Study Design: Prospective cohort study

Objective: To determine the rate of curve progression and factors related to curve progression in untreated adolescent idiopathic scoliosis in a prospective cohort study within a national school screening program.

Methods: Over 140,000 school children are screened annually in Singapore for common health conditions, including scoliosis. In 1996–97, a randomized sample in four age groups consisting of 72,699 children was enrolled in a scoliosis prevalence study, 263 were found to have spinal curvatures of 10 degrees or more. After exclusions, 250 children were followed up over a five year period up to 2001–02. Basic demographic data, age at menarche or break of voice, scoliometer reading, curve type, Cobb angle, curve rotation, and Risser grade were recorded. Curve progression was correlated to individual factors such as age, sex, puberty, curve type and magnitude as well as combinations of factors.

Results: Overall, 28% of the 250 curves progressed. Age at diagnosis, sex, pre-menarche status, and curve magnitude were statistically correlated to curve progression. Taking curve magnitude and age together, 53% of 11–12 year-olds with curves 20 degrees or more progressed compared to 10% of 13–14 year-olds with curves less than 20 degrees. 56% of children with curves 20 degrees or more and Risser grades 0–2 progressed, compared to 17% with curves less than 20 degrees and Risser grades 3–5. Combining curve magnitude, age, sex, and puberty together, a pre-pubertal female under 13 years old with a curve of 25 degrees or more has a 70% chance of curve progression. In comparison, a post-pubertal female older than 13 years of age and a curve of less than 25 degrees has only a 10% chance of progression. Curve progression in adolescent idiopathic scoliosis has been reported to vary from 5.2% to 56%, with the lower rates being found in school screening studies. Nachemson et al (1982) reported that 10–12 year old girls with untreated scoliosis of 20–29 degrees had a 60% risk of curve progression. Lonstein and Carlson (1984) reported progression in 23.2% of untreated children and that curve magnitude, skeletal immaturity, and curve pattern were associated with progression.

Conclusions: Our findings are similar, with pre-pubertal females under the age of 13 years old and with large curves at diagnosis having the greatest risk of progression.