A comparison of the effects of local analgesic solution in the navicular bursa of horses with lameness caused by solar toe or solar heel pain.
Authors: Schumacher J, Schumacher J, de Graves F, Schramme M, Smith R, Coker M, Steiger R
Journal: Equine veterinary journal
Summary
# Editorial Summary This 2001 study challenged a widely held assumption in equine lameness diagnosis: that navicular bursa analgesia specifically identifies navicular apparatus pathology. Schumacher and colleagues induced controlled pain at different sole locations (dorsal margin and palmar angles) in six horses using set-screw pressure shoes, then evaluated whether injecting 3.5 ml local anaesthetic into the navicular bursa would mask this non-navicular pain. Lameness scores improved significantly (P<0.05) in all horses following navicular bursa analgesia when dorsal sole pain was present, though the analgesic effect was notably less reliable for palmar heel pain. The findings have important diagnostic implications: a positive response to navicular bursa injection cannot be interpreted as confirmation of navicular apparatus disease, as superficial or mid-sole pain can produce identical responses through diffuse anaesthetic spread or neurological cross-talk. Clinicians should therefore interpret analgesia results cautiously and incorporate additional diagnostic methods—such as diagnostic imaging, pressure mapping, or sole palpation—rather than relying solely on bursa injections to differentiate between navicular and solar pathology.
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Practical Takeaways
- •Do not assume lameness relief from navicular bursa injection definitively indicates navicular apparatus pathology—solar pain involvement must be ruled out through diagnostic imaging and palpation
- •When using navicular bursa analgesia diagnostically, recognize that it may mask concurrent dorsal sole pain, potentially leading to incomplete diagnosis
- •Consider sole pain (especially dorsal margin lesions) as a differential diagnosis in cases where navicular bursa blocks provide unexpected lameness improvement
Key Findings
- •Local analgesic solution in the navicular bursa significantly reduced lameness caused by dorsal sole pain in all 6 horses (P<0.05)
- •Navicular bursa analgesia was less effective at desensitizing the sole angles than the dorsal margin of the sole
- •Pain from the sole should not be excluded as a cause of lameness even when analgesia of the navicular bursa attenuates lameness
- •Navicular bursa analgesia is not selective for the navicular apparatus alone