < 0.05; **: p < 0.001; see values in the text). Vertical gray dashed lines indicate regional limits (Ce: cervical; T: thoracic; L: lumbar; S: sacral; Ca: caudal)