Fig. 1

Intraoperative fluoroscopy of percutaneous tricortical S1 pedicle screw fixation. (A) Bilateral Jamshidi needle. Placement demonstrated by an a.p. radiograph, (B) a.p. radiograph confirming correct positions of the pedicle screws. (C) Anterior sacral cortex, exceeded by two threads of the pedicle screw tips. Lateral radiograph.