The position of the aorta in relation to the vertebra in patients with idiopathic thoracic scoliosis

Abstract

One CT-scan at the central part of the vertebral body of the apical vertebra of 32 patients with right convex thoracic idiopathic scoliosis and one CT-scan of either T8 or T9 of 22 normal subjects are included in this study. The position of the aorta in relation to the apical vertebra of the scoliotic patients and the corresponding vertebra of the normal subjects was determined at the horizontal plane. The mean lateral translation of the aorta in relation to the mid axis of the vertebral body increased from 19.7 +/- 4.3 mm in the normal group to 26.4 +/- 4.1 mm in the scoliotic group (p = 0.0001). In the normal group the aorta was located 41.7 +/- 8.6 mm in front of a perpendicular line to the mid axis of the vertebral body and in the scoliotic group this distance was reduced to 30.0 +/- 9.0 mm making the position of the aorta more posterior in the scoliotic group (p = 0.0001). This was in accordance with a decreased mean kyphosis-lordosis index from 0.53 +/- 0.06 in the normal group to 0.46 +/- 0.07 in the scoliotic group (p = 0.01). The position of the aorta, also expressed as the angle formed between the aorta and the vertebral body, the "aorto-vertebral angle", was increased from 24.4 degrees +/- 6.9 degrees in the normal group to 41.4 degrees +/- 8.4 degrees the scoliotic patients, (p = 0.0001). The aorto-vertebral angle did not change significantly with increasing Cobb angle (p = 0.26) but was positively correlated to the vertebral rotation (p = 0.0001). An estimation of the length of the intercostal arteries revealed a significantly greater R (right)/L (left) index in the scoliotic patients 1.18 +/- 0.11 than in the normal subjects 1.08 +/- 0.06 (p = 0.0003). It is concluded that the rotation and the anterior displacement of the vertebral body in scoliosis result in a deviation of the aorta along the left (concave) side of the vertebral body to a more posterior position relative to the vertebral body with a possible increased length of the intercostal artery on the right (convex) side.

The changes of relative position of the thoracic aorta after anterior or posterior instrumentation of type I Lenke curve in adolescent idiopathic thoracic scoliosis

“…Because of the posterior and lateral location of aorta relative to vertebral body [21,28,30], the risk of impinging or eroding the thoracic aorta by vertebral screw was increased. Because of this, removing part of rib heads were recommended at the cephalad thoracic spine (T4, T5, T6, and T7) or giving up bi-cortical purchase at periapical vertebrae have been suggested [21,33].…”

“…The screws placed from right side of thoracic vertebrae, however, have the potential risk of injuring the thoracic aorta or penetrating the spinal canal. In patients with main right thoracic adolescent idiopathic scoliosis (AIS), the thoracic aorta were found to displace more laterally and posteriorly relative to the vertebral body, which could increase the potential risk [21,26,28,30]. In a bovine model, Faro et al [7] found that screw tip impinging on the aorta could lead to erosion of the aortic wall [3,10,15,31].…”

Application of CT Scanning in the Studies of Minimal Invasive Thoracoscopic Surgery of Adolescent Idiopathic Scoliosis

“…The displacement of the aorta in patients with scoliosis was expressed as the aortavertebral angle or angle in the present study. Both Sucato et al (Sucato DJ, et al 2003a) and Sevastik et al (Sevastik B, et al 1996) found that the aorta was positioned more posteriorly in patients with AIS than in patients with a normal spine. The present study showed that angle was smaller in the scoliosis group than that in the age matched control group at every vertebra, and the differences were significant from T5 to T10 (p< 0.01) particularly close to the apex of the curve (T7 to T9), with an angle of 45.2° and 26.9°, respectively, at the seventh thoracic vertebrae in control and scoliosis group; 50.3° and 31.5°, respectively, at the eighth thoracic vertebraae; and 54.8° and 37.6°, respectively, at the ninth thoracic vertebrae.…”

“…Despite these studies, there was little information documenting the relationship of the aorta to the thoracic scoliotic spine and little anatomic data based on the pathological morphology of scoliosis. Through analyzing the CT images of the apical vertebra T8 or T9, Sevastik et al (Sevastik B, et al 1996) found that the mean lateral translation distance from the aorta to the mid axis of the vertebral body in the scoliosis group increased, while the vertical distance from the aorta to the mid axis of the vertebral body reduced compared with the adult control group. Liljenqvist et al (Liljenqvist UR, et al 2002) got the same result by measuring the distance from the aorta to the vertebra, without comparing with the normal spine.…”

“…Furthermore, comparing with the control subjects, the thoracic aorta in patients with RT-AIS was found to shift more posteriorly and closely to the vertebra because of the vertebral rotation and morphological anomaly at the vertical plane. (Sevastik B, et al 1996 Huitema GC, et al 2006) Hence a well knowledge on the anatomic relationship between the para spinal tissues and the thoracic vertebral bodies, and the dynamic changes of the relationship during operation is critical for accurate screw insertion and the other procedures so that a satisfied instrumentation and fusion could be achieved in patients with RT-AIS. With these objectives, a series computed tomography (CT) based studies were carried out in our centre.…”