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 degrees; moderate: >20-40 degrees; severe: >40 degrees) and PI (low: <35<degrees>; average: 35-50 degrees; high: >50 degrees) 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 (30.18.3 degrees vs 44.8 +/- 7.7 degrees; p<0.001), PT (-0.3<plus/minus>8.1 degrees vs 14.4 +/- 7.5 degrees; p<0.001), and LL (42.0<plus/minus>13.2 degrees vs 55.1 +/- 10.6 degrees; p<0.001), negative PI-LL mismatch (-12.1<plus/minus>13.1 degrees vs 4.1 +/- 10.5 degrees; 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 degrees.