Tackling Tough-to-Heal Wounds

When a horse’s healing process gets derailed, wounds can become chronic. Here’s how to prevent complications.

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Tackling Tough-to-Heal Wounds
When any of the healing stages are compromised, wounds can become chronic, yielding ongoing complications and damage. | Photo: Anne M. Eberhardt/The Horse

When a horse’s healing process gets derailed, wounds can become chronic; here’s how to handle injuries and prevent complications.

As a journalist, I’ve learned to expect one response before all others when calling to interview a source on equine wounds: the rueful chuckle. As a veterinarian, I understand why. Horses have a sharp-object-detecting superpower. If there is a single edge or point within reach, eventually a horse’s skin will come in contact with it. More than one owner has contemplated bubble-wrapping his or her equine friends or possibly housing them in giant, indestructible hamster balls.

Because manufacturing a horse-sized hamster ball would be impractical (let’s face it: the horse would probably still find a way to get injured, ending up with legs in a tangle), and the staccato sound of popping bubble wrap would cause more pasture havoc than it would prevent, horse wound management is a topic we simply can’t get enough of.

How Wounds Heal

In many instances, horses are wound-healing superheroes, capable of filling in huge skin and even muscle defects, given enough time.

In the initial inflammatory phase of healing, blood clots form and white blood cells (WBCs) infiltrate the affected area to fight potentially infection-causing bacteria. Next, some of these WBCs, the neutrophils, move in to break down and remove dead or damaged tissue and debris. This is what creates the pus we commonly see in and around wounds.

Within a few days, new skin cells develop along the edges of the wound as the skin regrowth process begins. A thin margin of delicate-looking skin starts to appear around the wound’s perimeter.

The proteins fibrin and collagen begin to lay down scaffolding within the wound around Day 4 or 5 of healing; this becomes the foundation for what is known as the granulation bed, which is made up of new connective tissue and tiny blood vessels. This pink, bumpy tissue helps fill the defect and creates a surface that allows the wound edges to contract and new skin to move across. This contraction causes the wound’s surface area to shrink and speeds healing.  

Factors That Delay Healing

Sometimes, however, the above–described process gets derailed. When any of the healing stages are compromised, wounds can become chronic, yielding ongoing complications and damage.

Infection is a major cause of delayed healing, says Lisa Fortier, DVM, PhD, professor of surgery at Cornell University, in Ithaca, New York. She points out that wounds can become contaminated with every bacterial organism in the environment. “Treating chronic infection of four to five days’ duration is much more difficult than if the infection is caught acutely, within one day,” simply because there are fewer pathogens at play, she says.  

Like real estate value, wound healing quality is all about location. Horses’ upper body regions tend to heal even large wounds well, but lower leg injuries are trickier. Most upper body skin is loose, facilitating the contraction phase, and plenty of underlying muscle is available to support the new tissue and provide adequate blood supply.

“When I think about chronic wounds, the very first thing (I think of) is the location,” says Anthony Blikslager, DVM, PhD, Dipl. ACVS, professor of equine surgery and gastroenterology at North Carolina State University College of Veterinary Medicine, in Raleigh. Injuries that penetrate joints or tendon sheaths, for instance, can pose particular problems.

Fortier says that in her experience the most common wound-complicating scenario “is a lack of recognition that a joint can be contaminated. Even if the cut is two or three inches away from where most people think the joint is, that doesn’t mean that joint couldn’t have been contaminated at the time of injury.”

Joint and tendon sheath infections not only challenge wound-healing but also potentially ruin a horse’s athletic potential or even end his life. “When a joint is infected, the infection has no place to drain out,” says Fortier. “The body responds (to the presence of bacteria) with WBCs, just like in skin, but in the joint WBCs are needed until they can clear the infection.”  

This means the WBCs are present longer in the joint, and the enzymes those cells use to kill bacteria can also damage the cartilage and joint lining. This, Fortier says, “produces severe inflammation and causes a tremendous amount of pain. The joint capsule doesn’t tolerate this inflammation well.” The cartilage damage that results can produce career-ending arthritis, she adds.  

When you encounter a wound, first try to determine if it is, in fact, located over a joint or tendon. If there is any question as to the wound’s location, depth, direction, or associated structures, Blikslager suggests the veterinarian tap (use a needle to draw fluid from) potentially affected structures, such as joints or tendon sheaths, at a site away from the wound and infuse sterile saline to distend the joint capsule or tendon sheath. If saline leaks from the wound, it has penetrated and contaminated that structure.

