Skin Grafting

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Skin Grafting



Grafting is an effective method for the management of granulation tissue but is not usually suitable for managing cases where there are identifiable reasons for the non-healing of the wound14.


If the wound is affected by chronic and deep-seated infection or has foreign bodies, sarcoid cells, excessive movement, poor blood supply, an inappropriate pH for healing, or necrotic tissue or impaired blood supply it is unlikely to heal with grafts15.


Skin grafting should not be attempted until the wound is in a suitably healthy state. It is sometimes possible to divide a wound site into healthy and unhealthy areas. The former can be grafted while the latter is managed to restore a healthy bed of granulation tissue free of infection or clefting.


Free skin grafts should be considered in situations when there is a full thickness skin deficits, epithelialization is not active or is retarded, and when wound contraction is not occurring. Grafting should also be considered when conventional suturing techniques and sliding flaps are not possible; large defects below the carpus and hock frequently fall into this category. Spontaneous healing in these cases will be protracted and often results finally in dense (cheloid or hypertrophic) scar (see p. 89).


Skin grafting can result in a more cosmetic and functional scar than would result from second intention healing. It can also improve wound healing with fewer functional problems, shorten recuperation time, and decrease the chance of long-term medical problems which in turn decreases the need for long-term nursing care. Grafts incur positive cost–benefit, as long-term wound management is one of the most expensive procedures.




Pedicle Graft


At least one attachment to the donor site is maintained during healing. Flaps of skin with a broad attachment can sometimes be used to cover difficult wound sites (e.g. eyelid injuries). In some locations it may be possible to use skin stretching (balloon) systems before attempting to perform a pedicle graft. The commonest form of pedicle graft in horses is conjunctival grafting for corneal injuries and ulcerations (Figure 62). There are various forms of flap graft that can be used, including Y- and Z-plasty and tube grafts. These are described in surgical texts.



Vascular pedicle grafts are flaps of skin transferred with their intact vascular supply. This is not used significantly in horses yet. Likewise, free vascular pedicle grafts consist of donor skin removed with its major blood vessels, which are anastomosed at the recipient site to convenient local vessels. These are increasingly used in human cosmetic and reconstructive surgery, but not yet in the horse.



Free Grafts


The donor skin is dependent from the outset on the recipient site for its nutrition. There are two main forms that are simply classified in terms of the thickness of the skin graft, and therefore on the extent of adnexal structures. The thinner grafts (split thickness grafts) have no hair follicles, while the thicker ones (full thickness grafts) have intact hair follicles (Figure 63).




Full Thickness Grafts


All elements of epidermis and dermis are retained in full thickness grafts without subcutaneous tissue and fascia. They can only be used to cover a limited area because of the restrictions imposed by the donor site. The major problem with full thickness grafts (of all types) is shearing force between the graft and the recipient bed, and unless the recipient site can be immobilized there is a relatively high failure rate. However, the cosmetic effects are much better because the adnexa are also transferred.


There are several different methods including meshed grafts and ‘postage stamp’ grafts (modified Meek method). Meshed grafts can be expanded to cover a larger area than the donor area (up to 150% of the original donor site area). Meshing also allows drainage of fluids, an important benefit as accumulation of fluids under grafts is a common cause of failure of non-meshed grafts. The cosmetic effects are better than split skin grafts and pinch grafts because the adnexa survive. Meshed grafts are an all or nothing option: if part of the graft fails then usually it will all fail.


‘Postage stamp’ grafts (modified Meek method) uses small squares of skin (usually around 3–5 mm square) attached to an adhesive dressing. A special machine is used for preparation of the squares but simply cutting the skin into small squares could in theory produce suitable donor skin. The method allows the further expansion of the donor area to 1.5–2 times the original. The grafts are not dependent on the survival of all the squares: if a few do not survive they do not affect the others. Cosmetically the results are excellent, but the major disadvantage is the need to ensure the grafts are immobilized. To this end a rigid limb cast is usually applied16.



Tunnel (Strip) Grafts


Tunnel (strip) grafts can be used when the graft bed is less than ideal. The cosmetic effects are inferior to mesh grafting but the technique is more practical17. It requires less time, effort and expertise, and can be performed with minimal equipment in the standing animal. Success is not usually the all or nothing phenomenon associated with mesh grafts.


Narrow strips of donor skin are obtained by parallel incisions 2 mm apart (Figure 64). All subcutaneous tissue is removed with a scalpel. About four or five strips can be obtained from a single site, which is then closed with sutures. The grafts are placed using 8 cm-long alligator forceps with a 2 mm diameter. Starting at the periphery of the wound, the forceps are inserted 5–10 mm deep into the granulation tissue and then passed horizontally through it to emerge on the opposite side. The grafts are drawn through the newly created tunnel. Care is taken not to twist them. The exposed ends are sutured or glued to the skin at the wound margin.


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Related posts:

  1. Definition of Wounds/Wound Types
  2. Factors that Delay Healing
  3. The Pathophysiology of Wound Healing
  4. Basic Wound Management

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Jul 8, 2016 | Posted by in EQUINE MEDICINE | Comments Off on Skin Grafting

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