Predictors of postoperative shoulder imbalance in adolescent idiopathic scoliosis: a retrospective cohort of 468 patients.

STUDY

DESIGN

Retrospective cohort study.

PURPOSE: To determine the independent risk factors associated with postoperative shoulder imbalance (PSI) in adolescent idiopathic scoliosis (AIS) patients after posterior spinal fusion.

BACKGROUND

Postoperative shoulder imbalance is one of the most frequent complications following surgery in cases of adolescent idiopathic scoliosis (AIS). Quantitative Radiographic parameters that can be used for the preoperative planning of surgery are not clearly identified. The purpose of this study was to determine independent predictors of postoperative shoulder imbalance and to examine the correction PT/MT ratio as a quantitative radiographic predictor.

METHODS

For this study, 468 consecutive AIS patients subjected to posterior spinal fusion surgery, during January 2018 through December 2025 have been reviewed retrospectively. Data for this study were collected from the Hakeem electronic medical records system while radiographic measurements were obtained from the Picture Archiving and Communication System (PACS). PT and MT Cobb angles, T1 inclination, clavicle angle, radiographic shoulder height (RSH), and number of fusion segments were some of the radiographic measurements taken. PSI was diagnosed as RSH ≥ 15 mm after at least 24 months of follow up period. Independent predictors of PSI were found using multivariate logistic.

RESULTS

Female patients comprised 82%, while the mean age was 14.7 ± 1.9 years. PSI occurred 20.9% (n = 98). In comparison to the non-PSI group, the PSI group had low levels of UIV (below T3, p = 0.003), high preoperative left shoulder elevation, large PT Cobb angles (p < 0.001), and low PT correction rate (p < 0.001). Univariate analysis showed that residual proximal thoracic curvature ≥ 15° (OR 3.1, 95% CI 1.8-5.4, p < 0.001), UIV below T3 (OR 2.8, 95% CI 1.6-4.9, p = 0.001), preoperative left shoulder elevation, and PT/MT correction ratio below 0.59 (r=-0.53, p < 0.001) were independent factors of postoperative shoulder imbalance. The ROC curve analysis revealed an optimal PT/MT correction ratio threshold of 0.59.

CONCLUSIONS

Residual proximal thoracic deformity and UIV lower than T3 were significant independent risk factors for shoulder imbalance. A PT/MT correction ratio less than 0.59 was an independent risk factor and might serve as a quantifiable radiographic criterion for surgical planning. These findings require prospective external validation before routine clinical implementation.

LEVEL OF EVIDENCE: III.