Skin Grafts

Introduction

Grafts are a method of covering a skin defect.

By comparison with other wound management techniques they score relatively poorly for cosmesis but are technically easy to perform.

 Indications

Where skin coverage is considered essential, there is a suitable vascularised base for the graft and other better techniques cannot be readily used. 

Types of Graft

Split Skin Graft

The cut is made through the skin taking the epidermis and a proportion of the dermis from the donor site, leaving the follicular epithelium from whence the donor site will be re-epithelialised. Skin can be taken using a manual knife (eg small grafts – Silver’s knife, larger – Humbey). This manual techniques require practice and is difficult to perfect unless used regularly.

Mechanical devices (Dermatome – either electrically or gas pressure driven) are expensive but much easier to use and produce a predictably good piece of donor skin. The split skin graft can be meshed (manually or using a purpose designed mesher). This turns the skin into a fish-net stocking type of covering material that can be stretched out to cover a wider area. The gaps between the meshed skin epithelialise from the surrounding grafted skin. Meshing is useful on the lower limb, where the gaps act as an exit point for exudate from an oedematous or oozy surface, and when covering an uneven surface, e.g. ear, where the graft has to follow the irregular contour.

Split skin grafts are not widely used in dermatological surgery. Once an adequate split skin graft has been harvested the technique is simple. However, it does take practice to harvest the correct thickness and size of skin without producing delayed or non-healing problems at the donor site or producing a too thin graft as these can look terrible and are functionally often useless. Split skin grafting is a specialised technique and not appropriate to the introductory work shop.

Full Thickness Grafts

The skin from the donor site is completely excised. The donor site then has to be either closed directly, allowed to granulate or covered with a split skin graft! Full thickness grafts are fairly easy to do and with attention to detail can produce satisfactory cosmetic results.

Composite Grafts

In dermatology these refer to the transfer of skin and cartilage. They are used when covering a defect on the ala rim of the nose with skin taken from the ear. The results are variable. This specialised technique is not applicable to the introductory workshop.

Method

Full thickness graft 4.6.1 a-m

Possible Donor Sites

• Behind ear
• In front of ear
• Upper eyelid
• Inner aspect upper arm
• Lower abdomen wall
• Supraclavicular fossa

1. Assess amount of skin required.
2. Note the colour, adenexal structures, skin markings, thickness and texture of the recipient skin site.
3. Look for matching skin somewhere else on body.
4. Select donor site.
5. Prepare donor and recipient skin sites – anaesthetise, clean and drape skin sites.
6. Excise lesion.
7. Careful haemostasis.
8. Cut out template, using piece of sterile paper (suture packet, etc.) to indicate size and shape of graft. Allow for shrinkage of graft especially when grafting on the lower eyelid (25% bigger than the apparent graft size required).
9. Place template over donor site, mark round edge with Bonnies’ blue or equivalent.
10. Cut out graft down to fat.
11. Put graft to one side (ie. in saline dampened, sterile gauze kept in a safe place).
12. Repair donor defect or allow to granulate.
13. 13. De-fat graft, ie. remove all fat from under surface (drape over finger end, fat side up and snip off the fat using curved scissors).
14. Check recipient site haemostasis.
15. Site and suture donor skin. Carefully appose skin edges. Ensure skin edges are at the same height as the surrounding skin because part of the blood supply comes laterally and not just from the base of the graft.
16. Suture using monofilament sutures. Running suture to finish off.
17. Ensure base does not lift off using tie over dressing or basting sutures.
18. Remove sutures at 6-10 days depending on site.

Note: There is no theoretical limitation to the size of a full thickness graft. Size depends entirely on how much donor skin can be harvested.

Donor base suitability for grafting

Disadvantages / Advantages

These depend more critically on the experience and expertise of the operator than the intrinsic nature of the technique. The common sense advice is not to attempt anything unless you are sure that there is a good change of success or there is no apparent alternative. In general, flaps are more difficult to do correctly than grafts but are worth trying to do because they result in better cosmetic results. In some situations, e.g. where bare bone or cartilage has to be covered they are the only option if the wound is too big to be allowed to heal by second intention.

Reading list:

• Skouge. Skin Grafting. Churchill Livingstone Practical Manuals in Dermatologic Surgery (Consulting Ed RC Grekin)
• R K Roenigk and M J Zalla. Full-thickness grafts. Chapter 14 in Atlas of Cutaneous Surgery Ed Robinson, Arndt, Le Boit, Wintroub Pub W B Saunders Philadelphia. 1996 *SBN 0-7216-5404-5.