Fig. 13

Axial vertebral rotation assessed by the EOS method. This 3D method shows position and rotation of the apical vertebra (in yellow) on a top view (a). With this method, each vertebra is represented by a vector, which is placed in a coordinate system (x, y and z where x corresponds to the interacetabular axis). This vertebral vector gives information about position and rotation of the vertebra in horizontal plane (note: the scale is based on the interacetabular distance). Apical (yellow) and end (dark blue) vertebrae are indicated (a). Another way of showing position and rotation of apical (T8) and end (T6, T12) vertebrae in horizontal plane is given by a diagram (b)