Idiopathic scoliosis in three dimensions: a succession of two-dimensional deformities?

STUDY DESIGN: A geometric analysis of computerized three-dimensional (3-D) reconstructions of the spine of adolescents with idiopathic scoliosis. OBJECTIVES: To analyze and describe the 3-D location of scoliotic curves with respect to the global frontal, sagittal, and transverse planes of each subject. SUMMARY OF BACKGROUND DATA: Clinical two-dimensional (2-D) measurements cannot fully describe the 3-D deformity of a scoliotic spine because they are done in the 2-D frontal or sagittal plane projection of a subject and do not correspond to the actual deformity. METHODS: The spinal deformity from T1 to L5 of 50 adolescents with thoracic idiopathic scoliosis was reconstructed in 3-D using a multiplanar digital radiographic technique allowing the visualization of the vertebral line of the spine in any projection using auto CAD software. The curvature was segmented in three distinct curves for each subject: a high thoracic, a thoracic, and a lumbar. A regional plane passing through the two end-vertebrae and the apical vertebra was defined, and a series of geometric manipulations were performed to realign each regional plane with the global axis system of each subject. RESULTS: A total of 91% of the 147 curves studied were found to be entirely contained within its 2-D regional plane, and all scoliotic curves were found to be oriented in a 3-D location different from the classic frontal, sagittal, and transverse orthogonal planes of each subject. CONCLUSION: In thoracic idiopathic scoliosis the deformity of the spine is 3-D, but the regional deformity of each high thoracic, thoracic, or lumbar curve is almost always 2-D. The orientation in space of each 2-D plane is such that it cannot be seen in its true frontal or sagittal projection using standard frontal or sagittal radiologic views of the subject.

Mechanical process and growth cartilages. Essential factors in the progression of scoliosis.

This study showed that the worsening of scoliosis was the result of a mechanical phenomenon. The key feature in this mechanical process was the finding that cuneal deformation affects only part of the vertebral body. The onset of scoliotic curvature occurred as a result of intervertebral motions. However, the worsening was essentially caused by deformation of the vertebral bodies. After the onset of scoliosis, the orientations of the vertebrae were modified in all three planes, and as a result, the spine became mechanically unstable. As a result of this mechanical instability, intervertebral pressures no longer were distributed equally but were concentrated at the junction of the growth cartilages of the vertebral body, near the pedicle on the concave side. Osseous growth was perturbed in this area, the vertebra became deformed, and the vertebral body became wedge shaped. These cuneal deformations resulted in a relative change of position between adjacent vertebral bodies and led to a worsening of the scoliotic curve without involving any articular motion. This phenomenon occurred mostly in the apical region because of the geometric shape of the curvature.

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.

Thoracic idiopathic scoliosis curve evolution and prognosis.

This study is a retrospective review of 221 patients with untreated idiopathic thoracic and thoracolumbar scoliosis that were observed from the first months of life until maturity. There are three stages in the evolution of these curves: a single main period of progression, a secondary period of progression, and a stable period. The chronology of these different periods varies. In "infantile scoliosis," the main period of accelerated increase of the curve occurs prior to 6 years of age. In "juvenile-puberal scoliosis," it occurs from 6 years of age to the first stages of puberty, and in "puberal scoliosis," the main increase occurs during puberty or adolescence. The prognosis of the scoliosis can be established at any age based on different parameters, such as the specific angle of rotation from birth to 6 years of age, the torsion angle from 6 years of age to P2, and the Cobb angle after puberty.

[A study of scoliotic curve. The importance of extension and vertebral rotation (author's transl)]. / Etude de la courbure scoliotique. Importance de l'extension et de la rotation vertébrale.

The authors consider that scoliotic curves should be studied in the spatial planes, not only in the frontal plane. Lateral views show that the displaced segments of the spine are always an extension even when there is a kypho-scoliosis. This element must be considered when the deformity is about to be reduced or treated by bracing. In the axial plane, the rotational displacement must be measured. In a dorsal curve, there is specific rotation of the upper vertebrae. The measurement of this rotation may make it possible to predict the extent of the curve at the end of growth in cases of spontaneous evolution.

[Conservative treatment of deformities of the anterior chest wall]. / Traitement orthopédique des déformations thoraciques vers l'avant Résultats.

The authors have treated 55 deformities of the anterior chest wall in children. There were 37 cases of symmetrical pectus carinatum, 15 cases of asymmetrical pectus carinatum and 3 cases of pectus arcuatum. Associated lesions of the ribs, scapulae and spine are described. Treatment in every case was by plaster casts followed by a plaster jacket and exercises. The results were much more satisfactory in deformities associated with prominence than with depression of the sternum. In pectus carinatum, the results were better when the apex of the deformity was more distal. The best age for treatment was between 12 and 13 years. No patient was treated by operation.

[Orthopedic reduction of scoliosis by Maguelone's technic. Indications and first results]. / Réduction orthopédique des scolioses par la technique de "Maguelone". Indications et premiers résultats

The authors describe an original technique for rapid closed reduction of scoliosis (Maguelone technique). It is based on mild distraction in suspension associated with derotation without pressure points. It is painless and efficient. In 50 cases it was followed by a conservative treatment using plaster casts. In 15 other cases it was the first stage of a surgical treatment of the deformity.