Changes in Vertebral Rotation Following Segmental Pedicle Screw Instrumentation and Rod Derotation in Idiopathic Thoracic Scoliosis : Part I - CT Evaluation

Kim, Won Jung; Suk, Se Il; Kwon, Chil Soo; Kim, Jin Hyok; Kim, Dong Soo; Lee, Sang Min; Whang, Hoon

Abstract

The employment of segmental pedicle screw instrumentation has greatly enhanced the correction of scoliotic deformity. However there is still much controversy on the ability of the system to correct the rotational deformity. This prospective study with 12 idiopathic throacic scoliosis patients subjected to segmental pedicle screw instrumentation was performed to determine the effect of the system on the rotational deformity of idiopathic throacic scoliosis. In addition to the standing films to measure the magnitude of scoliotic curvatures, preand postoperative CT were utilized for the measurement and comparison of angle of rotation relative to the sagittal plane(RAsag.), relative rotation with reference to the upper and lower end vertebrae(RAend), relative rotation with reference to the sacrum(RAsac.), frontal translation(TF) and sagittal translation(TS) for the apical vertebrae. Despite the high correction rate obtained in the frontal plane(average 71.1%) and normalization of sagittal contour, the rotational corrections were statistically insignificant in all parameters and showed no significant correlation to the correction of the curvatures nor horizontal plane displacement as represented by the frontal and sagittal displacement. In conclusions, the segmental pedicle screw instrumentation with rod derotation does not produce significant derotation by itself.