#13943 - Equine Wound Management - Veterinary Practical Techniques

Wounds can be traumatic, surgical, chemical, thermal or irradiation wounds. They can also have varying degrees of contamination – clean, clean-contaminated, contaminated or dirty/infected.

The location of a wound will affect the rate of healing. Distal limb wounds heal slowly due to movement and blood supply, whereas wounds on the trunk heal much faster. The underlying structures must also be considered, such as joints, tendons, bone etc.

If the smooth cortical surface of bone is exposed, fibroblasts cannot adhere to it. If the periosteum is exposed and dries out, there will be no blood supply to the outer surface of the bone and so it will die off.

There are four stages of healing. These are the inflammatory stage, debridement, proliferation and finally maturation.

The duration and intensity of the inflammatory stage is determined by the nature of the injury. A pro-longed inflammatory phase retards long-term healing. It also encourages chronic proliferation and fibroblastic granulation.

Debridement is often considered part of the inflammatory stage. Neutrophils and macrophages phagocytose bacteria and enzymatically remove necrotic tissue.

Proliferation involves fibroplasia, epithelialisation and angiogenesis.

Fibroplasia involves fibroblast migration and proliferation. Granulation tissue becomes evident if there is a health wound environment. Myofibroblasts cause wound contraction. Epithelialsation is a slow process and very sensitive stage in healing. Angiogenesis is a complex series of events involving formation of a new capillary bed out of underlying microvasculature. It is mediated by soluble cytokines and chemotactic agents.

Maturation is characterised by the change from collagen type III to collagen type I. Re-organisation and structural cross-linking ensues and the tensile strength of the wound increases. Eventually the strength reaches 80% of normal skin.

Initial evaluation of the wound should be as follows:

• Initial first aid – stop blood flow if bleeding and assess volume of blood loss if severe.

• Sedation – for horses detomidine/romifine and butorphanol

• Regional anaesthesia

Small puncture wounds overlying synovial structures may be more significant than large wounds.

Wounds can be prepared using:

• 0.05% chlorhexidine

• 0.1-0.2% povidone iodine solution

• Isotinic fluids

• Just water

Lavage of wounds removes contamination and shortens inflammatory and debridement stages. Using a pressure of 8psi overcomes the adhesive ability of bacteria, but over 15psi forces bacteria deeper into the wound. Lavage can be done using a 50ml syringe and 18 gauge needle.

The wound should then be protected with water-based gel and the surrounding area clipped. The wound can then be examined and palpated further.

Radiography or ultrasonography may be used to further diagnose the wound.

If synoviocentesis is performed it must be done aseptically. Additional fluids may be infused into the joint, such as intra-synovial antibiotics or sterile balanced electrolyte solution.

Synovial fluid should be pale yellow and translucent, string between the fingers and contain less than 10% neutrophils. Synovial samples should be collected prior to antibiotic administration. It synovial sepsis or an open fracture is suspected, give gentamycin or penicillin.

It is important to check the horse’s tetanus vaccination history. If it has been previously vaccinated against tetanus, administering tetanus anti-toxin and tetanus toxoid will produce a quick antibody response.

Primary wound closure closes wounds by opposing and suturing skin edges. It provides the fastest healing and return to function, but can only be considered in wounds where there is minimal trauma and contamination.

Devitalised tissue, foreign material and bacteria should be removed. This is most commonly done by sharp dissection.

Drains may be used when dead space cannot be eliminated. They should be placed through separate incisions proximal and distal to the wound and left in place for...