King classification: Idiopathic scoliosis is categorized into five types based on the scoliosis site, parietal vertebrae, severity of scoliosis, flexibility and compensatory bending. Type I: lumbar and thoracic curves both exceed the sacral center vertical line (CSVL), and the Cobb angle of the lumbar curve is larger, and its flexibility is poorer than that of the thoracic curve (if the thoracic curve is larger than the lumbar curve in the standing position, but the lateral curvature is softer than that of the upper thoracic curve, it will also be categorized as type I). Type II: thoracic and lumbar curves both exceed the CSVL, and the Cobb angle of the thoracic curve is larger and its flexibility is poorer. Type III: uni-thoracic curvature with compensatory lumbar curvature not exceeding the CSVL; Type IV: long thoracic curvature with L5 bisected by the CSVL and L4 tilted into the long thoracic curvature; Type V: structural bi-thoracic curvature with T1 tilted towards the concave side of the upper thoracic curvature or the convex side of the lower thoracic curvature. This typology is a landmark in the history of orthopedic spine surgery. Lenke’s typology can be divided into three steps: In the first step, the type of scoliosis is determined according to the position of the primary scoliosis and the structural features of the secondary scoliosis (6 types). Type 1: primary thoracic curve, thoracic curve is the primary curve, proximal thoracic curve and thoracolumbar/lumbar curve are non-structural secondary lateral curves; Type 2: double thoracic curve, thoracic curve is the primary curve, proximal thoracic curve is a structural secondary lateral curve, thoracolumbar/lumbar curve is a non-structural secondary lateral curve; Type 3: double primary curve, thoracic and thoracolumbar/lumbar curves are structural lateral curves, and proximal thoracic curve is a non-structural lateral curve. The thoracic flexion is the primary scoliosis with a Cobb angle greater than or equal to the thoracic girdle/lumbar flexion or a difference of no more than 5° between the two; Type 4: triple primary scoliosis, with the proximal thoracic flexion, thoracic flexion, and thoracic girdle/lumbar flexion being structural scoliosis. Both the thoracic and thoracolumbar/lumbar bending may be primary lateral bends; Type 5: thoracolumbar or lumbar bending, thoracolumbar/lumbar bending is a structural primary lateral bend, and both the proximal thoracic and thoracic bends are nonstructural lateral bends; Type 6: thoracolumbar/lumbar and thoracic bending, thoracolumbar thoracolumbar/lumbar bending is a primary lateral bend with an angle of at least 5° greater than that of the thoracic bending, the thoracic bending is a structural secondary lateral bend, and the proximal thoracic bending is a nonstructural lateral bend. In the second step, the lumbar curvature was further modified into 3 types, A, B, and C, based on the position of the median sacral vertical line (CSVL) in relation to the lumbar curvature. Type A: The CSVL passes between the lumbar vertebral bodies below the stabilizing vertebrae on both sides of the pedicles, and if there is any doubt about whether the CSVL passes between the pedicles bilaterally, the scoliosis is determined to be type B. In this type of scoliosis, there must be a thoracic scoliosis with the parietal vertebrae located at or above the T11/T12 intervertebral space. Type B: The CSVL is located between the posterolateral boundaries of the pedicles of the concave side of the lumbar vertebrae to the outer edges of the lumbar vertebral bodies or intervertebral discs. If there is any question as to whether the CSVL is in contact with the vertebral body or outer edge of the intervertebral disc, it is determined to be Type B. This type of scoliosis is also seen only when the parietal vertebrae are located in the main thoracic vertebrae and therefore does not include thoracolumbar/lumbar scoliosis; Type C: The CSVL is located outside the lumbar vertebral body or outer edge of the intervertebral disc. The primary scoliosis in this type of deformity may be located in the thoracic, lumbar, and/or thoracolumbar segments. If there is any question as to whether the CSVL is in contact with the vertebral body or outer edge of the intervertebral disc, the same is true for Type B. Type C may include all deformities in which the primary thoracic scoliosis is the dominant scoliosis, and will necessarily include all thoracolumbar/lumbar scoliosis. In the third step, three types of thoracic curvature modification were identified based on the characteristics of the sagittal thoracic (T5-12) lordosis: a T5-12 lordosis angle of less than 10° was determined to be negative (-), 10° to 40° was considered normal (N), and greater than 40° was considered positive (+). This completes the Lenke classification of idiopathic scoliosis.