Skin Grafting

S.M. Leal-Khouri (*)

Department of Dermatology and Cutaneous Surgery, University of Miami, Key Biscayne, Dade, FL, USA

Florida International University School of Medicine, Key Biscayne, Dade, FL, USA

e-mail: susanalealkhouri@aol.com

S.E. Grummer

Department of Mohs Surgery, Dermatology and Plastic Surgery,

Key Biscayne, Dade, FL, USA

Summary: Introduction

•Skin grafts involve transfer of skin, which has been separated from its vascular supply, to a wound bed.

•May be classified based on origin: autografts, allografts, or xenografts.

•May be classified based on thickness: fullthickness grafts or split-thickness grafts.

34.1Introduction

A skin graft may be necessary when closure of a wound is required, but primary closure or use of a flap is not feasible due to size or location of a wound. By definition, grafting involves the transfer of noncontiguous skin, which has been separated from its vascular supply, to a wound bed. Grafts may be categorized based on the origin or thickness of the donor tissue. In terms of origin, grafts may be classified as autografts, allografts, or xenografts. An autograft is derived from the patient’s skin and is the most frequently used graft in dermatologic surgery. When the donor tissue is harvested from another person, then the graft is referred to as an allograft. Finally, a xenograft is one that is derived from another species, for example, a porcine graft. Allografts and xenografts are often used for chronic wounds or burn wounds. The utility of an alloor xenograft is derived from the stimulation of wound healing, protection, and debridement.

The thickness of a graft can also be used as a method of categorization. Specifically, a full-thickness skin graft (FTSG) includes epidermis and the entire dermis. Adnexal structures are preserved. On the other hand, a split-thickness skin graft (STSG) contains epidermis and only a part of the dermis, with little or no preservation of adnexal structures. Finally, a composite graft includes not only skin but also another type of tissue, such as cartilage, perichondrium, or adipose tissue.

Summary: Physiology

elucidated distinct phases in which nutrition is supplied to the graft, specifically, plasmatic imbibition, inosculation/anastomosis, and capillary ingrowth/ revascularization [1].

Plasma imbibition is the first phase and occurs during the first 2 days after a graft has been performed. In this phase, the transferred tissue receives nutrition by imbibing exudate from the wound bed and can increase in weight by up to 40%. During imbibition, the graft and the wound bed are held together via a layer of fibrin [2]. The second phase, inosculation, is defined by an anastomosis of the preexistent vessels of the graft and the wound base [3]. This phase occurs during the second and third postoperative days. Revascularization involves the growth, proliferation, and connection of vessels from the recipient base and sidewalls [1, 4]. The rate of revascularization is dependent on the thickness of the graft and the vascularity of the recipient bed. During the fifth to seventh postoperative days, blood flow occurs. Lymphatic flow also reestablishes around postoperative day seven [5]. As a result, the graft often loses a significant amount of the weight that was gained during the imbibition phase. During the second to third postoperative months, sensory reinnervation commences and proceeds from the periphery to the center of the graft. It is important to note that the reinnervation is a slow process and full sensory capacity may not be regained at the graft site [6].

Primary contraction of a graft occurs once the graft has been harvested due to elastic fiber recoil. On the other hand, secondary contraction is due to contraction of myofibroblasts and contractile proteins and com-

tion, inosculation/anastomosis, and capillary ingrowth/revascularization.

•Primary contraction of a graft occurs once the graft is harvested due to elastic fiber recoil. Secondary contraction occurs after graft placement and is due to contraction of myofibroblasts and contractile proteins.

experience greater secondary contraction, while FTSG experience greater primary contraction.

Summary: Indications

•A skin graft can be used to address the cosmetic, functional, or practical needs of a patient’s surgical defect or wound.

Of paramount importance to graft survival is the ability of the transferred tissue to revascularize with the wound bed. Investigation of graft wound healing has

Skin grafts can have cosmetic, functional, and practical purposes. A graft can have cosmetic benefits by preventing contracture. On the other hand, grafts can

be used to restore function, such as when used for wounds secondary to burns or for chronic ulcers. Often a graft may be used when healing by second intention, a primary closure, or utilization of a local flap are not feasible options.

Summary: Preoperative Assessment

•Review of a patient’s medication list and medical and social history is important to ensure proper patient selection prior to performing a graft in a given clinical scenario.

