Scott McClure, DVM, PhD, an assistant professor in the Department of Veterinary Clinical Sciences at Iowa State University, recently evaluated extracorporeal shock wave therapy (ESWT) in treating 32 horses with navicular syndrome diagnoses. He presented the results of his research study during the 2004 American Association of Equine Practitioners convention, held Dec. 4-8 in Denver, Colo.

Horses were treated one time with 2,000 shock wave pulses under general anesthesia in lateral recumbency.

Part of the challenge of treating this area with ESWT is, "To do this, you have to be able to get the shock wave (through the thick tissues of the foot) to the navicular bone, so you do two approaches, through the heel bulbs and the frog," explained McClure. "Pare them down the evening before the treatment, soak the foot, and come back and freshen the edges to get the shock in the foot where you'd like to have it."

After treatment, the horses were discharged and the owners were instructed to maintain the horses' current shoeing regimens and add no additional treatment. Bute was given to the horses for one week, and they were given a week of stall rest followed by a week of hand walking.

An unmasked veterinary evaluation (meaning the veterinarian had performed the treatment and was familiar with the case) was done at six months post-treatment, client perception was gauged at six and 12 months post-treatment, masked radiograph evaluations were completed (meaning the radiologist was not familiar with the cases), and masked veterinary evaluations were performed via videotape (these reviewers were not associated with the study and were unfamiliar with the cases) .

In the unmasked vet evaluation, 27 of the 32 horses (84%) were available for follow-up. Of those 27, 22 (81%) had improved according to evaluation as they trotted in-hand in a straight line on a hard surface. When trotted in a circle, 19 of the 27 (70%) had improved. The decrease in lameness was statistically significant for those trotted in hand or on a circle.

The clients' evaluations (on 27 of the 32 horses) at six months post-treatment showed that 22 of the 27 (81%) had improved, four remained the same (15%), and one horse (4%) got worse. At 12 months post-treatment, 16 horses were available for follow-up, and none of these horses were reported to have increased lameness associated with navicular syndrome.

In the masked veterinary evaluation, "We had videotapes of the (32) horses pre-treatment and (for 16 horses) six months post-treatment," said McClure. "They were randomly mixed and evaluated by three equine veterinarians (not associated with the study)."

In the 16 horses, the duration of the navicular syndrome-associated lameness prior to presentation to McClure was anywhere from two weeks to three years. In-hand videotape evaluations at six months post-treatment showed that nine of 16 improved (56%), two had no change (8%), and five had progression of the disease. Eleven of the 16 horses (69%) had returned to their intended use by the time of the six month follow-up.

Radiographs were looked at blindly six months post-treatment and scored. McClure said there were no significant changes in the radiographic scores between pre-treatment and six months post-treatment evaluations.

"So you ask yourself why it would work," said McClure. "Is ischemic necrosis (cell death caused by oxygen deprivation) a component? From things that we're learning every day, it may well be. We know there's some neurovascularization (or regeneration of blood supply in tissues, knowledge of which stems from studies on canine bone-tendon junctions). There are a lot more capillaries in shock wave therapy-treated tendons rather than control tendons."

A number of applications of ESWT in horses have shown positive responses. He said as magnetic resonance imaging progresses, a wealth of more information will be understood about ESWT.

"The decreased lameness in these horses is encouraging because many of these horses had been chronically lame and most had been unresponsive to previous conventional treatments," McClure said. He suggested that to make the study more objective and exact, gait analysis and controls could be incorporated into the study. "While it is possible that there could be spontaneous improvement in some horses, the duration and severity of the disease in these horses makes it unlikely."

He said 56% was a very conservative number for the success rate, because he knew that some of the horses not submitted for re-evaluation had been successful in their various riding disciplines post-treatment.

About the Author

Stephanie L. Church, Editor-in-Chief

Stephanie L. Church, Editor-in-Chief, received a B.A. in Journalism and Equestrian Studies from Averett College in Danville, Virginia. A Pony Club and 4-H graduate, her background is in eventing, and she is schooling her recently retired Thoroughbred racehorse, Happy, toward a career in that discipline. She also enjoys traveling, photography, cycling, and cooking in her free time.

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