The Measurement of Size of the Pedicle Using 3 Dimensional Reconstruction Image in Idiopathic Scoliosis

Heo, Jae Hee; Ahn, Myun Hwan

Abstract

BACKGROUND
This study was conducted to analyze the height and width of the pedicle of the upper and lower levels on the concave and the convex sides. In addition, we checked for the appropriate pedicle screw size which could be screwed in without complications. MATERIALS AND METHODS: Taking a simple AP radiography in a standing position, 99 vertebrae on the major curve with the possibility of 3-D reconstruction were analyzed after checking the CT in a supine position of 22 idiopathic scoliosis. We measured Cobb's angle from a simple radiograph, and measured the size of the isthmus by the Inner Space 3-D Editor after 3-D reconstruction with the Inner Space 3-D program in the DICOM file transformed from CT image. We then analyzed the size of pedicles of the upper and lower levels on the concave and the convex sides by measuring the height and width of the pedicle. RESULTS: All pedicles on the concave side were smaller than those on the convex side. Their size increased as the measurement moved from the upper to lower vertebra, except for the upper thoracic vertebra. When the width of the pedicle through 3-D reconstruction was compared with the narrowest width of the pedicle measured by using CT, the width of the pedicles through 3-D reconstruction was statistically smaller (P< 0.01). Most of the pedicles were tear-drop or kidney shaped rather than cylindrical. CONCLUSION: These results suggest that the use of the coronal plane through 3-D reconstruction would be necessary for an accurate measurement of the size of the pedicle. It is important to pay careful attention to the screw size and the screwing method considering the pedicle shape through 3-D reconstruction.