Does the Severity of the Curve in Lenke 1 and 2 Adolescent Idiopathic Scoliosis Patients Affect the Distance and Position of the Aorta From Vertebra?

Understanding the Aorta-Spine Relation in Idiopathic Scoliosis: Value of Noncontrast CT-Derived Curved Coronal Reformats and 3D Volume Images

BACKGROUND

Investigating axial position and longitudinal bending of the aorta in relation to spine curvature in adolescent idiopathic scoliosis patients could help surgeons in planning of spine surgeries.

METHODS

Noncontrast computed tomography (CT) scans of 27 consecutive patients with adolescent idiopathic scoliosis (19 right and 8 left curves) and 16 control subjects were retrospectively reviewed. Using semiautomated software, centerline was drawn along the descending aorta, and curved reformat was generated. Aorta tortuosity index (TI) was calculated as (centerline length/straight line distance) - 1 × 100. The spine centerline was drawn from T1 to L5, and curve index (CI) was similarly calculated. The aorta centerline angle was measured. Apical vertebral-rotation angle and multilevel aorto-vertebral angles were measured on axial CT. Three-dimensional volume-rendered images of the aorta were generated using a manual region grow function.

RESULTS

Mean (± standard deviation) Cobb's angle was 63.8 ± 34.6°. The spine CI of patients (9.7 ± 7.11) was significantly higher than controls (0.28 ± 0.22), P = .00001. Aorta TI in scoliosis was significantly higher than controls (6.4 ± 7.2 versus 0.6 ± 0.5, P = .0001). The aorta centerline angle was steeper in scoliosis than controls (140 ± 26.8° versus 170 ± 3.6°). Correlations were excellent between the aorta TI and each of Cobb's angle, spine CI, and vertebral rotation angle (r = 0.851 to 0.867, all P < .001). Aorto-vertebral angles were significantly different between right scoliosis and left scoliosis patients and control groups at T6, T7, T8, L2, and L3 levels.

CONCLUSIONS

Aortic curvature increases in proportion to the degree of scoliosis. The aorta follows the concavity of scoliosis in right and left curves. In the axial CT plane, the aorta in both right and left scoliosis is maximally rotated away from its normal position at T7 and is closest to its normal position at T11 to T12.

CLINICAL RELEVANCE

Quantitative evaluation of aortic curvature combined with preoperative reconstructed CT images could be beneficial for surgeons in planning of spine surgeries.

Variations in the position of the aorta and vertebral safe zones in supine, prone, and lateral decubitus for adolescent idiopathic scoliosis

PURPOSE

Analyze the modifications in the "safe zones" of T4-L4 vertebral bodies relative to aorta according to patient positioning, as well as in the relationship between the aorta and the vertebrae.

METHODS

Patients with adolescent idiopathic scoliosis who underwent surgical treatment during 2017 were included. Preoperative whole spine MRI in supine, prone, and LD positions was performed. The safe zone right (SZR) was defined as the angle formed between X-axis (0º) and a line connecting the origin and the edge of the aorta, and the safe zone left (SZL) was the angle between the edge of the aorta to 180º (X-axis).

RESULTS

A total of 21 patients were studied, median age was 15.2 years, and 71.4% were female. The mean SZR lied from 0°-86.1º at T4 to 0°-76.9º at L4 in supine, from 0°-84.05º at T4 to 0º-78.5º at L4 in prone, and from 0° to 91.75º at T4 to 0°-80.4º at L4 in LD. While the mean SZL was located from 155.4º-180º at T4 to 107.9º-180º at L4 in supine, from 134°-180° at T4 to 103.9°-180° at L4 in prone, and from 143.8º-180º at T4 to 106º-180º at L4 in LD. Statistically significant differences were found almost at all levels when comparing supine versus prone and LD.

CONCLUSIONS

Patient positioning during spinal surgery significantly modifies T4-L4 vertebral safe zones relative to aorta. These variations should be taken into account when analyzing an MRI performed in supine if the patient is undergoing surgery in a different position, to avoid vascular-related injuries.

Is the Risk of Aorta Injury or Impingement Higher During Correction Surgery in Patients with Severe and Rigid Scoliosis?

OBJECTIVE

To evaluate the position of the aorta relative to the spine and the risk of aortic injury during correction surgery in patients with idiopathic severe and rigid scoliosis (main curve Cobb angle >90° and flexibility <30%).

METHODS

Twenty-seven patients with severe right thoracic/thoracolumbar scoliosis were recruited. The entry point-aorta distance (EAD), the left pedicle-aorta angle (α), the left aorta angle (β), and the vertebral rotation angle (γ) were measured from 4 vertebrae above (A4) to 4 below (B4) the apical vertebra (Apex) to quantify the spatial relationship between aorta and spine. We simulated the pedicle screw misplacement with variable direction error, length, and diameter to analyze the potential risk of aortic injury.

RESULTS

The aorta shifted laterally and posteriorly as it descended from A4 and moved back medially and anteriorly from Apex. The potential risk of aortic injury increased with the augment of direction error and/or length of the screw, but the tendency was not significant with the augment of diameter. The risk peaked at A4, A3, and B2, when the screw length was 40 mm and diameter was 5.0 mm, and the direction error was 30°, whereas the risk was lowest at the apical level 14.3% (0%-40.7%) in any scenarios.

CONCLUSIONS

In patients with severe and rigid scoliosis, the aorta shifted more laterally and posteriorly, and the injury risk was lower at the apical level, compared with moderate scoliosis. Most potential risks can be minimized by careful preoperative planning and the assistance of intraoperative navigation or robotics.