A method for radiographic evaluation of pedicle screw violation of the vertebral endplate. Technique

Study Design. This study evaluated the utility of intraoperative radiographs for minimizing the risk of pedicle screw tip violation of the superior vertebral endplate. Objectives. An intraoperative radiographic technique is demonstrated that ensures that a screw has not penetrated the intervertebral disk. Summary of Background Data. Although methods to avoid penetration of the medial pedicle cortex and the anterior body cortex have been described, no study has discussed screw penetration of the superior endplate and disc. Methods. Pedicle screws were inserted into 11 cadaveric lumbar spines, randomly, with the tip inferior to the endplate, at the endplate, and through the endplate. Radiographs were evaluated to measure the penetration, if any, of the screws. Spine segments were dissected and evaluated anatomically. The anatomic and radiographic results were then compared. Results. The overall error rate for radiographs was 22/312 (7%). Oblique radiographs gave a much higher error rate. Conclusions. A true lateral or anteroposterior radiographic view of the vertebra provides a high degree of certainty that the screw has not crossed the endplate when a 'safe zone' of 3 mm remains superior to the screw tip. Intraoperative radiography can reduce concern about violation of the superior vertebral endplate.