The application of a functional-anatomical model in pulmonary risk assessment for adolescent idiopathic scoliosis.

OBJECTIVE

Severe thoracic adolescent idiopathic scoliosis (AIS) often compromises pulmonary function. We sought to identify the radiographic parameters that best predict pulmonary impairment in these patients.

METHODS

110 thoracic AIS patients (mean age 14.3 ± 2.3) who underwent full-spine radiography and pulmonary function tests (PFTs) were retrospectively reviewed. Cobb angle, Rotation angle relative to the midline (RAml), rotation angle relative to the sagittal plane (RAsag), rib-hump index (RHi), vertebral translation (VT), the angle of lateral deviation of the apical vertebrae from the midline (MLdev), kyphosis–lordosis index (KLi), posterior hemithoracic symmetry ratio (PHSr), thoracic width ratio (THWr), lung height–width ratio (LHWr) and the angle of the sternum relative to the apical vertebral body (α) were measured. Pulmonary outcomes were recorded as predicted percentages of vital capacity (VC%), forced vital capacity (FVC%), forced expiratory volume in 1 s (FEV₁%) and FEV₁/FVC%. Spearman correlation, LASSO regression and k-means clustering were used to relate radiographic variables to pulmonary function.

RESULTS

RAml (r = − 0.51), RAsag (r = − 0.49) and RHi (r = − 0.42) showed the strongest negative correlations with FEV₁% (all p < 0.001). LASSO regression identified RAml, RHi as the most influential predictors, explaining 52% of the variance in predicted FVC%. Two clusters were identified: a “mild” group (n = 78; mean RAml 25.4°; RHi 0.19; predicted FVC% 83.7%) and a “severe” group (n = 32; mean RAml 41.8°; RHi 0.58; predicted FVC% 58.3%).

CONCLUSIONS

RAml, RHi are robust radiographic predictors of pulmonary dysfunction in thoracic AIS and should be prioritised in pre-operative risk assessment.