Nonoperative treatment is the first-line treatment in AIS. Skeletally immature patients with curves exceeding 40 degrees and skeletally mature patients with curves greater than 50 degrees are advised to undergo surgical treatment. Patients should be classified using the Lenke system, with selective fusion performed when appropriate. The selection of the upper instrumented vertebra is based on the structurality of the proximal curve, proximal kyphosis, and clinical shoulder balance. The lowest instrumented vertebra is chosen based on the last touched vertebra, the end vertebra in structural lumbar curves, and the stable sagittal vertebra.