The experimental basis of idiopathic scoliosis.

Idiopathic scoliosis is a complex three-dimensional deformity of the spine of which the scoliotic deformity and rotation are entirely secondary to an abnormality of shape in the median sagittal plane. In the thoracic region, there is a lordosis where a kyphosis should exist. In a controlled series of animal experiments using the growing New Zealand white rabbit as the model, idiopathic scoliosis can readily be produced if an asymmetric lordosis is created in the lower thoracic spine. Neither pure lordosis nor pure scoliosis produces the progressive idiopathic deformity. In the experimental animal when the normal thoracic kyphosis is reconstituted before maturity, the idiopathic deformity spontaneously improves. This lays the foundation for a more physiologic approach to treatment.