How Common Is Medial and Lateral Shoulder Discordance in Lenke 1 and 2 Curves?

Study Design. Retrospective study of prospectively collected data. Objective. To analyze the incidence and the patterns of medial and lateral shoulder discordance among Lenke 1 and 2 patients. Summary of Background Data. Postoperative shoulder imbalance (PSI) is still common in Lenke 1 and 2 adolescent idiopathic scoliosis (AIS). This could be due to presence of medial dan lateral shoulder discordance. Methods. One hundred fifty-one Lenke 1 and 2 AIS patients were recruited. Lenke 1 curves were subclassified into Lenke 1ve (flexible) (proximal thoracic side bending [PTSB] Cobb angle < 158) and 1thornve curves (stiff) (PTSB Cobb angle between 158 and 24.98). T1 tilt represented "medial shoulder balance'' and radiological shoulder height (RSH) represented "lateral shoulder balance.'' We categorized patients into three concordant shoulder pattern types (medial balanced/lateral balanced [MBLB], medial imbalancedthornve/lateral imbalancedthornve (MIthornve/LIthornve), medial imbalanced-ve/lateral Imbalanced-ve (MI-ve/LI-ve), and six discordant shoulder pattern types. Results. The mean age was 16.2 +/- 5.7 years. Eighty-one patients (53.6%) had concordant pattern and 70 patients (46.4%) had discordant pattern. Lateral shoulder imbalance was noted in 35.1% of patients and medial shoulder imbalance in 43.7% of patients. In Lenke 1-ve curves, 35 patients (68.6%) had concordant shoulder imbalance with medial imbalanced-ve/lateral imbalanced-ve (MI-ve/LI-ve) being the commonest pattern (68.6%). In Lenke 1thornve curves, 33 patients (55.0%) had concordant shoulder pattern with medial balanced/lateral balanced (MB/LB) being the commonest type (57.6%). In Lenke 2 AIS, 27 patients (67.5%) had discordant pattern with medial imbalancedthornve/lateral balanced (MIthornve/LB) being the commonest pattern (44.4%) (P value = 0.002). Conclusion. 46.4% Lenke 1 and 2 AIS patients had shoulder discordant pattern. This was more prevalent in Lenke 2 curves (67.5%). In Lenke 1-ve (flexible) curves, MI-ve/LI-ve pattern was the commonest pattern. In Lenke 1thornve curves (stiff), there were almost equal number of concordant and discordant shoulder pattern. In Lenke 2 patients, the most common pattern was MIthornve/LB.