Adolescent idiopathic scoliosis (AIS) poses challenges in achieving optimal three-dimensional correction. While posterior fusion with pedicle screws has shown success, osteotomy techniques, such as Ponte osteotomy, have further improved outcomes. However, residual vertebral rotation remains a concern, impacting long-term complications. Intervertebral disc release (IDR) presents a potential solution to enhance derotation and reduce fusion levels, particularly in Lenke Type 5 AIS. This prospective randomized controlled trial aims to evaluate the clinical effectiveness of IDR in treating Lenke 5 AIS, comparing it to Ponte osteotomy. The study focuses on axial vertebral rotation correction, coronal curve improvement, blood loss, hospital stay, and adverse events. Participants aged 10-18 with Lenke 5 AIS will undergo either IDR or Ponte osteotomy, randomly assigned. Outcome measures include axial rotation correction rate, radiographic parameters, and clinical assessments. A total of 132 participants will be recruited. The IDR technique, through posterior disc removal, presents a promising approach to optimize derotation in Lenke 5 AIS. While offering potential advantages, challenges like limited working space and bleeding risks require careful consideration. The study's findings aim to provide robust clinical evidence, enhancing treatment strategies for Lenke 5 AIS and offering innovative approaches for AIS as a whole.

Hypotheses To examine the clinical effectiveness of intervertebral disc release in treating Lenke 5 adolescent idiopathic scoliosis, our working hypothesis posits that participants treated with intervertebral disc release achieve a higher rate of correction for axial vertebral rotation (especially the rotation of the apex vertebrae), demonstrate improved correction rate for coronal curve, experience no additional blood loss or allogeneic transfusions, and do not experience an increase in the length of hospital stay (LOH) or adverse event (AE) rate compared to individuals treated with Ponte osteotomy.

Objectives Based on the aforementioned hypothesis, this study aims to evaluate the clinical effectiveness of intervertebral disc release in treating Lenke 5 adolescent idiopathic scoliosis. The evaluation includes assessing the efficacy of vertebral derotation and the change in Cobb angle following the correction surgery, as well as perioperative blood loss, transfusion volume/rate, length of hospital stay, and the rate of adverse events (AEs).

Study setting and investigators The trial will take place at a tertiary care teaching hospital. The study will be conducted in the wards and operating rooms of the orthopedic department, which has 200 beds, at this comprehensive hospital with a total of 2500 beds. Participants will be recruited from the outpatient clinic by one investigator and will provide their consent to the investigators. All investigators have practical experience in clinical orthopedic research projects. A single team of surgeons, who have completed a clinical fellowship in spinal surgery, will perform the surgeries.

Participants The study will enroll patients between the ages of 10 and 18, with an American Society of Anesthesiologists (ASA) physical status classification of I-II. These patients will be diagnosed with Lenke 5 type adolescent idiopathic scoliosis and will require posterior correction, internal fixation, and bone graft fusion. Enrollment in the study will be contingent upon signing a written informed consent.

Patients with a history of previous corrective surgery, or with sharp, angulated short-segmental scoliosis, and those with congenital scoliosis requiring 3-column osteotomy will be excluded. Participants who experience dura mater laceration or unexpected massive bleeding during the operation will be excluded as well.

Randomization and concealment Before commencing the study, an independent researcher with no participant contact will utilize SAS 9.4 software (SPSS Inc., Chicago, IL, USA) to generate a blocked random number table (block size = 4). This table will be used to allocate eligible participants in a 1:1 ratio to 2 groups. A group designated as the IDR group will undergo subsequent intervertebral disc release following Ponte osteotomy on the predetermined vertebral levels, whereas the PO group will solely undergo Ponte osteotomy.

Data collection and monitoring The collected data will be entered into electronic case report forms (eCRFs) through a process of double data entry and logic validation. Subsequently, the eCRFs will be uploaded to a central server. To uphold the trial's quality standards, a proficient clinical trial expert will be invited to perform audits of both the trial implementation process and data entry on a bimonthly basis. The purpose of the regular audit is to ensure adherence to the protocol and Good Clinical Practices (GCPs). The expert may review source documents to verify the accuracy of the data recorded on CRFs. During each audit, all study records from the past 2 months will be thoroughly examined to ensure the quality of the trial conduct and the consistency between the source data and the data entered in the database. This study will not include any interim analysis.

Sample size and statistical analysis This trial will recruit 132 participants (66 participants per group) to confirm the primary outcome equivalence between IDR group and PO group. According to a prior study, the correction rate of axial rotation of the apex vertebrae is 0.60±0.23. Assuming that alpha = 0.05, power = 0.95, two-sided 95% CI, and the follow-up loss = 15%, 66 participants are needed for each group. G-power software version 3.1.9 was used for calculating the sample size. The primary outcome measures the correction rate of axial vertebral derotation. The mean values and standard deviations of these outcomes will be calculated for both the intervention and control groups. To assess the differences between the two groups, independent sample t-tests or Mann-Whitney U tests will be performed. Secondary outcomes measureå such as blood loss, allogeneic transfusions, length of hospital stay (LOH), and adverse events (AEs) will also be analyzed. Continuous variables (e.g., blood loss, LOH) will be analyzed using independent sample ttests or Mann-Whitney U tests, while categorical variables (e.g., allogeneic transfusions, AEs) will be analyzed using chi-square tests or Fisher's exact tests, as appropriate. The difference between the IDR group and PO group will be reported as mean difference and lower one-sided 95% confidence interval (CI), along with a one-sided p < 0.05. Statistical analyses will be conducted using SPSS.

Dissemination plan The trial results will be submitted to an international peer-reviewed journal. Additionally, the findings will be presented at relevant national and international conferences.

Inclusion Criteria:

• Between the ages of 10 and 18
• American Society of Anesthesiologists (ASA) physical statusclassification of I-II
• Lenke 5 type adolescent idiopathic scoliosis

Exclusion Criteria:

• A history of previous corrective surgery
• With sharp, angulated short-segmental scoliosis
• With congenital scoliosis requiring 3-column osteotomy