Comparison between preoperative and postoperative three-dimensional reconstructions of idiopathic scoliosis with the Cotrel-Dubousset procedure.

Study Design. Pre- and postoperative three-dimensional reconstructions of the spine and rib cage were done and compared in a group of adolescents with idiopathic scoliosis. Objective. Changes in the shape of the thoracic spine and rib cage induced by the Cotrel-Dubousset instrumentation and procedure were documented. Summary of Background Data. Although many authors have reported significant curve improvement in the frontal plane, attempts to document derotation of the spine have shown only limited correction of apical vertebral rotation. Methods. Three-dimensional reconstructions were obtained pre- and postoperatively using a stereoradiographic technique in a group of 37 adolescents with idiopathic scoliosis. Several geometrical indices of the spine and rib cage were compared using Student t tests. Results. The curve correction averaged 50% in the frontal plane and 24% in the plane of maximum curvature, while normal thoracic kyphosis was maintained in the sagittal plane. The orientation of the plane of maximum curvature was shifted very significantly toward the sagittal plane, indicating en bloc movement of the thoracic spine and three-dimensional correction of the deformity. A small but significant change in vertebral axial rotation and rib hump was found and improvement in the overall orientation of the ribs was documented. Conclusions. The Cotrel-Dubousset instrumentation and procedure are effective in producing three-dimensional improvement of the thoracic spine by en bloc relocation of the instrumented spine rather than by vertebral axial derotation.