Development and testing of an animal-specific and string-of-pearls (SOP) plate specific, three-dimensionally (3D) printed drilling guide: A proof of concept study for canine thoracolumbar spinal stabilization.

Objective: To describe novel patient-specific, string-of-pearls (SOP) plate specific, three-dimensionally (3D) printed, drilling guides for spinal stabilization.

Study design: Model- and cadaveric-based experimental, proof of concept study.

Sample population: Three normal cadaver spines, three normal cadaver spinal models, and three historical canine spinal fracture models were used bilaterally, allowing 18 mock surgeries from T12-L5, and 140 screws.

Methods: Computed tomography (CT) was used to virtually straighten all spines and virtually reduce the fractures in the spinal fracture cases. Spinal models and animal-specific drill guides for a SOP plate were created. Screw holes were predrilled using guides, and the spines stabilized with a SOP plate and screws. Post-surgical CTs were performed. Screw placement accuracy was assessed with both the Zdichavski classification and by comparing the post-surgical measurements to the presurgical planning.

Results: All 140 screw trajectories were optimally placed (grade 1 modified Zdichavski score). The transverse and craniocaudal angles were similar across all groups. All but two entry and exit measurements were different, with mean deviations <1 mm from the planned measurements.

Conclusion: Patient-specific, SOP plate specific, 3D-printed drilling guides allowed safe and relatively accurate placement of screws in the T12-L5 vertebra of dogs.

Clinical significance: With presurgical planning and the described drilling guides, spinal stabilization using a SOP plate may be a safe method of repair. The technique may allow for easier reduction and fixation of vertebral fractures/luxations, but further clinical studies are needed.