Accuracy of rapid cervical vertebral prototyping and feasibility of its application in cervical screw placement

English Keywords:Rapid prototyping  Emulate error  Ｃervical navigation

English Abstract:

  【Abstract】 Objective：To test the accuracy of rapid prototyping of cervical vertebrae and investigate the feasibility of its application in screw placement.Method：8 adult cervical specimens soaked with formalin，perforated in the vertebral plate and spinal process prior to CT scan were used.The CT data were converted from DICOM format into STL format by software Mimics，then different types，material and methods were used to establish 2 group models using rapid prototyping.The distance of the bores between the models and the specimens were compared and analyzed to acquire the accuracy of the cervical vertebrae model using rapid prototyping technology.In model group 2，K-wire was inserted into the vertebrae plate（levels C3-C7），stacking the gypsum around the vertebrae plate near the K-wire to manufacture templates，then then the K-wire was pulled out.Accordingly the ventral surface of the foraminiferous template was the faying surface.The faying surface of the template was sticked onto the vertebrae plate of each group 1.K-wire was used to verify the accuracy of the perforation in the templates of the specimens and models，and the CT data were acquired to manufacture models and templates for intra-operative navigation of pedicel screws placement in 7 patients.The accuracy of screw placement was evaluated after operation.Result：There was no significant difference in the distance of bores among specimens，model group 1 and 2.The precise error between model group 1 and 2 was less than 3mm.There was no significant difference in three dimensional error between 2 model groups.There was a significant consistence among the template and the model group 1 and 2. 24 screws were inserted into pedicles of the cervical spine.Under the guidance of model and template，the accuracy was 100%.Conclusion：The accuracy of rapid prototyping has high，which can be used as an intra-operative navigation for the cervical screw placement.