The radiographic anatomy of the thoracic pedicle.

A cadaveric study of the radiographic characteristics of the thoracic pedicle was performed. Dried vertebrae at T6 and T7 were mounted and x-rayed at varying angles. The relationship of the pedicles to wire markers, methyl methacrylate cores, and Cotrel Dubousset hooks was analyzed. The oval image of the pedicle on radiographs is its waist. This image narrows with axial rotation of the x-ray beam. The relationship of a correctly placed pedicle hook to its pedicle is radiographically unchanged by rotation. Conversely, an incorrectly placed hook cannot be made to appear in position by rotating the x-ray beam.