Life-Size 3D Modeling for C1–C2 Fixation Planning: A Preoperative Tool for Atlantoaxial Stabilization Techniques

Spine instrumentation can be performed with intraoperative computed tomography (CT) guidance, fluoroscopy guidance, or freehand techniques. Surgical fixation of the atlantoaxial (C1–C2) junction without CT guidance remains technically challenging due to complex anatomy and proximity to critical neurovascular structures. To evaluate the feasibility of low-cost, patient-specific three-dimensional (3D)-printed anatomical models for preoperative planning of C1–C2 instrumentation. High-resolution CT and CT angiography data from 20 individuals were used to generate patient-specific 3D models of the C1–C2 vertebrae and vertebral arteries using open-source segmentation software (3D Slicer®). Models were produced as life-size replicas, with multiple fixation techniques simulated and screw angulations measured in axial and sagittal planes. Twenty patient-specific C1–C2 anatomical models were successfully produced and instrumented. Screw angulations and lengths across all fixation techniques—including C1 lateral mass, C2 pedicle, pars, translaminar, and transarticular screws—remained within established safe anatomical ranges. Each model required approximately 215 minutes of active printing time and a total hands-on preparation time of approximately 275–320 minutes, with an additional 24-hour curing period for silicone processing. The material cost per model was approximately USD 0.56 using a desktop fused deposition modeling printer. Low-cost, patient-specific 3D-printed models provide anatomically consistent, life-size representations of the complex atlantoaxial region. These models may represent a practical adjunct for surgical planning, feasibility assessment, and preoperative rehearsal for various C1–C2 fixation strategies without advanced intraoperative technology. Further studies are needed to evaluate their clinical impact. • Low-cost patient-specific 3D models for C1–C2 fixation planning • Life-size models enable simulation of multiple fixation techniques • Vertebral artery anatomy incorporated into anatomical models • Screw trajectories consistent with known anatomical parameters • Open-source workflow enables accessible and reproducible modeling