Page 61 - ONLINE PROCEEDING BOOK WSAVA 2017
P. 61

Free skin grafts
Skin grafts consist of transposing free portions of skin to a wound. The transposed skin is therefore no longer perfused and relies on the development of a neovascularisation from the receiving bed for survival. The receiving bed must therefore be healthy and well- vascularised, so that suf cient neovascularisation can develop from it.
Graft can be harvested as full-thickness (epidermis and entire dermis) or partial-thickness (epidermis and variable portions of dermis). In practice, harvesting partial- thickness grafts in dogs and cats is technically dif cult without dedicated devices (dermatome). In consequence, only full-thickness grafts will be discussed here.
Graft types
In veterinary surgery full-thickness grafts, harvested from the ventrolateral portions of the trunk, are most commonly used. Different forms of grafts exist: meshed, unmeshed, pinch, punch and strip grafts.
Punch grafts are harvested with a punch biopsy instrument. Matching-size holes are created in the granulation tissue of the recipient bed to accommodate the grafts. The main advantages of these grafts are that they are easy to perform, allow very good drainage of the wound and withstand infection better than other types of graft. However, the resulting cosmetic aspect is rather poor.
Meshed and unmeshed grafts use a single skin portion to cover the recipient bed. Meshed grafts are obtained by creating incisions throughout the graft. These incisions allow postoperative drainage, which favours graft adhesion and survival, and enable grafts to cover greater areas compared to unmeshed grafts of similar size. Meshed grafts can be prepared manually or with a dedicated device, which produces more even and expandable meshes, but relying more on second- intention healing and therefore possibly resulting in a poorer cosmetic result. The author almost exclusively uses meshed full-thickness free skin grafts.
Principles of free skin-grafting techniques
A free skin graft is transferred without any vascular supply and therefore relies on the rapid development of neovascularisation from the recipient bed, which should either be a healthy granulating wound or a fresh, well-vascularised surgical wound. Every effort must be made to minimise the time required for new vessels to grow from the recipient bed to the dermis of the graft. The hypodermis is removed from the graft as thoroughly as possible before it is placed on the recipient bed, on which the graft must be tacked as much as possible. Tacking the graft minimises the gap new vessels have to cross to reach the dermis,
An Urban Experience
prevents movements of the graft relative to the recipient bed which would impair neovascularisation and avoids accumulation of any  uid interface (seroma, blood) between the graft and the recipient bed. The applied graft must also be immobilised and any  uid which may accumulate between the graft and the recipient bed must be drained and absorbed. A bandage is placed aseptically at the end of surgery and is left unchanged for 3 to 5 days, to avoid disrupting the graft in the early, critical stages of its adhesion on the recipient bed. The utilisation of vacuum-assisted wound closure (VAC) for a few days after surgery was recently shown to increase the surviving proportion of free skin-grafts in dogs.
The bandage is  rst changed with extreme care 3 to 5 days after surgery, under general anaesthesia or deep sedation, depending on the compliance of the patient.
The aspect of the graft can be variable and appear concerning during the  rst week after surgery. It can
be either pale or dark, before becoming pink again. Consequently, unless the graft is clearly necrotic, it should not be touched regardless of its aspect, and bandage changes must be continued every 2 to 4 days, as needed. In most cases, the aspect of the graft will improve as it takes, at least partially.
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