Plate 235

Full-thickness skin loss can occur from burn, trauma, infection, or surgical excision. A skin graft should be considered when the defect cannot be closed primarily or with local tissue flaps and the wound base can adequately support a skin graft. Exposed bone, joint, tendon, blood vessels, and other significant structures are not good candidates for skin grafting and need other methods of reconstruction (pedicled or free flaps). Active infection and poor blood supply to the recipient sites are contraindications. Weight bearing is a relative contraindication for skin grafting, although glabrous skin grafts can sometimes provide an adequate reconstruction.

Skin grafts can be categorized as split thickness or full thickness (Figure 1). Full-thickness skin grafts (FTSGs) remove all layers of the skin and create a secondary defect at the donor site, which must be closed primarily or left open to heal secondarily. For this reason, FTSGs are not frequently used for large defects. Split-thickness skin grafts (STSGs) can be of variable thickness, with the amount of dermis taken with the graft the determinant of graft thickness. In general, the thinner the skin graft, the more likely the graft will survive or “take” and the quicker the donor site will reepithelialize. Donor sites heal by epithelial cells in the sweat gland and hair follicles dividing and migrating superficially and then across the donor site until contact inhibition occurs. Thicker skin grafts tend to have better cosmesis because they display less secondary contracture and deformity. In cosmetic areas, including the face and hands, full-thickness grafting is more common because of its better cosmesis.

Because of the large amount of dermis present, the buttock and lateral hip can supply large quantities of STSG when needed (Figure 2). The thinner the graft taken, the higher the number of skin grafts that can be harvested from that donor site. The surgeon should be reluctant to use a donor site that will be exposed with normal dress patterns. In the face, color match is important for cosmesis. For this reason, the supraclavicular area, neck, and scalp are better color matches for defects on the face, if available.

In the case of the burn patient, early excision of the burned tissue and skin grafting (within 2 to 3 weeks) will limit the amount of hypertrophic scarring and contracture. For all cases of skin grafting, the wound bed must be clean and clear of any evidence of infection. Frequent debridements and dressing changes may be required prior to skin grafting. Negative pressure dressings may help stimulate granulation tissue and prepare the wound bed. Medical issues (including nutritional status) should be optimized.

Generally, local anesthesia can be used for small excisions and skin grafts. Where extensive skin grafting must be carried out, general anesthesia is usually indicated.

The patient's position is determined by the field of operation. Frequent position changes are required sometimes because of the multi-site nature of the surgery. Care must be taken to cover the patient at all times except for the area being operating on, as hypothermia can become a serious problem. If possible, the donor and recipient sites should be ipsilateral to allow the patient to have one part of his body without any surgical site, allowing for improved comfort.

A variety of instruments are available for use in obtaining STSGs. The choice will depend on the individual case and the surgeon's experience. The most common method of harvesting STSGs is using a powered dermatome (Figure 3), although free-hand harvesting with a scalpel or skin knife can be performed for small grafts. For irregular donor site areas, infiltration of a tumescent solution under the skin can provide increased tissue turgor that may make harvesting the graft easier.

The donor site must be a flat, firm surface, the back and thighs being commonly used. The blade is checked carefully, inserted into the dermatome, and secured. When the desired width and thickness calibrations are determined and settings made, a thin layer of mineral oil is spread over the donor site and carefully on the dermatome. A surgical assistant helps keep tension on the donor site. The dermatome should be started prior to making contact with the skin and approached at approximately a 45-degree angle. Once the dermatome has engaged the skin and a couple of centimeters of advancement occurred, the dermatome should be lowered to approximately a 30-degree angle. The dermatome is advanced until the desired length of skin is obtained. The amount of pressure exerted becomes important, as too great a pressure may produce a thicker graft of skin than is desired. If large areas need grafting, as in extensive burns, the skin graft can be placed through a mesher to increase the surface area grafted with each graft. In most applications, meshing beyond a ratio of 3:1 makes handling the mesh difficult with mixed results. Most meshing occurs with a ratio of 1.5:1.0 (Figure 4). In general, meshing should not take place for grafting of the face or hands. Placing the graft dermis side up on the mesh board will facilitate application of the graft onto the recipient area.

Hemostasis must be complete in the recipient area before application of the graft. The graft is carefully placed into the defect. Grafts are very sensitive to crush injury and should be handled with extreme care. Saline irrigation can assist in moving the graft around the wound bed. Excessive skin is trimmed from the edges, and the graft is carefully sutured to the adjacent skin with either continuous or interrupted absorbable sutures. Before application of the dressing, the wound is checked for the presence of any blood clots under the graft. Irrigating gently under the graft after fixation, confirming that the irrigation is clear, is a good indicator that there is no bleeding under the graft. The external dressing is then applied with nonadherent gauze adjacent to the graft, supported by a firm compression dressing that is carefully applied and immobilized. If a bolster dressing is required to hold the graft in place, nonabsorbable sutures are placed around the periphery and the tails left long. One layer of nonadherent gauze is placed over the graft, and the area is then covered with fluffed gauze (Figure 5). The long bolster sutures are then tied to each other firmly without being too tight (Figure 6). Alternatively, a negative pressure dressing placed on low, continuous suction can be placed over the graft with a nonadherent, oil immersion gauze providing a barrier layer between the graft and the dressing sponge. Immobilization of the extremities is extremely important.

There are several options for dressing the donor area. Small to medium donor sites can be treated well with semi-occlusive transparent films. These dressings create a moist environment and may decrease pain in the donor site and accelerate reepithelialization. The downside is that they can create seroma collections and leak, particularly if the donor site is large. Conversely, nonadherent gauze can be applied as a single layer over the donor area and supported by a bulky nonocclusive gauze dressing. On the following day, the outer dressing is removed from the donor site, leaving the inner gauze adjacent to the wound and allowed to dry, preferably with assistance of a heat lamp. This dressing can be left in place until it falls off as the donor site reepithelializes.

Postoperative Care

The frequency with which the dressing is changed will vary with the case. When a tie-over dressing is used, it may be left in place for 5 to 7 days. Inspection around the periphery of the bolus dressing from time to time will give an indication of the accumulation of fluid. A negative pressure dressing can be removed after 3 to 7 days, depending on the graft. When the dressing is changed, the presence of a fluid collection beneath the graft does not necessarily indicate a loss of the graft. The graft should be incised over the fluid collection and evacuated, and a firm dressing reapplied for 24 to 48 hours. Function should be resumed gradually. Grafts on the lower extremities should not be allowed to become dependent, particularly in those individuals with venous insufficiency. Increased venous pressure can cause an accumulation of edema fluid beneath the graft and loss of the graft as late as 14 to 21 days after grafting. After the graft has healed fully, the daily application of cold cream, lanolin, or other hydrophilic cream in small amounts will help keep it from scaling and make it pliable. The donor area should be healed in 8 to 14 days and be ready for harvesting of a new graft if necessary.