Morphology of scoliosis: three-dimensional evolution.

The clinical examination of the scoliotic child's profile shows that it does not correspond to the physiological curvatures. This three-dimensional study of scoliosis shows evidence of the existence of three components, frontal, sagittal, and axial. Each generates a pathological displacement of the vertebrae maximal at the apical vertebral level. Because of rotation, in order to analyze each of the components, radiographs must be taken along the frontal or sagittal plane of the vertebrae. A comparative study of the sagittal and frontal components during progression of scoliosis indicates that the apical vertebrae are displaced not only laterally but also forward and then backward. The apical vertebrae are situated anteriorly with respect to the end vertebrae. If the scoliotic curves progress, the apical vertebrae eventually become displaced backward. During this displacement at a given moment they are situated in the frontal plane of the child at the same level as the upper end vertebra; then they come to lie behind this if the scoliosis continues to progress. This explains why, when observed from the side, the appearance changes and passes through three successive stages, lordosis, flat back, and kyphosis.