Wound wise

As vets we still regularly get called out to wounds that have “gone bad” and should have been seen  earlier. Often there’s a combination of good intentions, a restricted budget and not enough know-how to properly evaluate the wound to make an informed decision. This is understandable, but can result in having to spend even more money and in keeping your horse out of training for longer.

The body has certain tools to aid healing. Inflammation is an important one. Mind you, inflammation is not the same as infection. Where infection is a bad thing involving bacteria or other pathogens, inflammation is actually a good thing that is necessary for wound healing, as long as it doesn’t spin out of control.

When wound healing begins, the body starts the process of inflammation. The body has to determine which tissue cells are dead or alive, kill any bacteria, and get rid of these things together with any debris that’s been left in the wound (sand, dust particles, etc.). The body produces wound fluid to achieve these things. When the wound has been cleaned out by this process, the inflammation should go down.

The next step is tissue repair. This can either be the mending of wound edges in a stitched wound, or when a wound is not stitched the body will first try to fill up the defect with granulation tissue and then grow new skin to cover the gap. When a wound is not stitched, this tissue repair process obviously takes much longer. Also, wounds usually become bigger first, because of tension on the wound edges pulling them apart – especially on legs!

When the wound has just closed up, the new tissue is still fragile. Therefore, the last phase in wound healing is strengthening of the new tissue. In damaged tendons (which is like an internal wound), this is actually quite an important phase. A tendon can look healed on an ultrasound, but because the new tendon fibers are still fragile and not aligned properly, there’s an increased risk of damaging it again when you do too much too soon. It’s therefore important to keep to a good schedule while the tendon adjusts and strengthens. This means that we have to estimate what level of activity the horse can do, and check after a certain amount of time whether the fibers have adjusted themselves properly. If so, we go up a level, then check again and so on, until a horse is fully back into work. Factors like work-load/intensity, duration and training surface are all taken into account. The process of strengthening also happens when other tissue (for instance skin or muscle) heals, but we don’t usually notice it as much.

In reality these three phases of wound healing overlap a little in time, so several processes can sometimes be going on at the same time. A wound can also linger in the inflammatory phase or relapse into it if the wound is irritated too much. For example when a wound becomes too dry, or when a wound can’t settle because there’s too much movement in that body-part, or when the wound isn’t bandaged. When a wound isn’t bandaged it gets daily insults from its environment causing new micro-trauma, and new debris (sand, dust particles, etc.) and bacteria will also cause a continuous stimulus for the body to create inflammation to clean the wound out. Ongoing irritation and inflammation causes tissue repair of lesser quality and less tensile capacities, proud flesh, delayed wound healing and an end result that’s just less pretty.

When we treat a wound we first assess which phase the wound is in at that time. Then by using either medicine or special veterinary wound dressings we can influence the process of inflammation and tissue repair. That way we can achieve more effective and faster wound healing with better cosmetic results (scar tissue).