Simplified ultrasound-guided technique improves accuracy of median nerve perineural injection compared to "blind" techniques in equine ex vivo specimens.

OBJECTIVE: To assess the feasibility of a simplified ultrasound-guided technique (SUGT) for perineural injection of the median nerve ex vivo, to determine and compare the accuracy of 3 techniques for perineural injection of the median nerve (SUGT, "blind" proximal, and "blind" distal), and to evaluate and compare the dye distribution following perineural injection of the median nerve following each technique. METHODS: This was an ex vivo experimental study performed on thoracic limbs (from April through October 2025). Simplified ultrasound-guided technique and blind proximal were performed in paired limbs; in a separate group, blind distal was performed. One milliliter of methylene blue was injected for each technique. After 5 minutes, the limbs were dissected to assess median nerve staining and measure dye diffusion in proximodistal and craniocaudal directions. Accuracy was compared using McNemar and Fisher exact tests, and the extent of dye diffusion was compared using the Wilcoxon signed-rank test (P < .05). RESULTS: 22 forelimbs were included. The SUGT stained the median nerve in all specimens (11 of 11; 100% success rate). The success rates for blind proximal and blind distal techniques were 27.3% (3 of 11) and 0% (0 of 11), respectively. The SUGT was significantly more accurate than both blind techniques. There was no significant difference between blind proximal and blind distal. No significant differences in dye diffusion were detected among techniques. CONCLUSIONS: Perineural injection of the median nerve using SUGT is superior to blind proximal and blind distal techniques. CLINICAL RELEVANCE: The use of SUGT in clinical cases should be considered when performing diagnostic analgesia of the median nerve in horses.