Skin Grafting Treatment & Management

Several methods and materials have been used in harvesting and securing skin grafts; procedures for STSGs and FTSGs vary substantially. The procedures also vary among surgeons and circumstances; variations in the tools and techniques of graft harvesting, placement, and care are discussed in Intraoperative details.

No specific preoperative evaluation is unique to skin grafting.

As with all dermatologic surgery, thorough preoperative history taking is critical; the history should include information about the patient's medications (particularly those with anticoagulant properties), allergies, bleeding diatheses, frequent or recurrent infections, and general wound healing.

Other preoperative considerations include the potential for postoperative trauma to the area caused by patient activities (particularly those involving shearing forces), the patient's ability to care for the wounds (at both the donor and recipient sites), and the surgeon's assessment of the patient's expectations.

Split-thickness skin grafts

Once the surgical defect is created and an STSG is selected to reconstruct the defect, the defect is measured accurately. If feasible, a purse-string suture may be placed around the defect to reduce its overall size, which reduces the size of the donor graft required for coverage ^[8] (see images below).

An appropriate donor site, typically the anterior, lateral, or medial part of the thigh; the buttock; or the medial aspect of the arm is selected. For larger defects, a large, flat donor surface is ideal for harvesting an STSG. The selection of the donor site should account for the size of the graft to be harvested, ability to hide the donor site under clothing, and ease of access to the area for follow-up care.

A study by Hexsel et al indicated that the postauricular region is an excellent site for harvesting small to moderate-sized STSGs (< 10 cm) for the head, neck, and upper chest. In the study, patients who underwent split-thickness skin grafting following Mohs micrographic surgery (total of 41 surgical defects) healed well at the postauricular donor site, scoring low on the Vancouver Scar Scale at 6-11 weeks (18 donor sites), 3-6 months (7 donor sites), and 6 months or more (16 donor sites), postsurgery. ^[9]

A retrospective study by Rotatori et al indicated that in pediatric burn patients who undergo treatment with STSGs, the thigh, if used as a donor site, is particularly likely to develop hypertrophic scarring, while, among all possible sites, the scalp, arm, foot, and lower legs are less likely. ^[10]

Once a donor site has been selected, it is prepared in a sterile fashion and infiltrated with local anesthesia, either with or without epinephrine. Raising a wheal in the skin with the anesthesia is helpful in harvesting the graft.

Instruments used to harvest the STSG can be divided into freehand and powered dermatomes. Freehand dermatomes, such as scalpel blades, double-edged blades (eg, blue blade, Gillette blade) (see first image below), Weck knives (see second and third images below), and others are useful for harvesting small STSGs. However, such freehand devices are not typically used to harvest larger STSGs, because they require substantial technical expertise to obtain a consistent thickness over a broad area.

Powered dermatomes, such as the battery-operated Davol dermatome (see first and second images below); alternating current (AC)–operated Padgett dermatome (see third image below); and the compressed water-pumped nitrogen-driven Zimmer air dermatome are often used to harvest large grafts.

The Davol dermatome lends itself well to use in office-based surgery; it has a disposable head, a preset width, and a rechargeable battery, although the thickness of the graft to be harvested is operator dependent. The Padgett dermatome allows the surgeon to adjust the graft thickness and width. Despite the fact that both the Padgett and Davol dermatomes reliably produce STSGs of even thickness, the quality of the graft has been described as highly technique dependent. The Zimmer air dermatome tends to be less technique dependent in harvesting STSGs of predetermined uniform width and thickness.

After the selection of the appropriate device, the donor site is lubricated with sterile sodium chloride solution or mineral oil, and a surgical assistant draws a sterile tongue depressor across the donor site immediately in front of the dermatome cutting surface to provide a flat surface for the surgeon (see image below). Sometimes, the donor site can be covered with a material such as OpSite before harvesting to aid in handling the tissue after harvesting. Then, the surgeon applies the dermatome to the donor site with consistent light pressure, holding the device at a 30-45° angle to the skin surface. The movement of the dermatome in the surgeon's hand has been likened to a plane's landing and taking off. Another assistant carefully removes the harvested skin from the dermatome by using gentle traction. The newly harvested graft is placed in sterile sodium chloride solution.

At this point, the STSG skin can be meshed if the surgeon desires. A scalpel is often used to create slits or fenestrations to allow for drainage of serosanguineous fluid and accommodate minor expansion of the graft. A graft-meshing machine (see image below), more commonly used in hospital-based surgical practices than in other settings, may be used if further expansion of the overall surface area of the graft is required; the machine allows for an expansion ratio of 3:1 to 9:1.

