Research On The Positional Relationship Between Vertebral Idiopathic Scoliosis Thoracic Aorta Adjacent

Study Design. A retrospective study is performed to evaluate the anatomical relationship between the aorta and the thoracic vertebral bodies in patients with adolescent idiopathic scoliosis by using magnetic resonance imaging (MRI).Objective. Study the anatomical relationship between the aorta and the thoracic vertebral bodies in patients with adolescent idiopathic scoliosis, and discuss the safety area in posterior surgery.Summary of Background Data. Pedicle screw instrumentation is gaining popularity in treating adolescent idiopathic scoliosis. But complication such as injury of aorta or spinal cord because of malposition of pedicle screw also appears at the same time. At present researches about relationship between pedicle and aorta, spinal cord in patients with scoliosis are very deficiency.Methods. This study retrospectively analyzed97patients with idiopathic thoracic scoliosis (mean age14.9yr, mean Cobb angel40.1°,91F,6M) by using magnetic resonance imaging (MRI). Measure the smallest angel al in which the pedicle screw comes into contact with the aorta and the shortest distance OM in different vertebral level of T5-T12, then through statistical methods study the relationship between gender, age, type of pumc, main thoracic Cobb angel and vertebral rotation angel and al, OM, evaluate its influence on surgical safety; We simulated placement of the pedicle screw with a direction error, Sensitivity analysis was performed by changing the direction error and the length of the screw independently. The direction error started from20°up to40°with10°increments, The length of the screw was25mm to40mm with increments of5mm. We defined a warning pedicle as that when the aorta enters the expected area of the screw. The ratio of warning pedicles was calculated from T5to T12in the12scenarios. Measure the smallest angel γ、γ’ in which the pedicle screw injuries spinal cord in different vertebral level of T5-T12both sides. Define right pedicle entry point as O’, and the distance from vena cava to O’ as O’N’, the angle between O’N’and axis y asa3. Measure O’N’and a3in T10-T12and evaluate safety area.Results. Gender and type of Pumc has no significant correlation with the position of aorta; Age has some correlation with the position of aorta in upper vertebral (T5-T7); Main thoracic Cobb angel and vertebral rotation angel have significant correlation with the position of aorta, and T8、T9has the most correlation. With an increasing of Main thoracic Cobb angel and vertebral rotation angel, the aorta comes more close to the vertebral body. Between the vertebral level T5-T12the safety area of T5, T12is bigger than that of middle thoracic vertebral body. The smallest angelγ、γ’ in which the pedicle screw damages spinal cord have Significant differences(P<0.05), especially in T8、T9vertebral body. The safety area for vena cava becomes smaller from T10to T12in right side and it is the same as in left side for aorta.Conclusions. The position of aorta has no correlation with gender, age, type of pumc, but has significant correlation with Main thoracic Cobb angel and vertebral rotation angel. The safety area of T5,T12is bigger than that of middle thoracic vertebral body. Because of spinal cord with axial traction γ、γ’ have Significant differences, especially in T8、T9vertebral body.