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 system (Medtronic Surgical Navigation Technologies, Louisville, CO). The relative position of the screw to the pedicle was graded as follows: A = completely in; B = 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 appears to be a safe adjunct for the placement of thoracic and LS pedicle screws.