Because navicular problems might affect soft tissue as well as bone, MRI is a better diagnostic tool than X ray in these cases, said Robert K. Schneider, DVM, MS, professor at Washington State University College of Veterinary Medicine, and part owner of MREquine, a mobile MRI unit.
Horses with navicular syndrome--a degenerative condition within the navicular apparatus, which includes several structures--tend to experience multiple problems, many of which cannot be seen on X ray, said Schneider at the 2010 Western Veterinary Conference, held Feb. 14-18 in Las Vegas, Nev.
"To know what the horse has, and to know how to treat, you need an MRI," said Schneider, although he noted that the imaging is expensive and might not change treatment.
In a study of horses with recent and chronic disease, MRI showed problems that were not apparent on X rays. Specifically, the researchers saw two patterns of navicular syndrome that would require different treatment: one with abnormalities in the collateral seasmoidean ligament and the deep digital flexor tendon with adhesions in the navicular bursa, and another with inflammation and fluid within the navicular bone and surrounding soft tissue. Of these, only the first group would benefit from injection therapy, Schneider said.
Although there is no cure for navicular syndrome, proper management can help many horses perform normally. Some horses require rest and rehabilitation, especially if they have deep flexor tendonitis.
"A good farrier can help a navicular horse as much as anyone," Schneider said. He recommended the horse's toe be kept short and the shoe set at the horse's natural angle, stating he avoids elevating horses with deep flexor tendonitis or with navicular problems.
Schneider teaches owners to perform stretching exercises with these horses. "I ask them to stretch the tendon by picking up the opposite limb and forcing (the horse) to stand in an extended position for 1 minute, three times in succession," he said. "The idea is to make a more functional leg. Stretching is important to maintain the length and function of the structure."
Although many veterinarians use isoxsuprine, aspirin, and/or the injectable tiludronate (Tildren), Schneider said he prefers low doses of phenylbutazone or "bute," which can reduce inflammation for some. Some horses also require injections of corticosteroids or hyaluronic acid in the navicular bursa.
Unresponsive cases can be managed with chemical blocking agents or surgery.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.