Thoracic sagittal plane variations between patients with thoracic adolescent idiopathic scoliosis and healthy adolescents.

Abstract

To analyze the sagittal thoracic parameters of different types of progressive thoracic adolescent idiopathic scoliosis (AIS) patients and compare them with healthy adolescents. 115 AIS patients with main thoracic curves (Cobb: 59.4 ± 12.7) were prospectively compared with 116 healthy adolescents. The AIS and control (C) groups were homogeneous in terms of age and gender. Standing sagittal radiographs were analyzed for differences in T5-T12 kyphosis, T5-T8 and T9-T12 segmental kyphosis, the change between these two angles, and the double rib contour sign. Statistical analyses were performed using the χ ², one-way ANOVA, Mann-Whitney U and Student's t tests. The sagittal parameters of Lenke 1 curves did not differ from healthy adolescents (T5-T8: 17.1 ± 10 vs C: 16 ± 7; T9-T12: 6.3 ± 7 vs C: 7.9 ± 5; T5-T12: 23.9 ± 14 vs C: 23.9 ± 8). Compared with the controls, Lenke type 3 curves were globally more hypokyphotic (T5-T12: 18.9 ± 12 vs C: 23.9 ± 8, P = 0.027) due to a "lordosis" of the lower thoracic segment (T9-T12: 0.9 ± 10 vs C: 7.9 ± 5, P = 0.001). Type 2 curves tended to exhibit more pronounced upper thoracic kyphosis (T5-T8: 20.7 ± 12 vs C: 16 ± 7). Both types 2 and 3 require a marked TK changes in the transition between the upper and lower thoracic segments to compensate for global (T5-T12) kyphosis. In this 2D analysis of moderate AIS, Lenke 1 curves exhibited normal thoracic sagittal parameters, which brings into question the effect of lordosis on the development of single thoracic curves. Lenke 3 curves exhibited lower thoracic segmental hypokyphosis, and the type 2 showed upper segmental hyperkyphosis. These results should be considered when planning a surgical strategy.