Scoliosis: discs and vertebrae. Cobb angle: friend or foe?

Introduction Both vertebral and disc deformity contribute to scoliosis deformity, but the Cobb angle measures both, without distinguishing their relative magnitudes, which are approximately equal. (The disc deformity is greater in the lumbar region than in the thoracic.) Most attention has been given to the vertebral deformity, which apparently develops because of growth disturbance, and some subsequent remodeling. Conversely, discs do not grow in height while adolescent deformity is progressing. It appears from a few studies that progression of scoliosis occurs initially in the discs and subsequently in the vertebrae. Nutritional compromise has been implicated premature disc degeneration on the concave side in scoliosis. Our rat-tail model in which a curvature is imposed along with compression develops a ‘structural’ disc deformity with tissue remodeling after 5 weeks, and we are studying the underlying mechanisms.