CHAPTER TWENTY: HOOF DISEASE
Podotrochleosis
Podotrochleosis is commonly called disease. It is a form of osteonecrosis where there is inflammation and degeneration of the navicular bone and the surrounding soft tissue. to the navicular bone, navicular bursa, impar ligament, or the digital cushion and artery. This can be due to poor biomechanics of the foot or due to iatrogenic interference. Genetics may play a role in the development of podotrochleosis as conformation and breed predispositions are known. It is thought that podotrochleosis is caused by repeated
There are four pathogeneses that are known to result in navicular disease:
The first involves of the navicular bursa. Increased pressure between the tendon of the deep digital flexor and the navicular bone cause bursitis in the navicular bursa. Swelling of the navicular bursa exerts pressure and causes irritation of the flexor surface of the navicular bone. Over time this pressure wears away the articular cartilage of the navicular bone and triggers into the impar ligament. Exostosis and roughening of the articular surface of the navicular bone cause abrasive lesions in the deep digital flexor tendon.
The second pathogenesis involves the
necrosis of the navicular bone. Repeated
concussion form the foot impacting the ground causes damage and to the digital vein causing congestion of the foot. In response the limb develops an increased number of arteriovenous anastomes (AVA’s), which allow the blood flow to bypass the foot causing ischemic necrosis of the navicular bone. The arterioles that enter the navicular bone through the nutrient foramina increase in number in an attempt to compensate for the reduced blood flow to the foot, causing a decrease in the density of the navicular bone. . The osteoclast activity exceeds the osteoblast activity, causing an osteoporosis-type degeneration of the navicular bone. The decrease in bone density makes the navicular bone more vulnerable to fracture caused either by the concussive force of the hoof contacting the ground or by the compressive force of the deep digital flexor tendon over the navicular bone. The third pathogenesis describes an imbalance in bone The final pathogenesis is the least developed theory. It attributes the development of navicular disease to some factor found in some male Thoroughbreds and Quarter horses. This indicates that the “navicular trait” is heritable and is linked to the Y sex chromosome. Further
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