Introduction: Standing radiograph Cobb measurement is the standard for clinical assessment of coronal spinal deformity. Angle of trunk inclination (ATI) is an accepted clinical measurement of transverse plane trunk deformity, and has variable reported correlations with Cobb angles. Transverse plane spine deformity is most accurately measured using axial computed tomography (RAsag). To our knowledge no study has correlated ATI with RAsag.
Objectives: To determine the relationship, or lack thereof, between commonly used measures of trunk and spine deformity.
Materials and Methods: Sixteen females that underwent preoperative apical vertebra(e) CT scans were retrospectively studied. Thoracic and thoracolumbar RAsag measurements were date-matched to clinically obtained ATI and Cobb measurements. Two-tailed Pearson correlations were calculated; α<0.01.
Results: Patient age was 14.9 years (11.2−19.0); BMI 19.4 (16.0−25.5). Curve patterns: Lenke 1:5; 2:5; 3:1; 4:1; 5:2: 6:2. Twenty-six curves (15T; 11TL) with complete, date-matched data points were analyzed (Table 1). Relative to RAsag, thoracolumbar ATI is smaller than thoracic. In thoracic curves, ATI correlated with Cobb (r=0.711, P<0.004), Cobb flexibility (r=−0.647, P<0.01), and RAsag (r=0.730, P<0.003). In thoracolumbar curves, ATI correlated with Cobb (r=0.789, P<0.005) and RAsag (r=0.771, P<0.006) but not with Cobb flexibility (r=−0.452, P=0.190).
Conclusions: Trunk and spine thoracic and thoracolumbar transverse plane deformity are correlated, as are trunk transverse plane and spine coronal plane deformity. Increasing trunk deformity limits thoracic, but not thoracolumbar spine flexibility.
Significance: In the un-operated AIS patient, clinically measured ATI accurately reflects the magnitude of transverse plane spine deformity.