How to deal with a wound that won't heal [H&H VIP]

Wounds are common in horses and most will heal well with correct management .

[subscriber-content] Smaller superficial wounds should clear up within a matter of days with little or no veterinary input.

A wound that has been stitched should heal within 10-14 days, after which the area should be dry with minimal swelling and with no signs of pain.

But wounds unsuitable for suturing, such as very large wounds with loss of skin and muscle or those already heavily infected, can take much longer to heal. In these cases, healing occurs by secondary intention.

This complex process relies on the body’s control of any infection before producing pink, fleshy-looking granulation tissue to fill the gap. The skin cells then multiply and start to migrate across the wound.

These delicate new skin cells progress across the wound bed slowly, between 0.1-0.2mm per day. They must be protected from chemical irritants, bacteria and movement, which may damage or kill them and delay healing.

Large wounds on or below the knee or hock are notoriously slow to heal — particularly in horses compared with ponies — and can require weeks to months of bandaging and ongoing veterinary care.

This is not only expensive but prevents the horse returning to his normal use for a prolonged period. In some cases, surgery to close the wound — once infection has been controlled — or skin grafting may speed up this process.

Barriers to healing Proper initial care can enable wounds to heal as quickly and normally as possible.

Always seek veterinary advice for wounds near vital structures such as the eye, joints or tendon sheaths.

Infection within a joint or tendon sheath can be life-threatening if not identified and dealt with promptly, while wounds affecting the margins of the eyelids and nostrils can result in permanent scarring and deformity if correct treatment is delayed.

Signs that a wound is not healing properly include heat, pain, swelling or discharge from the site after it appears to have healed. A wound may also fail to show signs of sealing over.

In the case of wounds healing by secondary intention, the wound bed should be smooth, pink and shiny and should continue to shrink.

Uncontrolled bacterial infection at the wound site, failure to protect it with dressings, or too much movement — particularly over joints — can all delay healing. Other factors include death of tissue below the skin or the presence of foreign material not removed at the time of initial injury.

Proud flesh problems Granulation tissue is normal tissue produced by the body that enables wounds not suitable for suturing to heal.

Horses tend to produce a lot of this tissue, and where it becomes excessive and billows up above the level of the surrounding skin, it is often termed proud flesh.

Proud flesh can delay movement of skin cells across the wound and indicate that the wound is being irritated — either by too much movement or from factors in the environment.

It is important to consult your vet about proud flesh. Different dressings or bandaging methods may be required, or there could be an underlying reason for its presence. This could include foreign material remaining within a wound, indicating the need for X-rays or ultrasound assessment.

Occasionally, persistent and marked proud flesh is due to sarcoid development. More rarely in the UK, it occurs because of a parasite infection called habronemiasis.

These conditions can be diagnosed by taking a sample for microscopic examination, a process termed histopathology. Appropriate treatment can then be initiated.

Scarring and skin grafts Skin scarring is generally less of an issue cosmetically in horses than humans, due to hair covering the area. Functional healing is much more important, enabling the skin and underlying tissues to do their normal job.

This is particularly important for wounds that affect the eye, where scarring or loss of tissue can result in painful, long-term conditions such as chronic corneal ulceration. Nasal wounds may affect the normal functioning of the nostrils in allowing air to move in and out of the airways.

In general, wounds that are fresh, minimally contaminated and which can be sutured tend to heal with less scarring than those that heal by secondary intention. Some areas of the body and some horses, however, do appear more prone to scarring.

Skin grafting – where skin is taken from elsewhere in the body and placed on a wound – can speed up healing. It can also improve the cosmetic appearance and normal function of skin.

Grafting is usually delayed until any infection has resolved and the wound bed is smooth and healthy.

Simple grafting techniques can be performed with the horse sedated, using standard veterinary equipment. More complex methods requiring specialist surgical skills and equipment may be carried out under anaesthetic, usually at a referral clinic.

Ensuring that these grafts survive can be a challenge. The additional expense, however, must be weighed up against the delay in the horse’s return to normal work if grafting is not performed.

This article was first published in Horse & Hound magazine (21 August 2014)

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