The ApiFix MID-C System is a unidirectional expandable rod, designed to be connected unilaterally to the spine via 2 anchor points on the concave side of a scoliotic deformity above and below the apex of the major curvature to treat adolescent idiopathic scoliosis. The MID-C System is designed to act as an internal brace. Patients implanted with the device in the US within 2 years of FDA's approval of H17001 should be enrolled in the study. A minimum number of 200 patients will be enrolled in this study.

Inclusion Criteria:

• Adolescent Idiopathic Scoliosis classified as Lenke Type 1 or Type 5 curves;
• Cobb angle between 35-60 degrees (inclusive);
• Flexible curve that that reduces to ≤ 30 degrees on lateral side-bending radiographs or as evident by traction x-ray;
• Kyphosis angles of ≤ 55 degrees measured from T5 to T12;
• Appropriate candidate for posterior surgical approach;
• Patient has good general health;
• Patient has no known hypersensitivity or allergies to titanium;
• Patient's guardian signs a written informed consent form (ICF).

Exclusion Criteria:

• Any type of non-idiopathic scoliosis;
• Any main thoracic deformity that includes vertebral levels and cranial including to T2;
• Known history of existing malignancy, or any systemic or local infection;
• Spinal cord abnormalities that require treatment;
• Known neurological deficit (defined as motor grade < 5/5);
• Known poor bone quality defined as T score -1.5 or less;
• For female Patient, pregnancy;
• Previous spine surgery that would prevent the successful performance of the MID-C system ;
• Active systemic disease, such as AIDS, HIV, or active infection;
• Active infection or the skin is compromised at the surgical site;
• Systemic disease that would affect the Patient's welfare or overall outcome of the study.