research is needed to define the role of genetics in the development of navicular disease and to determine if genetics alone can be responsible for the clinical manifestations of the disease. As there are multiple processes that result in the clinical signs and symptoms, we call navicular disease there are a number of factors that predispose a horse to each of the four described disease processes. conformation of the foot and the pastern increase the concussive force experienced by the navicular bone and predispose the horse to developing ischemia/thrombosis related navicular disease. A low heel, long toe hoof configuration as well as a long sloping pastern increases the compressive forces on the navicular bursa and therefore predispose the horse to the bursitis related navicular disease. Horses with a small in comparison to their body size tend to have a reduced blood flow to the foot, to have increased compression on the navicular bursa and to have increased concussive force on the structures of the foot, making these horses predisposed to developing either ischemia/thrombosis type navicular disease or the bursitis type navicular disease. High impact work such as racing or jumping on hard or footing increases the concussive forces in the foot, predisposing the horse to thrombosis/ischemia type navicular disease. Finally, navicular is reported to occur primarily in male Thoroughbred and Quarter horses regardless of conformation, which is indicative of a genetic factor having a role in the development of navicular disease. mild lameness that improves with rest. At rest the horse may point one toe in the forelimb or may alternate toes depending on whether one or both feet are affected. The stride of a horse suffering from navicular disease will have a shortened phase of the stride and the foot will appear to contact the ground toe Clinically navicular disease is seen as first. Lameness is more clearly seen at the trot than at other gates. As the disease progresses the foot will change shape to develop contracted heels, a flattened sole and a square toe. Hoof testers applied over the area of the frog will elicit a positive response for pain in the area of the digital cushion. Radiology may reveal bony changes or roughening of the articular surface of the navicular bone and in advanced cases may show fracture or degeneration of the navicular bone, especially around the nutrient foramina. Diagnosis of navicular disease can be made through clinical signs and symptoms, gait analysis, positive response to hoof testers in the area of the frog, fracture or degeneration visible on radiology, MRI and a decrease in lameness with a palmar digital block. There is no definitive treatment for Navicular disease as it is progressive. It is recommended that the horse be rested for ten days maximum and given oral Isoxuprine hydrochloride during this time. If bursitis is the suspected cause it may be necessary to inject corticosteroids into the navicular bursa to relieve the pressure on the navicular bone. After the ten days rest the horse should be correctively by a farrier and should be turned out either barefoot, or in egg bar shoes with a silicon rim pad. Glue-on shoes that allow the foot to stretch and contract may also be used on horses with navicular disease though these shoes tend to come off more easily than conventional shoes. In advanced cases of navicular disease, it may become necessary to perform a of the palmar digital nerve to allow the horse to
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