Early onset scoliosis: A comprehensive review of aetiology, diagnosis and classification.

Early-onset scoliosis (EOS) encompasses spinal deformities that develop before ten years of age, occurring during the critical period of thoracic and pulmonary growth. Beyond spinal curvature, EOS represents a developmental disorder in which structural imbalance compromises thoracic expansion and lung maturation, predisposing to thoracic insufficiency syndrome (TIS). The historical evolution of the term-from infantile and juvenile scoliosis to the comprehensive framework of EOS-reflects a shift from age-based categorization to one integrating growth dynamics and physiological impact. The Classification of Early-Onset Scoliosis (C-EOS) introduced a multidimensional approach incorporating aetiology, curve magnitude, progression rate, and sagittal alignment. Recent concepts further redefine EOS as a disorder of thoracic growth interference rather than a purely age-limited condition, emphasizing thoracic height, skeletal maturity, and pulmonary function as key determinants. Although uncommon, with an estimated prevalence of four to ten per 10,000 children, EOS imposes a disproportionate burden through progressive deformity, repeated interventions, and long-term respiratory morbidity. Diagnosis requires careful clinical assessment and advanced low-dose imaging, complemented by MRI for structural and functional evaluation. Accurate diagnosis and classification are therefore essential to stratify severity, anticipate progression, and guide timely referral. EOS thus exemplifies the intersection of orthopaedics, pulmonology, and developmental biology, and future research should focus on biologically grounded classification that aligns diagnostic stratification with functional prognosis.