Risk Factors for Postoperative Shoulder Imbalance in Patients with Lenke Type 1 and 2 Scoliosis Treated using the Vertebral Coplanar Alignment Technique.

Study Design: This was a multicenter retrospective cohort study.

Objective: We investigated the incidence of postoperative shoulder imbalance (PSI) and its risk factors in patients with Lenke types 1 and 2 scoliosis corrected using vertebral coplanar alignment (VCA).

Summary Of Background Data: PSI in scoliosis affects patient quality of life. While other correction methods have reported a high correction rate for the main thoracic curve (MTC) in relation to PSI, this correlation has not been confirmed for the VCA technique.

Methods: We studied 176 patients with Lenke types 1 and 2 scoliosis who underwent posterior corrective fusion surgery using the VCA technique at 11 institutions. At two years postoperatively, patients were divided into two groups based on radiographic shoulder height (RSH): PSI- (RSH<2 cm) and PSI+ (RSH≧2 cm) groups. We analyzed the risk factors for PSI.

Results: The overall incidence of PSI two years postoperatively was 11.4% (20/176), with 9.2% (11/119) and 15.8% (9/57) in patients with Lenke types 1 and 2, respectively. Contrary to a previous study, a high MTC correction rate did not emerge as a risk factor for PSI. Instead, preoperative left shoulder elevation and low postoperative thoracic kyphosis and greater T1 tilt and high apical vertebral body-to-rib ratio were associated with PSI in patients with Lenke type 1. Preoperative left shoulder elevation and a low postoperative proximal thoracic curve (PTC) correction rate were identified as risk factors for PSI in patients with Lenke type 2.

Conclusion: Our results suggest that proper correction of the PTC, rather than compromise MTC correction, may help prevent PSI in the VCA technique. This method is particularly advantageous for addressing Lenke type 1 scoliosis and yields favorable outcomes in shoulder balance. Patients with preoperative left shoulder elevation, especially Lenke type 2, are at high risk of developing PSI.

Level Of Evidence: 4.