by Brad Jackman, DVM, MS, Dipl. ACVS
My horse suffered an injury on his leg earlier this year, then developed a mass over the injury that wouldn't grow hair, was unsightly, and very puffy. My veterinarian called this proud flesh. Can you explain a little more about this problem?
Proud flesh is an excessive growth of granulation tissue that has the appearance of cauliflower. It usually develops over an open wound, and most often occurs in areas of excessive tension and motion. Proud flesh usually is seen in injuries of the distal limbs (below the knee or hock) due to the lack of underlying soft tissue structures, which allows for an excessive amount of tension in those areas. These distal areas mainly are comprised of bone, ligaments, and tendons, and lacks underlying muscle. This anatomy causes the skin surface to be tense, which increases the risk of proud flesh because of the difficulty for skin to grow back over a wound.
The best treatment of proud flesh is prevention, and the best prevention i performing a primary closure (suturing) of the wound immediately, or as soon as possible, after the wound occurs. Proud flesh can become a problem when primary closure is not an option, and the skin has to heal through second intention healing. Second intention healing is when the skin has to heal first by granulation tissue forming over the wound, then the skin grows over the granulation tissue. It is at this point you get proud flesh. Another preventative method is to limit the motion in the area of the wound as much as possible. This is generally done by bandaging, or placing the lower limb in a cast. By reducing the motion in the area, you speed the healing process allowing skin to grow over the granulation tissue, which greatly reduces the occurrence of proud flesh.
If proud flesh does occur, there are a couple of options for the horse owner. First, surgical removal of the exuberant granulation tissue generally provides the best results. In this process, the granulated tissue is excised to be level with the skin's edges. In some horses, sedation is not necessary as granulation tissue is devoid of a verve supply. While there are no nerve endings in the tissue, there is a tremendous blood supply. Once the tissue is debrided, a pressure bandage is applied to help stop the bleeding. This debridement process might need to be performed more than once, depending on the size of the wound and how much proud flesh is present.
The second option in treating proud flesh is to use a caustic substance to eat away the granulation tissue. There are several caustic products on the market. The problem with caustic substances is that their purpose is to destroy cells, and in addition to destroying exuberant granulation tissue, they also destroy healthy cells and might cause further damage to the wound. Using a caustic substance slows the healing process when compared to the surgical treatment of proud flesh. The surgical method is generally preferred because it removes much of the unwanted granulated tissue and leaves healthy tissue underneath, whereas the caustic method destroys all cells whether or not they need to be destroyed.
Once the excess granulation tissue is removed, a steroid cream or ointment is applied to the area. Steroids have been shown to inhibit the formation of granulation tissue without inhibiting epithelialization. Epithelialization is the process of skin cells growing from around the edge of a wound and slowly covering the damaged area.
The healing process all depends on the size of the wound, and how large the proud flesh area has become. Since skin cells have to grow from the edge, the larger the wound, the more time it takes to heal. If the horse is put in a cast to restrict his movement, it generally takes two to three weeks. However, in most lower limb wounds, it is usually a minimum of three to four weeks if a bandage is applied, but it could be as long as several months.
Another factor that affects the healing process is the physical condition of the horse. If the horse is in peak condition and is having all of his nutritional requirements met, then the immune system is working at peak performance and the healing process will be shortened. But, if you have an older horse, or one that has been nutritionally compromised, then the healing process will take longer.
In some cases where large wounds are involved, skin grafting is performed to try and aid in the healing process. With large wounds, proud flesh often leaves a hairless scar that will crack and bleed. Skin grafting improves the healing of these large wounds by decreasing scar tissue. This also leaves an area that is more cosmetically appealing.
Although not a common complication, there is a small risk that a sarcoid could develop. A sarcoid occurs when the scar tissue changes its characteristics to become a benign skin tumor. While not common, it has been reported and is occasionally seen in association with proud flesh.
Brad Jackman, DVM, MS, Diplomate ACVS, is the surgeon at Pioneer Equine Hospital located in Oakdale, Calif.
Reprinted from The Horse: Your Guide to Equine Health Care
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