The newly harvested skin is placed on a specific template, depending on the expansion ratio desired, and the template and graft are pressed through the mesher by using a hand-crank mechanism; the process is analogous to the pressing of dough through a pasta machine. The use of skin meshed by using a machine often leads to a permanent diamond-plate appearance of the skin graft upon healing (see image below).

After the graft is harvested, the STSG is trimmed to fit the donor site. Some overlapping of the donor tissue with the recipient bed is acceptable; this overlap can be trimmed later upon suture or bolster removal. The STSG is then secured in place by using either staples or interrupted 6-0 fast-absorbing gut sutures around the periphery. In the author's experience, a running suture around the periphery of the graft may inhibit revascularization and thus lead to poor graft survival. Next, a bolster may be applied to aid in graft apposition to the recipient bed, to decrease shearing forces, and to maintain a moist environment for the graft (see image below).

An alternative to bolster placement is the use of basting sutures and a pressure dressing over a nonadherent dressing applied directly over the graft. If a bolster is used, it and any nonabsorbing sutures or staples can be removed in 7-10 days. In certain instances, the surgeon may wish to delay graft harvesting and transplantation for 2-3 weeks, allowing the defect to partially granulate. This technique of delayed grafting may correct for a thickness mismatch and provide a more receptive recipient bed in the case of relative avascularity.

A study by Evangelista et al indicated that although negative pressure wound therapy to aid graft healing is often set at -125 mm Hg, a lower negative pressure may be effective for STSGs. The study, which involved 48 STSG patients, found that graft incorporation was similar at pressures of -50, -75, -100, and -125 mm Hg. ^[11]

As with all grafting procedures, a donor site wound is created when the graft is harvested; in the case of STSGs, the wound is a partial-thickness wound that heals by granulation. Often, the secondary defect is the slowest to heal, and it is the source of most of the postoperative discomfort. To aid in the healing of this partial-thickness wound, occlusive dressings (eg, Scarlet Red gauze) or semipermeable dressings (eg, OpSite, Vigilon) are used during the period of re-epithelialization, which may last 7-21 days, depending on the depth of the wound (see image below). To avoid unnecessary concerns, the patient should be aware that a significant amount of serous and serosanguineous fluid may drain from the wound during the period of re-epithelialization.

The videos below depict split-thickness skin grafting being performed.

A study by Lee et al indicated that treatment of large full-thickness skin defects with a combination of an STSG and an acellular dermal matrix graft leads to better scar quality than does the use of an STSG alone. Using the Patient and Observer Scar Assessment Scale, the investigators found that the STSG/acellular dermal matrix group had significantly lower pain and stiffness subscores, as well as a significantly lower total score, than did the other patients. ^[12]

Full-thickness skin grafts

If an FTSG is planned in the reconstruction of a surgical defect, an appropriate donor site must be selected. Areas free of premalignant or malignant lesions that have color, texture, and sebaceous qualities similar to those of the area surrounding the defect must be sought. Common donor locations for FTSGs include areas of preauricular and postauricular, conchal bowl, supraclavicular, upper eyelid, nasolabial fold, axillary, antecubital, and inguinal fold skin. Another excellent source for FTSG skin is any redundant skin that is removed in the planning and reconstruction of the defect, such as dog-ear skin, standing cone skin, or tips removed from an elliptical complex linear closure. Any tissue removed from the patient should not be discarded until after the reconstruction is completed.

As with STSGs, the defect size must be measured accurately. Here again, the placement of a purse-string suture around the defect may substantially decrease the size of the graft required to repair the defect. Most often, a template of the defect is created by using a flexible material such as Telfa, gauze, or the foil packaging from the suture material. The template is transposed to the selected donor site (see images below). Then, the donor tissue is excised after it is infiltrated with Xylocaine to the level of the subcutaneous adipose by using a scalpel. In most cases, the tissue is removed with an elliptical incision that can easily be closed primarily.

In contrast to STSG harvesting, FTSG harvesting does not require the use of additional surgical instruments. The donor graft tissue is placed in sterile sodium chloride solution until it is used. The graft can remain viable for as long as 24 hours after harvesting if it is refrigerated or kept on ice.

