Abstract: Objective To compare the safety and accuracy of the free-hand technique and 3D printing guide plate technique in the placement of cortical bone trajectory screws in the lumbar spine.
Methods The lumbar spine CT data of 9 patients in our hospital were selected,and the three-dimensional model of the lumbar spine was established using computer software and the drill guide plate was designed based on the cortical bone screw trajectory.A 3D printer was used to print 2 sets of lumbar spine models and 1 set of drill guide plates for each case.Three cases were randomly selected by three operators with different experience,and the screws were placed by free-hand and guide plate respectively.According to different screw placement methods,it is divided into free-hand group and guide plate group.Postoperative X-ray film examination,according to the screw contact cortical bone area,screw penetration position and penetration distance to evaluate the effect of screw placement.
Results 90 screws were placed in each group.In free-hand group,the success rate was 73.3%,and the acceptability rate was 85.6%;in guide plate group,the success rate was 92.2%,and the acceptability rate was 98.9%.Success rate and acceptability rate of the guide group were higher than that of the free-hand group(P<0.05).The success rate and acceptance rate of screw placement between operator 2 and operator 3 were both higher than that of operator 1,but there was no significant statistical difference between operator 2 and operator 3(P>0.05).
Conclusion Compared with freehand technique,3D printed guide plate technology is more safe and accurate in the placement of lumbar cortical bone trajectory screw.

Key words: lumbar spine, cortical bone channel screw, pedicle screw, 3D printing technology