PURPOSE The origin of the deformity due to adolescent idiopathic scoliosis (AIS) is not known, but mechanical instability of the spine could be involved in its progression. Spine slenderness (the ratio of vertebral height to transversal size) could facilitate this instability, thus playing a role in scoliosis progression. The purpose of this work was to investigate slenderness and wedging of vertebrae and intervertebral discs in AIS patients, relative to their curve topology and to the morphology of control subjects. METHODS A total of 321 AIS patients (272 girls, 14 ± 2 years old, median Risser sign 3, Cobb angle 35° ± 18°) and 83 controls were retrospectively included (56 girls, median Risser 2, 14 ± 3 years). Standing biplanar radiography and 3D reconstruction of the spine were performed. Geometrical features were computed: spinal length, vertebral and disc sizes, slenderness ratio, frontal and sagittal wedging angles. Measurement reproducibility was evaluated. RESULTS AIS girls before 11 years of age had slightly longer spines than controls (p = 0.04, Mann-Whitney test). AIS vertebrae were significantly more slender than controls at almost all levels, almost independently of topology. Frontal wedging of apical vertebrae was higher in AIS, as expected, but also lower junctional discs showed higher wedging than controls. CONCLUSION AIS patients showed more slender spines than the asymptomatic population. Analysis of wedging suggests that lower junctional discs and apex vertebra could be locations of mechanical instability. Numerical simulation and longitudinal clinical follow-up of patients could clarify the impact of wedging, slenderness and growth on the biomechanics of scoliosis progression. These slides can be retrieved under Electronic Supplementary Material.

中文翻译：

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青少年特发性脊柱侧凸和无症状人群的脊柱细长和楔入：一项观察性回顾性研究。

目的青春期特发性脊柱侧弯（AIS）引起的畸形的起源尚不清楚，但脊柱的机械不稳定可能参与其发展。脊柱细长（椎高与横向尺寸之比）可以促进这种不稳定性，从而在脊柱侧弯的进展中起作用。这项工作的目的是调查AIS患者的椎骨和椎间盘的细长度和楔形程度，相对于它们的曲线拓扑结构和对照组的形态。方法回顾性分析了321例AIS患者（272例女孩，14±2岁，中位Risser征3，Cobb角35°±18°）和83例对照（56例女孩，中位Risser 2、14±3岁）。进行站立式双平面放射线照相术和脊柱3D重建。计算几何特征：脊柱长度，椎骨和椎间盘的大小，细长比，额叶和矢状楔角。评价了测量再现性。结果11岁之前的AIS女孩的脊椎长于对照组（p = 0.04，Mann-Whitney检验）。在几乎所有级别上，AIS椎骨都比对照组明显细长，几乎与拓扑无关。正如预期的那样，AIS的椎骨的前缘楔合较高，但较低的结节椎间盘楔合也比对照高。结论AIS患者比无症状人群显示出更多的细长脊椎。楔入的分析表明，较低的连接盘和先端椎骨可能是机械不稳定的部位。患者的数值模拟和纵向临床随访可以阐明楔入的影响，脊柱侧弯进展的生物力学上的细长和增长。这些幻灯片可以在电子补充材料下找到。