Objective:To systematicly investigate the risks of shoulder imbalance in Lenke type 2 adolescent idiopathic scoliosis（AIS） patients underwent selective posterior thoracic fusion surgery. Methods:Preoperative

postoperative and the last follow-up standing whole-spine radiographs of 168 consecutive patients with Lenke type 2 curves who underwent selective posterior thoracic fusion surgery were analyzed. Imaging parameters

including clavicle angle（CA）

radiographic shoulder height（RSH）

T1 title

proximal thoracic（PT）curve Cobb angle

Main thoracic curve（MT）Cobb angle etc were analyzed first by univariate analysis and Chi-squared analysis

and then stepwise logistic regression analysis. Results:Shoulder imbalance occurred in 28 patients（16.7%）at the last follow-up. Factors significantly associated with shoulder imbalance by univariate and Chi-squared analysis were magnitude of preoperative MT curve

the radiographic shoulder height（RSH）after surgery

T1 tilt

clavicle angle and RSH at follow-up

and the difference in levels between lower instrumented vertebra（LIV） and end vertebra（EV）

neutral vertebra（NV）

stable vertebra（SV） and the last toughing vertebra of CSVL（LTV）. Stepwise logistic regression analysis identified the magnitude of preoperative MT curve（OR=1.112

95%CI=1.017 to 1.088

P=0.010）and LIV-LTV（OR =2.635

95% CI =1.363 to 9.442

P =0.012） as factors significantly associated with shoulder imbalance.Conclusion:The magnitude of preoperative MT curve and selection of LIV may mainly influence the postoperative shoulder balance in Lenke type 2 curve.