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Navicular

Navicular Disease
By Walter BergerADip AppSc (H. Mgt)

Navicular Disease. Two words that can send shivers up the back and through the bank accounts of horse owners. But what is it? What are the causes, symptoms and treatments for it? Can it be prevented?

The diagram below tries to show some of the anatomy involved with this syndrome. Disease is probably too inaccurate a term as often more than the navicular bone and surrounding structures are involved. Often similar symptoms such as shortened strides, pointing or actual lameness in the horse are present, but Navicular structures play no part in the problem. These symptoms could also be caused other problems within the foot, leg or elsewhere within the horse, which have to be eliminated before diagnosing the horse as having Navicular disease.

Hoof Structure Pastern and Coffin Joint

Navicular disease involves mostly problems involving the Navicular bone and the deep digital flexor tendon where it passes under the navicular bone. In hard working horses these structures can undergo great stresses, which over time may cause problems.

Problems may be caused by any of the following, or a combination of the same. There could also be other factors involved.

  • Arthritic and other changes to the Navicular bone.
  • Adhesions between the Deep Digital Flexor Tendon and the Navicular bone.
  • Nerve damage.
  • Changes to the blood supply in the area.
  • Damage to the navicular bursa (a fluid filled sack which assists with tendon and bone movement).
  • Damage to the ligaments holding the Navicular bone in place.

Diagnosis may involve a combination of Hoof testing, X-rays, Flexion tests, Nerve blocks, Ultrasound, Nuclear Scintigraphy or Thermal Imaging. For all of these experienced practitioners would be almost essential. Probably several avenues need to be explored in order to eliminate other possibilities before settling on the prognosis of Navicular disease.

X-rays are commonly used to try to identify problems with the navicular area. It may also used in conjunction with vet checks in order to predict horses soundness for whatever lives we have planned for them. But while X-rays may show details of the navicular bone and irregularities within the bone such as spurs, channels or cysts, their presence does not always mean the horse will be unsound or develop Navicular disease. But they are more likely to. Research done recently in the Netherlands discovered that while 85% of lame horses had abnormalities of the Navicular bone, 15% did not. The same research also showed that the shape of the Navicular bone is pretty much set at birth. (Susan Piscopo, DVM, PhD, January 2002, The Horse). Also autopsies on horses have shown that older horses have been sound and competing, while having abnormalities of the Navicular bone (Fran Jurga, August 1997, The Horse). This could mean that it may be useful to monitor for changes to the bone over time as they may indicate development of problems, which of course comes at a cost as X-rays and Vets do not come cheap. It becomes a matter of weighing up the costs versus any possibly benefits.

Prevention and Treatment can be very similar in some respects. Proper foot trimming and shoeing if needed are almost essential in the working horse to maintain healthy feet in the end. A healthy balanced foot will help prevent undue stresses to all the tendons, ligaments and joints that make up the horses suspensory apparatus. Often horses which end up being diagnosed with navicular disease have feet which are too long in the toe, or don’t have enough heel or contracted heels, or are simply out of balance. So corrective shoeing is often the first thing that is tried in order to relief the horse’s pain. Preventing problems from happening is usually easier and cheaper than trying to fix things when they go wrong. Once a degenerative process has started it can be difficult to stop.

There are a couple of other things which may help prevent problems from occurring, and which may be useful in the rehabilitation of a horse with navicular disease. A good set of neoprene boots (the ones that wrap around the fetlock) may help absorb some of the shocks of hard work. Also in a study by Auburn University in the USA a joint supplement has been shown to be effective in reducing lameness due to navicular disease. This can also help things running smoothly before problems occur, as it assists with maintaining gliding surfaces such as tendon over bone.

So your horse’s feet are taken care of properly, you boot him, supplement him and take care of the rest of him, and he still develops a navicular problem. Don’t hang up your spurs yet in order to take up breeding goldfish. It may still be possible to reduce your horses discomfort to a level where he is sound enough to use. Often rest itself may resolve or improve matters, as it has been shown that a lot of work can increase lameness caused by navicular disease. Then there are anti-inflammatory and other drugs that can be used on your vets advice. Just be careful as drugs and competing may not mix, watch that swabbing. There are also nerving operations, which cut nerves in the horse’s leg to remove sensations to part of the horse’s foot and thereby remove pain. But this would have to be used very cautiously, because if the horse cannot feel part of his foot, he may be more susceptible to injury and accidents. Again, there may be competition implications again. But all these may just be temporary fixes, with the problem resurfacing at some other time.

Overall, prevention is the best cure. Take care of your horse’s feet and legs. Do not work the horse too hard before he is fit. Warm your horse up properly. Ensure your horse has proper nutrition for what he is doing. And cross your fingers.

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