The position of the aorta relative to the spine: is it mobile or not?

STUDY DESIGN

This study analyzes the mobility of the aorta relative to the spine in patients with a herniated thoracic disc requiring surgical intervention.

OBJECTIVES

To determine the mobility of the aorta relative to the spine with the patient in prone and supine position.

SUMMARY OF BACKGROUND DATA

In anterior scoliosis surgery, safe screw placement is important and knowledge of the position of the aorta relative to the spine is crucial. To the authors' knowledge, there are no studies on the mobility of the aorta relative to the spine with the patient in different positions.

METHODS

All 50 patients before surgery had a computed tomography (CT) and/or magnetic resonance (MR) scans of the involved spinal segment in supine position, as well as a CT with intrathecal contrast in prone position. The aorta-vertebral angle and the aorta-vertebral distance were measured on as many levels as possible.

RESULTS

In supine position, the aorta is positioned left lateral to the vertebral body at midthoracic levels (T4-T8) and more anterior to the vertebral body at lower thoracic levels (T9-L2). In prone position, the aorta moves to a more anteromedial position relative to the vertebra, which is most significant at levels T4 to T8. The mediolateral aorta-vertebral distance according to Sevastik is shorter in prone position, whereas the anterior-posterior distance according to Sucato is larger, especially at levels T5 to T10.

CONCLUSIONS

We demonstrate a substantial difference in the position of the aorta relative to the spine in prone and in supine position, which is most markedly seen at levels T4 to T8. The aorta is positioned posterolateral to the spine in supine position and more anteromedial in prone position. Before performing anterior thoracolumbar spine surgery, we suggest to measure vertebral body width, as well as the position of the aorta in the prone and in the supine patient to decide if his approach is technically feasible, or if an alternative (contralateral) approach is preferable.