Accuracy of pedicle screw placement in Lenke 1 adolescent idiopathic scoliosis surgery using intraoperative navigation with a simple calibration technique

Objective:To compare the position and the grade of screw perforation in Lenke 1 adolescent idiopathic scoliosis(AIS)surgery using intraoperative navigation system with and without calibration technique,and to explore the related factors of navigation deviation and the clinical significance of calibration technique.Methods:From 2014 to 2017,a total of 45 Lenke 1 AIS surgical cases were enrolled in this study.The 23 surgical cases were assisted with intraoperative navigation system(Navigation group)and another 22 cases received surgery using intraoperative navigation system with calibration technique(Calibration group).In two groups,the basic information and radiological data were all recorded.Postoperative CT scan with 3D reconstruction was used to analyze the accuracy of pedicle screw placement,as well as the length and position of cortical perforation.Results:There was no statistical difference between two groups in gender,age,Risser sign,both preoperative Cobb angles and flexibility of the major curve,as well as numbers of pedicle screws.477 and 469 pedicle screws were implanted in the navigation group and the calibration group respectively.The rate for major pedicle perforations 2 mm(grades 2,3)was 7.8%in navigation group.It was statistically significant difference from the 4.3%screw misplacement in calibration group(P=0.014).In navigation group,the rates of major pedicle perforations 2 mm were medial:3.4%,lateral:3.6%and anterior:0.6%respectively.The corresponding rates were 1.1%,2.6%and 0.4%in calibration group respectively.The rates of the medial cortical perforation 2 mm showed statistical difference between two groups(P=0.016).No serious complications,such as nerve or vascular injury,were found in all patients.Conclusion:Intraoperative navigation system with calibration technique provides the real-time monitoring of navigation deviation,the higher accuracy of pedicle screw insertion,the lower medial cortical perforation rate and the less complication rate,as well as a simple calibration technique with higher accuracy of screw placement in comparison to intraoperative navigation system for Lenke 1AIS surgery.