The aortic-vertebral distance is more associated with axial plane deformities than coronal and sagittal deformities in idiopathic scoliosis patients of Lenke types I and II.

Purpose: Although idiopathic scoliosis is a common three-dimensional deformity, there is a lack of studies evaluating the associations between the aortic-vertebral distance (AVD) and spinal deformities in all planes. The study therefore aimed to evaluate how the coronal and sagittal curvature, vertebral rotation and aortic-vertebral angle (AVA) affect the AVD in idiopathic scoliosis.

Methods: The AVD, AVA, vertebral rotation and curve angles were measured on preoperative magnetic resonance imaging and radiographs in 46 patients who underwent posterior spinal fusion with pedicle screw instrumentation for idiopathic scoliosis Lenke types 1 and 2. Associations between variables were examined using correlation and multivariable regression analyses.

Results: A significant weak to strong correlation was found between the AVD and AVA, and the AVD and vertebral rotation (r = 0.315 to 0.712) within the thoracic curve. The sagittal kyphosis and coronal Cobb angles showed weak correlations with the AVD (r = -0.311 to 0.338). The regression model for the apical vertebral level, which included the four variables, explained 40% (R²=0.40) of the variation in AVD. AVA and vertebral rotation were significantly associated with AVD (p < 0.01 for each), together accounting for 34% (R²=0.34) of the variation.

Conclusion: The shortest distance from the aortic wall to the vertebral body wall is primarily influenced by vertebral rotation and the AVA within the thoracic curve. Thus, these factors need to be taken into consideration when planning pedicle screw placement especially in freehand techniques.