Terminology

Flaps can be classified by their blood supply into axial pattern flaps, which have a larger, typically named artery supplying their vascular needs (such as the paramedian forehead flap, which depends on the supratrochlear arteries of the medial lower forehead), and random pattern flaps, which rely on the unnamed vasculature of the dermis, subcutaneous fat, and in some cases, the superficial musculature of facial structures. Because the blood supply of the skin and soft tissues of the scalp, face, and neck is so rich, the random pattern flaps enjoy very high rates of success. These local, random pattern flaps are by far the more commonly employed flaps and will be the focus of this chapter.

The random pattern flap is further classified by its movement. The three basic types of movement are (Figure 13-1):

FIGURE 13-1 The three basic types of random pattern flap movement: (A) advancement; (B) transposition; (C) rotation. The circles are the primary defects. Red triangles are Burow’s triangles that need excising for the flap to work.

The initial wound that is to be reconstructed is the primary defect, and here it refers to the result of the removal of a skin tumor (Figure 13-2). Once a flap has been advanced, transposed, or rotated into position to close the primary defect, the wound that remains behind at the donor site of the flap is the secondary defect. The primary motion of a flap is the movement that the flap makes when it advances, transposes, or rotates into and closes the primary defect (Figure 13-2). The secondary motion is the movement that the tissue adjacent to and surrounding the flap makes when the final defect is closed. Both the primary and secondary motion of a flap are important in proper flap design. The very end of the flap that fills the primary defect, furthest from the donor site is the flap tip. The flap pedicle is that portion of the flap that connects it to the surrounding skin, and is the conduit for the vascular supply of the flap. The key suture of a local flap is the location in which the first suture is typically placed to provide the initial correct alignment of a flap to fill the primary defect and to direct additional placement of sutures to close the secondary defect. Standing cutaneous cones (dog ears) are areas of local tissue redundancy that occur in wound closure, but that can be minimized, eliminated, or moved to more cosmetically advantageous locations by the correct choice of and meticulous planning for a flap.

FIGURE 13-2 The initial wound to be reconstructed is the primary defect and the wound that remains behind at the donor site of the flap is the secondary defect. The primary motion of a flap is the movement that the flap makes when it advances, transposes, or rotates into and closes the primary defect. The secondary motion is the movement that the tissue adjacent to and surrounding the flap makes when the final defect is closed.

Use of Flaps Following Treatment of Malignant Tumors

Although malignant tumor clearance is always very important, it is even more critical prior to employing flap reconstruction. If a flap is used, and later the surgical margins are determined to be positive histologically for persistence of tumor, the cure rate for a subsequent excision may be reduced due to the loss of the true surgical margins by the significant movement of tissue that occurs in flap mobilization. In addition, using a flap prematurely may “burn bridges” and prevent further reconstruction using adjacent tissue if a re-excision is necessary. A potentially worse scenario can arise if there is a persistence of tumor that is buried under a flap. Such tumors can grow to great size and depth before they become clinically obvious, and may lead to severe morbidity and need for extensive reconstruction at the time of re-excision. Mohs micrographic surgery can achieve cure rates of up to 99% in primary tumors and is the gold standard for margin clearance of cutaneous malignancy. Mohs surgery should be strongly considered for more aggressive tumors or those in critical anatomic areas. Margin control of skin tumors can be achieved using standard frozen section pathology, but if this is not available, wounds can be bandaged following tumor excision with a plan for delayed repair following clearance of the tumor with permanent section pathology.

