Postoperative shoulder balances of Lenke 2 adolescent idiopathic scoliosis patients with preoperative right-elevated shoulder after selective thoracic fusion

Background: Until now, whether the fusion of proximal thoracic curve is necessary in Lenke 2 adolescent idiopathic scoliosis patients remains controversial.Objective: To evaluate shoulder balances of Lenke 2 adolescent idiopathic scoliosis patients with preoperative right-elevated shoulder after selective thoracic fusion and to analyze the factors associated with postoperative shoulder imbalance.Methods: Eighteen Lenke 2 adolescent idiopathic scoliosis patients with right-elevated shoulder were included in the study.Thoracic spine was proximally fused to T3 or below(proximal thoracic [PT] curve was partially fused or unfused). The incidences of postoperative shoulder imbalance(radiographic shoulder height [RSH]1 cm) were calculated 3 months after operation and at the last follow up. Correlations between postoperative RSH and preoperative radiographic parameters(T1 tilt,clavicle angle, RSH, PT curve Cobb angle, PT bending Cobb angle, main thoracic [MT] curve Cobb angle, and MT bending Cobb angle) were analyzed. The correlations between the change of RSH and PT Cobb angle change, MT Cobb angle change, PT curve correction as well as MT curve correction were also evaluated.Results: The incidences of postoperative shoulder imbalance were 11.1% and 16.7%, respectively, 3 months after operation and at the last follow up. Preoperative radiographic parameters were not correlated with postoperative RSH(P0.05). The change and correction rate of MT curve were significantly correlated with the change of RSH(P0.05).Conclusions: Lenke 2 adolescent idiopathic scoliosis does not necessarily imply full fusion of PT curve. Overcorrection of MT curve is considered as an important risk factor of postoperative shoulder imbalance.