Previous study has reported that kyphoscoliosis in the thoracolumbar junction often have bad prognosis if no proper intervention was performed . For patients with posterior-lateral two ipsilateral thoracolumbar HV, although this condition is less common, paraplegia is a far greater risk. Besides progressive kyphosis, these vertebral abnormalities may also lead to lateral curvature and resulted in kyphoscoliosis. Other than the risk of spinal cord compression in apex vertebra site, it produces a compensatory lumbar hyperlordosis causing low back pain. Therefore, surgical treatment usually was required at the early age to prevent further severe spinal deformity.
In spite of the developments by leaps and bounds in spinal surgical technologies in three decades, the treatment of congenital scoliosis caused by HV is still controversial. Excision of the HV addresses the deformity directly and allows reliable correction immediately in very young patients. Satisfactory correction and restoration of balance can be achieved . Generally speaking, severe global imbalance is not common if curve located in the thoracolumbar spine. Because of the compensatory space was enough in coronal plane (cranial and caudal) and sagittal plane (thoracic kyphosis and lumbar lordosis). In present study, posterior hemivertebrectomy with unilateral short fusion in patients less than 10 years old were performed. The aim is to preserve vertebral growth potential on the concavity, making for further correction of deformity as spine growth. As for unilateral fusion, previous studies had indicated it was effective and safe for very young children at long-term follow-up . Excision of HV removes the primary cause of the scoliosis, which can achieve immediately good correction. However, for patients with congenital scoliosis caused by two ipsilateral HV more than 10 years old, the flexibility of curve is often lower and presenting more rigid in late adolescent than juvenile. Due to asymmetrical growth of hemivertebra, larger gap closure force after HV resection requires strong anchor points. Therefore, bilateral transpedicular screw fixation and fusion are indispensable for these patients.
The fusion level depends on severity of spine deformity, scope and flexibility of curve. For very young children, one vertebra above and below after HV resection were fixated and fused. If the scoliotic curve was large or with focal kyphosis, two vertebrae above and below after HV resection were fused. Of course, for severe and rigid scoliosis or kyphoscoliosis, more fusion level may be needed. Our results showed that correction rate of the major scoliotic and kyphotic curvatures were 74.2 and 65.3% respectively, which is similar to previously reported results for HV excision [4, 7, 10].
Coronal decompensation after HV resection with short fusion is also a problem which can’t be neglected. A large series reported by Li, et al. showed that the overall rate of coronal decompensation is approximately 10.1%, which including 179 cases in children younger than 5 years. Preoperative lower instrumented vertebra (LIV) translation and postoperative LIV disc angle were identified as two independent risk factors . In our study, there are two cases presented the coronal decompensation. We think too short fusion segment and incomplete excision of proximal HV were main reasons. In young children with congenital scoliosis, fusion span determination relies mainly on optimal correction of scoliosis with solid screws and maximal preservation of spinal mobility and growth potential. However, more failure rates and residual curve progression were found in cases with double ispilateral full segmental HV if too short fusion or partial resection in corrective surgery. It is indicated that radical excision of HV could remove the causes of deformity immediately and stop the curve progressive.
Another concern is neurological complication after HV resection via posterior approach. Aydogan M, et al.  reported 11 cases with kyphoscoliosis due to HV by hemivertebrectomy and posterior instrumentation. None of the patients exhibited neurological problems associated with surgery. Our results suggest that HV excision in thoraco-lumbar region is not associated with an increased risk of neurological complications. Only in one patient undergoing one stage excision of three HV, intraoperative mild neurological injury was found. Based on our experience, the correction and balancing of congenital thoraco-lumbar curves are more effectively achieved by HV resection than other treatments. It should be undertaken only by those experienced with this technique.
Some cases presented residual curve progression after surgery, which may be attributed to a variety of factors, including multiple malformed vertebra, failure of segmentation, concave fused ribs, improper maneuver, shorter fusion level, incomplete HV resection and implants failure. Shi Z et al. investigate the causes of failure in the first operation and the revision procedure for patients with congenital scoliosis due to HV . They suggested that limitations of the primary surgery, no or incomplete resection of HV, improper operation during surgery, improper internal fixation material and fixation scope were main cause of revision surgery. A study including 28 children less than 6 years old with HV were reported by Ruf M et al. . They found two patients additional operations were performed because of new developing deformities. One was a bar formation at the operative site and an adjacent segment; another was a new bone mass at the site of the HV excision. They suggested that short fusion may increase the risk of a new deformity and may require re-operation, but this risk was acceptable to minimize the compromise of normal spinal development for very young patients. In our present study, three patients required additional surgery due to residual curve progression during follow-up. They had larger and rigid curve in coronal and sagittal plane before primary surgery. Incompletely excision of proximal HV was the major cause in two cases. Too short fusion and malformed vertebra growth was the major cause in another patient. The revision surgeries were performed and satisfactory outcome were achieved at the latest follow up.
In terms of anterior column reconstruction (ACR), a titanium mesh cage was used for anterior column support and fusion in patients who had residual anterior gap after HV resection. Aydogan M et al.  reported on 19 patients undergoing HV removal with 15 cases experiencing anterior mesh cage support to fill interbody space. They found anterior support in short segmental fusion could correct thoracolumbar kyphosis and increase the stability. In our cases, six cases showed anterior larger gap after HV excision; and titanium mesh cage were used in order to support anterior column and avoid spinal cord shorten too much. In addition to, it was beneficial to get solid fusion in bone cutting area.
This study has some limitations. First, it was a retrospective study with the inherent risk of data inaccuracy. Second, the wide range of the patients’ age makes this small series inhomogeneous and comparison is quite difficult. Finally, this study does not contain results about quality of life in the follow-up. Further study including quality of life and mental health status are needed in the future.