Contraindications

Although there are no absolute contraindications, factors to consider when planning for the use of a flap include underlying disorders that may lead to increased rates of intraoperative or postoperative complications. These include patients who are highly anticoagulated or with bleeding diatheses who may experience troublesome intraoperative bleeding or postoperative hematoma formation. Patients who smoke excessively experience a much higher risk of flap tip necrosis and flap failure, and encouraging smoking cessation in the perioperative and postoperative course is helpful to achieve the best healing. The use of flaps must also be carefully weighed in those patients who may have underlying skin conditions that can lead to increased complications. Decreased flexibility and therefore impaired movement of skin can be seen in patients with extensive scarring from burns or other injuries, previous radiotherapy, or an underlying skin disease such as scleroderma. Decreased perfusion of skin leading to flap failure or infection can be seen in conditions such as diabetes mellitus, lung disease, or poor circulation secondary to atherosclerosis, especially in peripheral areas. Finally, the use of a flap may not be possible in patients with extremely thin skin that will not bear the stresses of flap movement. Examples includes elderly patients who have extreme photodamage or long-term users of corticosteroids.

Planning the Flap

Careful planning is essential for successful flap reconstruction. Following confirmed tumor clearance of the surgical margins, the primary defect is lightly infiltrated with local anesthetic so that it may be manipulated without patient discomfort. It is important for the surgeon not to proceed immediately with an anticipated flap procedure before carefully considering the ramifications of tissue movement for surrounding structures. At this point the defect should be evaluated for surrounding tissue laxity and any potential reservoirs of loose skin that may be recruited for repair. This may be done by pinching the skin with gloved fingers. If the fingers are inadequate in more inflexible areas, the skin hook is a very useful surgical instrument for gauging tissue movement without tissue damage even in large defects of inflexible skin. Careful flap planning will then include not only the evaluation of possible sources of skin for flap creation, but also the consideration of nearby anatomic structures that could be distorted by either the primary or secondary movement of the flap. Especially vulnerable areas are the free margins of the eyelids, lips, and the nasal tip. The vectors of flap movement should be placed perpendicular to such structures, lest tissue movement distort their anatomy.

Tissue texture, and color should be matched whenever possible; a flap from similar adjacent skin will lead to the best results. A defect on the nose should be filled with similar-appearing skin from the nose instead of skin from a flap on the cheek. Finally, anticipated tissue redundancies from wound closure should be considered, with thought to how these redundancies or dog ears may be best camouflaged along anatomic borders. The proposed flap should always be drawn out prior to incision, and this may be done with a surgical marker.

Advancement Flap

Conceptual

The primary motion of the advancement flap is the sliding of the flap, usually in a single linear vector as it advances into the primary defect. This sliding motion may be unidirectional (single advancement flap) or bidirectional (double advancement flap).³ Although there are several variations on this type of flap, the two main benefits of the advancement flap are as follows:

1. Redirection of tissue movement. It may be critical to keep the repair within a single cosmetic subunit or to selectively move certain skin into the primary defect. This can be helpful when a defect lies within an eyebrow or the mustache, and the advancing primary motion can restore uninterrupted hair growth (Figure 13-3).

2. Reorientation of tissue redundancy. When closing a skin defect, tissue redundancies (dog ears) are inevitable. A properly employed advancement flap can redistribute tissue redundancies to more acceptable locations that may be far from the primary defect. This is useful in moving the tissue redundancies away from a certain structure (lips or eyebrow), or aligning them along the boundary of an anatomic subunit (alar crease) to camouflage the scar (Figure 13-4).

FIGURE 13-3 Double advancement flap (bidirectional) within an eyebrow to restore uninterrupted hair growth after resecting a tumor within the eyebrow.

FIGURE 13-4 Reorientation of tissue redundancy to a more acceptable location away from the primary defect.

Note that the purpose of the advancement flap is not to increase laxity to close a wound under high tension. Although an advancement flap may appear to provide superior tissue movement over a primary linear closure, this is rarely the case. In preoperative planning, if a defect cannot be approximated primarily by pinching the skin or mobilizing the skin edges with hooks, an advancement flap will not be the best option because the amount of additional tissue movement that it provides over primary closure is often minimal.

Advancement flaps are also limited by their blood supply. The pedicle of skin and soft tissue must not be compromised. A length:width ratio should ideally not exceed 3 : 1. A long, thin advancement flap in violation of this ratio runs a high risk of distal flap tip necrosis (Figure 13-5).

FIGURE 13-5

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