The different parts of the lumbar pedicle were identified on an anteroposterior (AP) radiograph to determine reliable reference points to be used to quantify vertebral rotation. Standard AP radiographs were taken of dry lumbar vertebrae with 5 degrees increments in rotation in the transverse plane, ranging from 0 degrees to 30 degrees both to left and right. Identical sets of radiographs were taken with radiopaque markers around the middle and in the anterior and posterior parts of the pedicles. The anatomic center of the pedicle was found to lie slightly more lateral than the center of the pedicle halo. The inferior edge of the pedicle corresponded with the anterior part of the pedicle and the superior edge, with the posterior part.