Apport de la morphologie tridimensionnelle de la colonne vertébrale et du bassin à la scoliose idiopathique de l’adolescence

Adolescent idiopathic scoliosis (AIS) is a deviation of the spine of unknown origin. Although it is still classified and measured using two-dimensional X-ray, it is widely reported in the literature that scoliosis is a deviation in the three planes of space. Also, it seems that the pelvis is involved in the scoliosis deformity, as it is the foundation of the spine and its orientation influence on postural balance. Thus, the asymmetry of the pelvis and postural attitude could be compensatory mechanisms of idiopathic scoliosis or be agents that trigger this disease. The aim of this work is to determine the relationship between the three-dimensional morphology of the spine and pelvis of scoliosis grouped according to Lenke’s classification and to know the links between morphological parameters and the Cobb angle. Eighty girls with the SIA participated in this study. Specifically, 32 subjects were suffering from thoracic scoliosis, 23 thoracolumbar scoliosis and 25 lumbar scoliosis. Simultaneous radiographs of posterior-anterior and lateral planes in standing position were taken with the EOS system. Fifteen anatomical landmarks on each of the vertebrae between T1 and L5 on the spine and twenty-one on the pelvis, have been identified on the pairs of radiographs. The three-dimensional reconstruction of the spine and pelvis was made from the two radiographs and the anatomic landmarks. A total of five parameters on the spine and three on the pelvis were calculated to identify the morphology of thoracic, thoracolumbar and lumbar deformations. The unsupervised classification algorithm of fuzzy c-means (FCM) was used to classify subjects. Classifications with two and three classes were made with non-standardized and normalized data, i.e. by omitting the level of the scoliosis curve. Analysis of variance (ANOVA) with post-hoc was conducted on classifications with two groups and classes and multivariate analysis (MANOVA) with post-hoc were made on classifications with three groups and classes.  The Cobb angle of the main thoracic segment was significantly different for the three types of scoliosis. However, these differences might be attributed to the analyzed segment and severity of the curve. With the normalized data, the thoracic scoliosis L1 subjects regroup in classification with two classes and divides into two classes in the classification with three classes. These classes are divided according to the kyphosis (p = 0.000), lordosis (p = 0.000) and the orientation of plane of maximum curvature (PMC) (p = 0.000) parameters. Regardless of classification, L5 and L6 usually gather in the same class. Also, Pearson correlations were made according to the Cobb angle, in order to detect the relationship between the types of deformation and morphological parameters. Finally, the pelvis had no impact on classifications, but it is correlated with the scoliotic deviation of the lumbar scoliosis. The pelvic tilt (r = -0.433; p = 0.031) is inversely correlated, while the sacral slope has a direct relationship (r = 0.419; p = 0.037).  In conclusion, the results of this study indicate that the contribution of the 3D morphology of the spine and pelvis to the thoracic (L1), thoracolumbar (L5) and lumbar (L6) scoliosis provides clinically relevant information. Our results gained by fuzzy-c-means support those in the literature, according to which these subjects are not all hypokyphotic. New parameters such as lordosis and orientation of the PMC, reinforce the idea that there are subgroups within the thoracic scoliosis. Finally, although the thoracolumbar and lumbar subjects appear to differ from a visual standpoint, these subjects are inseparable according to the three-dimensional morphology parameters.

Keyphrases: classification de Lenke, Adolescent idiopathic scoliosis, Lenke classification, fuzzy c-means, three-dimensional morphology, spine, pelvis