The Scoliosis Research Society has defined scoliosis as a lateral curvature of the spine greater than 10 degrees as measured using the Cobb method on a standing radiograph. Idiopathic scoliosis is a structural curve with no clear underlying cause.
Idiopathic scoliosis is classified based on the age of the patient when it is first identified. Infantile scoliosis has an onset before three years of age. The infantile form accounts for fewer than 1 percent of all cases. Juvenile scoliosis is first detected between three and 10 years of age. The juvenile form occurs in 12 to 21 percent of all patients with idiopathic scoliosis. Adolescent idiopathic scoliosis is found between age 10 and skeletal maturity. The adolescent form accounts for the majority of cases of idiopathic scoliosis.
Scoliosis is present in 2 to 4 percent of children between 10 and 16yearsofage. The ratio of girls to boys with small curves of 10 degrees is equal but increases to a ratio of 10 girls for every one boy with curves greater than 30 degrees. Scoliosis in girls tends to progress more often and, therefore, girls more commonly need treatment than boys. The prevalence of curves greater than 30 degrees is approximately 0.2 percent, and the prevalence for curves greater than 40 degrees is approximately 0.1 percent.
The risk of curve progression can be estimated by taking into account the patient's sex, time of menarche and growth potential (Tanner stage and Risser grade), and the magnitude of the curve.
Curves less than 30 degrees at bone maturity are unlikely to progress, whereas curves measuring from 30 to 50 degrees progress an average of 10 to 15 degrees over a lifetime. Curves greater than 50 degrees at maturity progress steadily at a rate of 1 degree per year. In most patients, life-threatening effects on pulmonary function do not occur until the scoliotic curve is 100 degrees or greater. Of equal significance is the fact that significant psychologic illness has been found in up to 19 percent of females who have curves greater than 40 degrees as adults.
We usually recommend surgery for patients with a curvature greater then 50 degrees.