Patterns of coronal and sagittal deformities in adolescent idiopathic scoliosis

Abstract Background: Thoracic scoliosis has been shown to be associated with hypokyphosis in adolescent idiopathic scoliosis (AIS). However, the relationship of sagittal spino-pelvic parameters with different coronal curve patterns and their influence on patient-perceived quality of life is unknown. This study aims to determine the association between coronal and sagittal malalignment in patients with AIS and to determine their effects on SRS-22r scores. Methods: A cross-sectional study was conducted on 1054 consecutive patients with AIS. The coronal Cobb angle, thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), PI-LL mismatch (PI-LL), pelvic tilt (PT), and sacral slope (SS) were measured on standing radiographs. The coronal Cobb angle (mild: 10-20°; moderate: >20-40°; severe: >40°) and PI (low: <35°; average: 35-50°; high: >50°) were divided into 3 sub-groups for comparison. Relationship between coronal curve magnitudes and sagittal parameters was studied as was their association with SRS-22r scores. Results: Low PI had smaller SS (30.1±8.3° vs 44.8±7.7°; p<0.001), PT (-0.3±8.1° vs 14.4±7.5°; p<0.001), and LL (42.0±13.2° vs 55.1±10.6°; p<0.001), negative PI-LL mismatch (-12.1±13.1° vs 4.1±10.5°; p<0.001) as compared to large PI. There were no significant relationships with PI and TK (p=0.905) or curve magnitude (p=0.431). No differences in sagittal parameters were observed for mild, moderate or severe coronal Cobb angles. SRS-22r scores only correlated with coronal Cobb angle and larger Cobb angles were negatively correlated with the function, appearance and pain domains. Conclusions: The sagittal profile for AIS is associated with the pelvic parameters especially PI but not with the coronal curve pattern. All patients have a similar TK regardless of coronal curve type. However, it appears that the coronal deformity is a greater influence on quality of life outcomes especially those >40°.