Sagittal spinopelvic parameters in adolescent idiopathic scoliosis: divergence between Lenke type 5, 6, and healthy adolescents.

BACKGROUND

Understanding the sagittal alignment of the pelvis and spine is essential for evaluating adolescent idiopathic scoliosis (AIS). Comparative studies of sagittal characteristics between AIS subtypes (especially lumbar scoliosis) and healthy Chinese adolescents remain limited.

OBJECTIVE

This study evaluates differences in sagittal spinopelvic alignment between adolescent females with Lenke type 5 and 6 AIS and the healthy counterparts.

METHODS

This study enrolled 156 female patients with AIS (118 Lenke type 5 and 38 Lenke type 6) and 110 age-matched healthy female adolescents. Spinal and pelvic parameters were measured from standing full spine anteroposterior and lateral radiographs, including the main Cobb angle (MCC), minor thoracic curve for type 6, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), pelvic incidence to lumbar lordosis (PI-LL) mismatch, and pelvic tilt (PT). ANOVA compared the dependent variables between the two AIS subtypes (Lenke type 5 and 6) and healthy adolescents, and Pearson's correlation coefficient (r) was used to determine the relationships among the parameters.

RESULTS

PI, LL, SS and PI-LL did not significantly differ between AIS patients and controls. PT differed significantly among groups (p = 0.04). TK was significantly lower in Lenke type 6 compared to Lenke type 5 (p < 0.017 ). Subgroup analysis revealed no significant correlations between sagittal parameters and curve severity or direction in Lenke type 5. The difference between the major and minor curves of type 6 showed a statistically significant correlation with thoracic kyphosis (r = 0.372, p = 0.036) and PI-LL (r = -0.342, p = 0.043). There was statistically significant correlation between the MCC of Lenke type 6 and PI-LL (r =-0.38, p = 0.032).

CONCLUSION

PT reduction as a potential early compensatory trend in Lenke 5, though its predictive utility requires longitudinal validation. The stability of PT across different severities highlights its potential as a marker for early intervention, whereas Lenke 6 appeared to rely more on thoracic curvature adjustments. Dynamic changes in PT and TK may serve as early predictors for lumbar scoliosis progression and elucidate compensatory mechanisms of spinal curvature. These findings could provide clinical guidance for early prevention and targeted therapeutic interventions.