Authors: Gruyaert Mounia, Oosterlinck Maarten, Haspeslagh Maarten, Nagy Annamaria
Journal: Frontiers in veterinary science
Summary
# Editorial Summary: Palmar Digital Nerve Block Safety and Synovial Structures Palmar digital nerve blocks are routine regional anaesthetic techniques in equine practice, yet the risk of inadvertent needle penetration into adjacent synovial structures—the navicular bursa, distal interphalangeal joint and digital flexor tendon sheath—has never been systematically evaluated. Using CT imaging on 18 cadaver forelimbs, Gruyaert and colleagues mapped needle placement in relation to these structures under varying conditions, including artificially distended synovial sacs that might mimic clinical effusion. Synovial penetration occurred in 3% of 420 needle placements overall, with distal needle positioning carrying particular risk: the navicular bursa was breached in 5 cases and the DIPJ in 2 cases, predominantly when needles were placed distally. Critically, synovial distension significantly reduced the mean distance between needle tips and both the navicular bursa and DIPJ, suggesting that horses with pre-existing joint or bursa effusion face increased penetration risk. Whilst the absolute incidence remains low, practitioners should heighten vigilance when performing palmar digital blocks on limbs with existing synovial fluid accumulation, and consider proximal needle placement as a potential strategy to reduce DFTS involvement, though the clinical significance of transient needle contact versus actual intra-synovial injection warrants further investigation.
Read the full abstract on PubMed
Practical Takeaways
- •Palmar digital nerve blocks carry a small but real risk (3%) of accidentally penetrating nearby synovial structures—consider this when selecting injection technique and location
- •If synovial structures are already distended (effusion, inflammation), the risk of unintended penetration increases; adjust needle placement accordingly or consider alternative blocking methods
- •Distal needle placements near the ungular cartilages carry higher risk to the navicular bursa and joint; proximal placements (1 cm further up) reduce this particular risk but increase risk to the flexor tendon sheath
Key Findings
- •Synovial penetration occurred in 12/420 (3%) needle placements during palmar digital nerve blocks
- •Distal needle placements showed significantly smaller distance to navicular bursa and DIPJ compared to proximal placements
- •Synovial distension increased the risk of needle proximity to navicular bursa and DIPJ structures
- •Proximal needle placements showed significantly smaller distance to digital flexor tendon sheath