🔍 Key Findings

• A patient-specific dorsal implant for atlantoaxial stabilization was developed using CT-based 3D modeling, enabling customized implant design and safe screw trajectory planning.
• The implant accommodates six 1.7-mm bicortical locking screws, including two transarticular screws plus two screws in each vertebra (atlas lateral masses and axis lamina/spinous base).
• The implant also functions as a drilling guide, allowing the screw-head housing to accept a threaded drill guide that ensures accurate drilling along predefined safe corridors.
• An opening around the C1–C2 intervertebral foramen was incorporated to avoid injury to the C2 nerve root during dorsal instrumentation.
• Finite element analysis evaluated implant behavior under flexion, extension, lateral flexion, and torsion using loads of 50 N (physiologic) and 107 N (supraphysiologic).
• Maximum stress occurred during lateral flexion with axis fixation (425 MPa), which remained well below the titanium alloy yield strength of 880 MPa, indicating no mechanical failure.
• Maximum implant displacement was minimal (0.13 mm), far less than the approximately 2 mm movement of the intact atlantoaxial joint under physiologic loading.
• The implant design demonstrated adequate rigidity and mechanical safety in simulation, suggesting potential to improve dorsal stabilization while avoiding complications associated with PMMA constructs.