After harvesting the graft, the secondary defect should be closed, and the FTSG defatted. Defatting the graft, which is performed to allow more efficient revascularization, is accomplished by draping the graft skin over the finger with the adipose side facing up and with hemostats on each tip. The yellow globular adipose is removed by using iris scissors until the dermis is visualized (see image below). The dermis also can be sculpted to account for irregularities in the thickness of the graft required. If additional thickness is required to properly contour the graft, small fragments of the dermis trimmed from the donor skin can be used later as dermal grafts under the FTSG once the skin is placed in the recipient bed. ^[13]

Next, the graft is tacked into place by using 2 interrupted sutures of 6-0 fast-absorbing gut in opposing cardinal directions; then it is trimmed and secured in place along its circumference. The authors prefer to use interrupted sutures rather than running sutures around the circumference of the graft. These sutures may allow better revascularization from the periphery of the recipient bed and ultimately improve graft survival. In suturing the FTSG into place, precise epidermal approximation is essential for optimal graft take and subsequent cosmetic results.

The graft can be further stabilized by the placement of a tie-over bolster dressing, a method favored by the authors (see image below). The bolster dressing is composed of Xeroform gauze, cotton balls, and petrolatum or bacitracin. It is held in place over the FTSG by using 5-0 silk sutures sewn into the skin at opposing points around the circumference of the graft for 1 week. The free ends of the silk suture are tied to one another over the top of the bolster, and a light dressing is applied over the entire bolster.

Similar to what was previously described with STSG dressings, the bolster provides firm apposition between the graft and the bed, decreases potential shearing forces, prevents the patient from manipulating the graft, and provides a moist environment. Both the bolster and any nonabsorbable sutures are removed in 7-10 days. Wound care during that interval is performed around the bolster.

Some surgeons forego the use of a bolster and instead apply basting sutures and a pressure dressing directly over the graft. A literature review by Kromka et al indicated that in full-thickness skin grafting, tie-over bolsters are comparable to quilting with basting sutures in terms of graft take, cosmetic results, and postsurgical complications. ^[14]

Similarly, a literature review by Steele et al indicated that compared with tie-over dressings for FTSGs, other fixation methods for such grafts—including modified tie-over dressings, quilting/mattress suturing, simple pressure dressings, hydrocolloid dressings, and double tie-over dressings—demonstrate no significant difference with regard to graft take and hematoma and infection rates. However, the investigators found much of the evidence to be derived from small retrospective, observational studies. ^[15]

Whatever the method of securing the graft, the dressing must remain moist, well apposed to the recipient base, and protected from shearing forces to increase the likelihood of the survival of the graft.

Ideally, when the patient returns for suture removal, the graft will have a light pink appearance and minimal crusting around the edges of the graft. As in any dermatologic surgery, the appearance varies widely. Emphasizing to the patient that the skin grafts do not look "normal" for many weeks to months is important.

Certainly, the newly grafted skin is more fragile and more vulnerable to trauma and sun damage for several weeks after surgery. If a slight amount of bleeding occurs postoperatively or if the periphery of the graft losses viability, a slight crust of serosanguineous material or necrotic debris can be gently removed by using hydrogen peroxide and a swab or by gently teasing it with a forceps.

More extensive black necrotic tissue or eschar involving part or all of the grafted skin may signal partial or complete loss of the graft. Generally, this eschar should not be initially debrided because it functions as a biologic dressing for the underlying tissues. Debridement should not be performed until the area of necrosis is clearly demarcated.

Complications that the dermatologic surgeon may encounter include infection, seroma and/or hematoma formation, and graft contracture. Although wound infection is rare in skin grafting on the head and neck if good surgical technique is maintained, patients with diabetes, those with immunosuppression, and those in whom the intraoperative time is prolonged may be predisposed to infection. In such patients, oral antibiotics covering staphylococcal, streptococcal, and, occasionally, gram-negative infections should be prescribed.

Hematoma or seroma formation may occur despite meticulous hemostasis if inadequate pressure dressings are used, if the graft is subjected to trauma, or if the patient participates in vigorous activity. Because of this, the authors recommend that tie-over bolster dressings be used and that patients avoid any increased activity for approximately 2 weeks.

Furthermore, many individuals undergoing dermatologic surgery may be taking agents such as aspirin, nonsteroidal anti-inflammatory drugs (NSAIDs), Coumadin, alcohol, or vitamin E, which also may contribute to postoperative hematoma or seroma formation. After appropriate medical clearance, patients should abstain from taking aspirin for 10-14 days before surgery; alcohol, vitamin E, and NSAIDs for 4-5 days before surgery; and Coumadin for 3-5 days before surgery. With the exception of Coumadin, which may be restarted 1 day after surgery, the authors recommend that the other agents should not be resumed until 5-7 days after surgery.

