When it comes to healing wounds in horses, Dean A. Hendrickson, DVM, steers clear at first from topicals and ointments.
For Dr. Hendrickson, the associate dean for professional veterinary medicine in the College of Veterinary Medicine and Biomedical Sciences at Colorado State University, it’s all about the dressings.
“The most important thing in current wound healing is to minimize the amount of stuff you put on the wound that delays healing and apply the things that will improve healing,” Hendrickson said.
“In general, I stay away from ointments and other topicals, and focus on advanced dressings that are designed for the specific stage of the wound healing process. Moist wounds heal faster than dry wounds. The dressings need to be chosen based upon what is happening with the wound.”
And Hendrickson isn’t hesitant to seek the latest developments in dressings for his patients.
“Advanced wound care dressings are fantastic,” he said. “They take a little while to learn, but the results are amazing.”
Based on the characteristics of the wound, Hendrickson advises other vets treating equine wounds to consider foam dressings, alginate dressings, gel dressings or debridement dressings.
“The practitioner needs to learn how to read the wound to determine the right dressing and the amount of time the dressing needs to stay in place,” he added.
James Brown, DVM, clinical assistant professor in equine surgery and emergency care at Virginia Tech’s Marion duPont Scott Equine Medical Center, has also been working with bandaging and diagnostics.
“I have recently worked with a company that is providing microbial DNA testing to identify what pathogens are present at a wound site,” Dr. Brown said. “Once the pathogens are identified, a specific wound dressing is custom made based on the known antimicrobial sensitivities of the bacteria identified in the test. We have used this technology to treat chronic draining wounds in a draft horse mare with good success.”
The approach one takes should be dictated by evaluating the wound, advises Shannon Murray, DVM, of Rhinebeck Equine in Rhinebeck, N.Y.
“Depending on the location of the wound, different steps may have to be taken,” Dr. Murray said.
If, for example, a laceration or injury is observed close to or involves a joint space or tendon sheath (synovial structures), Murray believes potentially serious consequences exist and the wound must be treated as an emergency.
“If communication, between the wound and the synovial structure, does occur it could result in a career-ending or life-threatening lameness,” he said. “Immediate and aggressive treatment is recommended.”
Several additional steps are required in this case, according to Murray.
“First, care must be taken in preparation of the wound,” he said.
If sepsis is suspected, a wound should be aseptically cleaned and prepped before digital examination to prevent additional contamination of the deeper structures within the wound. Then once the wound has been prepared, sterile digital palpation can be performed using either a gloved hand or sterile probe, Murray said.
In small wounds, a probe may enable a practitioner to better determine of the extent and depth of the wound. “With the probe in place, the extent of the wound can be further assessed by taking a full series of radiographs.”
When synovial contamination is suspected, evaluating the synovial fluid is important, and one can consider a number of different approaches for joints, Murray said.
“A site distant from the wound in non-traumatized tissues should be aseptically prepared for synoviocentesis and synovial structure distension,” he said. “If an appropriate site can be identified, a sample of the synovial fluid should be obtained and cytologic values measured.”
Following that step sterile irrigation fluids should be infused through the needle into the synovial space, and the wound should be observed for any leakage of the fluid.
“If leakage from the wound occurs, communication between the synovial space and wound has been confirmed,” Murray said. “In such cases, aggressive and early multi-modal treatment is needed to eliminate the infection.”
The treatment may include antibiotics—Murray recommends IV for the acute phase of the infection, switching to oral for at least two weeks following resolution of the clinical signs; NSAIDs like phenylbutazone, firocoxib or flunixin), joint lavage including through-and-through needle lavage or arthroscopic lavage, intra-synovial antibiotics, and regional limb perfusions.
The type of wound is key to treatment, and Hendrickson is seeing a great number of wire cuts, for which he has a specific approach.
“First, I debride carefully and completely,” Hendrickson said. “Then I use a debridement dressing to get the small areas that are too hard to debride. If possible, I close the wound with sutures. If not, once the wound is clean I use an alginate dressing to encourage wound contraction and granulation tissue formation. At the end I use a semi-occlusive foam dressing to epithelialize the wound.”
An advance in wound care that has caught Murray’s fancy is platelet rich plasma, a product that is derived from the horse’s own blood.
Platelets are loaded with numerous growth factors, which Murray notes act in synergy to enhance the access of healthy inflammatory cells to the area of the tissue injury. PRP also helps the formation of new blood vessels (angiogenesis), the formation of new connective tissue (fibroplasia) and the regeneration of skin (re-epithelialization).
PRP can be obtained in a matter of minutes, even stallside, and delivered to the site of injury in a standing, sedate horse, Murray said.
“PRP is most commonly used to treat tendon and ligament injuries, but it can also be delivered to a wound,” he said. “Data regarding PRP supports potential benefits for wound healing.”
Just as in companion animals, chronic wounds sometimes call for a watchful eye in the equine practice.
For Brown, of Virginia Tech, a key to attacking a chronic wound is to ferret out the underlying condition.
“We use radiographs and/or ultrasound to determine any underlying condition,” he said. “We also use digital exploration to feel for any foreign body, such as a piece of wood. When we are suspicious about synovial structure involvement, we will often distend the synovial structure with sterile polyionic fluid and observe for any leakage of fluid out of the wound. When a joint communicates with a joint I am very aggressive at treating septic arthritis, as unresolved septic arthritis can be life-threatening.”
Horse Owner Talk
Brown also takes a dogged approach when it comes to talking with horse owners.
“I usually discuss the stages of wound healing and this sets the scene for how they will care for the wound and what they should expect,” Brown said.
A thorough talking-to is particularly important when dealing with horse owners whose animals have open wounds that are going to heal by second-intention, such as the formation of granulation tissue, Brown said.
Brown outlined the four stages of healing: The inflammatory/cellular reaction stage; the debridement stage; the tissue formation/proliferation stage; and the maturation stage.
“During the first two stages there will be some swelling and purulent drainage, and so the dressings need to be changed frequently,” he said. “Later on, during the proliferation stage, exuberant granulation tissue (also known as proud flesh) may develop and will need to be treated.
“Based on the size and location of the wound, I try to give my clients a rough estimate of total wound healing time so that they are clued in to any lack of progression that may indicate a problem. Wound healing is a little difficult to grasp for first-timers, but after they observe the process once, people become very knowledgeable.”
Hendrickson often takes a “show and tell” approach.
“I show the clients pictures of successful wound healing and how we achieved it,” he said. “That really gets their attention.”