WOUND healing, by definition, is “the restoration of the normal anatomic continuity to a damaged area of tissue.”

In order to manage wounds in horses successfully, we must first understand the normal process of wound healing.

There are four stages involved in wound healing:

1. Inflammation is the first stage and it begins immediately following an injury. Vasoconstriction facilitates homeostasis (stops or slows bleeding). An increase in vascular permeability quickly follows, allowing cells and inflammatory mediators to leak into the wound area initiating the next stage.

2. Debridement of damaged tissue debris and infectious organisms from a wound. This process forms exudates (pus) which discharge from a wound until it is clean.

3. Repair of a wound is carried out by several cells of the body consisting of fibroblasts (connective tissue forming cells), capillary and epithelial cell growth and proliferation. Fibroblasts are the cells (connective tissue forming cells), capillary and epithelial cell growth and proliferation. Fibroblasts are cells that build the framework for reconstruction of a wound.

Capillary migration occurs to provide blood supply and epithelial cells migrate across wounds to re-establish skin continuity.

4. Maturation of the reconstructed tissues over the time they are organised, providing wound strength and flexibility.

The initial goal when preparing a wound for primary treatment is to decrease the threat of infection by cleaning the wound. If possible, hair in the wound edges should be removed prior to cleaning. Mild antiseptic solutions are generally used to clean the wound edges, but not inside deep wounds. Copious lavage or irrigation of the wound will wash away visible and microscopic debris and organisms. The best solution for irrigation is sterile saline with or without very dilute antiseptics (Povidine Iodine or Chlorhexadine).

Debridement is the removal of dead and/or compromised tissue. Wounds are often not discovered for hours and portions of traumatised tissue may start to die.

Devitalised and necrotic tissue may have to be surgically removed in order to facilitate healing.

Once initial inspection, wound cleaning and debridement have taken place, the decision to close the wound or manage it as an open wound can be considered. The amount of contamination, infection, the age of wound and the availability of skin are all factors that dictate whether to close a wound or not.

One of the following is then taken:

Primary Closure: This consists of wound closure at the time of the initial examination. Wounds may be closed primarily by sutures, staples, or tissue glue (rarely used in horses as it is not strong enough in most areas, but it is very useful on the eyelids and delicate regions). These are the easiest wounds to manage and generally heal the fastest. With deeper wounds, subcutaneous tissues and muscles may require suturing in a separate layer to the skin, and to do this naturally dissolving suture materials are used. Special suturing patterns can be used to relieve tension on the skin at wound edges in an attempt to prevent repair breakdown. In large and deep wounds where repair is attempted, small portions of the wound are often left open to allow blood and exudates to drain.

Delayed Primary Closure: This refers to the closing of a round after several days, generally after daily lavage and debridement. Contaminated incised wounds or those containing foreign bodies, such as grit from falling on a road, can be closed in this way to try to give the wound a chance to be clean and healthy before closure is attempted.

Open Wound Management is followed commonly when veterinarians are unable to close traumatic injuries to a horse’s limbs. This is usually due to either a loss of tissue or excessive tension in the skin when the wound edges are brought together, preventing the sutures or staples from opposing the skin edges.

Subsequently these wounds are left to heal by second intention (wound healing is carried out by the body with some medical help and cleaning) and managed as open wounds.

With appropriate treatment and bandaging techniques, these wounds heal completely, but over a longer period of time.

Veterinary surgeon Neil Mechie is a graduate of the University of London and is in practice in Mark Johnston Racing. This article first appeared in the Kingsley Klarion.