Navicular disease is a chronic illness that commonly affects the forelimbs of athletic horses. Although the exact etiology is largely unknown, it is believed that it is the result of many factors that culminate in the degeneration of the navicular bone, one of the components of the foot. Not only does the condition reduce competitiveness, it is also associated with marked pain. In this article, we will explore some important aspects of navicular disease in horses.
The onset of this condition is gradual and characteristically presents with intermittent lameness. When both the anterior and posterior limbs are affected, as happens frequently, making the diagnosis becomes very difficult. This is because the disability on the two limbs cancel out each other. Taking the horse for a lunge might help you notice the abnormality. A more objective way of examining is performing a nerve block in one of the affected limbs.
There are several factors that have been established to predispose to the condition. Conformational abnormalities relating to the hoofs are one of the commonest problems. Those at the greatest risk are narrow, upright, small or have long toes. With such abnormalities, the distribution of weight through the feet is uneven. Some of the tarsal bones such as the navicular bone are progressively damaged leading to lameness.
The terrain on which the animal trains is also important. The risk of navicular disease increases if the ground used is irregular and hard. The train that is exerted on the bones and tendons is a lot more and so is the damage. The weight transmitted through the feet also increases a great deal when the horse stands for prolonged periods of time and increases damage to the bony structures in the feet.
Improper fitting shoes are a known cause of damage to feet. This has been affirmed by the fact that the incidence of this problem is higher in domesticated horses compared to those living freely in the wild. Metallic shoes do not allow for expansion of the toes during movement. This impairs the flow of blood into the tarsal ligaments and bones. Barefoot trimming and proper shoe section can help reduce this problem.
There are a number of treatment options that can be considered once the disease has established itself. These options may be either conservative or invasive. Using NSAIDs such as phenylbutazone and firocoxib helps to minimize the pain. Prolonged use of NSAIDs is associated with some adverse effects in the kidney and the gastrointestinal tract hence should be stopped intermittently to allow for recovery of these systems.
The other class of drugs that is commonly used is corticosteroids. They are a particularly good choice if the animal has failed to respond to NSAIDs. Up to 80% of affected animals will exhibit some improvement within 4 months of initiating treatment. The drug is injected around the bone (navicular bursa) once or twice a day as prescribed by the vet. The main downside of such intra bursa injections is the increased risk of tendon rupture.
There are several surgical procedures that may be performed but only as a last resort. It should be emphasized that these surgical operations will by no means cure the condition; they only provide symptomatic relief. One of those that are commonly performed is known as palmer digital neurectomy. Apart from relieving pain, this operation helps to improve competitiveness.
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