MIMICS Software Virtual Technique Guided C1 Lateral Mass Screw Placement In Atlantoaxial Dislocation

Objective:This study explored the use of MIMICS Software virtual technique to obtain personalized C1 lateral mass screw trajectory parameters,and try to apply the parameters to assist screw implantation.The clinical value of this MIMICS Software virtual technique is also evaluated in this research.Method:A total of 88 cases of patients with atlantoaxial dislocation were included in this study.All patients were examined by thin slice CT scanning.The original DICOM data were imputed in MIMICS workstation.In mimic workstation,the reference coordinate system was established,a 3D images of atlanto occipital bone fusion was reconstructed of,and then a cylinder with 3.5 mm diameter was created as a simulation of lateral mass screw in the system.The simulated screw position was adjusted in 3D view in order to avoid the violation ipsilateral vertebral artery,hypoglossal canal and other important structures.Its horizontal axis plane angle and sagittal angle was calculated,and then the simulation of screw placement to the C1 side block the ideal,the axial angle(angle)and sagittal angle(angle),axial and sagittal angles were measured in size.The measurements of the screw trajectory length was measured based on a bicortical screw,which from the entry point and the exit point of the screw.Then the parameters of ideal trajectory was applied in real operation.Preoperative simulation and parameter reconstruction of the reference anatomical markers are in operation,including the direction of screw,screw and screw length,to the direction of the hole.After drilling,nailing walls integrity detection scout road and depth,gradually increase the depth of the nail to the desired depth,scout screw has exceeded C1 detection side abdominal block the lateral bone cortex,tapping along the ideal screw expansion screw(to prevent the nail when the bone cortex was breaking,and then along the road)screw implant diameter of 3.5 mm.All patients after CT review,the DICOM image into mimics simulation system in 2 dimensional image safety assessment C1 LMS.Result:A total of 176 screws were analyzed.The mean ideal axial angle was 14.2°±5.0°medially and the mean ideal sagittal angle was 20.5°±9.1°superiorly.The mean ideal trajectory length was 19.1mm±2.2mm.The radiographic evaluation showed that 170(96.6%)screws were ideally placed(Type?),6 screws were malpositioned(Type?).Overall,100% screws were rated as safe(Type?and?).Conclusion: The C1 LMS trajectory in patients with AAD should be individually planned before operation.With assist of the virtual reality technique,C1 LMS could be safely implanted in the assimilated C1 lateral mass.