Retrograde maxillary nerve perineural injection: A tomographic and anatomical evaluation of the infraorbital canal and evaluation of needle type and size in equine cadavers.

The study analysed a new approach for equine maxillary nerve blocks aimed at facilitating specific types of facial surgeries on horses. This new method, termed retrograde maxillary nerve perineural injection, uses a different entry point to inject anesthesia, which limits the chances of damaging sensitive structures in the target area.

Research Methodology

• The researchers carried out their investigation on 13 horse skulls that had been preserved after death. They looked specifically at the infraorbital canal and the structures around it. This canal, an area of interest for this study, was analysed using computed tomography (CT scans) and anatomy dissection.
• The measurements taken included the canal length, volume, its conformation (shape and structure), and the relationship it has with the structures it houses, such as the enclosed infraorbital nerve and vessels.
• The research team also measured the infraorbital foramen diameters, the holes at the base of the skull through which the infraorbital nerve, artery, and vein pass.

Injection Technique Testing

• After the physical anatomy was studied, the researchers simulated the distribution of the local anesthetic within the infraorbital canal.
• They tested the seven different types of needles to understand which would be best suited in terms of insertion ease, minimal trauma to surrounding tissues, and effective spread of a contrast medium to the target area.
• The contrast medium revealed how the anesthesia would spread in a real surgical context and helped identify potential complications.

Validation of Technique

• To validate their technique, the researchers injected 10ml of contrast medium into infraorbital foramina using two randomly selected Tuohy needles.
• They then used CT scans to confirm the spread of the injected solution and evaluate any possible complications.
• It was noted that the actual canal had a winding, snake-like path, and that there were spaces between the infraorbital nerve and vessels and the canal itself.

Conclusion

• This study suggests a feasible approach to the maxillary nerve block within the infraorbital canal.
• The selected Tuohy needles demonstrated the ability to effectively deliver an anesthetic without causing harm to the enclosed structures of the infraorbital foramen.
• The researchers indicate that with the right needle selection and technique, the chances of complications can be minimized.