Key Features

The skin is the largest organ of the human body, representing ~ 16% of the total body weight. Skin transplanted from one location to another on the same individual is termed an autogenous graft or autograft. Despite the development of sophisticated reconstructive methods utilized after ablative surgery, such as microvascular free flaps, much simpler approaches to reconstruction continue to be appropriate in many cases. Skin grafting in particular remains an excellent option for defects of the oral cavity, face, and scalp.

Anatomy and Physiology

From superficial to deep, layers include the epidermis, the dermis, and the subcutaneous tissue. The epidermis constitutes ~ 5% of the skin; the remaining 95% is dermis. The epidermis is further divided into the superficial stratum corneum (no nuclei), stratum lucidum, stratum granulosum, and stratum basale. The dermis is further divided into the more superficial papillary dermis and the deeper reticular dermis, which contains hair follicles and sebaceous glands.

STSGs are composed of epidermis and a variable portion of the dermis. FTSGs include the epidermis and the entire dermis. The thickness of STSGs typically used ranges from ~ 0.012 to 0.018 inches (0.3–0.45 mm). Although thinner STSGs contract more, they “take” more consistently; thicker grafts contract less but are also more prone to fail. The thickness of FTSGs depends on the thickness of the donor site skin.

Skin graft healing is considered a three-step process. In the first stage, imbibition, the graft derives its nutrients from the underlying recipient bed. During the second stage, inosculation, preexisting blood vessels in both the graft and the recipient bed meet and form a network. Healing is completed by neovascularization, wherein new vessels form within the graft and grow into the underlying tissue.

Properties of the recipient bed are critical to skin graft healing. Skin grafts will “take” on most well-vascularized tissue, including granulation tissue, muscle, fat, perichondrium, periosteum, and cancellous bone. Conversely, skin grafts will not survive on naked cortical bone or bare cartilage (i.e., tissues without their periosteum or perichondrium). Actively infected tissue should not be skin grafted. Radiated tissue is also a much less favorable recipient bed.

Indications

Common settings for skin grafting in head and neck surgery include oral cavity defects after cancer resection, cutaneous defects of the face after lesion excision or trauma, closure of free flap donor sites (radial forearm, fibula, etc.), and the framework elevation step of microtia repair.

Operative Technique

Full-Thickness Skin Graft

FTSGs may be harvested from essentially any area; however, it is important to approximate a color and texture match to the recipient site if possible. Common donor sites include the post- or preauricular area and the supraclavicular neck. Chest wall and groin donor sites are common in microtia reconstruction. Grafts are typically designed in fusiform fashion to facilitate primary closure. The borders of the graft are incised sharply with a scalpel. The edges of the graft are held with a skin hook, and the remainder of the graft is elevated in a subdermal plane from underlying subcutaneous tissue using a knife or sharp scissors. The graft is thoroughly defatted with scissors or a knife prior to inset. Donor site hemostasis is secured with cautery, and elevation of surrounding skin flaps with primary closure is achieved. The graft is then trimmed and inset similar to an STSG as previously described ( Fig. 9.14 ).

Complications

The major complication of skin grafting is partial or complete graft loss. Reasons for graft failure include hematoma, seroma, infection, and inadequate stabilization. Discoloration at the STSG donor site is to be expected, and skin grafts may have a “patch” appearance due to color or texture mismatch, shininess of the graft site, and volume differences.

Postoperative Care

Feeding via a nasogastric feeding tube may be considered for oral cavity skin graft placement. Bolsters may be left in place for 3 to 10 days.

Management of the STSG donor site is quite variable; this area may be a source of discomfort for the patient. The STSG donor site epidermis regenerates by secondary epithelialization from the wound edges and from migration of dermal cells originating in the shafts of hair follicles as well as adnexal structures remaining in the dermis.

Key Features

Cutaneous defects can arise from a host of different causes, but skin cancer remains the most common etiology in the Caucasian population. Local facial flaps are widely used for defects that are too large for primary closure or second-intention healing. They remain the workhorse for facial reconstruction.

Defect Evaluation

When analyzing a cutaneous defect of the face, there is a series of steps that one should go through to help identify the optimal flap or, more importantly, which flaps will create significant problems, such as distortion, asymmetry, or functional issues.

Flap Nomenclature

The different systems for classification of local flaps include tissue content, proximity of the flap, blood supply, and method of tissue transfer, the last two of which are the principal methods of nomenclature. The blood supply within a flap can be random (based on the rich dermal plexus of the face), can have an axial pattern (supplied by numerous larger-caliber vessels in the dermis and subcutaneous layer, which are arranged in an axial pattern along the flap), or can be pedicled (maintained by larger, named vessels). The other system is based on the method of tissue transfer ( Table 9.3 ).

Advancement flaps refer to skin paddles that are mobilized in a linear vector to resurface a given defect. They create no distortion to the adjacent tissues, although standing cutaneous deformities may occasionally arise and require excision. Such flaps are rarely used in their truest form but rather follow the natural skin lines. They are further subclassified based on their vascular pedicle, be it a unilateral pedicle, a bipedicle, or a subcutaneous pedicle (island flap). The maximum length-to-width ratio for an advancement flap is typically 4:1.

