Hemivertebra is the most common type of congenital scoliosis (46%), which develops slowly at first and peaks in progression during adolescence [1]. Spinal cord and nerve damage can occur when the deformity is severe, so early diagnosis and appropriate surgical treatment can prevent worsening of the deformity and nerve damage and can maximize correction of the deformity before the spine develops structural compensation. Hemivertebral body resection can effectively correct the spinal deformity and restore the balance of the spine, which is the most reasonable and fundamental treatment for pediatric scoliosis caused by hemivertebral body. Since March 2002, 12 cases of pediatric scoliosis due to completely segmented half vertebrae were treated with Ⅰ stage posterior hemivertebral body resection and pedicle root instrumentation, and are reported as follows. 1 .Materials and Methods 1.1 General information In this group, there were 7 cases of male and 5 cases of female, aged 2.3~6.5 years old, average 4.2 years old. 8 cases were diagnosed with spinal deformity or shoulder inequality, 2 cases were diagnosed with lumbosacral lipomas and dorsal hirsutism, and 2 cases were diagnosed with X-ray examination for other reasons. All cases had no symptoms of nerve damage, normal sensation and muscle strength in both lower limbs, and normal urination and defecation. Before the operation, all of them had standing spinal orthopantomograms (Figure 1), and Cobb’s angle was measured. All of them were completely segmented half vertebrae, located in the thoracic spine (T5~T9) in 4 cases, the thoracolumbar spine (T10~L2) in 6 cases, and the lumbar spine (L3~L4) in 2 cases. All of them underwent MRI examination before surgery, and it was found that 3 cases were combined with spinal cord tethering and conus hypoglossus (among which 2 cases were end-filament thickening type and 1 case was lipoma type), and 2 cases were combined with longitudinal fissure of the spinal cord. 9 cases underwent three-dimensional CT examination before surgery. 1.2 Surgical methods The children were extubated under general anesthesia, lying prone on a pediatric spinal surgical frame or with chest and pelvic padding and abdominal suspension. For children with combined spinal cord tethering or longitudinal spinal cord dehiscence, the lumbosacral spinal cord tethering or longitudinal spinal cord dehiscence was treated first. A small longitudinal incision is made in the lumbosacral region to expose the end of the cones and the cauda equina, and the tethering is released by cutting off the thickened end filaments or removing the conical lipomas. The bony crest of the longitudinal spinal cord fracture is often located in the vicinity of the deformed hemivertebra. A longitudinal incision of about 6-8 cm is made with the hemivertebra as the center, stripping the paraspinal muscles and exposing the transverse processes of the adjacent vertebrae. If necessary, the hemivertebrae are identified by X-ray fluoroscopy, and the vertebral plates, articular eminences, transverse processes, and posterior portions of the pedicles of the hemivertebrae are resected. In the case of combined longitudinal spinal cord dissections, the longitudinal bony ridge was removed after further exposure. When the posterior part of the semivertebra is removed, the dura mater of the spinal cord and the nerve roots passing through the superior and inferior intervertebral foramina of the semivertebral body can be visualized, and the dura mater of the spinal cord and the nerve roots can be protected under direct visualization. The hemivertebra located in the thoracic spine was resected with the head of the rib and the proximal ribs for 3~4 cm, and the pleura or peritoneum on the anterolateral side of the hemivertebra was bluntly stripped to expose the anterolateral part of the hemivertebra. Intraoperatively, the upper and lower discs of the semivertebral body were first bitten off to expose the semivertebral body, and then quickly bitten off. The upper and lower vertebral body endplates were resected to the cancellous bone, and the contralateral intervertebral disc was scraped off as much as possible. For intraoperative blood seepage, gelatin sponge impregnated with thrombin can be used to stop bleeding by compression, which is effective. Then, the pedicles of the upper and lower vertebrae were marked with Kirschner’s needle (a nerve probe could be used to help determine the sites of the upper and lower pedicles from the resected intervertebral plate space), and further fluoroscopic localization of the C-arm was used to determine the direction of the drilling, and then the cervical pedicle screws (diameter of 3.5 mm, length of 2.5-3.5 cm) were placed after confirming that there was no error. After probing without bleeding, fixation rods were placed, and the convex side was corrected with compression until the half vertebral body gap disappeared (if the gap remained, implantation of occluded fragments of bone was performed). Finally, the convex side of the vertebral plate was decorticated and the retained fragmented bone was implanted for fusion. Intraoperative wake-up tests were performed in all cases. For combined longitudinal spinal fracture and spinal cord tethering, epidural silicone drains were placed. After the operation, the polyester bandage was externally immobilized for 3~4 months. 1.3 Follow-up All cases were followed up for 6-42 months, with an average of 18 months. 2. Results 2.1 The duration of surgery for this group of patients was 150~330 minutes, with an average of 210 minutes, and blood transfusion ranged from 0~600 ml, with an average of 350 ml. Parents of all the children were very satisfied with the treatment results at the final follow-up. 2.2 The normal and lateral spinal radiographs (Figure 2) were reviewed within 1 week after the operation, and the average Cobb’s angle of scoliosis was 42.5°±6.7° before the operation, and it was corrected to 16.2°±3.2° after the operation, with a correction rate of 64.7%.The Cobb’s angle of the 5 cases with obvious retroconvexity was corrected from 33.5°±5.2° to 13.3 ° ± 5.6°, a correction rate of 53.2%. Lateral and posterior convexity were 15.6° ± 5.8° and 14.2° ± 3.3°, respectively, at the final follow-up. 2.3 There were no intraoperative and postoperative complications, no wound infection or nerve injury, no internal fixation detachment or breakage, and local segmental fusion was obtained. 