Abstract
INTRODUCTION: An accurate assessment of three-dimensional (3D) intervertebral deviation is crucial to the better surgical correction of adolescent idiopathic scoliosis (AIS). However, a precise 3D study of intervertebral deviation has not been previously reported. OBJECTIVE: The purpose of the present study is to evaluate the intervertebral coronal inclination, axial rotation and sagittal angulation of AIS using 3D bone models and a local coordinate system. MATERIALS AND METHODS: 3D bone models of the thoracic and lumbar spine of ten AIS patients were constructed using computed tomography. The local coordinate axis was determined semi-automatically for each vertebra. By using these local coordinates, the intervertebral deviation angles were calculated in the coronal, axial and sagittal planes and projected to subjacent local coordinates. RESULT: The intervertebral deformity in the coronal plane was larger near the apical region and smaller near the junctional region. Conversely, the intervertebral rotation in the axial plane was smaller near the apical region, and larger near the junctional region. Concerning the sagittal plane deformity, the constant tendency was not recognized. CONCLUSION: Using a local coordinate system for the vertebra of AIS, we measured the 3D intervertebral coronal, axial and sagittal deviation of the thoracolumbar spine and found that the change in the intervertebral inclination angle in the coronal plane increased toward the apical region and decreased toward the junctional region, and that the converse tendency was noted for the axial intervertebral rotational angle. This analysis provides an improved 3D guide for the surgical correction of AIS.