Association between trunk rotation and pelvic rotation in adolescents with idiopathic scoliosis

BACKGROUND: Previous studies have suggested an association between pelvic rotation (PR) and scoliotic deformity in severe adolescent idiopathic scoliosis (AIS), but none have investigated this relationship in mild to moderate AIS. OBJECTIVE: To investigate the relationship between PR and trunk rotation in mild to moderate AIS. METHODS: This was a case-control study. The cases were 32 AIS patients with PR in the opposite direction to the thoracic curve, and the controls were 32 AIS patients with PR in the same direction as the thoracic curve. All patients were assessed with the Adams forwards bend test. Type II trunk rotation was selected as exposure. Logistic regression was used to estimate the association between PR direction and types of trunk rotation while accounting for confounders. Multiple linear regression was used to analyse the relationships between PR magnitude and the angle of trunk rotation (ATR). RESULTS: Logistic regression showed an unadjusted OR of 9.13 (95% CI 2.92-28.50, P < 0.001), and adjustment for sex and Cobb angle only slightly changed the OR (adjusted OR, 8.23; 95% CI, 2.51-27.01; P = 0.001). The concave/convex ratio was associated with ATR measurements in both cases (beta = 0.379; P = 0.030) and controls (beta = 0.468, P = 0.008). CONCLUSION: An association was found between PR and trunk rotation, which may help achieve more effective physiotherapy in mild to moderate AIS.