Imaging study of coronal and sagittal parameters in adolescent idiopathic scoliosis patients with thoracic curve or thoraco-lumbar/lumbar curve

English Keywords:Adolescent idiopathic scoliosis  Sagittal alignment  Coronal alignment  Compensatory mechanisms

English Abstract:

  【Abstract】 Objectives: To investigate the changes of coronal and sagittal plane parameters in adolescent idiopathic scoliosis(AIS) patients with thoracic curve or thoraco-lumbar/lumbar curve, and to analyze the correlation of sagittal parameters between the two types of curve. Methods: 71 AIS patients with thoracic curve and 64 AIS patients with thoraco-lumbar/lumbar curve were divided into two groups according to their types of curve. And 40 normal adolescents were enrolled as the control group. All the subjects took anteroposterior and lateral full-length spine X-rays(standing), and the related coronal and sagittal parameters were measured with Surgimap software. The sagittal plane parameters included cervical lordosis(CL), C2-7 sagittal vertical axis(C2-7SVA), T1 slope, T1 tilt, thoracic kyphosis(TK), lumbar lordosis(LL), pelvic incidence(PI), pelvic tilt(PT), sacral slope(SS), and C7 sagittal vertical axis(C7SVA). The coronal parameters included major curve Cobb(MCC), apical vertebral translation(AVT), distance between C7 plumb line and the central sacral vertical line(C7PL-CSVL), T1 coronal angle(T1CA), and lumbar pelvic relationship(LPR). Pearson correlation coefficient was used to test the correlation between coronal plane and sagittal plane in thoracic curve group and thoraco-lumbar/lumbar curve group, and independent sample T test or Mann-Whitney U test and Pearson was used to analyze the correlation. Results: There was no correlation between coronal plane parameters and sagittal plane parameters in thoracic curve group. In thoraco-lumbar/lumbar curve group, there was a significant correlation between PT and C7PL-CSVL and LPR(r=0.320, r=0.339), and there was no correlation between other parameters. There were significant differences in CL(P<0.001) and TK(P<0.001) between thoracic curve group and control group, while there were significant differences in C2-7SVA(P<0.001), PI(P<0.001), PT(P<0.001) and C7SVA(P<0.01) between thoraco-lumbar/lumbar curve group and control group. Intra-group analysis showed that in thoracic curve group, CL was negatively correlated with T1 slope(r=-0.598) and TK(r=-0.602), TK was positively correlated with T1 slope(r=0.710), LL was negatively correlated with TK(r=-0.495), PI(r=-0.332) and SS(r=-0.726), and positively correlated with T1 tilt(r=0.342) and C7SVA(r=0.458), while C7SVA was positively correlated with T1 tilt(r=0.849). In thoraco-lumbar/lumbar curve group, CL was negatively correlated with T1 slope(r=-0.431), TK was positively correlated with T1 slope(r=0.373), LL was negatively correlated with PI(r=-0.339) and SS(r=-0.858) and positively correlated with PT(r=0.319), while C7SVA was positively correlated with T1 tilt(r=0.386) and PI(r=0.338). Conclusions: The correlation between coronal deformities and sagittal plane in thoracic curve and thoraco-lumbar/lumbar curve AIS patients is low. T1 slope is the key to predict the sagittal plane balance between cervical and thoracic vertebrae in AIS patients with thoracic curve. Pelvic incidence plays an important role in regulating the normal spino-pelvic position relationship in AIS patients with thoraco-lumbar/lumbar curve.