Cadaveric comparison of the accuracy of ultrasound-guided versus 'blind' perineural injection of the tibial nerve in horses.
Authors: van der Laan Maylin, Raes Els, Oosterlinck Maarten
Journal: Veterinary journal (London, England : 1997)
Summary
# Editorial Summary: Ultrasound-Guided vs Blind Tibial Nerve Blocks in Horses Accurate tibial nerve blocks are essential for diagnostic lameness evaluation in horses, yet the traditional blind technique—relying solely on anatomical landmarks—frequently fails to deliver consistent local anaesthesia. Researchers compared these two injection approaches using 21 pairs of cadaver hindlimbs, administering 1 mL methylene blue via either blind or ultrasound-guided technique to visualise whether the injectate successfully stained the nerve. Ultrasound guidance substantially improved the success rate of nerve staining to 85.7%, compared with just 47.6% for the blind method (odds ratio 6.6), although the distribution characteristics of injectate (width, length) and the total length of stained nerve were similar between techniques. Whilst this finding supports adoption of ultrasound guidance for more reliable nerve blocks in clinical practice, the failure of even US-guided injections to consistently achieve complete nerve staining in roughly 14% of attempts suggests that clinicians should remain aware of diagnostic limitations and consider repeat injections or supplementary techniques when clinical response is inconsistent with anatomical predictions.
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Practical Takeaways
- •US-guided tibial nerve blocks are significantly more likely to successfully stain the nerve than blind anatomical techniques, which may improve diagnostic anaesthesia efficacy in lameness work-ups
- •Even with ultrasound guidance, nerve staining was not achieved in ~14% of attempts, suggesting that technique refinement or multiple injections may sometimes be necessary
- •Consider ultrasound guidance for tibial nerve blocks in practice to increase reliability of diagnostic blocks during hindlimb lameness evaluation
Key Findings
- •US-guided tibial nerve injection achieved 85.7% nerve staining success rate compared to 47.6% with blind technique (P = 0.02)
- •US-guided technique showed 6.6-fold higher odds of successful nerve staining (95% CI: 1.5-29.4)
- •No significant difference in stain dimensions or coloured nerve length between US-guided and blind techniques
- •Single US-guided injection did not consistently result in nerve staining despite improved accuracy