Comparison The Safety And Accuracy Of Pedicle Screw Placement Between The Robot Technique And Navigation Technique In Scoliosis Surgery

Backgrounds:Scoliosis is a common three-dimensional(3D)deformity of the spine,defined as a lateral curvature of the spine in the coronal plane,often accompanied by varying degrees of spinal rotation.Scoliosis is usually defined by a curve of≥ 10°(Cobb Angle measurement),and the disorder can affect respiratory function and body balance,and have other effects,in severe cases.Posterior scoliosis correction with pedicle screws has become the standard treatment for patients with severe spinal curvature,rapid progression of disease in adolescence,and neurologic symptoms.However,screw placement in scoliosis surgery is challenging owing to vertebral rotation and smaller pedicle size(especially at the concave side)and a more complex 3D structure than normal.These issues increase the potential risk of screw misplacement and cause complications,such as vascular,nerve,and pleural injury.Currently,the fluoroscopyassisted free-hand technique is the principal method for pedicle screw implantation.Previous studies reported that the rate of screw malpositioning caused by free-hand pedicle screw insertion during scoliosis correction range from 1.5%to 43%,with an overall average perforation rate of 20.3%.In scoliosis cases,even when the pedicles’ rajectories are predetermined and tapped correctly,screws may be inserted into the pedicles incorrectly owing to axial rotation,especially at the apical levels.To improve pedicle screw positioning,several techniques have been developed,including navigation technologies,such as computed tomography(CT)-guided or robot-assisted technologies,to decrease the risk of misplaced screws and the associated complications.In recent years,intraoperative computed tomography(CT),which includes the use of O-arm and 3D C-arm,has been used in spinal surgery for navigation assistance.Moreover,O-arm navigation provides intraoperative 3D fluoroscopic imaging with an image quality similar to that of CT,and reduces the time needed for computerassisted surgery.However,navigation techniques may still be subject to human error and surgeon tremor to some extent.Robot technology has been developing since its inception.The orthopedic robot adds a mechanical arm on the basis of navigation technology,which makes the placement of pedicle screws more convenient and accurate.The advantages of roboticguided techniques include increased accuracy,shorter surgical time,and reduction of intraoperative radiation exposure.At present,the Tianji robot independently developed in China(Beijing Tianzhihang Medical Technology Co.,Ltd.)has been successfully applied.The advantage of Tianji robot lies in the combination of robot and navigation system,and it can track the position of screw placement and the respiratory movement of patients in real time,thus reducing the misplacement rate of pedicle screws.However,at present,the research on the application of Tianji robot technique and navigation technique in scoliosis correction is limited.In addition,the comparison of the accuracy and safety of pedicle screw placement between robot technique and navigation technique also needs to be further explored.Objectives:We reported the clinical use of robot-assisted pedicle screw placement and navigationguided pedicle screw placement for scoliosis surgery and compared the clinical outcomes,accuracy,and safety between the two techniques.Methods:The imaging data and clinical score data of 66 patients with scoliosis who underwent scoliosis surgery in Qilu Hospital of Shandong University from January 2020 to December 2022 were analyzed retrospectively.Thirty-two patients were treated with robot-assisted pedicle screw implantation(robot group),including 6 males and 26 females,with an average of 14.9±3.1 years,including 23 cases of idiopathic scoliosis,7 cases of congenital scoliosis,and 2 cases of neuromuscular scoliosis.Thirty-four patients were treated with pedicle screw implantation assisted by navigation technique(navigation group),including 7 males and 27 females,with an average of 15.3±2.9 years,including 27 cases of idiopathic scoliosis,5 cases of congenital scoliosis,and 2 cases of neuromuscular scoliosis.In the present study,3D images were used to evaluate the accuracy of the first pedicle screw placement during operation.The accuracy of placement of all pedicle screws postoperatively was evaluated using reconstructed CT image data to improve accuracy.Perforation was assessed using the following screw misplacement grading systems.Each screw position was classified as grade 0(no perforation,with the screw