Objective:To investigate the effects of the correction rate of the proximal thoracic curve and main thoracic curve on postoperative shoulder balance in patients with Lenke1 type idiopathic scoliosis (AIS).Methods:Data of 50 patients with AIS who received posterior spinal deformity correction surgery from January 2013 to January 2020 and were followed up for more than 6 months were retrospectively analyzed, including 12 males and 38 females. The median age was 15 years (14,16) years (range 13 to 18 years). According to the clavicle angle (CA) absolute value >2° and 2.5° and 3° for shoulder imbalances standard, the patients were divided into the postoperative shoulder balance group and shoulder imbalance group. Main thoracic curve Cobb angle, proximal thoracic curve Cobb angle and clavicle angle (CA) were measured preoperative, postoperative and at the last follow-up, and the flexibility of proximal thoracic curve, the flexibility of main thoracic curve, correction rate of proximal thoracic curve, correction rate of the main thoracic curve and other indicators were calculated. Univariate analysis was conducted on the shoulder balance group's related indicators and the shoulder imbalance group, and correlation analysis was conducted with the postoperative shoulder balance and the last follow-up shoulder balance. Multivariate binary logistic regression was performed on statistically significant univariate factors to determine independent risk factors for postoperative shoulder imbalance and the last follow-up shoulder imbalance.Results:The median follow-up time of 50 patients was 18 months (11, 24) months (range 6-36 months). According to the three criteria of shoulder balance, the postoperative correction rate of the proximal thoracic curve in the shoulder imbalance group was significantly lower than that in the shoulder balance group. Under the standard of shoulder imbalance with CA absolute value >2° and 2.5°, there were significant differences in the postoperative correction rate of the main thoracic curve, and the postoperative correction rate of the main thoracic curve in the shoulder balance group was higher than that in the shoulder imbalance group. No matter which shoulder imbalance criteria were used, the postoperative correction rate of the proximal thoracic curve, the correction rate of the main thoracic curve, and the ratio of the correction rate of the main thoracic curve to the proximal thoracic curve was found to be correlated with the postoperative shoulder balance. Only in the group of CA absolute >3°, no correlation was found between the postoperative correction rate of the main thoracic curve and postoperative shoulder balance. The correlation between the correction rate of the proximal thoracic curve and shoulder balance was more significant in the three groups ( P<0.01). Logistic regression analysis showed that the postoperative correction rate of the proximal thoracic curve was an independent protective factor of postoperative shoulder balance ( P<0.05). A better postoperative shoulder balance can be obtained when the main thoracic curve/proximal thoracic curve correction rate was less than 1.5. However, at the last follow-up, no correlation was found between the correction rate and shoulder balance in all three groups. Binary logistic regression analysis showed that preoperative CA was a risk factor for the last follow-up shoulder imbalance. Conclusion:IIn patients with Lenke1 type AIS, the correction rate of the proximal thoracic curve, the correction rate of the main thoracic curve, and their ratio were correlated with postoperative shoulder balance. The matching of the amount of correction of the proximal thoracic curve and main thoracic curve can ensure postoperative shoulder balance, and the amount of correction of the proximal thoracic curve may be a protective factor of postoperative shoulder balance. However, for long-term shoulder balance, the effect of the proximal thoracic curve and main thoracic curve correction rate is not obvious. In contrast, compensatory factors such as proximal thoracic cure aggravation, torso tilt, and lumbar curve aggravation mayaffect.