Congenital scoliosis is a three-dimensional deformity of the spine due to congenital abnormalities in the development of vertebral segments that can cause an imbalance in the growth of the spine. There are various types of congenital scoliosis, and the deformity is complex and difficult to treat clinically. I. Classification Based on embryological causes, congenital scoliosis can be divided into two major categories: formation insufficiency and segmentation disorders. 1. Incomplete formation Incomplete vertebral segment formation, also known as type I malformation, can be partial, forming a cuneiform vertebra, or complete, forming a hemivertebral body. The longitudinal growth of the vertebral body is attributed to the epiphyseal cartilage at the upper and lower ends. The growth capacity of the upper and lower ends of the hemivertebral body and the severity of the resulting deformity are related to its specific morphology: (1) Well-segmented hemivertebral body: both its upper and lower ends have growth potential and the morphology of the adjacent vertebral body is normal. (2) Partially segmented hemivertebrae: the upper or lower end of the hemivertebrae has growth potential and the other end is fused to the adjacent vertebrae. (3) Unsegmented hemivertebrae: the upper and lower ends have no growth potential, and the hemivertebrae are completely fused with the upper and lower vertebrae. (4) Butterfly vertebrae: more symmetrical hemivertebrae are formed on both sides, and both upper and lower ends have growth potential. (5) embedded hemivertebrae: the upper and lower ends of the hemivertebrae have growth potential, but the adjacent vertebrae have compensation for them, and this hemivertebrae is equivalent to “cutting into” the adjacent segment. 2.Segmental disorders Segmental disorders, also known as type II deformities, can be partial or complete (blocked vertebrae). For partial subluxation, the location can be anterior, posterior, lateral or mixed. In the case of one-sided bone bridge formation or asymmetrical bone bridges, severe scoliosis can result due to impaired development of the side with the bridge. In many cases, the different types of deformities mentioned above are often combined, some involving several segments, forming a mixed deformity, such as incomplete formation combined with segmental disorders (type III deformity). The embryogenesis of the spine occurs at the same time as many organ systems, so it is not uncommon for malformations of other organ systems to be present in combination. 30-60% of children with congenital spinal deformities have malformations of other organ systems in combination. The most common coexisting malformations are spinal cord and urogenital malformations. Spinal cord malformations include spinal cord embolism, spinal cord longitudinal fracture, and spinal cord cavernosity. The most common genitourinary anomalies are renal hypoplasia and ectopic kidney. II. Etiology Congenital scoliosis is uncommon in the general population and its exact incidence is not known; most cases are found sporadically, but the family incidence has been reported in the literature to be 1-5%. Female patients are slightly more common than male patients, with a female to male ratio of approximately 3 or 2 to 1. It has been suggested in the literature that the occurrence of congenital scoliosis is related to genetic and environmental factors. Genetic factors have been reported during the study of congenital scoliosis in twins, and more recently, genetic mutations have been suggested as a cause of congenital scoliosis. The influence of environmental factors has also been studied. It has been found that maternal exposure to carbon monoxide during somite formation induces vertebral malformations in mouse and rabbit models of embryonic development. However, the mechanism of action of carbon monoxide is not clear. What is known is that carbon monoxide can affect the cartilage of the spine by causing hypoxemia or genetic mutations. In addition, it has been found that there is an increased incidence of idiopathic scoliosis in families with congenital scoliosis. III. Natural course Regardless of the etiology, congenital scoliosis tends to continue to worsen during growth and development. The risk of worsening scoliosis is related to the imbalance in the number of epiphyseal growth zones and the location of the vertebral deformity. In the absence of any treatment, approximately 85% of patients with congenital scoliosis have an aggravation of curvature greater than 41o at developmental maturity. e.g., segmented hemivertebrae have a more pronounced tendency to aggravate because they continue to grow during growth. By the same token, the deformity most likely to be aggravated by the presence of a concave unilateral segmentation disorder with a well-segmented hemivertebra on the convex side because there is little growth potential on the growth-retarded side. In contrast, cuneate vertebrae are at less risk of aggravation, whereas fully blocked or embedded hemivertebrae do not produce progressive scoliosis. Therefore, it can be assumed that the more unbalanced the bilateral growth potential, the more severe the development of the deformity. In addition, the location of the deformity also has an impact on the progression of scoliosis. The most severe deformity is caused by scoliosis located in the thoracolumbar segment, while the deformity in the upper thoracic spine is relatively mild. For the natural course of congenital scoliosis, the following issues need to be considered: type of deformity, location of deformity, number of deformities, initial severity of scoliosis, and overall growth trend above and below. Analysis of the above issues can help determine the likelihood of progression of scoliosis and select an appropriate treatment method. IV. Treatment 1. Non-surgical treatment Congenital scoliosis requires continuous and close clinical observation, and this observation should be performed periodically during the growth and development process. During clinical observation, attention should be paid to the evaluation of the progression of the curvature to determine whether surgical treatment is needed. For complex deformities, early treatment is often simpler and safer. Compared to idiopathic scoliosis, conservative treatment of congenital scoliosis is of less value. Longer-term conservative treatment and close observation is possible only for butterfly vertebrae, unsegmented hemivertebrae or fully blocked segmentation disorders, and for the few cases where multiple hemivertebrae above and below are located on exactly two sides with mutual compensatory properties. For flexion with some flexibility, bracing is the only conservative treatment that may be effective. For the few patients with a long and flexible curvature, bracing can be used. However, most congenital scoliosis curves are short and rigid. Because of this characteristic and the long time required before skeletal maturation, bracing is often used only as a temporary treatment. Therefore, there are two options for the treatment of congenital scoliosis: (1) clinical observation for static deformities; (2) surgical treatment for persistently aggravated scoliosis. 2. Surgical treatment Most patients with congenital scoliosis require surgery to avoid severe curvature and spinal imbalance at skeletal maturity. Its treatment is very different from idiopathic scoliosis, and because its surgical approach and timing are determined by a variety of factors, the operator needs to develop an individualized treatment plan based on the characteristics of each patient, after a thorough evaluation of the type of deformity and its potential risk of progression. Congenital scoliosis progresses because one side of the spine grows faster than the other, so the main rationale for surgical treatment is to stop this unbalanced growth, allowing for simultaneous correction of the deformity. There are four main surgical approaches: posterior spinal fusion, combined anterior and posterior spinal fusion, hemivertebral epiphyseal fusion on the convex side, and hemivertebral resection.