Laminitis Rehab: 'If the Corium is Happy, There's Hope'
This is an example of managing chronic laminitis case with a hoof wall bevel and a hoof wall grooving.
Photo: Debra Taylor, DVM, MS, Dipl. ACVIM
The devastating hoof disease laminitis can have life-threatening consequences for affected horses, and successful rehabilitation can be challenging for even the most experienced veterinarians. However, said one veterinarian, there's a telltale sign practitioners can assess to gauge a horse's likelihood of recovering from a laminitic episode: the perfusion (or the amount of blood that fills) the hoof's corium.
At the 2013 Western Veterinary Conference, Debra Taylor, DVM, MS, Dipl. ACVIM, of the Auburn University College of Veterinary Medicine, described what the corium can tell us about an affected horse's chances of recovery.
The corium, Taylor said, is another term for the hoof's dermis: the middle soft tissue layer that connects the coffin bone to the rigid hoof capsule and contains the hoof's blood supply. If the corium is fully perfused with blood new healthier hoof growth often ensues; if it's not, however, "you're not going to get anywhere" with new hoof growth, Taylor said.
When laminitis sets in and causes lamellar failure, the corium becomes compressed between the coffin bone and the hoof capsule, Taylor said: "The corium is essentially between a rock and a hard place in a foundered horse."
This compression reduces or eliminates the corium's blood flow, she explained (which, as mentioned, prevents new, healthy hoof growth).
"Just because horses have laminitis doesn't mean the corium is done for," Taylor said. "Sometimes it is, but in case the corium might be salvageable, you need to give it some blood."
Minimizing compression is the only way to ensure the corium gets the blood it needs. However, before treatment it's important to determine how compromised the corium is.
Identifying Corium Compression
Veterinarians use two methods to identify and evaluate corium compression: a physical exam and a venogram.
If a horse has been laminitic for less than two weeks, Taylor said a venogram is the best diagnostic option. A venogram is a radiograph (or X ray) of the foot taken after contrast media has been injected into the blood vessels. This allows veterinarians to visualize any blood flow problems in the foot. If the corium fills well and uniformly with contrast, there is a better chance the horse
will be able to produce new hoof growth. Conversely, she said, the "corium regions that do not fill with contrast on a properly performed venogram are at risk of necrosis" if prompt steps aren't taken to correct the compression. The worst case scenario, Taylor said, is when parts or all of the corium fail to fill with contrast. These cases require immediate and aggressive treatment and often have an "unfavorable" outcome, she said.
If horses have been laminitic for more than two weeks, a physical examination of the hoof can reveal corium compression. Normal blood flow to the corium is demonstrated by new hoof growth visible on the outside of the capsule as smooth bands originating from the coronary band. Initially these will be narrow smooth bands emerging from under the coronary band hair, she explained.
Compression, however, is evidenced on upper hoof wall by a scaly or crusty appearance along the hairline, Taylor said, with little or no new hoof growth being produced from the coronary band. She recommended lifting the hair on the coronary band to check closely for any new growth at the hoof-skin margin, and she also suggested palpating the coronary band.
"If there is evidence of a ledge at the top of the hoof capsule, then compression is likely to occur," she said.
Once a problem is noted, Taylor stressed the importance of treating the horse early to achieve the best possible results.
When it comes to managing compression, Taylor suggested veterinarians "work from the ground up."
Remove hoof wall's ground reaction force—The first option for managing compression is to remove the ground reaction force from the hoof wall by transferring weight bearing axially, Taylor said. In fact, she said, this might be the only necessary step if executed in a timely fashion. To achieve this weight transfer, Taylor recommended using corrective shoeing, impression putty and casts, soft hoof boots with pads, a hoof trim to bevel the hoof wall, a combination of these, or "whatever makes the horse most comfortable."
Taylor said she prefers options that avoid rigid or hard materials until quality new hoof growth emerges from the hairline. She said if there is less than eight millimeters of sole under the rim (or distal margin) of the coffin bone (which can indicate a risk of solar corium compression), she often uses pads with a custom cut-out air space under the rim of the coffin bone that are then secured to the horse's feet with elastic medical tape to relieve the solar corium compression.
If this option relieves compression, new hoof growth will be evident in a few weeks. Ideally, she said, veterinarians should use venograms to monitor treatment efforts' effects on relieving compression.
Another method by which to counteract the compressive effects of ground reaction force is to create hoof capsule grooves, Taylor said; however, she noted that controversy remains among some veterinarians as to whether this tactic is beneficial. It involves thinning the outer hoof capsule just below the coronary groove to minimize compression of the coronary corium, thereby increasing hoof growth. Taylor said that while grooves might need to be freshened a few times, they can show good—and relatively quick—results and eliminate the need for further treatment in some cases. Taylor suggested waiting about three weeks after removing the hoof wall's ground reaction force before moving on to this step.
Taylor cautioned, however, that complications can arise if capsule grooves aren't created properly.
"Improperly done, hoof grooves could theoretically allow the hoof wall to bend inward and make the situation worse," she said. This adverse effect is more likely to occur if the grooved section of hoof wall is receiving ground reaction force distal to (or beneath) the groove, she noted.
Hoof wall resection—If the first two treatment methods fail, Taylor recommended performing a partial hoof wall resection. A resection—literally removing the compression-causing part of the upper hoof wall—can relieve the pressure on the coronary corium and thereby allow the critical blood circulation to be restored. And with proper bandaging and aftercare, the foot's underlying tissues can repair quite quickly.
Taylor described how to perform the procedure and how to properly bandage a hoof with a newly resected wall (serious complications can ensue if resected hooves are bandaged improperly) and noted that horses that have this procedure performed correctly often "become more comfortable almost overnight."
"The horse doesn't care about the current hoof wall after it has become disconnected from it and the corium is being compressed," Taylor said. "If you have to alter the current hoof capsule to save the corium, do it."
During treatment it's important to monitor the hoof for changes that could indicate success or failure, Taylor said.
Horses that produce new, uniform hoof growth are generally responding well to treatment, she said. However, "if hoof growth is still scaly or crusty with non-uniform rings, you are not reaching success," she noted.
Veterinarians can also perform serial venograms to determine how a horse is responding to treatment, she said.
And finally, Taylor noted that if treatments aren't successful and "if you know the corium is dying, sometimes the most humane thing for the animal is to euthanize."
Treating laminitic horses early is always a better option than waiting.
"Do whatever is necessary to establish uniform perfusion of the corium if you expect a favorable outcome," Taylor said. "If uniform perfusion cannot, has not, or will not be reestablished, then there is no hope for rehabilitating the horse and euthanasia is indicated. However if the corium is happy, then there is hope to rehabilitate the horse."
About the Author
Erica Larson, news editor, holds a degree in journalism with an external specialty in equine science from Michigan State University in East Lansing. A Massachusetts native, she grew up in the saddle and has dabbled in a variety of disciplines including foxhunting, saddle seat, and mounted games. Currently, Erica competes in eventing with her OTTB, Dorado.
POLL: Radiographs for Hoof Care