PediGuardTM: A Solution for the Challenges of Pedicle Screw Placement

Much of the variation in the literature depends on the method used to determine the perforation. Studies using a postoperative CT scan reviewed by independent or blinded reviewers show higher rates of perforation than those determined by radiograph. Laine, et al. reviewed 30 low back operations. In this series of 152 pedicle screws, 32 screw perforations (21%) were detected by CT scan, whereas only 3 were detected by plain radiographs. Screw perforations less than 4 mm caused no neurological problems. In only 10 of the 30 patients were all the screws located within the pedicle. Many surgeons rely on plain radiographs to assess screw perforation postoperatively. However, the number of malpositioned screws are underestimated. In an article by Learch, et al. using cadaver specimens of the lumbar spine, only 63% of the screw positions were correctly identified on radiograph as compared to 87% with CT scan. The reported perforation rates are higher in the thoracic spine. Belmont, et al. reported a perforation rate of 43% in the thoracic spine determined by CT scan. Fourteen percent of the 279 screws studied had penetrated medially into the spinal canal, and 29% were malpositioned through the lateral vertebral body cortex.