One of the primary goals of wound management is to not allow it to become chronic. For whatever reason (sometimes a decreased immune system - older horses, Cushing's disease, or chronic steroid use), this isn't always possible. When wounds do become chronic, we have to keep a few things in mind and may need to treat them a bit differently than acute wounds.
Treatment of proud flesh often requires surgical intervention. The excess tissue is trimmed to debulk it. It is highly vascularized and a significant amount of bleeding does occur, but that is expected. Once debrided, the area can be treated with topical steroids and a pressure bandage - typically a snug standing wrap will do. Repeat trimming is sometimes necessary to continue to reduce the tissue, but over time the skin edges should start to pull across the wound. A rule of thumb is that "skin cells don't climb mountains" - so, if there is a protrusion of granulation tissue, the skin edges will not close.
Not all wounds become proud, however. That doesn't mean that they aren't obnoxious, and some take far longer than we'd like before they finally heal. Sometimes, due diligence with bandaging and topical ointments will be enough to return the skin to normal. Other times, further action needs to be taken.
One of the first steps that may be taken is surgical debridement and closure. In some instances, simply freshening the edges and creating bleeding can increase the viability of the tissue and thereby increase healing. If possible, the wound edges may be opposed and sutured closed at this time. However, this is sometimes not option as the wound has been around just a bit too long, and there may not be enough skin around the wound to close it. So now what do we do?
If after all of this, the wound is still present, a skin graft can be performed. Typically, this procedure is used on larger wounds that won't heal cosmetically. To do this, small pieces of skin, or "punches" (think biopsy) are taken from a donor site. The donor site is typically in area that will not leave an obvious cosmetic scar such as on the neck under the mane or along the ventral abdomen (belly). Small incisions are then made into the granulation tissue bed that is present over the wound. The plugs then get inserted into these incisions. While not all of the replacement plugs remain viable, the hope is that enough will remain to increase the amount of healing that occurs. Only now, the wound is healing from multiple directions as opposed to just from the outside in. Once the graft is applied, a non-stick sterile pad is applied over the area and then maintained in a bandage until appropriate healing has occurred.
Chronic wounds can be very difficult to treat. While we want to be able to fix them as soon as possible, we don't have a lot of options to pursue. Many times, we just have to give the body the time and supportive care it needs to fully heal. Sometimes, nature is going to dictate the course and we have no other option but to follow it.