A Prospective Randomized Controlled Trial of the Drum Tower Rule Machine Learning Model for Lowest Instrumented Vertebra Selection in Lenke Type 1 and Type 5 Adolescent Idiopathic Scoliosis

Inclusion Criteria

Inclusion Criteria: * Diagnosis of adolescent idiopathic scoliosis classified as Lenke type 1A or Lenke type 5C. * Age 10 to 18 years, inclusive. * Scheduled to undergo posterior spinal fusion using an all-pedicle screw instrumentation system. * Planned selective thoracic fusion or selective lumbar fusion, with a clinical need for lowest instrumented vertebra decision-making. * Availability of required preoperative standing full-spine radiographs and bending radiographs. * Ability and willingness to complete the planned 24-month postoperative follow-up. * Written informed consent provided by the participant and legal guardian. Exclusion Criteria: * \- Congenital scoliosis, neuromuscular scoliosis, syndromic scoliosis, or other non-idiopathic scoliosis. * History of spinal trauma, spinal tumor, spinal tuberculosis, or spinal infection. * Previous spinal surgery. * Severe sagittal spinal deformity, such as Scheuermann disease, for which the study model is not applicable. * Neurological symptoms or signs. * Leg length discrepancy greater than 10 mm. * The surgeon determines that there is no clinical equipoise for lowest instrumented vertebra selection because one option is clearly contraindicated for safety or anatomical reasons. * Inability to complete follow-up or required study assessments.