Adolescent idiopathic scoliosis (AIS), which develops between the ages of 10 and 18 years, accounts for approximately 90% of cases of idiopathic scoliosis.[8]Konieczny MR, Senyurt H, Krauspe R. Epidemiology of adolescent idiopathic scoliosis. J Child Orthop. 2013 Feb;7(1):3-9.
https://www.doi.org/10.1007/s11832-012-0457-4
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Infantile idiopathic scoliosis develops before the age of 3 years, with a male-to-female ratio of 3:2, and accounts for <1% of idiopathic scoliosis cases; juvenile idiopathic scoliosis accounts for the remainder and develops between the ages of 3 and 10 years. Together, infantile and juvenile idiopathic scoliosis are referred to as early onset scoliosis.[2]Yaszay B, Newton PO. Idiopathic scoliosis. In: Weinstein SL, Flynn JM, Crawford HA, eds. Lovell and Winter's Pediatric Orthopaedics. 8th ed. Philadelphia: Wolters Kluwer, 2021:659-720.
AIS is a diagnosis that falls along a spectrum of spinal deformity disorders. The exact incidence of asymptomatic spinal deformity is not known, as most patients with minor curvatures have no signs or symptoms related to the deformity. In the US, the reported prevalence of patients with a curve of >10° ranges from 0.5 to 3 per 100 children and adolescents, and the estimated prevalence of patients who will require treatment for spinal deformity ranges from 0.5 to 3 per 1000.[9]Kane WJ. Scoliosis prevalence: a call for a statement of terms. Clin Orthop Relat Res. 1977 Jul-Aug;(126):43-6.
http://www.ncbi.nlm.nih.gov/pubmed/598138?tool=bestpractice.com
[10]Montgomery F, Willner S. The natural history of idiopathic scoliosis. Incidence of treatment in 15 cohorts of children born between 1963 and 1977. Spine. 1997 Apr 1;22(7):772-4.
http://www.ncbi.nlm.nih.gov/pubmed/9106318?tool=bestpractice.com
[11]Cheng JC, Castelein RM, Chu WC, et al. Adolescent idiopathic scoliosis. Nat Rev Dis Primers. 2015 Sep 24;1:15030.
http://www.ncbi.nlm.nih.gov/pubmed/27188385?tool=bestpractice.com
In the UK, prevalence of idiopathic scoliosis is estimated at 2% to 3% in 10 to 16 year olds.[12]Lenssinck ML, Frijlink AC, Berger MY, et al. Effect of bracing and other conservative interventions in the treatment of idiopathic scoliosis in adolescents: a systematic review of clinical trials. Phys Ther. 2005 Dec;85(12):1329-39.
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The male-to-female ratio is thought to be equal for mild curves. However, curve progression requiring treatment is much more common in female adolescents, with an estimated ratio of 7-8:1.[13]Bunnell WP. The natural history of idiopathic scoliosis before skeletal maturity. Spine. 1986 Oct;11(8):773-6.
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Additionally, the number of affected girls increases exponentially with the magnitude of the curvature.[13]Bunnell WP. The natural history of idiopathic scoliosis before skeletal maturity. Spine. 1986 Oct;11(8):773-6.
http://www.ncbi.nlm.nih.gov/pubmed/3810290?tool=bestpractice.com