John Crowley BVSc (Hons.) MRCVS
Not so long ago,, Veterinarians and horse owners were petrified when the term "NAVICULAR DISEASE" was used in diagnosis of a trusted horse.
The owner assumed the only answer was a bullet, the Farrier made and shod an egg bar shoe, and the Veterinarian prescribed Phenylbutazone (bute) and scratched his head wondering whether this case would proceed like the last one with similar symptoms.
The truth is the back half of the foot is a "diagnostic nightmare". Many Veterinarians diagnose Navicular Disease when they block the palmar digital nerve and see an improvement in the lameness, then take X-rays and see radiographic changes in the navicular bone.
The limitations of using this procedure are:
i. There are almost 30 different conditions that cause pain in the back half of the hoof (that may respond to palmar digital nerve blocks).
ii. Many horses with no signs of lameness or soreness have radiographic changes on X-rays.
Let's begin to clarify the problem of differential diagnosis of "Navicular Disease" by outlining a range conditions that cause pain in the back half of the foot:
1. Corns caused by the shoe being left on for too long, resulting in bruising of the area of the seat of corn.
2. Corns caused by the inward movement of the wall with subsequent bruising of the sensitive tissues in the area of the seat of corn.
3. Corns caused by tearing of the laminae of the wall just behind the quarter as seen in hooves with a flaring of the wall in that area.
4. Quarter cracks.
5. Cracks in the wall of the foot.
6. Puncture wounds, especially in the area of the sulci of the frog.
7. Bruising of the sensitive sole and frog.
8. Thrush, especially in the central sulcus of the frog.
9. Compression of the sensitive structures of the foot as seen in those horses with contracted feet where the foot is wider at the coronet at the quarter than it is at the bearing surface.
10. Shearing of the heels, with resulting tearing of the digital cushion.
11. Crushing of the heels, especially in horses with underslung heels.
12. Nail prick or press, especially if the last nail is behind the widest part of the quarter.
13. Separation of the white line at or behind the quarters, with or without infection.
14. Bruising of the coronet at the heel.
15. Infection in the bulb of the heel.
16. Overloading of a heel because of an imbalance in the foot or because of an uneven footfall.
17. Lack of circulation because of inactivity (prolonged stabling).
18. Cross firing injuries to the inside heel or over-reaching injuries to either heel.
19. Fracture to the wing of the pedal bone.
20. Osteitis (inflammation) of the wings of the pedal bone.
21. Quittor (infection of the lateral cartilage).
22. Tearing of the attachment of the lateral cartilage to the pedal bone.
23. Sidebone.
24. Inflammation of the deep digital flexor tendon at its attachment to the pedal bone.
25. Inflammation of the coronet at the heel or quarter.
26. Navicular bursitis, or inflammation of the Navicular bursa.
27. Tearing of the suspensory ligament of the navicular bone at its attachment to the Navicular bone.
28. Damage to the flexor surface of the Navicular bone, especially in horses with broken back hoof pastern axis.
29. Adhesions of the deep flexor tendon to the Navicular bone and/or other parts of the sheath of the flexor tendon.
30. Inflammation of the Navicular bone or true Navicular disease.
No wonder many posterior hoof problems are labelled Navicular Disease.
Here are 30 separate possible causes of pain in the posterior part of the foot, and there are more.
An accurate diagnosis of the Navicular syndrome requires: experience, a keen eye, judicious use of the hoof testers, flexion and extension tests, local anaesthetic, an eye for balance, an accurate history, good quality radiographs, and you could still be left guessing.
No wonder there are so many "cures" for the syndrome.
Because there are so many causes of pain in the posterior half of the foot, there is no single shoeing method that is likely to be effective.
To be able to give an accurate prognosis and treat the condition effectively, the diagnosis must be accurate, and the corrective or therapeutic shoeing must be designed to correct the condition causing the pain.
