# Ultrasound-Guided Mandibular Alveolar Nerve Block in Rabbits: A Cadaveric Comparison of In-Plane and Out-of-Plane Approaches

## TL;DR

This study compares two ultrasound-guided techniques for nerve blocks in rabbits to improve pain management during dental procedures.

## Contribution

The study introduces an ultrasound-guided mandibular alveolar nerve block technique in rabbits and compares two needle insertion approaches.

## Key findings

- Both in-plane and out-of-plane ultrasound-guided approaches resulted in similar dye distribution around the nerve.
- Ultrasound guidance enabled consistent identification of the target nerve region in rabbit cadavers.
- No significant differences were found between the two techniques in image quality or staining scores.

## Abstract

Dental procedures involving the lower jaw are common in pet rabbits and are often associated with significant pain. Effective perioperative analgesia is therefore essential, particularly in a species that may show subtle signs of pain and is highly sensitive to stress. The mandibular alveolar nerve block can provide targeted analgesia for procedures involving the mandibular teeth; however, in rabbits, it has been described only as a blind technique based on anatomical landmarks. In this cadaveric study, we describe an ultrasound-guided approach to the mandibular alveolar nerve in rabbits and compare two different needle insertion techniques. Ultrasound guidance allowed visualisation of relevant anatomical structures and needle placement near the target nerve. Both techniques resulted in a comparable distribution of the injected solution around the nerve, suggesting that either approach may be technically suitable. The use of an ultrasound-guided approach may be particularly useful in challenging cases or in animals with altered anatomy. Further clinical studies in live rabbits are now needed to confirm its effectiveness and safety in routine practice.

Mandibular dental disease is common in pet rabbits and often requires invasive procedures associated with significant nociceptive input. Mandibular alveolar nerve blocks have been described in this species using blind techniques; however, their accuracy has not been objectively evaluated, and ultrasound-guided approaches have not been reported. This cadaveric study aimed to describe an ultrasound-guided mandibular alveolar nerve block in rabbits and to compare in-plane and out-of-plane approaches. Twelve adult New Zealand White rabbit cadavers (24 mandibular alveolar nerves) were included. For each rabbit, one nerve was assigned to an in-plane ultrasound-guided approach, while the contralateral nerve was assigned to an out-of-plane approach. Following ultrasound-guided needle placement, 0.1 mL/kg of a mixture of 2% lidocaine and 1% methylene blue was injected. Ultrasound image quality and perineural staining were assessed and scored, and longitudinal dye spread was measured after anatomical dissection. Both approaches allowed consistent identification of the target region and resulted in comparable ultrasound image quality scores, staining scores, and longitudinal dye spread, with no statistically significant differences between techniques. These results demonstrate the anatomical feasibility of ultrasound-guided mandibular alveolar nerve blocks in rabbits using either approach. Further in vivo studies are required to assess clinical efficacy and safety.