A new approach for perineural injection of the lateral palmar nerve in the horse.
Authors: Castro Fernando A, Schumacher James S, Pauwels Frederik, Blackford James T
Journal: Veterinary surgery : VS
Summary
# Editorial Summary: Perineural Injection of the Lateral Palmar Nerve Localising the source of forelimb pain in horses requires precise nerve blocks, particularly when distinguishing between carpal and metacarpal pathology. Castro and colleagues evaluated a new injection technique for blocking the lateral palmar nerve at the accessory carpal bone, assessing both accuracy and the risk of inadvertently entering the carpal synovial sheath—a critical concern given the potential for iatrogenic joint contamination. Using methylene blue as a tracer dye injected by three clinicians into 30 cadaver forelimbs, 29 limbs (97%) showed dye directly surrounding the lateral palmar nerve, with one specimen showing dye within 2 mm; crucially, no dye was detected within the carpal synovial sheath in any specimen. This medial approach provides a reliable, technically straightforward method for achieving perineural anaesthesia of the lateral palmar nerve proximal to its deep branch division, enabling clinicians to confidently block sensation to the palmaroproximal metacarpus during diagnostic investigations without the complication of carpal joint penetration. The consistency and safety profile demonstrated here suggests this technique represents a valuable refinement for equine practitioners performing regional analgesia protocols.
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Practical Takeaways
- •This injection technique reliably blocks the lateral palmar nerve without risking accidental joint penetration, making it safer for diagnostic lameness work in the distal metacarpus
- •The medial accessory carpal bone landmark approach is straightforward and reproducible across different clinicians
- •Practitioners can confidently use this block to isolate pain from the palmaroproximal metacarpus during lameness evaluation
Key Findings
- •Perineural injection of lateral palmar nerve achieved in 29/30 limbs (96.7%) with dye surrounding or within 2mm of nerve
- •No dye penetration into carpal synovial sheath in any of 30 specimens
- •Technique provides consistent, accurate perineural placement proximal to deep branch origin