Idiopathic scoliosis and growth--a biomechanical consideration

Growth force proposed as an etiological factor in idiopathic scoliosis was analysed by a mathematical simulation; the results were compared with clinical roentgenograms of patients with idiopathic scoliosis. Growth force is a self-equilibrating internal stress derived from unbalanced growth between two adjacent structures with different growth rates. In the simulation, the localized growth force made the whole spinal column buckle. Two hundred anteroposterior roentgenograms were then compared with the buckling curves. The three most similar buckling curves for each roentgenogram were selected. Of the 600 selected curves, 406 were considered to have produced a high similarity. The curves produced by a growth force extending over a small area, especially at the mid-lower thoracic and lumbar regions, were qualified as curves with a high similarity. The growth force thus does not appear uniformly all over the spinal column but locally and at the mid-lower thoracic or lumbar region. This growth force may represent a factor in the etiology of idiopathic scoliosis.