Background:Although pedicle screw placement (PSP) is a well-established technique for spine surgery,the treatment of patients with primary invasive spinal tumor (PIST) has high surgical risks secondary to destroyed pedicles.Intraoperative three-dimensional fluoroscopy-based navigation (ITFN) system permits safe and accurate instrumentation of the spine with the advantage of obtaining intraoperative real-time three-dimensional images and automatic registration.The aim of this study is to evaluate the feasibility and accuracy of PSP using ITFN system for patients afflicted with PIST in the thoracic spine.Methods:Fifty-one patients diagnosed with PISTs were retrospectively analyzed,and 157 pedicles screws were implanted in 23 patients using the free-hand technique (free-hand group) and 197 pedicle screws were implanted in 28 patients using the ITFN system (ITFN group).Modified classification of Gertzbein and Robbins was used to evaluate the accuracy of PSP,and McCormick classification was applied for assessment of neurological function.Demographic data and factors affecting accuracy of screw insertion were compared using independent t-test while comparison of accuracy of screw insertion between the two groups was analyzed with Chi-square test.Results:Of 51 patients,39 demonstrated improved neurological status and the other 12 patients reported that symptoms remained the same.In the free-hand group,145 screws (92.4％) were Grade Ⅰ,9 screws (5.7％) were Grade Ⅱ,and 3 screws (1.9％) were Grade Ⅲ.In the ITFN group,192 screws (97.4％) were Grade Ⅰ,5 screws (2.6％) were Grade Ⅱ,and no Grade Ⅲ screw was detected.Statistical analysis showed that the accuracies of pedicle screws in the two groups are significantly different (x2 =4.981,P =0.026).Conclusions:The treatments of PISTs include total tumor resection and reconstruction of spine stability.The ITFN system provides a high accuracy of pedicle screw placement.