en ستون فقرات Spine surgery پژوهشی Research Article <div style="text-align: justify;"><strong>Background</strong>: Surgical correction of Lenke type 2 adolescent idiopathic scoliosis (AIS) is challenging, particularly when selecting the upper instrumented vertebra (UIV) in the proximal thoracic (PT) curve. Although incorporating PT curve into fusion is standard practice, the effect of UIV selection on postoperative shoulder imbalance is uncertain.<br> <strong>Objectives</strong>: This study aims to evaluate shoulder imbalance in patients with lenke type 2 AIS undergoing corrective surgery.<br> <strong>Methods</strong>: This retrospective cohort study included 12 Lenke type 2 AIS patients who underwent corrective surgery. Data, including demographic details, radiological features, and shoulder balance, were collected preoperatively, postoperatively, and during follow-up. Statistical analyses were performed to evaluate changes in radiographic angles and shoulder balance.<br> <strong>Results</strong>: Significant postoperative reductions were observed in Cobb angles, sagittal alignment, shoulder balance, and lumbar lordosis. The median shoulder balance deviation decreased from the preoperative to the final follow-up. The type of UIV device used showed no significant relationship with changes in shoulder balance. However, the UIV inclination demonstrated a median change of 4.5&deg;, with no significant relationship with the device used.<br> <strong>Conclusion</strong>: Preoperative lateral shoulder balance considerably influences postoperative balance, surpassing the impact of UIV selection. Our results underscore the importance of considering shoulder balance when selecting UIV for patients with Lenke type 2 AIS.</div> Adolescent idiopathic scoliosis (AIS), Lenke classification, Spinal fusion, Upper instrumented vertebra (UIV), Shoulder balance, Radiographic analysis 173 182 http://jros.iums.ac.ir/browse.php?a_code=A-10-1355-2&slc_lang=en&sid=1 Mohammadreza Chehrassan morchehrasan@yahoo.com 10031947532846007906 10031947532846007906 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Farshad Nikouei nikouei.f@iums.ac.ir 10031947532846007907 10031947532846007907 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Mohammadreza Shakeri mshakeri3116@gmail.com 10031947532846007908 10031947532846007908 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Ali Valiollahpour Amiri Hamidortho50@gmail.com 10031947532846007909 0009-0000-5108-2606 Yes Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Mahdi Yaqubnejad myn.iums@gmail.com 10031947532846007910 10031947532846007910 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Ebrahim Ameri Ameri.e@iums.ac.ir 10031947532846007911 10031947532846007911 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran. Hasan Ghandhari Ghandhari.h@iums.ac.ir 10031947532846007912 10031947532846007912 No Department of Orthopedics, School of Medicine, Bone and Joint Reconstruction Research Center, Shafayahyaeian Hospital, Iran University of Medical Sciences, Tehran, Iran.