Clavicle Chest Cage Angle Difference: Is It a Radiographic and Clinical Predictor of Postoperative Shoulder Imbalance in Lenke I Adolescent Idiopathic Scoliosis?

STUDY DESIGN A retrospective study. OBJECTIVE To evaluate the effect of preoperative clavicle chest cage angle difference (CCAD) on postoperative radiographic shoulder imbalance, cosmetic shoulder balance, patient's satisfaction, and surgeon's fulfillment in Lenke I adolescent idiopathic scoliosis (AIS). SUMMARY OF BACKGROUND DATA CCAD is a novel predictor of postoperative radiographic shoulder imbalance in AIS. However, radiographic shoulder balance does not always correspond to cosmetic shoulder balance. METHODS Forty-four Lenke I AIS patients treated with posterior spinal fusion with a minimum 2-year follow-up were analyzed. Shoulder height difference (SHD) and CCAD were measured on anteroposterior standing radiographs. The inner shoulder height (SHi) and the outer shoulder height (SHo) were measured using the patients' photographs. The patients' satisfaction and the surgeons' fulfillment were evaluated using a questionnaire. A receiver operative characteristic curve analysis was performed to explore the threshold values of preoperative CCAD in the prediction of the final follow-up radiographic shoulder imbalance, patients' satisfaction, and surgeons' fulfillment. RESULTS At the final follow-up, the preoperative CCAD was significantly greater in patients with unbalanced shoulders (SHD ≥1 cm). For cosmetic shoulder balance at the final follow-up, there was no significant difference in preoperative CCAD between Group 1i (SHi ≥1 cm, n = 14) and Group 2i (SHi <1 cm, n = 30), and the preoperative CCAD was also similar between Group 1o (SHo ≥1 cm, n = 17) and Group 2o (SHo <1 cm, n = 27). For patients' satisfaction and surgeons' fulfillment, the preoperative CCAD was significantly greater in patients with unsatisfied outcomes. The threshold value of preoperative CCAD to predict the final follow-up radiographic shoulder imbalance, patients' satisfaction, and surgeons' fulfillment was 5.5°. CONCLUSION CCAD is a good radiographic predictor for postoperative radiographic shoulder imbalance in Lenke I AIS patients. Moreover, it is also associated with the patients' satisfaction and surgeons' fulfillment postoperatively. However, CCAD cannot predict postoperative cosmetic shoulder balance. LEVEL OF EVIDENCE 4.