Noteworthy Research: 02/04

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Injection For Heel-Pain Syndrome
Texas A&M study published in the November 2003 Journal of the American Veterinary Medical Association offers encouraging news for horses suffering from heel-pain syndrome.

The researchers injected the navicular bursas of 25 horses with refractory heel/navicular area pain with a mixture of corticosteroid, hyaluronic acid and an antibiotic drug (amikacin). The horses had been unresponsive to corrective shoeing and NSAIDs and lame for an average of more than nine months.

All the horses showed substantial improvement or complete resolution of pain with a heel-nerve block, and 20 of them returned to soundness within two weeks, remaining sound for over four months. The remaining five had multiple injections, and two with multiple injections had a rupture of their deep digital flexor tendon at the level of the pastern.

This study shows a navicular-bursa injection with this mixture is a viable treatment option. As with any injection, there are risks, including infection, local bleeding and a worsening of the underlying degenerative problem. It also is not a cure for the problem.

If your horse develops hind-foot pain, start by being certain the foot is correctly balanced and trimmed to an angle and configuration appropriate for the horse’s anatomy. If you see early signs of heel contracture — which could lead to heel-pain syndrome — pull the shoes, trim and balance the feet and give the horse some turnout in hopes of reversing this immediately and avoiding any later consequences.

A short course, a week or so, of anti-inflammatory drugs to get initial control of the inflammation is reasonable, but long-term use is counterproductive and not likely to be effective. If the condition can’t be controlled, navicular-bursa injection is a reasonable next step, before neurectomy.

Also With This Article
”But, Is It Really Heel-Pain Syndrome'”

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Pain Sensation: Front vs. Hind
A study at the University of Berne, Switzerland, published in the American Journal of Veterinary Research, compared the sensitivity to pain and the time it took for the horse to react to pain in the front vs. the hind limbs. The researchers applied gradually increasing electrical currents to the digital nerves of the front and back limbs of the test horses.

The forelimbs were determined to be more sensitive, with the current being perceived at intensities at about half of what was needed to get a hind-limb response. The front legs were also somewhat quicker to respond to the stimulus, as in they had a shorter time interval between the application of the current and the horse appearing to feel it. However, the behavioral reactions to hind-limb stimulation were described as being “significantly stronger,” which we’re translating to “horse trying to kick your head off.”

Anatomical and physiological explanations for these differences aside, it’s not too difficult to theorize why these results were found. The natural reactions to pain and sensation would serve the horse well in the wild.

It makes sense that the horse would be more sensitive to problems in the front legs, since they carry approximately 60% of the horse’s total body weight. And, of course, the more violent reactions that were noted to the hind-end stimulations guarantee a swift and no-nonsense response to attacks from behind, protecting the horse from his natural predators in the wild.