The remaining method of tissue transfer is the pivotal flap, in which the tissue transposition has a rotational element as well. A true rotation flap moves tissue along the circumference of a circle, around a single, fixed pivot point, such as a scalp rotation flap. Most other flaps have a combined advancement and rotational element to them. A transposition flap involves mobilizing tissue over an incomplete bridge of skin (e.g., rhombic and bilobed flaps). Interposition flaps are similar to transposition flaps but include elevation of the incomplete skin bridge to the site of the donor defect, such as a Z-plasty. Finally, interpolated flaps move the skin paddle and pedicle over an intact skin bridge with its pedicle base removed from the defect. These interpolated flaps are two-staged flaps that require a secondary pedicle division, usually 3 weeks later. The forehead flap is such an example.

Advancement Flaps

The most simple advancement flap is the lateral undermining and mobilization along the margin of a defect with primary closure. When closing a defect primarily, the apices of the defect should be less than 30° to avoid a standing cutaneous deformity. Traditional unipedicled (U-plasty) and bipedicled (H-plasty) advancement flaps without any rotational component have a narrow indication such as in closure of forehead and lip defects. These flaps are used when minimal tension is desired perpendicular to the direction of advancement to avoid distortion of adjacent anatomic landmarks such as the eyebrow. Secondary defects created along the axis of advancement can be addressed by the “halving technique,” direct excision of the standing cutaneous deformity, or by advanced excision of a Burrow triangle ( Fig. 9.15 ).

The leading edge of any advancement flap is the point of maximum tension. One can often design the flap such that the parallel resultant scar lies within the wrinkles or RSTLs of the facial aesthetic unit. The V-Y island advancement flap is a unipedicled triangular flap based on a subcutaneous pedicle that is mobilized in a linear vector toward the defect. The V-Y flap creates minimal distortion around the primary defect, but its reach is limited by the subcutaneous pedicle ( Fig. 9.16 ). It is well suited for small defects of the upper lip and medial cheek that are in proximity to important anatomic landmarks.

Pivotal Flaps

The rotation flap is a pivotal flap mobilized along a curvilinear incision around a fixed point used for tissue that is not extensible, such as the scalp. Two standing cutaneous deformities are created and can be directly excised. The ratio between the peripheral arc of the flap and diameter of the defect is generally 4:1, but rotation flaps on the scalp often require a 6:1 ratio. The cheek flap is a combination advancement and rotation flap. The large area from which skin is recruited, together with the natural extensibility of cheek skin, make this flap particularly apt for large defects of the medial cheek. Resultant scars can be camouflaged along the melolabial fold, lower eyelid, and preauricular crease. It is imperative to avoid inferior tension on the eyelid by placing anchoring stitches between the periosteum of the malar eminence and infraorbital rim and the undersurface of the flap.

Transposition Flaps

A transposition flap mobilizes a broad-based skin paddle over an incomplete bridge of skin (as opposed to the interpolated flap, which crosses a complete bridge of skin). The rhombic flap is a precise mathematical design that leaves minimal tension or distortion around the defect. The point of greatest tension and its vector are consistent and should be oriented along a line of maximal skin extensibility, perpendicular to RSTLs. This point should be secured with a long-lasting buried suture ( Fig. 9.17 ). Small modifications in design, such as a narrower arc of rotation, can reduce the amount of tension from the donor site and distribute this to the tissues surrounding the defect.

The bilobed flap is a double transposition flap that minimizes distortion at the primary site by distributing the soft tissue tension over the perimeter of two separate flaps. As such, it is ideal for use near immobile anatomic structures such as the alar rim. Refinement of the bilobed flap design has led to a tighter arc of rotation, reducing the standing cutaneous deformity. Each flap is usually separated by a 45° arc of rotation rather than 90° ( Fig. 9.18 ). The primary lobe should be aggressively thinned to minimize the amount of pincushioning that typically occurs. The bilobed flap is excellent for repair of nasal tip defects up to 1.5 cm in diameter but can also be used for reconstruction of cheek defects away from the central face.

The melolabial flap is another transposition flap adjacent to the nose and lips, which provides a source of well-vascularized, color-matched skin for reconstruction of the nasal ala, sidewall, and lips. It can be based inferiorly or superiorly, but the aesthetic junction between the cheek and nose is often blunted.

The two-staged melolabial flap and the forehead flap are interpolated flaps commonly used in reconstruction of larger defects of the nose. In general, nasal defects > 2.5 cm in diameter, defects with denuded bone or cartilage, or wounds in irradiated fields are best reconstructed by heartier flaps such as these. With its ancient history, the forehead flap remains a robust and versatile flap and the workhorse technique for major nasal repair. The pedicle is based over the medial eyebrow area, centered on the consistent supratrochlear artery, which captures the perfusion pressure from the area rich in collaterals. The pedicle is kept narrow (i.e., < 1.5 cm) to facilitate rotation. The pedicle can be based on the ipsilateral side of the nasal defect for greater inferior reach, or on the contralateral side for reduced torsion on the pedicle base and visual obstruction to the patient. The donor site defect is closed primarily, and the pedicle division and flap inset is performed after 3 weeks.