Fig. 1: Definition of auxiliary landmarks and geometric measures:
Midplanes angle: Angle between neighboring midplanes, counted positive if the wedge opens ventrally.
Mean depth: Mean of cranial depth between corner points 1 and 2 and caudal depth between corner points 3 and 4. Two other dorsal corner points, which are not included in the protocol but necessary for re-identification, are not depicted here.
Sagittal translation tr as given by the distance Dc between the projections of the center points measured in direction of the bisectrix, and divided by the mean depth of the cranial vertebra. Positive values are counted for anterior displacement of the cranial vertebra.
The sum of the perpendicular distance of corner points 4 and 2 from the bisectrix between the two midplanes divided by the mean depth of the cranial vertebra gives the "disc height", dh.