Like Fortier, Blikslager says it’s much easier to treat a contaminated joint or tendon sheath before the bacteria have days to set up shop. This typically requires referral to a clinic or specialist to fully flush the joint and remove debris.  

Even when joints are uncompromised, lower leg wounds can still be tricky to treat. Blikslager says anything from the hock or knee down can pose problems for healing. In these areas, he says, “the skin seems to have increased tension compared to other body areas and little tissue beneath. Wounds will spread open with very little flesh beneath to support, so when the wound attempts to heal, the ability for the skin to migrate back over the wound is limited.”

Other areas Blikslager lists as problematic for healing include the axilla, or “armpit,” as forelimb movement can suck air into those wounds, and the front of the stifle because movement disrupts the wound edges, pulling them apart as they attempt to heal.

Movement is the enemy, says Fortier, who stresses that “wounds need to be essentially immobilized to heal.” She points to wounds over the knee, stifle, and front of the hock as difficult to immobilize.  

Another challenging wound site in horses, says Fortier, is the cannon bone, as “there’s no muscle there to bring blood supply in or to contract the tissue and make the wound smaller.” Because the critical factor in treating these wounds is protecting the infection-prone exposed bone, veterinarians typically suggest -applying an antibiotic ointment barrier (e.g., silver sulfadiazine) and bandages until the protective granulation tissue forms.

Blunt trauma associated with a wound, such as that from crashing through a fence or being kicked by a pasturemate, can also delay healing, says Fortier. This is because such trauma crushes tissue and blood vessels, compromising circulation to the region surrounding the wound. In many of these cases, tissue that looks healthy initially might die and slough days later, causing sutured wounds to fall apart.  

Treat, Don’t Trick

While there are legions of commercial wound-dressing products, and even more old-wives’-tale-based approaches, only a handful of these actually enhance wound-healing, and many impair the process.

There is no magic cure to speed-heal a recalcitrant wound, but cooperation and communication between the veterinarian and owner and quick action can minimize complications.

First, says Blikslager, you need to control any bleeding by applying direct pressure and bandaging. Once hemorrhaging stops, clean the wound. Initially, he says, the goal is simply to remove dirt, hair, and debris. You can accomplish this with tools as simple as a gentle stream of hose water and a mild soap.  

The next step, say both Blikslager and Fortier, is to determine the extent of the wound and what structures could be damaged. “X-rays at the time of injury are highly underutilized,” says Fortier, and can yield extensive information about the wound. She also recommends using ultrasound to look for gas pockets (which might indicate a puncture or open space) near joint or tendon sheaths.

Fortier advises owners waiting for the veterinarian not to “put any goop on the wound.” If not fresh out of their packaging, ointments and oils can be contaminated from previous use; they can also make it more difficult for the veterinarian to clean and examine the injury. Caustic powders purported to minimize proud flesh (excessive granulation tissue) can damage tissues, say both Fortier and Blikslager. Even preparations such as meat tenderizer (which some people claim prevents proud flesh formation), while likely harmless, says Fortier, don’t substitute for proper care.  

“There are just two things I would want on a truck or in a barn (for treating wounds): an antibacterial ointment and a steroid cream,” says Blikslager, explaining that he applies the antibacterial early on, particularly if the wound has been contaminated, and switches to the steroid cream as the wound begins to granulate.

To prevent granulation tissue from pushing up past the skin margins and preventing the wound from closing, Blikslager suggests veterinarians trim the proud flesh back, even though it bleeds tremendously.

He acknowledges that bandage changes can become expensive and suggests that owners and veterinarians discuss the practicalities and desirability of keeping a particular wound bandaged based on location, owner resources and expectations, and the horse’s environment.

Blikslager calls regenerative therapies, such as platelet rich plasma or stem cell therapy, “experimental and expensive” at this time for wound-healing. He acknowledges, however, that the right cocktail of tissue growth factors could be useful in the future. There is some evidence that approaches such as hyperbaric oxygen therapy and shock wave therapy might also promote wound healing, but more research on their use in horses is needed.

Take-Home Message

For now, say both Blikslager and Fortier, the best treatment for poor-healing equine wounds is to minimize the circumstances that lead to delayed healing in the first place: infection and motion.

“Some of those basic steps get skipped,” notes Blikslager. “We need to protect the wound until it can heal.”  

Ultimately, says Fortier, it’s important to listen to the patient: “If the horse is more lame than it should be for the wound, then something else is going on.”


Written by:

Christy Corp-Minamiji, DVM, practices large animal medicine in Northern California, with particular interests in equine wound management and geriatric equine care. She and her husband have three children, and she writes fiction and creative nonfiction in her spare time.

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