Radiation Exposure during Pedicle Screw Placement using the Pediguard Pedicle Probe
Authors: Lisoni Andrés , Silva Alvaro , Krainz Pablo , Illanes Juan Cristobal 
Published: May 2015

Introduction Pedicle screws have been used for decades. Both the advantages and complications related to this technique are well documented. Screw malposition has been described in 10 to 55% of the cases, especially with the free-hand technique. Complications related to screw malposition are neurologic involvement in 1.8 to 6.9% of the cases, great vessel injury in 4.5%. Another consideration is the radiation exposure for the patients and the physicians. There are studies suggesting that spine surgeons can overwhelm the maximum radiation recommended during their whole life during 10 years of clinical practice. In addition to that, there is evidence showing that the radiation exposure during spine surgeries is between 10 to 12 times higher than the one in nonspine orthopedic procedures. Recently, the 2D fluoroscopy, intraoperative neurologic monitoring and electromyography, intraoperative CT scan, and navigation systems have reduced the incidence of these complications, but they can still happen. In the year 2000, a special pedicle probe was developed; it has a bipolar sensor on its tip that produces a direct current, thus, an electromagnetic field that is able to detect changes in the different tissues conductivity. This may help to reduce the time and radiation exposure during pedicle screw insertion. Material and Methods Prospective study that compares two pedicle screw insertion techniques in thoracic, lumbar spine, and in the sacrum; Group 1: X-rays and bipolar pedicle probe-guided screw insertion. Group 2: X-ray–guided pedicle screw insertion. The patients were randomly assigned to either group and all the surgeries were performed by the same surgical team. This study had the local ethics committee approval. Technique for group 1; Identification of the entry point for the pedicle screw in anteroposterior (AP) and lateral (lat) X-rays. The pedicle was penetrated using the bipolar probe. The wall integrity was verified. The pedicle screw insertion was done. AP and lat X-rays were taken. Technique for group 2; the same technique than group 1 using a regular probe, X-ray was used as needed. Results Overall, 20 patients were performed a surgery between 2013 and 2014. Of the 20 patients, 11 women and 9 men with an average age of 59.5 years (range, 37–84 years). Overall, eight patients had a spinal stenosis, five isthmic spondylolisthesis, five degenerative spondylolisthesis, and one transitional syndrome. A posterolateral fusion was performed in two patients; 14 posterolateral fusion and decompression, 4 posterolateral fusion and decompression and TLIF. Surgical time; 183 minutes (range, 110–240 minutes). Bleeding; 442 mL (range, 300–1,300 mL). Average X-ray use time per patient; Group 1: 12 patients, 64 screws, and 34.9 seconds. Group 2: 8 patients, 36 screws, and 17.4 seconds. Average time to put the screws; Group 1: 105 seconds, Group 2: 111.6 seconds. Conclusion Although the time spent in screw positioning was similar in both groups, there was a significant difference in the X-ray time between both the groups. The X-ray time required in group 2 almost doubled the X-ray time required in group 1 for an equivalent surgery. The use of bipolar probe during pedicle screw placement reduces both the patient and surgical team radiation exposure.