A Comparative Study Of 3D Navigation Template And Free-Hand Technique In Posterior Scoliosis Surgery

Purpose Pedicle screw instrumentation is considered as the gold standard for scoliosis correction surgery,however,anatomical variations make pedicle screw insertion more challenging,accurate screw placement is the main concern during surgery for surgeons.The purpose of this study was to compare the accuracy and safety of pedicle screw placements with3 D printing navigation template comparing to free-hand technique in scoliotic patients,especially in thoracic region.Besides,we investigate further the difference of pedicle screw accuracy between concave side and convex side,and to evaluate the accuracy of pedicle screw placement with 3D printing navigation template in vertebrae with different rotation angle.MethodsWe retrospectively reviewed the data of 15 scoliotic patients undergoing corrective surgeries for deformity in our institution between 2014 and 2021(fourteen females,one male,mean age: 28.7±15.1 years).All patients received the radiographs and threedimensional CT of the spine.Pedicle width,Pedicle-rib-unit width and vertebral rotation were measured on preoperative images,and rotational vertebrae were evaluated and graded according to Nash-Moe criteria.The patients were divided into template group(8cases)and free-hand group(7 cases)according to procedures of screw insertion.All patients received posterior corrective instrumented surgeries,and pedicle screw was placed with 3D printing navigation template or free-hand technique.After surgery,the positions of the pedicle screws were evaluated using three-dimensional CT scan and graded for validation with Raley-Mobbs classification.And Intraoperative blood loss,surgical time,postoperative drainage volume and complications were recorded.ResultsAll surgeries were performed successfully,a total of 264 pedicles screws were implanted in 15 patients.138 screws were placed with the guidance of 3D printing navigation templates,and 126 screws were placed by free-hand technique.The mean pedicle width or pedicle-rib unit width between the two groups were similar,the differences of pedicle width or pedicle-rib unit width between concave side and convex side were also not significant.And the overall accuracy and safety in the template group were 70.3% and89.9%,respectively;and in the free-hand group,the overall accuracy and safety were61.9% and 90.5%,respectively.The differences of total accuracy or safety of pedicle screws between the two group were not statistically significant.However,in thoracic region,template navigation could achieve higher accuracy than free-hand technique(75.3%vs 60.4%),but the safety was similar between the two groups(91.1% vs 90.1%).There was a total of 89 perforations in the two groups(template vs free-hand: 41 vs 48),and in both groups,medial perforations were most frequent(template vs free-hand: 26 vs 28).Besides,although the accuracy on convex side was higher than that on concave side both in the two groups,while on significant difference was seen(template: 77.3% vs 63.9%,P>0.05;free-hand: 69.8% vs 54.0%,P>0.05).In terms of rotational vertebrae,the accuracy rates were 76.1% and 55.0% for Grade I and Grade II vertebrae in the template group,respectively.In free-hand group,the accuracy rates were 69.2%,56.0% for Grade I and Grade II vertebrae,respectively.There was no significant difference of accuracy rates between the two groups for Grade I or Grade II vertebrae.In addition,we observed less intraoperative blood loss in template group.No severe complications caused by misplaced screws were reported in either group intraoperatively and postoperatively.Conclusion3D printing navigation template has the potential to increase the accuracy of thoracic pedicle screw placement and decrease the intraoperative blood volume compared to freehand technique,but the two techniques can attain a satisfactory safety of screw insertion.Besides,3D navigation template might increase the accuracy of pedicle screws on the convex side or in rotational vertebrae.This study confirmed further the value of 3D printing navigation in screw insertion for scoliotic patients,which might promote the use in clinical practice.