Role of Clavicle Chest Cage Angle Difference in Predicting Postoperative Shoulder Balance in Lenke 5C Adolescent Idiopathic Scoliosis Patients After Selective Posterior Fusion

Objective: To evaluate the role of preoperative clavicle chest cage angle difference (CCAD) on postoperative radiographic shoulder imbalance, patient's satisfaction and surgeon's fulfillment in Lenke 5 adolescent idiopathic scoliosis (AIS). CCAD, as a novel radiographic parameter, has proven to be a reliable predictor for postoperative shoulder imbalance in Lenke 1 AIS patients. However, the value of CCAD in predicting shoulder balance has never been evaluated in Lenke 5 AIS patients.

Methods: A total of 42 Lenke 5C AIS patients aged from 10 to 18 years old with a minimum 2-year follow-up were enrolled for evaluation. All patients underwent selective posterior spinal instrumentation and fusion using the all segmental pedicle screw technique by the same surgical team. The fusion levels were determined according to the Lenke criteria. Shoulder height difference (SHD) and CCAD were measured on anteroposterior (AP) standing radiographs. 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: The average preoperative Cobb angle of the main curve was 46.8° ± 4.8°, and the average immediate postoperative Cobb angle was 13.3° ± 2.6°, representing an average surgical correction rate of 75.6% ± 8.5%. The average follow-up time was 29.2 months. At the last follow-up, the value of preoperative CCAD was significantly higher in patients with unbalanced shoulders (SHD ≥ 10 mm). At the final follow-up, 66.7% (28/42) of the patients were satisfied with their appearance, while 33.3% (14/42) of the patients were not satisfied with their appearance. At the final follow-up, 61.9% (26/42) of the surgeons were fulfilled with their operation, while 38.1% (16/42) of the surgeons were not. For patients' satisfaction and surgeons' fulfillment, the preoperative CCAD was significantly greater in patients with unsatisfied outcomes.

Discussion: Clavicle chest cage angle difference could be a reliable predictor for evaluating postoperative shoulder imbalance in AIS patients undergoing selective posterior fusion for Lenke 5C curves. A greater preoperative CCAD was significantly correlated with a postoperative radiographic imbalance of shoulders and dissatisfaction, which will guide spine surgeons in their preoperative planning and in the surgical management of AIS to reduce postoperative shoulder imbalance.