Variation and its clinical relevance of the spinal cord at the apex of the curve in adolescent idiopathic scoliosis

English Keywords:Adolescent idiopathic scoliosis  Spinal cord shift  Spinal cord rotation  MRI

English Abstract:

  【Abstract】　Objective：To analyze the shift and rotation of spinal cord at the apex of the curve in adolescent idiopathic scoliosis（AIS） by MRI and explore its clinical relevance．Method：The MRI images from twenty-eight cases of AIS were collected and analyzed．The distance between the center of spinal cord and the four inner wall of vertebral canal，and the rotational angle of the spinal cord and vertebral body at the apex of the curve in AIS were recorded respectively．According to the relationship between the rotational angle of the spinal cord and vertebral body，the patients were classified into three distinct groups termed as type O，type U and type R.The relationship between rotation and shift of the spinal cord at apical region，as well as the rotation of vertebra，Cobb angle were analyzed either．Result：The average distance from the center of spinal cord to the inner wall of vertebral canal on the convex side was 13.68±2.93mm，and 7.13±1.89mm on the concave side，with the latter less than the former（t=-9.56，P<0.01）.The average distance from the center of spinal cord to the anterior inner wall and posterior inner wall of vertebral canal was 7.50±1.63mm and 6.99±1.61mm respectively with no significant difference（t=1.22，P=0.23） noted.The average rotational angle of vertebral was 17.53°±6.70° with the spinal cord average tilt angle of 16.46°±9.16°.There were 8 cases of type O，13 cases of type U，7 cases of type R.The spinal cord tilt was statistically correlated with the rotation angle of vertebral，Cobb angle and the distance variation from the center of spinal cord to the inner wall of vertebral canal on convex and concave side respectively（r=0.45，P=0.01. r=0.43，P=0.02. r=0.64，P<0.01），while the spinal cord shift was not statistically correlated with the distance variation from the center of spinal cord to the anterior and posterior inner wall of vertebral canal（r=0.28，P=0.15）．Conclusion：The shift of spinal cord to concavity occurred at the apex of the curve in AIS and the rotation of spinal cord occurred individually.It should be cautious to avoid injury to the spinal cord and nerve roots while implanting pedicle screw during posterior approach．