Curve Progression in Adolescent Idiopathic Scoliosis in an Asian Population

Purpose: 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 1996/1997, a randomized sample in 4 age groups consisting of 72,699 children was enrolled in a scoliosis prevalence study, where 263 were found to have spinal curvatures of 10 degrees and above. After exclusions, 250 children were followed up to evaluate curve progression over a five year period up to 2001/ 2002. 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 defined as five degrees or more. Curve progression was correlated to individual factors like age, sex, puberty, curve type and magnitude as well as combinations of factors like curve magnitude with age, sex, puberty and age at diagnosis. Summary of Findings: Overall, curves in 28% of children 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 prepubertal female under 13 years old and having 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.

Relationship Between Findings and Existing Knowledge: Curve progression in adolescent idiopathic scoliosis has been reported to vary from 5.2% to 56% depending on the patient population, 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) in a study on curve progression of cases detected through screening found that 23.2% children with untreated scoliosis progressed, and that curve magnitude, skeletal immaturity, and curve pattern were associated with progression. 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.

Overall Significance of Findings: Knowing the risk of curve progression in a local Asian population is important in the decision making process when giving advice on the management of the patient with adolescent idiopathic scoliosis. Data on the factors relating to curve progression has so far been available only from studies in Western populations. To the best of our knowledge, this is the first study on curve progression in a school screening population in Asia.