3 .Discussion Congenital scoliosis is a common spinal deformity in children, of which hemivertebra is the most important cause. Congenital scoliosis due to hemivertebrae often results in severe scoliosis deformities with a poor prognosis, and non-surgical treatments, including bracing, are unsuccessful in preventing the development of the deformity, so early surgery is necessary for many children.McMaster [5] suggested that hemivertebral deformities located in the thoracolumbar spine have the worst prognosis, with an average annual exacerbation of 7° by the age of 10 years, and an annual exacerbation of 14° in the peak of youthful growth, and that many of them are more than 3 years old by the age of 3 years. Many patients with a scoliosis of more than 50° at the age of 3 years can reach 140° to 180° after an average of 14 years of development. The children in this group were 2.3 to 6.5 years old, with a mean of 4.2 years, and were all younger and treated earlier. The advantages of early surgery for congenital scoliosis due to hemivertebra are firstly, less difficult and less invasive surgery, and less risk of neurological injury; secondly, pediatric congenital scoliosis is locally flexible and often does not yet have secondary structural compensatory curvature, and only short-segment fusion is needed; and lastly, early surgery not only achieves better immediate orthopedics, but also improves the near-term and even long-term outcomes. The main surgical methods for the treatment of congenital scoliosis due to hemivertebra are: ① Simple posterior in situ fusion: this procedure refers to posterior spinal fusion without instrumentation, which was the standard surgical method for the treatment of congenital scoliosis in the past, but is now less frequently used. ② Posterior fusion + instrumented orthopedic internal fixation, this method can maintain spinal stability, promote fusion, and reduce the incidence of pseudoarthrosis, but in younger children, the phenomenon of “curvature axis” may occur in the future. (iii) Combined anterior and posterior fusion, which can provide a higher rate of correction and reduce the incidence of pseudoarthrosis and “curvature”, but the operation needs to be carried out in one stage or in phases anteriorly and posteriorly, which is very traumatic. Convex lateral epiphyseal block, which is actually an anterior vertebral epiphyseal block + posterior convex lateral joint fusion, also requires an anterior and posterior one-stage or staged procedure, which is risky, and is only suitable for early stage and children with mild scoliosis. ⑤ Concave lateral staged bracing is only suitable for younger children who still have a large growth potential of the spine and need to wear external fixation support for a long time, which requires multiple surgeries. (6) Hemilaminectomy can directly remove the deformity-causing factors, especially in patients with coronal imbalance can obtain good orthopedics immediately. There are anterior and posterior one-stage or two-stage hemivertebrectomy and simple posterior resection. In this group of children, simple posterior hemilaminectomy with pedicle instrumentation was used to fix segmental fusion. Simple posterior hemivertebrectomy is most suitable for the removal of lower thoracic or thoracolumbar hemivertebrae in young children without obvious secondary structural scoliosis.Nukamura et al. reported five cases of one-stage posterior hemivertebrectomy for the treatment of a single, completely segmented hemivertebral deformity, noting that the pedicles of the hemivertebrae were thicker than normal, and therefore the hemivertebrae could be scraped off easily through the pedicles; moreover, young children’s vertebral bodies were covered by thicker cartilage and periosteum and could be easily and completely removed. Moreover, the vertebral body of young children is wrapped by thicker cartilage and periosteum, which makes it easy to be completely removed. The simple posterior hemivertebral body resection is less traumatic and does not require anterior exposure. For the thoracic hemivertebra, by removing part of the rib head, the hemivertebral body is ideally exposed and the hemivertebral body can be completely resected. Intraoperative visualization of the spinal dura mater and nerve roots is possible, so the procedure is safer and there is less risk of injury to the spinal cord and nerve roots. In order to close the gap after hemivertebral body resection and promote fusion, as well as to put pressure on the convex side to obtain ideal coronal and sagittal correction, it is necessary to have a strong internal fixation. We used 3.5-mm-diameter cervical pedicle screws to securely fix the upper and lower vertebrae to ensure ideal postoperative correction and secure fusion of the adjacent vertebrae. The use of pedicle pins in younger children does not affect the development of the vertebral body, and Ruf and Harms demonstrated that pedicle pinning in younger children is safe and effective, does not stunt the development of the vertebral body, is close to normal vertebral body development, and does not cause spinal stenosis as demonstrated by MRI and CT. For a young, growing and developing spine, the fusion segments should be as short as possible to minimize the impact on normal vertebral development, and the procedure is safe and minimally invasive. In this group, the children were young and had no obvious compensatory structural scoliosis, and only the fixed fusion of the adjacent upper and lower vertebrae on the convex side was performed, which not only achieved a better deformity correction effect, but also localized segmental fusion was achieved at the follow-up, and there was no rod breakage phenomenon. In order to achieve localized fusion, it is very important to completely remove the “Y”-shaped intervertebral disc around the hemivertebral body during the operation. In conclusion, the use of simple posterior hemivertebral body resection and pedicle instrumentation for the treatment of congenital scoliosis due to hemivertebral body in pediatric patients has achieved ideal results, not only through the short-segment segmental fusion, but also as a minimally invasive and safe surgical method.