Veterinarians use casts to help stabilize and treat a variety of equine foot and leg disorders, from lower limb injuries to severe foot infections to chronic laminitis cases. The latter condition, however, is one of the most challenging to treat—when the leaflike laminar tissues that suspend the coffin bone inside the hoof wall detach, allowing the bone to displace and rotate.
Vernon Dryden, DVM, CJF, APF, of Rood & Riddle Equine Hospital, in Lexington, Ky., has had success treating complicated laminitis cases with foot casts, and he discussed proper cast management at the 2013 International Equine Conference on Laminitis and Diseases of the Foot, held Nov. 1-3 in West Palm Beach, Fla.
"Chronic laminitis cases with distal displacement of the pedal (coffin) bone, or 'sinkers,' are very difficult and carry a poor prognosis," Dryden began. "Foot casts have been shown to be effective in aiding the rehabilitation of these cases."
Dryden said there are several ways foot casts can benefit these cases, including:
- Stabilizing the entire foot;
- Decreasing the individual movement of the hoof capsule and the displaced bony column, making them move as one unit;
- Reducing shearing forces on the laminae;
- Providing inner hoof wall support and ease of breakover in all directions; and
- Allowing the horse to choose the most comfortable standing position as a result of the dome created on the bottom of the cast.
Dryden then reviewed proper cast application with the audience, emphasizing the importance of trimming the foot first, applying the cast in a clean and dry environment, ensuring the limb is in full weight-bearing position before the cast sets (to prevent cast sores and rubs), and taking care not to pull the cast tape material too tight (which can cause discomfort and possibly reduce circulation).
Once a horse is outfitted with a well-applied cast, he still needs careful monitoring to ensure he's comfortable. "Evaluate the cast at least once a day, looking for abnormal swelling, odor, discharge/drainage, and any reduction in the patient's comfort," Dryden said. "If cast sores have developed (most commonly around the pastern or over the heel bulbs) or the patient is not wearing the cast well, remove the cast, assess, and reapply if necessary."
Dryden said a cast's longevity depends on its placement, hygiene, any infection, and horse comfort, but that a typical "sinker" will wear the cast for three to four weeks at a time before the veterinarian removes and reapplies it. When at least 50% of the length of the hoof wall is comprised of new growth, he said he generally transitions the horse into a wooden clog-type shoe (which has similar height and mechanics as the cast) for another four to six months.
"Complicated laminitis cases carry a poor prognosis but have responded to treatment with foot casts," Dryden concluded. "The foot cast must be monitored with great care and should not be left on for longer than four weeks at a time."
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.