Analyse de la geometrie externe du tronc scoliotique en flexion laterale.

摘要

Adolescent idiopathic scoliosis (AIS) is a complex 3D deformation of the entire musculoskeletal system of the trunk, whose cause is unknown.; The assessment of the flexibility of the whole scoliotic trunk through a quantitative analysis of external trunk asymmetries as well as of changes in external trunk deformities during the lateral bending tests would enable a better prediction of the reducibility of the three-dimensional deformities. Such an approach would therefore help the surgeon to choose the appropriate spinal instrumentation to use based on the projected result for the whole trunk rather than just the spinal correction.; The main objective of this project is to implement a method to analyze the external geometry of the scoliotic trunk in lateral bending. This method uses a non-invasive approach to quantify the changes in scoliotic deformities during the lateral bending tests. More specifically, it consists in (i) developing a novel method to extract sections from the surface of the trunk, (ii) quantifying the external asymmetries in standing posture before and after surgery using the proposed method, (iii) analyzing and quantifying the effect of lateral bending tests on the external trunk geometry, and lastly, (iv) identifying the clinical indices that express the strongest correlation between the surgical correction of the trunk's asymmetries and the changes in the deformities of the external trunk geometry during the lateral bending tests.; In order to analyze and quantify the external asymmetries of the scoliotic trunk in different postures, a novel algorithm for extracting trunk sections starting from the back valley was developed. This algorithm consists, as a first step, in defining and calculating the points belonging to the back valley, and as a second step, in calculating the 3D positions of points forming the sections. The points belonging to the back valley are determined by a semi-automatic method which consists firstly in selecting special markers on the surface of the trunk and secondly in calculating a set of geodesic curves delimited by these markers. The sections are then obtained by calculating the intersections of the three-dimensional mesh of the trunk with a series of inclined planes defined from the back valley curve.; The proposed method was validated by means of a set of clinical descriptors allowing to measure the external trunk asymmetries as well as surgical corrections. These asymmetries were evaluated both on transverse cross-sections and on sections obtained with the new method. A mannequin, a healthy subject and a cohort of scoliotic subjects were used for this validation study. The cohort available for this project includes 19 subjects, five of these having a thoracic curvature and 14 having a thoracolumbar curvature.; The evaluation of the effect of the lateral bending test on the external geometry of the trunk was performed by analyzing the changes in deformity of the trunk during the lateral bending test in comparison with the surgical correction of the trunk's asymmetries. The same cohort was used to evaluate the effect of the lateral bending test on the external trunk shape.; The sections obtained based on the back valley yielded very low measurements of the clinical indices calculated on the mannequin and on the healthy subject. A qualitative evaluation of post-operative geometries demonstrated that the corrections evaluated with the new method are more coherent than those evaluated with transverse cross-sections.; From this preliminary study, the indices that seem to show a good correlation between changes in the deformities during the lateral bending test and surgical correction of trunk asymmetries are those that measure gibbosity (rib hump), section rotations and back surface rotations.; In the short term, the proposed method could be the focus of clinical validation on a larger cohort. Secondly, a fully automatic detection of the back valley would allow automation of the tr