Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis in children older than 10 years in the United States. AIS is defined as a lateral spine curvature of 10° or more in the coronal plane, without congenital or neuromuscular comorbidities. The U.S. Preventive Services Task Force (USPSTF) and American Academy of Family Physicians (AAFP) do not recommend for or against AIS screening in asymptomatic patients. Physical examination includes the forward bend test with or without scoliometer, wherein scoliometer rotation between 5° and 7° warrants further evaluation with x-rays. Definitive diagnosis with x-rays allows for measurement of the Cobb angle. For Cobb angles less than 20°, watchful waiting and/or referral for physical therapy are indicated. Referral to a spine specialist for bracing is reasonable for curves between 20° and 26° and is recommended for curves between 26° and 45°. Surgical intervention is considered for initial Cobb angles greater than 40° and recommended for Cobb angles greater than 50°.
Case 3. MG is an 11-year-old patient who is brought to your office for truncal asymmetry that his parents first noticed 3 months ago. MG is asymptomatic. His medical history, growth, and development have been normal. The forward bend test reveals right thoracic prominence. Using a scoliometer smartphone app, you measure the angle of trunk rotation as 7°. X-rays show thoracic scoliosis with a Cobb angle of 20°.
Definitions and Epidemiology
Adolescent idiopathic scoliosis (AIS) is the most common type of scoliosis, accounting for 80% of cases and affecting 1% to 3% of children older than 10 years in the United States.100,101 Infantile idiopathic scoliosis affects children younger than 3 years, and juvenile idiopathic scoliosis affects children ages 4 to 10 years.100 The worldwide prevalence of AIS varies from 0.93% to 12% of adolescents.102 AIS is defined as lateral spine curvature of 10°or more in the coronal plane, without congenital and/or neuromuscular comorbidities.101,103
Two other types of scoliosis exist: congenital and neuromuscular.100,103 Congenital scoliosis derives from malformations of the spine developed in utero, although it may not appear until later in life. Neuromuscular scoliosis is secondary to neurologic or muscular disorders, such as cerebral palsy or spinal muscular atrophy.100
Traditionally, incidence of idiopathic scoliosis was reported as comparable between males and females.100,101 However, a 2021 Korean cohort study found that AIS was 1.44 times more likely in females and overall more common in urban over rural populations, irrespective of age at diagnosis.102 More importantly, clinically significant curvatures greater than 30° are 10 times more likely in females.101
Etiology
The etiology of AIS is multifactorial, with a genetic predisposition and proposed mechanical, metabolic, hormonal, neuromuscular, and growth contributions.103 The presence of genetic factors in the pathophysiology of AIS is well established; however, specific gene(s) or sequence variation(s) have not been identified.104 Though genetics are thought to play a role in the development of AIS, the manner of genetic inheritance is unclear and genetic testing is not currently recommended.101
Recent studies of vertebral growth plates from adolescents undergoing surgical intervention for AIS suggest that the pathogenesis is abnormal neural crest cell migration, specifically with incomplete migration to the anterior somites during early embryogenesis.104
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