Design and Application of a Customized 3D-Printed Plate-Screw Construct For O-C1 Fixation Via the Endoscopic Endonasal Corridor: A Cadaveric Study

Introduction: Following endonasal odontoidectomy, it is common for patients to require arthrodesis across O-C1 and/or C1-2. This generally requires a second stage procedure from a posterior approach, yet there are inherent risks and disadvantages associated with separate-stage posterior craniocervical instrumentation for stabilization. Previous cadaveric studies have described technically feasible and biomechanically sound methods for endoscopic, endonasal C1-2 fixation. To date, however, no validated investigational method exists for O-C1 fixation using an endoscopic endonasal approach. The aim of our study is to develop a minimally invasive plate-screw construct for stabilization across the O-C1 joint through the endonasal corridor.

Methods: Thin-slice CT scans of the OC junction were obtained from a cadaveric specimen and uploaded to 3D design software. A virtual 3D model of the O-C1 joint was constructed using image segmentation, and further processed in Computer-Aided Design (CAD) software to design and 3D print a customized plate.

Results: A customized plate-screw construct for fixation across the O-C1 joint was successfully 3D printed using image segmentation and CAD software. The plate features two vertical panels and one horizontal crosslink, all of which are designed to fit through the endonasal corridor.

Conclusion : In this proof-of-concept study, a customized plate-screw construct for endoscopic endonasal O-C1 fixation was successfully designed and 3D printed. Current work and future directions involve investigation into optimal materials, optimizing implantation and closure techniques, and biomechanical stability testing. A minimally invasive approach to the OC junction through the endonasal corridor may be a viable method for O-C1 fixation.