The Feasibility of Creating Image-Based Patient-Specific Drill Guides for the Atlantoaxial Instabilities Using Open-Source CAD Software and Desktop 3D Printers.

Objective: C1/2 cervical pedicle screw fixation is a well-known procedure for treating severely damaged and unstable C1/2 fractures. On the other hand, C1/C2 screw fixation is not safe and can lead to potentially disastrous consequences. The importance of personalized 3-dimensional (3D) printed navigational guides in avoiding these consequences cannot be overstated.

Methods: We retrospectively reviewed the neuroimaging data of 16 patients who had undergone fixation for treatment of C1/2 diseases. We created patient-specific C1/2 models and drill guide models using open-source 3D editing software and a desktop 3D printer. The drill guides were then placed over the respective vertebrae models and fixated with 3.5-mm screws. Following fixation, the parts were scanned with a thin-slice (01 mm) computed tomography scan, and the screw trajectories in the transverse and sagittal planes were measured at each level.

Results: Of the total of 62 screws, 58 were type I (93.54%), 4 were type II (6.45%), and no screws were type III. The results showed that there was no significant deviation in the screw trajectories and the accuracy of the drill guides was 93.54%. In our study, type I and type II screws were deemed acceptable, and the acceptable rates of C1/2 screw fixation were 100%.

Conclusions: In this preclinical study, we demonstrated that it is possible to create patient-specific pedicle drill guides using open-source editing software and a commercially available desktop polylactic acid printer, resulting in high accuracy rates in pedicle screw placement in C1/2 patient models.