34.4Preoperative Assessment

There are many factors which must be taken into account prior to performing a graft. First, a thorough review of the patient’s medical and social history must be performed. Pertinent information includes a history of coagulation abnormalities, alcohol consumption, arterial or venous insufficiency, collagen vascular disease, diabetes mellitus, poor nutrition, infections, need for antibiotic prophylaxis, use of tobacco, and/or prior radiation treatment [7]. Additionally, a review of the patient’s medications (e.g., steroids, chemotherapeutic agents) is also of paramount importance [8]. The likelihood of graft revascularization and successful healing of the graft is in part predicated on the patient’s medical history and medication list. One may advise patients to discontinue aspirin and nonsteroidal anti-inflammatory agents 1 week prior to the grafting procedure as excessive bleeding may cause blood to accumulate between the graft and wound bed, thereby leading to the potential for graft failure.

Summary: Site Selection

•Color and texture match are important factors to consider when choosing a harvest site so that cosmesis can be optimized.

34.5Site Selection

While grafts do not have quite the cosmetic match as tissue adjacent to the primary wound, harvesting from anatomic locations that are similar in color and texture

to the wound is beneficial and preferred. In order to maximize cosmesis, various factors must be taken into account when choosing a site to harvest, including photodamage, color, existing adnexal structures (e.g., hair), and the appearance of the donor site scar. Commonly used sites for FTSG are: preand postauricular regions, creases of the upper eyelids, nasolabial folds, supraclavicular region, lateral neck, antecubital fossa, and groin. Sites that can be concealed are often chosen as harvesting sites for STSG. These include: the abdomen, back, buttocks, anterior thighs, and upper inner arms.

Summary: Full-Thickness Skin Grafts

•Full-thickness skin grafts (FTSG) contain epidermis and dermis and retain adnexal structures.

•Given wound contraction upon harvesting donor tissue, a FTSG should be oversized ~10–20% to allow for contracture.

•It is important to defat the donor tissue after harvesting in order to improve contact between the graft and wound bed as well as to decrease the nourishment requirements.

•Close apposition of the graft to the wound bed promotes vascularization and minimizes risk of hematoma or seroma formation.

•Meticulous approximation of the wound edges to the graft is paramount to the optimal cosmesis of the graft. Bolsters are used to stabilize and protect the graft.

34.6Full-Thickness Skin Grafts

By definition, full-thickness skin grafts (FTSG) contain both epidermis and dermis. Often, adnexal structures are preserved. FTSG are more durable than STSG. Additionally, FTSG provide a good cosmetic outcome, especially when the color and texture of the surrounding recipient site are taken into consideration. In dermatologic surgery, especially after the removal of a skin cancer, areas that are conducive to FTSG include nasal ala and tip, helix, medial canthus, lower eyelid, digits, and extremities [5]. When choosing a donor site, the surgeon must consider both the ease of closure and appearance of the resultant scar.

Once the appropriate donor site has been chosen, anesthetized, cleansed, and prepared for harvest, a template of the recipient site is made in order to control for size and shape match. Given contracture of the donor tissue, one should harvest a greater amount (~10–20%) of tissue to allow for contracture [10]. When grafting eyelid defects, the harvested tissue should be oversized even more to allow for contraction and to avoid ectropion. Often a template is made with a blood imprint of the recipient site onto a nonadherent pad. Using the template, the donor site can be marked with a surgical marking pen. The use of an elliptical incision along the relaxed skin tension lines is beneficial. The graft should be large enough to align fully in the wound and should not be pulled tight as this can result in vascular compromise. FTSG should be limited to less than 5 cm to avoid necrosis as the new graft receives oxygen and nutrients via diffusion from the wound base for several weeks [5].

Once the graft has been harvested, it can be wrapped in sterile saline-soaked gauze and placed in a Petri dish. Hemostasis of the donor site is then achieved. The donor site is repaired later after the graft has been placed as it is important to allow nutrient diffusion to the graft to begin. Curved iris scissors are used to defat the graft until glistening white dermis is revealed (Fig. 34.1a, b). The amount of dermis that is removed varies according to the thickness of the tissue needed to fill the wound bed. It is important to remove the subcutaneous tissue in order to improve contact between

b

Fig. 34.1 (a, b) Curved iris scissors are used to defat the graft until glistening white dermis is revealed (All photos courtesy of Susana Leal-Khouri, M.D.)

the graft and wound bed as well as to decrease the nourishment requirements.

34.6.2 Graft Fixation

Close apposition of the graft to the wound bed is necessary to promote vascularization and to minimize