Development and Finite Element Analysis of a Patient-Specific Implant for Atlantoaxial Joint Stabilization via Dorsal Approach in Dogs.

Objective:  To develop a patient-specific implant designed for dorsal access instrumentation, which also serves as a guide for screw insertion, for use in dogs with atlantoaxial instability. The implant must demonstrate no failure in finite element analysis.

Study design:  The development of an implant utilizing computational resources based on a computed tomography scan of a patient with atlantoaxial instability. The final implant model was analysed using finite element methods in flexion, extension, lateral flexion, and torsion to evaluate stress distribution and displacement.

Results:  A patient-specific implant for dorsal instrumentation was developed, featuring six holes for the insertion of 1.7-mm bicortical locking screws, including two transarticular screws and two additional screws per vertebra. The implant demonstrated a maximum stress point of 425 MPa, well below the material yield strength of 880 MPa, with a maximum displacement of only 0.13 mm.

Conclusion:  The proposed implant shows promise as it can function as a drilling guide, potentially enhancing safety during instrumentation. Using safe corridors may improve the rigidity of the construct. The implant model did not exhibit any failure when subjected to finite element analysis according to the established criteria.