The Analysis Of The Accuracy And Influencing Factors Of Robot Assisted And Freehand Pedicle Screw Placement In Lumbosacral Vertebrae

Objective:To study the accuracy and influencing factors of robot assisted and freehand pedicle screw placement in lumbar and sacral vertebrae.Methods:A retrospective case-control study was conducted and 83 patients who underwent surgery for lumbar degenerative diseases in the people’s Hospital of Henan University from October 2017 to December 2018were analyzed.According to the way of pedicle screw placement,the patients were divided into two groups:40 patients in the robot assisted pedicle screw placement group were taken as the observation group,and 43patients in the freehand fluoroscopy pedicle screw placement group were taken as the control group.All patients underwent X-ray,CT and MRI of the lumbar vertebrae before operation.The type,diameter,length and quantity of screws,the operation method and approach,and the fixation mode of robotic operation platform were recorded.On the third days after operation,all patients underwent gemstone energy spectrum CT scan and three dimensional reconstruction of lumbar vertebrae.The violation to the facet joints due to the pedicle screws placement were evaluated according to Ranjith Babu’s facet joint violation classification of pedicle screws.Grade 0:the pedicle screw not in facet;Grade 1:the pedicle screw in lateral facet but not in facet articulation;Grade 2:the penetration of facet articulation by screw,invasion distance≤1mm;Grade 3:the pedicle screw travels within facet articulation,invasion distance>1mm.The accuracy of pedicle screw placement in the two groups was evaluated according to the Gertzbein-Robbins classification.Screws completely within the pedicle are Grade A;a breach of<2 mm is Grade B;a breach of 2 to<4 mm is Grade C;a breach of 4 to<6 mm is Grade D;and a breach of≥6 mm is Grade E.The penetration direction and quantity of pedicle screws in different diseases and segments were compared at the same time.The transverse section angle（TSA）of pedicle screws in axial CT was measured and compared between the two groups.The length of pedicle screws in each segment of the two groups was recorded and compared.Results:In the robot assisted pedicle screw placement group,40 cases were enrolled,and a total of 156 lumbar pedicle screws and 42 S₁pedicle screws were implanted.According to the Babu classification,there were177 Grade 0 screws,15 Grade 1 screws,6 Grade 2 screws and 0 Grade 3 screw;80 pedicle screws were inserted into the proximal fusion vertebral,including 71 Grade 0 screws,6 Grade 1 screws,3 Grade 2screws and 0 Grade 3 screw.All the screws were placed in the segment L₃-S₁,and there were 181 Class A screws,13 Class B screws and 4 Class C screws,according to the Gertzbein-Robbins classification.Of the17 screws with perforation,4 penetrated the medial cortical of pedicle,10 penetrated the lateral cortical of pedicle,and 3 penetrated the anterior cortical of pedicle.No serious complications such as nerve and blood vessel damage were found after operation.In the freehand fluoroscopy pedicle screw placement group,43 cases were enrolled,and a total of 174lumbar screws and 36 S₁pedicle screws were implanted.According to the Babu classification,there were128 Grade 0 screws,62 Grade 1 screws,15 Grade 2 screws,and 5 Grade 3 screws;86 pedicle screws were implanted in the proximal fusion vertebral,including 50 Grade 0 screws,28 Grade 1 screws,7 Grade 2screws and 1 Grade 3 screw.All the screws were placed in the segment L₃-S₁,and there were 178 Class A screws,19 Class B screws,11 Class C screws and 2 Class D screws,according to the Gertzbein-Robbins classification.Of the 32 screws with perforation,9 penetrated the medial cortical of pedicle,18 penetrated the lateral cortical of pedicle,and 5 penetrated the anterior cortical of pedicle.There were 5 patients with neurological symptoms after operation,including 3 patients with increased numbness and 2 patients with decreased muscle strength.They were given symptomatic supportive treatment such as detumescence and neurotrophic therapy,who all had Class C or D screws,and the neurological symptoms disappeared.The incidence of facet joint violation in the robot assisted screw placement group（10.61%）was lower than that in the free hand fluoroscopy screw placement group（39.05%）,and the difference was statistically significant（?2=43.683,P=0.000<0.05）.The incidence of adjacent superior segment facet joint violation in the robot assisted screw placement group（11.25%）was lower than that in the free hand fluoroscopy screw placement group（41.86%）,and the difference was statistically significant（?2=19.653,P=0.000<0.05）.The accuracy of the robot assisted screw placement group（91.41%）was higher than that of the free hand fluoroscopy screw placement group（84.76%）,and the difference was statistically significant（?2=4.268,P=0.039<0.05）.In the comparison of the same vertebral body,there was no significant statistical difference in the accuracy of screw placement between the two groups（P>0.05）.There was no significant statistical difference in the accuracy of screw placement between the two groups for patients with lumbar disc herniation and lumbar spinal stenosis（P>0.05）,but there was a statistical difference in the accuracy of screw placement between the two groups for patients with lumbar spondylolisthesis（?2=4.031,P=0.045<0.05）.The accuracy of the clamp mount fixation platform was higher than that of the bed mount fixation platform in the robot assisted screw placement group,and the difference was statistically significant（?2=8.765,P=0.003<0.05）.In L3,L4 and L5 segments,there was no significant statistical difference in the average TSA of pedicle screw between the two groups（P>0.05）.In S₁segment,the average TSA of pedicle screw in the robot assisted screw placement group（25.3±1.7°）was larger than that in the freehand fluoroscopy screw placement group（23.9±1.9°）,and the difference was statistically significant（t=-3.276,P=0.002<0.05）.In L3,L4 and L5 segments,there was no significant statistical difference in the average pedicle screw length between the two groups（P>0.05）.In S₁segment,the average pedicle screw length in the robot assisted screw placement group（43.8±3.5mm）was larger than that in the freehand screw placement group（35.8±3.0mm）,and the difference was statistically significant（t=-10.721,P=0.000<0.05）.Conclusion:Compared with the freehand fluoroscopy pedicle screw placement,the robot assisted pedicle screw placement can reduce the violation of pedicle screw to the facet joint and reduce the risk of adjacent segment degeneration.In the treatment of lumbar degenerative diseases,robot assisted pedicle screw placement can significantly improve the accuracy of screw placement and overcome anatomical differences in lumbar spondylolisthesis.The clamp mount fixation platform is more firmly connected than the bed mount fixation platform,which can avoid the relative displacement between the robot platform and the patient,and improve the accuracy of screw placement.Robot assisted S₁pedicle screw placement can use a larger TSA and a longer screw to achieve the tricortical pedicle screw fixation.