When a horse has pain in the rear half of the foot, injection of the navicular bursa (sac cushioning the navicular bone from the deep digital flexor tendon) is often considered as a treatment option. Corticosteroids (to control inflammation) and possibly hyaluronate (HA, to improve the bursa's lubrication and decrease synovial inflammation, or inflammation of the soft, pliable membrane lining a joint) are the usual substances injected, sometimes along with an antibiotic to guard against infection. Chris Bell, DVM, an equine surgical resident at the University of Saskatchewan, presented a study on the efficacy of these injections at the 2008 American Association of Equine Practitioners Convention, held Dec. 6-10 in San Diego, Calif. The study was conducted during Bell's internship at Arizona Equine Medical & Surgical Center.

Twenty-three horses with forefoot heel pain diagnosed with MRI and their navicular bursae injected as treatment were followed for at least four months to see how well the treatment worked. All 35 feet injected received triamcinolone acetate (TA, a corticosteroid), and 18 feet also received HA.

Seventeen of the 23 horses (74%) had "excellent" outcomes, defined as returning to full work (most within two to four weeks) with no recurrent lameness; soundness continued for an average of 7.3 months. Two horses had moderate outcomes, continuing light work, but with some lameness, while four did not return to athletic function, including two that were euthanized for various reasons. No difference in success between treatments (TA and HA vs. TA alone) was found.

"The poor and moderate outcomes correlated with erosion of the flexor surface of the navicular bone and adhesions of the deep digital flexor tendon to the navicular bone," Bell reported. "Outcomes were excellent for navicular bursitis cases, likely due to the anti-inflammatory effects of the corticosteroids. Horses receiving less than 10 mg of TA responded poorly.

"Use of MRI is important in the accurate diagnosis and prognostication for horses with specific lesions that will not respond favorably to navicular bursa injection," Bell concluded.

About the Author

Christy M. West

Christy West has a BS in Equine Science from the University of Kentucky, and an MS in Agricultural Journalism from the University of Wisconsin-Madison.

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