The natural history of idiopathic scoliosis.

Background. The natural history of idiopathic scoliosis is a crucial issue in the planning and assessment of different treatment methods. This article presents the evaluation of scoliotic deformity in immature patients who have been in observation without any treatment. Material and methods. 159 patients (128 girls, 31 boys) were examined between 1971 and 2002. Skoliosis was diagnosed at a mean age of 6 years 4 months (range 2.1-8.10), and observation was concluded at a mean age of 16 years 11 months (range 14.6-20.3). The mean follow-up was 10 years 5 months. The prognostic factors analyzed were: age, sex, Cobb angle, Mehta angle, apical vertebral rotation, specific rotation, Risser test. The progression and regression of curvature was analyzed in different biological age periods, and was measured by calculating the difference in the Cobb angle on successive x-rays divided by the interval between x-rays. Results. The mean progression of curvature before age 5 was 5.7 degrees per year; in the 6-10 age bracket, 2.3 degrees per year; in the 11-15 age bracket, 7.4 degrees per year; in the >15 age bracket, 0.3 degrees per year. The mean progression for patients with Risser 1 was 8.8 degrees per year; Risser 2, 7.3 degrees per year; Risser 3, 5.1 per year; Risser 4, 2.1 degrees per year; Risser 5, 0.3 degrees per year. Conclusions. The progression of curvature in idiopathic scoliosis is variable, and is influenced by age. Knowledge of the natural history of idiopathic scoliosis is a crucial tool in predicting the development of spinal curvature. The Risser test and biological age are the only effective predictors of progression.