An Explorative Anatomical Study on Inter-Individual Variation of the Tibial Nerve and Landmarks for Perineural Anesthesia in Horses.
Authors: De Schryver Margot, Oosterlinck Maarten
Journal: Animals : an open access journal from MDPI
Summary
# Editorial Summary: Tibial Nerve Anatomy and Landmarks for Equine Perineural Anesthesia Blind tibial nerve blocks remain routine in equine practice despite inferior success rates compared to ultrasound-guided techniques, prompting De Schryver and Oosterlinck to investigate whether anatomical variations might explain frequent block failures. Using detailed dissection of 20 cadaver hindlimbs (10 pairs), the researchers mapped the tibial nerve's course along the medial tibia and identified consistent anatomical landmarks, finding notably that anatomical variation was *not* a source of inconsistency—the nerve measured 6 ± 1 mm in diameter, with the crucial junction between tibial and plantar nerves occurring within 85 mm proximal to the calcaneal tubercle and maintaining a mean distance of 11 ± 6 mm from the superficial digital flexor tendon. Rather than anatomical irregularity, the study suggests that challenges in achieving reliable desensitisation relate to the nerve's modest diameter and the surrounding perineural tissue architecture, factors that likely demand precise needle placement and adequate volume infiltration. Their findings provide anatomically validated support for the widely recommended injection site of approximately 100 mm proximal to the calcaneal tubercle and 11 mm cranial to the superficial digital flexor, offering equine practitioners objective anatomical data to refine blind-block technique or reinforce the case for ultrasound guidance where available.
Read the full abstract on PubMed
Practical Takeaways
- •Blind tibial nerve blocks at 100 mm proximal to the calcaneal tubercle remain anatomically sound; consider ultrasound guidance to overcome challenges related to nerve calibre and perineural tissue rather than searching for anatomical variants
- •When performing tibial nerve injection by palpation, aim 11 mm cranial to the superficial digital flexor as a consistent landmark; failures are more likely due to technical injection factors than anatomical abnormalities
- •The relatively small nerve diameter (6 mm) and variable perineural tissue may explain inconsistent anesthesia outcomes with blind techniques—these practical challenges support transitioning to ultrasound-guided approaches in clinical practice
Key Findings
- •No anatomical variations of the tibial nerve were observed across 10 paired cadaver hindlimbs
- •Mean tibial nerve thickness was 6 ± 1 mm with mean distance of 11 ± 6 mm cranial to the superficial digital flexor
- •Junction with plantar nerves located at maximum 85 mm proximal to calcaneal tubercle; junction with medial cutaneous branch at maximum 150 mm proximal
- •Failures in blind tibial nerve perineural anesthesia are not attributable to anatomical variations but rather to nerve thickness and perineural tissue challenges