Design And Experiment Of Individual Drill Templates For The Atlantoaxial Pedicle Screw Fixation

Objective To explore and evaluate the accuracy and feasibility of individual rapid prototype drill templates which designed by CAD and manufactured by RP for atlantoaxial pedicle screw placement.Methods Volumetric CT scanning was performed in eight cadaveric atlas and axis to collect DICOM format dates. Then three dimensional (3D) images of atlas and axis were reconstructed and the parameters of pedicles of 3D model were measured by using software Mimics 10.01.The 3D model was saved by STL format in Mimics10.01.The scattered point cloud datas of 3D model was processed and the 3D coordinate system was located in software Imageware 12.1.The curves and surfaces of 3D model was processed in software Geomagic Studio 10.The optimal trajectory of pedicle screw was designed and a template was constructed which accorded with the anatomical morphology of posterior arch of atlas and lamina of axis by using software Pro/Engineer 4.0.The optimal trajectory of pedicle screw and the template were integrated into a drill template finally.The drill template and physical models of atlas and axis were manufactured by rapid prototyping(3D print technology).The accuracy of pilot holes of drill templates was assessed by visually inspecting and CT scanning.Results 32 pedicle screws were inserted, Imaging and visual inspection revealed that the majority of trajectories (96.9%)did not violate the pedicle cortex.Only one cortical violation was judged as noncritical and did not injury the adjacent spinal cord, nerve roots, and vertebral arteries .Conclusion The potential of individual drill templates to aid in the placement of atlantoaxial pedicle screw is promising because of its high accuracy.