In recent years, transpedicular screw fixation has emerged as one of the best techniques for stable 1) . However, in the thoracic spine, safe screw insertion is very difficult due to the anatomical complexity and a lack of morphometric data.
In this study, we established an anatomical pedicular axis in 11 cadavers for dissection then performed 3-dimensional morphological measurements. We evaluated the optimal insertion point and direction for screw fixation, the length and outside diameter of the pedicle screw, the intramedullary diameter, and the thickness of the cranial, caudal, lateral, and medial cortical bones at the site of the minimum transverse diameter of the pedicle. The pedicles in the thoracic spine showed a decrease in the angle between the pedicular axis and the sagittal plane on the horizontal plane from the upper level toward the lower level, and the minimum transverse diameter of the pedicle was less than 5 mm at some levels. The transverse diameter of the pedicle was consistently shorter than its longitudinal diameter, and the lateral cortical bone of the pedicle was consistently thinner than the medial cortical bone: These data were used to determine the optimal point of transpedicular screw insertion. Our results will aid the establishment of a safer transpedicular screw insertion method.
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