UKHSU - The United Kingdom Horse Shoers Union
Talk by Chris Colles to Herts and Beds Veterinary Society 19th March 2004
The literature on navicular disease goes back a long way, the first known reference being from 1750.
Navicular Disease is a part of Navicular syndrome. Navicular syndrome is not a precise diagnosis. Navicular syndrome can include:
a) navicular disease,
Anatomically the navicular bone is quite isolated, being surrounded largely by fluid.
During navicular disease the arteries to the navicular bone become occluded by thrombosis and the veins also become congested. As the disease progresses the cartilage becomes ulcerated and adhesions develop to the deep digital flexor tendon, and necrotic areas develop within the bone.
A typical horse with navicular disease will be between 6 and 12 years old and doing irregular work. There is usually an insidious onset of lameness, which improves with rest in the early stages.
A horse with navicular disease tends to react in a distinctive manner to a flexion test, not minding it at first but becoming fidgety, whereas a horse with navicular bursitis will resent the initial flexion. Lameness usually improves with work. The horse will dislike tight circles and hills, point its foot and rest its heel.
Enlarged digital blood vessels can often be felt. A posterior digital nerve block will usually abolish the lameness.
Dr Colles does not approve of injecting local anaesthetic into the navicular bursa because of the risk of causing adhesions.
X Rays can be difficult to interpret. When a horse starts work changes occur within the foraminae which can give the appearance of navicular disease. A good lateral X-ray picture is as useful as a skyline view.
Warfarin is still the most effective drug but is difficult to monitor. Bute hides the symptoms and allows the disease to progress. Neurectomy can be used as a last resort. The most important part of treatment is a cooperative farrier.
The important part of shoeing is to correct any broken back hoof pastern axis, something which restricts the blood flow. A normal shoe will work as well as an egg bar if it comes back to the widest part of the frog. Egg bar shoes are difficult to adjust, and getting a farrier to fit one the right size is not an easy thing to do. The centre of the coffin joint should be over the centre of the shoe. A problem with egg bar shoes is that the weight of the bar will aggravate limb movement if the medial- lateral balance is not right. There are not many farriers who can get the shoeing right.
Navicular disease is much less common than it was twenty years ago. This may be because horses are better shod or because they do less road work.
Report by Martin Humphrey talk about it on the horses mouth