From an anatomical standpoint, everything below a horse’s hock on their hind leg or the carpus (knee) of their front leg is just tendons, ligaments, joints, bone, and skin. As a result, there is less blood supplying nutrition to heal the wounds that occur on this part of a horse’s leg. The structures that are integral to a horse’s soundness, the joints, tendon, ligaments and bone, can become easily exposed with lower leg wounds. It is extremely important to manage these wounds effectively, so as to ensure optimal healing and minimal scaring.
After a horse has sustained a large wound to this area of their body, our first step is to evaluate which structures are involved and to what degree. If a joint is involved, that joint will need to be flushed and have antibiotics placed into it. If flexor tendons (on the back of the leg) are severed, they will need to be sutured back together. Other instances, if it is an extensor tendon (on the front of the leg) that is severed, it may be able to heal without the aid of sutures. Damage to the flexor tendons is much more serious than injury to the extensor tendons. In fact, significant damage to the flexor tendon can be career ending. In contrast, completely severed extensor tendons will heal and the horse can return to full athletic function in most cases.
Exposed or damaged bone will need to be scraped and debrided to expose healthy bone. If bone is exposed, the development of a dead piece of bone will occur. This is called a sequestrum. Usually taking 6 weeks to develop, it will need to be removed. Fortunately, most leg wounds do not develop this.
The assessment of the wound allows us to develop a plan to treat the wound as well as determine
the likely prognosis for the horse. Most horse owners know lower leg wounds are susceptible to the development of exuberant granulation tissue, often called proud flesh. This development can be minimized if the tissues involved in the wound are immobilized during the healing process. One way to do this is with a
good bandage, although a cast is preferable. The same fiberglass casts that are
often applied to people can be used on horses. If the wound is below the fetlock, a short pastern cast that incorporates the foot can be used, and it can be applied while the horse is standing under sedation. If the wound involves the canon bone region, it will require a cast that incorporates the foot and extends up the leg to either the bottom of the carpus (knee) on a front leg or the hock on a hind leg. This cast can only be applied while the horse is under anesthesia.
General anesthesia is needed for any wounds that involve bones, joints, tendons or ligaments. These wounds usually require surgical debridement, joint flushes, or tendon repair. It is best if this is done with the horse anesthetized. In conjunction with these procedures, we often do a regional limb perfusion with antibiotics. This involves putting a tourniquet above the wound and placing a catheter into a vessel below the tourniquet for injecting the antibiotics. This allows us to get a very high concentration of antibiotics into the injured tissues.
Once the wound is cleaned, flushed, perfused, and sutured back together, it is time to apply the cast. The limb is padded well and held in the position desired for the casting. The horse is allowed to recover from anesthesia, then treated with antibiotics and anti-inflammatory medications based on the severity of the wound and the level of contamination present when the wound first occurred. Most horses will wear the cast for 4 to 6 weeks. The horse is stall confined during this period and the cast is usually removed with the horse standing, unless the initial wound makes a second cast necessary
The mobilization of the wound in a cast provides a better healing environment than that of a bandage. The cost of the cast itself over the course of the healing process is often cheaper than the bandage costs over the same amount of time, given the number of bandage changes that would occur over the same time frame. Typically, the wounds will also heal faster in a cast then in a bandage due to the amount of motion present at the wound site when it is bandaged. Cast treated wounds heal with a healthy flat granulation bed, rather than the raised proud flesh tissue that occurs with a bandage. The flat granulation bed will usually stay flat as the skin cells migrate across the wound to finish the healing.
Dr. J.C. Thieke