Objective To evaluate the deviation between actual and simulated screw placement after cervical pedicle screw placement assisted by 3D printed navigation template, and analyze the correlation between screw placement deviation and navigation pipe length. Methods A total of 40 patients undergoing cervical 1-7 pedicle screw insertion assisted by 3D printed navigation template in Zigong Fourth People’s Hospital between February 2018 and August 2020 were included in this prospective study. These patients were divided into 3 groups randomly, including 12 patients with a 5-mm pipe length (5 mm group), 13 patients with a 10-mm pipe length (10 mm group), and 15 patients with a 15-mm pipe length (15 mm group). Three-dimensional modeling was performed on preoperative cervical CT images of these patients and simulated pedicle screw was placed. Individualized pedicle screw navigation templates were designed according to the position and direction of simulated pedicle screws, and 3D printing was performed on the cervical model and navigation templates. Preoperative 3D printed model and navigation templates were used to simulate the surgical process to confirm the safety of screws. During the operation, pedicle screw placement was performed according to the preoperative design and simulated surgical process. The postoperative CT images were registered with the preoperative CT images in 3D model. The safety of screw placement was evaluated by the postoperative screw placement Grade, and the accuracy of screw placement was evaluated by measuring the deviation of screw placement point and the deviation of screw placement direction in horizontal plane (inclination angle) and sagittal plane (head inclination angle). The influence of different navigation pipe lengths on the safety and accuracy of screw placement was analyzed. Results A total of 164 pedicle screws were inserted with navigation template assistance, including 48 screws (38 in Grade 0 and 10 in Grade 1) in the 5 mm group, 52 screws in the 10 mm group (all in Grade 0), and 64 screws (52 in Grade 0 and 12 in Grade 1) in the 15 mm group, and the difference in the grade among the three groups was statistically significant (P<0.05). When the navigation pipe length was 5, 10, and 15 mm, respectively, the screw entry point deviation was (1.87±0.63), (1.44±0.63), and (1.66±0.54) mm, respectively, the inclination angle deviation was (2.72±0.25), (0.90±0.21), and (1.84±0.35)°, respectively, and the head inclination angle deviation was (8.63±1.83), (7.15±1.38), and (8.24±1.52)°, respectively. The deviations in the 10 mm group were all significantly less than those in the other two groups (P<0.05). Conclusions In the cervical pedicle screw placement assisted by navigation template, all the screws were Grade 0 or Grade 1, with high safety. The mean deviation of the screw entry point is within 2 mm, with high accuracy. When the length of navigation pipe is 10 mm, the safety and accuracy of screw placement can be fully guaranteed.
Objective To investigating the safety and accuracy of artificial intelligence (AI) assisted automatic planning of pedicle screws parallel to sagittal plane for C1. Methods The subjects who completed cervical CT scan in Zigong Fourth People’s Hospital btween January 2020 and December 2023 were selected. The subjects who completed cervical CT scan were randomly divided into two groups using a random number table method. Among them, 80% were used as the training model (training group), and 20% were used as the validation model (validation group). The original cervical CT data of the training group were imported into ITK-SNAP software to mark the feature points. Four feature points were selected. In order to obtain the weighted function model of the four feature points, training group were trained with the spatial key point location algorithm. pedicle trajectory based on the four key points obtained. Finally, the algorithm was compiled to form a visual interface, and imported into the verification group of annular vertebral CT data to calculate the pedicle screw trajectory. Results A total of 500 patients were included. Among them, there were 400 cases in the training group and 100 cases in the validation group. The average positioning error of spatial key points is (0.47±0.16) mm. The average distance between the planned pedicle screw center line and the internal edge of the pedicle was (2.86±0.12) mm. Pedicle screw placement parallel to the sagittal plane and 3D display can be safely performed for the C1 pedicle that is large enough to accommodate a 3.5 mm diameter screw without cortical breakthrough. Conclusions For pedicle screw planning parallel to the sagittal plane in C1, training based on the spatial positioning algorithm of anterior and posterior tubercles and bilateral tangential points can obtain a safe and accurate pedicle screw trajectory. It provides theoretical basis for orthopedic robot automatic screw placement. For vertebral bodies with narrow or deformed pedicles, further expansion of the training data is needed to expand the adaptive range and improve the accuracy of the algorithm.