Rate of Pedicle Disruption after Screw Fixation

Kim, Nam Hyun; Lee, Hwan Mo; Lee, Dong Wha

Abstract

Postoperative CT scans for accuracy of pedicular screw placement were assessed in 20 patients (82 pedicular screws) treated with several kinds of pedicular screws. When putting screws, the position of the guide pin was confirmed by the image intensifier. The measurement of canal encroachment from the medial border of the pedicle and the angle of insertion through the body of each vertebra were assessed; 1. Fifty-five(69.1%) were placed within the pedicle. 2. Ten(12.2%) were placed within 2mm of the medial border of the pedicle. 3. Three(3.6%) had 2mm to 6mm canal encroachment with the patient developing neurologic complication that was improved 8 months after the operation. 4.Fourteen(17.1%) perforated the lateral border of the pedicle, but they were not associated with neurologic complication. 5. The screws placed within 2mm of the medial border of the pedicle had higher angle of insertion than the screws exactly within the pedicle. Even with the use of image intensifier, there was a high rate of pedicle disruption. We have to insert the screws more exactly according to true anatomic angle of the pedicle on each level of every vertebra from the entry point avoiding high angle of insertion to prevent any disruption of the medial border of the pedicle which may result in neurologic complication.