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Wound Healing

Imagine this scenario, you go out to visit your horse and you find some fresh blood on your horse’s leg and then you see a large gash that has exposed bright red tissue with the skin hanging strangely out of place. That’s when you realize that your horse has a major wound and it is time to call to get the wound looked at and repaired. If you have had horses for any amount of time, you probably have encountered some sort of wound on your horse.

Wound healing on a horse is a complex orchestration of the body’s different systems working together to counter the loss of the stability of skin. Our efforts in wound care is to promote the healing process and not hinder it in any way. The best way to do that is to be as gentle as possible to the wound. As soon as possible after your horse sustains a skin wound, and before veterinary care is available, apply pressure to the wound with a clean cloth to slow or stop any bleeding. There is no need to apply pressure if the wound is not bleeding. If the wound is contaminated with dirt and hair, flush it using a saline solution (1 teaspoon of salt per quart of water) or with gentle rinsing using clean water from a hose. If possible, bandage the wound, preferably with clean bandage material, or with a clean cloth. Do not apply medication to the wound, such as iodine, (Betadine), or chlorexhadine (Novolsan) or peroxide. These solutions need to be diluted properly by your veterinarian to protect the horse form indiscriminate cell damage.

When veterinary care is available and the wound is examined, evaluation of the wound can be made to see if it can be sutured or not. If the wound can be sutured, the healing process is termed as primary healing or first intention healing. If the wound is left open to heal on its own, this is termed second intention healing. It is most preferable from a healing stand point to surgically close the wound and have it heal from that condition. The decision to treat the wound with primary wound closure is a complex one and beyond the scope of this article. Wound care after primary closure is fairly easy and straight forward. Usually a non-stick dressing is applied over the incision and the wound is bandaged for protection and to decrease skin edge movement.

Ideally all wounds would be repaired with primary closure to allow for faster healing and the functional use of the horse once again. Since that is not always the case, some wounds have to heal by second intention healing. Second intention healing wounds involve a much greater amount of care for those wounds to heal. Depending on the condition of the wound, the stage of wound healing and the amount of contamination of the wound, several types of dressings are available. This is where a basic understanding of the stages of wound healing is helpful. Wound healing proceeds through three distinct phases, the acute inflammatory phase, the proliferative phase and the remodeling phase. All are distinct phases and have approximate time frames, but they all overlap from one phase to another in a continuum.

The first phase is the inflammatory phase. This phase prepares the wound for the next phase by cleaning foreign material and removing dead tissue. The blood that is present from the initial injury forms clots to stop bleeding and allows white blood cells to migrate into the wound and do the major cleanup of the area destroying bacteria and disposing of dead tissue. During the inflammatory stage we want to use dressings that reduce the material the wound produces (dead tissue, microbes and debris all termed “exudate”), release antimicrobials if needed and keep the wound bed from being too moist or dry. The phase starts when the wound occurs and lasts about 3-5 days.

The second phase of healing is call the proliferative stage. This is where different cell types begin to build new blood vessels to feed other tissue; where fibroblasts multiply to become a scaffolding for granulation tissue to form around; and finally where epithelial cells start to form to become the skin to cover the wound. The tissue we usually see at this time is red to pink fleshy granulation tissue. This can be a very fragile time for the wound healing. Any disruption of this process can delay the epithelialization progression and ultimate wound closure. In the proliferative phase we want to use dressings that promote the proper amount of granulation material without disrupting the fragile epithelial cells. This is the phase were we will see problems of excessive granulation tissue or “proud flesh”. The problem with excessive granulation material is that it delays the wound from closing. Epithelial cells are very fragile cells that need a good flat base of granulation tissue to migrate across. When excessive granulation material grows out from the wound the epithelial cells are forced to migrate “uphill” and these cells are too fragile to continue on, delaying wound healing. The proliferative phase begins during the first 3-5 days after an injury and usually lasts up to about 14 days.
The last phase is the remodeling phase. This phase is the longest phase, but may be the hardest one to visually identify. This process involves the realigning of the fibroblasts and collagen fibers to strengthen the healing process. The process also involves contraction of the wound to help reduce its size and bring the skin edges together. This stage begins as early as 7 days after the initial injury and can continue for several months and even years. All wounds go through these three phases including sutured wounds, but the amount of time these phases progress and ultimately how quickly wound closure occurs will depend on the size, severity, area of the body of the wound, and care of the wound.

There are several points to facilitate wound healing.

  • Proper wound preparation and examination

  • Proper wound dressing for the present condition of the wound and healing phase

  • Proper bandaging of the wound

  • Appropriate antibiotic and anti-inflammatory treatment

Any time your horse has a wound, the healing process can be greatly enhanced with proper examination, care and management by your veterinarian.