vendredi 9 janvier 2015

Understanding Navicular Disease In Horses

By Enid Hinton


The navicular bone and surrounding tissues sometimes get problems. This is the bone that is in the front part of the foot. It is located behind the coffin bone and next to small pastern bone. A strong bundle of tendons run across the part to the back part of the coffin bone. They also pass through the soft tissue. Some cartilage is found between these two bones. Moreover, there is a fluid sack just over the navicular bone to prevent it from getting abraded. The syndrome causes inflammation around this area and sometimes causing the bone to degenerate and causing disabling lameness to the horse. Therefore, there is much need to ensure navicular disease in horses is handled in the early stages.

There is no known single cause of this syndrome. However, there are two theories put forward to explain what could be the cause. First, it is believed that compressing of navicular under the tendons and the small pastern bones, as explained above, can cause degeneration of cartilage. This causes the cartilage to flatten and results to it becoming less springy and is unable to absorb bigger shock.Researchers have also found gradual cartilage erosion and degeneration along the surface next to this bone where there was suspected compression. This is associated with biochemical changes and has similarity to human osteoarthritis. This erosion may progress to a point that the underneath bone becomes exposed and thus not protected.

Research has shown gradual but persistent cartilage erosion along the navicular bone in horse with the syndrome. It is believed to be associated with some biochemical changes similar to osteoarthritis in humans. Persistent erosion wears off the cartilage and exposes the underneath bone. This bone constantly rubs against the tendons continually causing inflammation. Compression also makes the bone increase in density and thus becomes brittle. Brittle bones break easily.

Research has also indicated that tension on the ligaments that support the bone could lead to degeneration. Excess tension causes strain and inflammation that decreases blood flow to and fro the navicular bone. Most of these blood vessels run along this region. Persistent tension causes the ligament to permanently thicken and reduce blood flow.

If blood is restricted from one side of this bone, there is usually fluid buildup in this bone. The bone responds to pressure and reduced blood supply by absorbing mineral found at its center. Extreme tension also causes exostoses, a condition in which ligaments that are attached to the navicular bone force the bone to assume a canoe shape due to pressure. They may tear in some cases.

The treatment suggested by the vet is largely dependent on extent that the navicular region has been damaged. There are a range of interventions from conservative ones to aggressive ones. These include surgery, shoeing the hoof, trimming, and various medications, oral and intravenous.

When using shoe treatment, the vet places a bar across the horse heel to relieve pressure that build up on heels. The hoof wall quarters may be rasped or grooves cut to relieve contraction. The feet could also be trimmed to balance the foot. Most horses with the problem have long toes and small inner wall depth. Trimming also improves the hoof structure of the horse.

The use of medication involves injection with vasodilators to improve blood flow. There are also anti-inflammatory drugs to treat pain. There are also oral medications aimed at relieving the problem. Surgery involves severing the nerves that could be causing the pain but causes the horse to lose sensation in the back of a foot.




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