completely within the pedicle),grade 1(perforation ≤2 mm),grade 2(perforation>2 to ≤4 mm),or grade 3(perforation>4 mm or>1 screw diameter).Grade 0 and 1 screw positions were considered clinically acceptable,while grades 2 and 3 indicated perforation.In accordance with this grading system,the screw misplacement rates were determined.Operation time,radiation exposure,blood loss,postoperative hospital stay,and postoperative complications related to the surgeries were investigated and compared between the groups.Full-length radiographs were obtained using a standard protocol to measure the preoperative and postoperative Cobb angle.The apical vertebral rotation(AVR)in robot group and freehand group was measured on CT images preand postoperatively.The AVR grade was measured on a standard posteroanterior radiograph postoperatively.When both pedicle screw tips were visible central to the two rods(classified as Grade 0 vertebrae),CT measurements of vertebral rotation were between 0° and 8°.In Grade 1 vertebrae,one pedicle screw tip was hidden behind the ipsilateral rod,and CT measurements of vertebral rotation were between 9° and 12°.In Grade 2 vertebrae,one pedicle screw tip was lateral to its ipsilateral rod,and CT measurements of vertebral rotation were greater than 13°.This grading system could be used to quickly assess postoperative residual AVR and possibly to evaluate for the development of crankshaft over time.Results:There was no significant difference in sex,age,BMI and type of disease between the robot group and the navigation group,so there was comparability between the two groups.A total of 1259 pedicle screws were implanted in 66 patients,including 627 in the robot group and 632 in the navigation group.The accuracy of the first pedicle screw placement in the robot group was 94.7%,of which grade 0,grade 1,grade 2 and grade 3 screws accounted for 88.5%,6.2%,2.4%and 2.9%,respectively.The accuracy of the first pedicle screw placement in the navigation group was 89.2%,of which grade 0,grade 1,grade 2 and grade 3 screws accounted for 80.1%,9.2%,6.3%and 4.4%,respectively.The accuracy rate of the first pedicle screw placement during operation was significantly higher in robot group(94.7%)than in navigation group(89.2%;P=0.000).In the robot group,the accuracy of pedicle screw placement after operation was 96.7%,of which grade 0,grade 1,grade 2 and grade 3 screws accounted for 90.0%,6.7%,1.4%and 1.9%,respectively.The accuracy of postoperative pedicle screw placement in the navigation group was 93.0%,of which grade 0,grade 1,grade 2 and grade 3 screws accounted for 82.9%,10.1%,5.4%and 1.6%,respectively.The accuracy rate of pedicle screws placement postoperatively was significantly higher in robot group than in navigation group(96.7%vs 93.0%,P=0.004).The misplacement rate of pedicle screws was 3.3%in the robot group and 7.0%in the navigation group,and the difference was statistically significant(P=0.004).The misplacement rates of convex side and concave side in robot group were 1.9%and 1.4%,and those of navigation group were 4.8%and 2.2%,respectively.The misplacement rates of medial and lateral of robot group were 1.4%and 1.9%,and those of navigation group were 1.3%and 5.7%,respectively.There were no complications related to pedicle screw placement in robot group and navigation group.The operation time in the robot group(6.55±0.99 hours)was higher than that in the freehand group(6.12±0.92 hours),but there was no significant difference.There was no significant difference in intraoperative blood loss and postoperative hospital stay between the two groups(P>0.05).The patient’s intraoperative radiation dose of the robot group(44.22±5.34 μSv)was significantly higher than that of the navigation group(32.81±4.22 μSv,P=0.000),but there was no significant difference in surgeon’s intraoperative radiation dose between the two groups(P>0.05).There was no significant difference in preoperative and postoperative Cobb angles and AVR between robot group and navigation group(P>0.05).The Cobb angles of the main curve in robot group and navigation group improved significantly postoperatively(P<0.05).There were no significant differences in the AVR grade postoperatively between robot group and navigation group(p>0.05).Conclusions:Robot-assisted pedicle screw placement and navigation-guided pedicle screw placement can achieve good clinical results.Compared with the navigation-guided pedicle screw placement,robot-assisted pedicle screw placement can effectively improve the accuracy in scoliosis surgery.A three-dimensional scan after insertion of the K-wire may increase the accuracy of pedicle screw placement in the navigation technique.