Idiopathic Scoliosis

Idiopathic scoliosis is a three-dimensional structural spinal deformity with lateral curvature of the spine and associated vertebral rotation. The cause remains incompletely understood, and is likely multifactorial, with a well established, substantial familial tendency.

It is classified by age of onset:

• Infantile (before age three).
• Juvenile (age three to ten).
• Adolescent (age ten and older), by far the commonest, accounting for the substantial majority of cases.

Management is determined by curve magnitude, skeletal maturity (and so remaining growth potential and progression risk), and age of onset. It ranges from observation alone for mild curves, through bracing, to surgical correction for the most severe or progressive deformities.

Pathophysiology and classification

• Adolescent idiopathic scoliosis typically becomes apparent around the onset of the pubertal growth spurt. Progression risk is directly related to remaining skeletal growth potential. Curves identified earlier in the growth spurt, with more growth ahead, carry a higher risk of further progression than curves identified closer to skeletal maturity.
• Female adolescents have a substantially higher risk of progression requiring active treatment than males, despite a more modest difference in overall prevalence between the sexes. This is relevant to risk stratification and counselling.
• Infantile and juvenile scoliosis are much less common than the adolescent form but carry additional significance. The cumulative remaining growth period during which progression can occur is greater.
• Infantile scoliosis in particular is more often associated with an identifiable cause (including neuromuscular or syndromic conditions). This younger age group warrants more full evaluation to exclude alternative causes.
• The curve pattern (thoracic, thoracolumbar, lumbar, or a combined double curve), the curve magnitude (measured by the Cobb angle on standing spinal radiography) and the direction of curvature provide the essential framework for classification and treatment decisions.

• The typical presenting finding is asymmetry of the shoulders, scapulae, or waistline, with a visible or palpable rib or lumbar prominence. It is frequently first noticed by a parent or the adolescent, or found on school-based or routine clinical screening.
• The prominence is particularly apparent on forward bending, because of the vertebral rotation of true structural scoliosis. This is the basis of the Adams forward bend test used in clinical and school-based screening.
• The great majority of adolescent idiopathic scoliosis is entirely painless. Significant back pain warrants specific consideration of an alternative or additional cause (including, uncommonly, a spinal cord abnormality, tumour, or infection) rather than attribution to idiopathic scoliosis alone.
• Progression is generally gradual and painless. Regular, structured monitoring, rather than reliance on symptoms, is essential to identify progressive curves needing active treatment before they reach a magnitude with significant, potentially longer-term functional or cosmetic consequence.
• Any neurological symptom or sign (including altered reflexes, weakness, or sensory change) is a red flag needing specific investigation rather than attribution to idiopathic scoliosis.
• An atypical curve pattern is also a red flag. A left-sided thoracic curve is less typical of idiopathic scoliosis and warrants evaluation for an alternative cause.

• The standard initial clinical assessment is screening with the Adams forward bend test (observing for asymmetry and rib or lumbar prominence as the adolescent bends forward from the waist).
• Where available, add scoliometer measurement. This simple device measures trunk rotation at the point of maximum prominence. It gives an objective, quantifiable measure to support the decision on formal radiographic evaluation.
• Standing, full-length spinal radiography is the essential, definitive diagnostic and monitoring investigation. It allows measurement of the Cobb angle, the standardised angular measure of curve magnitude.
• It also allows assessment of skeletal maturity using the Risser sign, the degree of ossification of the iliac crest apophysis. This is an indirect measure of remaining growth potential, relevant to progression risk.
• Magnetic resonance imaging of the spine is indicated to exclude an alternative structural cause in specific scenarios: infantile or juvenile scoliosis (higher association with an identifiable cause), an atypical curve pattern, significant associated pain, or any neurological symptom or sign.
• It is not routinely required for typical, straightforward adolescent idiopathic scoliosis.
• Reassess regularly with clinical examination and, where indicated by curve magnitude and remaining growth potential, serial radiography. This monitors for progression throughout the remaining period of skeletal growth.

• Observation, with periodic clinical and, where indicated, radiographic reassessment, is appropriate for mild curves (generally under approximately 20 to 25 degrees). This applies particularly to adolescents with limited remaining growth potential, who have a lower risk of significant further progression.
• Bracing (most commonly a thoracolumbosacral orthosis) is generally recommended for moderate curves (approximately 25 to 40 degrees) in skeletally immature adolescents with substantial remaining growth potential.
• The goal of bracing is to prevent further progression during the remaining growth period, not to correct the existing deformity. Robust, high-quality evidence supports bracing in reducing the likelihood of progression to a magnitude needing surgery, provided brace wear is adequate and consistent.
• Compliance is an important practical consideration, given the substantial daily wear duration typically required.
• Surgical correction, typically posterior spinal instrumentation and fusion, is generally recommended for severe curves (generally exceeding approximately 45 to 50 degrees) or curves with significant, continued progression despite bracing.
• Curves of this magnitude carry a substantially increased risk of continued progression even into adulthood. Very severe, uncorrected curves also carry potential for longer-term cosmetic, functional, and, in the most severe cases, cardiopulmonary consequence.
• The timing and threshold for surgery are individualised according to curve magnitude, pattern, remaining growth potential, and the impact on the adolescent's appearance and function. Discuss the risks and benefits of surgery fully with the adolescent and family.
• Educate and support the patient and family on the practical aspects of bracing (where used) and the psychosocial impact of visible spinal deformity and its treatment during a developmentally sensitive period. Monitor regularly throughout the treatment course.