Safety and Effectiveness Evaluation of the Minimal Invasive Deformity Correction (MID-C) System in Adolescent Idiopathic Scoliosis (AIS)

Adolescent idiopathic scoliosis (AIS) is a common disorder of unknown etiology in which the vertebrae and discs gradually develop a curvature that is first detected in patients between 11 and 20 years of age. The deformity is 3-dimensional, with a coronal curve measured from radiographs by the Cobb angle . The Cobb angle measurement of scoliosis represents the sum of the angular wedging of each vertebra and disc between the superior and inferior end vertebrae . Although a small curve is well tolerated and does not require treatment, a large curve can progress to the point that it is cosmetically unacceptable, interferes with chest wall mechanics, and produces cardiac and pulmonary compromises. The natural history of AIS apparently includes 2 stages: the initiation of the curve and its subsequent progression. The factors responsible for the initiation of the curve are unknown, but the subsequent progression of the curve is clearly associated with the adolescent growth spurt . The primary risk factors for progression include age at onset and the magnitude of the curve; young patients with large curves are at the highest risk . Although numerous treatment methods have been recommended for patients with AIS, the only accepted treatment includes bracing for skeletally immature patients with curves between 25 and 40 degrees and operative correction with spinal fusion for patients with curves greater than 45 degrees. For many teenagers, the cosmetic and social concerns associated with bracing has caused compliance problems with wearing the brace and many patients only wear the brace at home . While operative intervention completely corrects the scoliosis or rib hump, it eliminates segmental spinal motion, and concentrates stresses at the ends of the fusion potentially leading to disc degeneration and back pain. Despite satisfactory short-term results of operative instrumentation and fusion, a less invasive technique preserving more motion with a smaller scar represents