Intraoperative quantitative accuracy assessment of pedicle screw insertion in spine surgery using a new 3D fluoroscopic imaging robotic system

Aim : To develop a new intraoperative quantitative measurement method of pedicle screw insertion accuracy using 3D fluoroscopic images. Materials and methods : The study was conducted using a synthetic model of a lumbar spine. The testbed consisted of a clamping device with five template supports, produced by additive manufacturing, to rigidly fix the lumbar spine. The test bed was scanned using a CT-scanner and a virtual 3D CT model of the test bed was reconstructed for the planning of the pedicle screw insertion. One operator freehandly performed the insertion of the pedicle screws. Fluoroscopic images of the test bed with the inserted screws have been acquired using the new Siemens Artis Zeego II intraoperative imaging robotic system. The errors in the desired pedicle screw insertion computed numerically with the intraoperative fluoroscopic images were compared to reference mechanical measurements using a Microscribe coordinate measuring machine. Results : Visual inspection of the synthetic lumbar spine and visual inspection of the intraoperative fluoroscopic images did not reveal any pedicle breach. The difference between the errors computed numerically with the intraoperative fluoroscopic images and mechanically with the coordinate measuring machine, averaged -0.8 mm for the entry points, -0.1° for the orientation axes and -0.3 mm for the target points of the inserted screws. The maximum differences were found in the right pedicle of L5 vertebra (-3.3 mm, 1.8° and 0.9 mm for entry point, orientation axis and target point respectively). Conclusion : This study showed the feasibility to compute the achieved errors on a predefined pedicle screw insertion planning using intraoperative fluoroscopic images with a very good accuracy when compared to reference mechanical measurements. The results observed here are currently undergoing complementary in vivo studies. Significance : Once completed, the quantitative accuracy measurement methodology using intraoperative fluoroscopic images may be useful to investigate further pedicle screw insertion performed with the aid of several assistance technologies such as navigation and robotic systems.