Blind Versus Ultrasound-Guided Low-Volume Perineural Injection of Tibial and Fibular Nerves in Equine Cadaver Limbs.
Authors: Colla Sandro, Seabaugh Kathryn A, Zanotto Gustavo Miranda, Selberg Kurt
Journal: Journal of equine veterinary science
Summary
# Editorial Summary Perineural nerve blocks of the tibial and fibular nerves are routine procedures in equine anaesthesia, but whether ultrasound guidance offers genuine advantages over traditional blind techniques has remained unclear. Researchers injected cadaver hindlimbs using either conventional blind injection (15 mL for tibial nerve, 10 mL per fibular nerve) or ultrasound-guided perineural injection with dramatically reduced volumes (3 mL and 1.5 mL respectively), then evaluated nerve coverage and injectate spread via radiography and cross-sectional dissection. Both approaches achieved comparable success rates for perineural placement, but ultrasound-guided injection produced significantly less diffusion of injectate distally around the tibial nerve and proximally, distally and medially around the fibular nerves—findings that suggest better anatomical containment of local anaesthetic with lower volumes. Whilst this cadaver study cannot definitively predict clinical efficacy, the reduced drug volumes required for successful ultrasound-guided blocks carry practical implications for minimising systemic absorption, reducing cost per block, and potentially lowering the risk of local anaesthetic toxicity, though practitioners should recognise that blind techniques remain equally reliable for perineural coverage if ultrasound equipment is unavailable.
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Practical Takeaways
- •Both blind and ultrasound-guided perineural blocks achieve similar success rates for tibial and fibular nerve anesthesia, so choice can be based on available equipment and operator experience
- •Ultrasound-guided technique allows substantial reduction in anesthetic volume (5-10 fold less), potentially reducing cost and systemic effects while improving localization
- •Reduced diffusion with ultrasound guidance means more precise nerve coverage with less spread to surrounding tissues, which may reduce complications and improve block quality
Key Findings
- •No statistically significant difference in success rate between blind and ultrasound-guided perineural injection techniques for tibial and fibular nerves
- •Ultrasound-guided technique achieved similar success using 80% less volume (3 mL vs 15 mL for tibial nerve; 1.5 mL vs 10 mL for fibular nerves)
- •Ultrasound-guided injection resulted in significantly less distal diffusion for tibial nerve and less proximal, distal and medial diffusion for fibular nerves compared to blind technique
- •Low-volume ultrasound-guided technique provides more localized anesthetic distribution while maintaining comparable success to traditional blind technique