A comparative study on the safety of atlantoaxial pedicle screw placement between free-hand technique and personalized 3D template technique in patients with atlantoaxial instability

English Keywords:Personalized  3D printing  Atlanto-axial  Pedicle screws

English Abstract:

  【Abstract】 Objectives: To compare the accuracy of traditional screw placement technique and improved personalized template assisted screw placement technique in the treatment of atlantoaxial instability. Methods: From June 2011 to July 2017, 56 patients (male 33, female 23) with atlantoaxial instability were analyzed retrospectively. The average age was 56.8±8.9 years(36-71 years) for male and 54.5±10.8 years (33-72 years) for female. The follow-up time was 14-26 months(19.4±4.1 months). A total of 30 patients underwent traditional posterior atlantoaxial pedicle screw internal fixation and fusion(control group), while the other 26 patients underwent atlantoaxial pedicle screw internal fixation and bone fusion assisted by personalized pointing and drilling template(test group). The pointing template of atlas and axis are designed with handrails. Three days after operation, all patients underwent CT reexamination to evaluate the safety of screw placement in atlas and axis, and the screw position was categorized into four grades: grade 0, the screw was completely located in the pedicle; grade 1, in the cross section or sagittal plane, the screw penetrated the osseous cortex ≤50%; grade 2, in the cross section or sagittal plane, the screw penetrated the osseous cortex >50%; grade 3, the screw completely penetrated the osseous cortex. Grade 0 was set as safety, and grade 1-3 was set as risk. The safety rate of screws, operation time, the times of intraoperative fluoroscopy and the amount of intraoperative hemorrhage were compared between the two groups. Results: As for C1 screw, there were 48 screws of grade 0, 7 screws of grade 1, 2 screws of grade 2 and 1 screw of grade 3 in the control group, while 49 screws of grade 0, 2 screws of grade 1, 1 screw of grade 2 and 0 screw of grade 3 in the test group. There was no statistically significant difference(P＞0.05) in each grade of screw classification between the two groups at C1 level. As for C2 screw, 53 screws of grade 0, 6 screws of grade 1, 1 screw of grade 2 and 0 screw of grade 3 in the control group, while 48 screws of grade 0, 2 screws of grade 1, 0 screw of grade 2 and 0 screw of grade 3 in the test group. There was no statistically significant difference in each grade of screw classification between the two groups at C2 level(P＞0.05). Significant statistical difference between the two groups was found in the safety rate of screws(P=0.019). For the control group and the test group, the average operation time was 109.2±17.1min and 115.2±16.6min respectively, with significant differences(P=0.009), and the average number of fluoroscopy was 12.50±1.95 and 6.85±2.44 respectively, with significant differences(P<0.0001). The average intraoperative hemorrhage was 198.1±108.3ml in the control group and 160.3±135.4ml in the double guide plate group, with no significant difference between the two groups(P=0.216). All cases obtained fusion after posterior atlantoaxial approach operation at the last follow up. Conclusions: Improved personalized template assisted screw placement technique can effectively reduce the times of X-ray fluoroscopy, and it can be more accurate than free-hand technique in atlantoaxial pedicle screw placement in clinics.