Saturday, September 5, 2015

The Management Of Navicular Disease Syndrome

By Daphne Bowen


The navicular bone is found in the ankle region between two other bones; the cuneiform and talus. In horses, this bone together with the surrounding supportive structures may degenerate leading to progressive lameness. The front feet are more frequently affected than the hind feet. Understanding the anatomy of the forelimb is important if you are to manage navicular disease successfully.

It is not clear what exactly causes this problem but a number of theories have been advanced. These include, among others, increased activity, diet and genetic disorders. Horses that take part in competitive activities are most likely to be affected than the sedentary ones. Repeated compression of the bones under flexor tendons such as the deep tendon flexor leads to cartilage degeneration and flattening.

Inflammation of surrounding ligaments reduces blood flow to the bone and increased pressure in the hoof. The earliest sign is heel pain and lameness follows within days or weeks and progresses in severity over time. Typically, the horses start exhibiting a tip-toeing gait as they attempt to exert pressure on the heel. They lose coordination and stumble frequently. Lameness may affect one or both feet with the second being involved due to overcompensation.

There are a number of conformational defects that serve as a risk factor for the disease. Most of the known defects increase the risk of concussion and by extension, bone damage. Narrow feet, small feet and long toes are all examples of conformations that increase pressure on the tarsal bones. This effect is multiplied several times during movement due to the large amount of shock produced.

Working on hard, irregular terrains is considered a major risk factor. Such terrain places a huge amount of stress on the main tendons and increases wear and tear. If this happens for a sustained period of time, the navicular bone may be exposed. This risk is also present among horses that spend a long time in an upright position. In the standing position, a lot of weight is transmitted through the hooves.

Improper shoe selection is a well-known cause of lameness. The problem is commoner among domesticated than in wild horses. Some experts have, for this reason, proposed barefoot trimming. It is argued that bare feet allow for contraction and expansion during movement. This does not happen when metallic shoes are worn. Consequently, blood flow is better in bare feet.

Due to the many causes that exist, there is no one known treatment. If the cause is due to degenerative changes, reversing the condition is possible. In this case, the treatment given will mainly be supportive and aimed at relieving symptoms. Proper trimming ensures that the foot is in neurological and biomechanical balance. Once the diseases has already established itself the intensity of work should be reduced.

There is room for pharmacotherapy. Drugs that improve blood flow such as vasodilators have been shown to be beneficial in some cases. Other groups of drugs that are useful include corticosteroids, NSAIDs, bisphosphonates and gallium nitrate. Surgery is reserved for cases that fail to respond to conservative therapies.




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