Clinical accuracy of fluoroscopic computer-assisted pedicle screw fixation: A CT analysis

Study Design. Observational cohort study with computerized tomography (CT) analysis of in vivo pedicle screw placement. Objective. To evaluate the clinical accuracy of computer-assisted fluoroscopy for the placement of thoracic and lumbosacral (LS) pedicle screws. Summary of Background Data. Computer-assisted fluoroscopy is an adjunct for the placement of pedicle screws. Methods. Postoperative CT of 360 titanium pedicle screws ( 281 LS [L1 - S1]; 79 thoracic [T2 - T12]) were independently assessed. All screws were placed using the FluoroNav(TM) system (Medtronic Surgical Navigation Technologies, Louisville, CO). The relative position of the screw to the pedicle was graded as follows: A = completely in; B = < 2 mm breach; C = 2 - 4 mm breach; and D = > 4 mm breach. If an osseous breach occurred, the direction of the breach was further classified. Results. Eight-five percent of screws were completely contained within the pedicle. Fifty-five-pedicle breaches ( 25 medial; 30 lateral) occurred. Pedicle breaches were graded B in 13.1% ( 47 breaches), C in 1.9% ( 7), and D in 0.3% ( 1) of screws. Pedicle breach was significantly higher in the thoracic compared to the LS spine, 31.6% (25/79) and 10.6% (30/281), respectively ( P < 0.0001). In the thoracic spine, 72% of pedicle breaches were lateral. In 49% of breaches, the screw diameter was larger than the pedicle diameter. None of the pedicle breaches were associated with neurologic or other clinical sequelae. Conclusions. The clinical pedicle breach rate in this study is comparable to those reported using conventional techniques with or without fluoroscopic assistance. FluoroNav(TM) appears to be a safe adjunct for the placement of thoracic and LS pedicle screws.