Wound contracture is more common in STSGs than in FTSGs, and it can lead to cosmetic and functional problems. Grafts contract in a centripetal fashion due to the movement of unopposed elastic fibers, and this may occur in the graft as well as in the recipient bed underlying the graft tissue. If significant functional impairment occurs secondary to graft contracture, surgical revision may be indicated.

Grafts may heal with a mismatch in texture, color, or topography, and surgical correction can be considered at 6 weeks to 6 months after grafting. Often, spot dermabrasion or laser resurfacing can be used to flatten elevations in a scar, although optimal results are achieved when an entire cosmetic unit is treated.

Vascular lasers are used to soften healing graft scars and decrease their visible vascularity. Gentle massage with or without the introduction of intralesional corticosteroids is often used to soften and reduce elevated or firm scar tissue formation in and around the graft site.

Future

Over the last several years, numerous treatment options have been developed as an alternative to autologous skin transplantation. Products such as cadaveric allograft skin, porcine xenograft skin, and bioengineered skin substitutes (including epidermal, dermal, and composite bilayer skin equivalents) have added to the dermatologic surgeon's therapeutic options.

In the past, both cadaveric allograft skin and porcine xenograft skin have been used to replace skin lost as a result of surgery, chronic wounds, and burns. Advantages to the use of such grafts include the elimination of the need to produce a second surgical wound, the relative abundance of material, and the immediate availability of the transplantable tissue. Disadvantages to the use of these materials include possible graft rejection and the potential for disease transmission. ^[16]

The use of cultured autograft keratinocytes (Epicel; Genzyme Tissue Repair, Cambridge, Mass) requires an initial small skin biopsy specimen, approximately 3 weeks to grow the keratinocytes graft in culture, and the use of a dermal substitute to stabilize the cultured epidermal layer. Although cosmetically acceptable results are possible, the use of such a skin substitute is costly and requires time. Cultured keratinocytes allografts obviate the initial biopsy and the time involved in culturing the graft, but they are also expensive and may lead to possible disease transmission. ^[16]

Several options for dermal graft skin substitutes exist. ^{[17, 18, 19]} These include human cryopreserved allograft skin; human allograft skin treated with decellularization, matrix stabilization, and freeze drying (AlloDerm; LifeCell Corp, The Woodlands, Tex); bovine collagen and chondroitin sulfate over silicone (Integra; Integra LifeSciences, Plainsboro, NJ); and fibroblast nylon or bioabsorbable mesh (Dermagraft; Advanced Tissue Sciences Inc, La Jolla, Calif). Despite the immediate availability of these products, their expense and potential for disease transmission in the case of allograft-derived dermal grafts limit their usefulness. ^[16]

Apligraf (Organogenis, Canton, Mass), a bioengineered bilayered skin equivalent composed of bovine type I collagen, allogeneic human skin fibroblasts, and cultured neonatal foreskin-derived keratinocytes, functions as an effective skin substitute. Although it is currently Food and Drug Administration approved for use in the treatment of venous ulcers, ongoing studies are being conducted to investigate its effectiveness in the treatment of cutaneous surgical defects. As with all the bioengineered skin substitutes, the cost of Apligrafts may limit its overall usefulness.

Some of the recent publications investigating the bioengineered skin construct Apligraf seem to imply that although the skin construct is beneficial in the treatment of chronic wounds, in many respects in does not measure up to native skin. In one study comparing the rate of epithelialization and morphology of Apligraf and normal skin explant, the Apligraf started epithelialization earlier; however, the authentic skin explant produced a multilayered and well-structured neoepidermis over twice the surface area of the bioengineered construct at the end of the culture period. ^[20]

Another study observing the safety and efficacy of a bilayered skin construct (BSC) compared application of the BSC to a surgical wound to healing by secondary intention. Although the BSC was found to be safe in this small study, the only positive outcome noted was the apparent decrease in postoperative pain using the BSC over those wounds healed by secondary intention. ^[21]

A literature review by Dunn et al suggested that the use of platelet-rich plasma (PRP) is an effective adjunct to split-thickness skin grafting. The report indicated that STSG patients treated with PRP have decreased healing time, length of hospital stay, and scarring and do not require sutures/staples. ^[22]

Conclusion

This article provides an overview of the use of skin grafts in reconstructive surgery. Thorough knowledge in the materials and methods used in skin grafting, as well as a complete understanding of wound healing, is essential so that cosmetic and functionally acceptable outcomes can be reliably achieved.