Shan R. Baker

Introduction

The melolabial crease delineates the cheek from the caudal nose and from the upper and lower lips. It is created by the insertion of the superficial muscular aponeurotic system into the skin at the junction of the cutaneous lips and the cheek. Medial to the crease, the skin of the lips is tightly attached to the orbicularis oris and there is minimal subcutaneous fat. Lateral to the crease, the skin of the cheek is loosely attached to the deep muscular fascia and there is an abundance of subcutaneous fat. With time, the forces of muscle contraction, gravity, and aging result in a progressive deepening of the melolabial crease. The subcutaneous fat immediately lateral to the crease forms the melolabial fold. The melolabial crease serves as a facial divide separating the lips from the cheeks and represents one of the most important facial aesthetic boundaries.

Because of the proximity of the melolabial fold to the nose and lips, melolabial flaps have long been used to repair these structures.1,2 During the 19th and 20th centuries, many varieties of melolabial flaps were described.³ In the past, such flaps have been called nasolabial flaps, but the term melolabial is more accurate in description as the prefix melo- refers to the cheek and the suffix -labial refers to the lips. Thus, it is more accurate to use the term melolabial crease rather than nasolabial crease because the crease separates the lips from the cheek, not the nose from the lip. This chapter discusses only cutaneous flaps harvested from the mound of skin immediately lateral to the melolabial crease and known as the melolabial fold.

Melolabial cutaneous flaps are skin flaps harvested from the melolabial fold lateral to the melolabial crease. The cheek skin in this region of the face has a rich blood supply from perforating branches of the facial artery and is drained by the facial angular vein. Because of the extensive vascularity of the medial cheek skin, melolabial flaps may be based either superiorly or inferiorly. Skin of the melolabial fold including the jowl area is the most redundant of all areas of the face. There is usually sufficient skin to enable the transfer of sizable flaps for reconstruction and at the same time allow closure of the donor site of the flap. In addition, the closure line of the flap donor defect can be positioned in or parallel to the melolabial crease to provide maximum scar camouflage. Because of proximity, the color, texture, and thickness of the skin of the melolabial fold closely match those of the lips and the caudal lateral nose. Therefore, melolabial flaps are particularly suited for repair of cutaneous defects of these areas of the face. In contrast, the skin of the nasal dorsum and cephalic portion of the nasal sidewall is thin and tends to have less sebaceous glandularity than the skin of the melolabial fold. As a consequence, melolabial flaps are less well suited for repair of cutaneous defects located in these areas of the nose. The skin of the melolabial fold is particularly similar in sebaceous glandularity and texture to the skin of the ala. It is for this reason that skin defects of the ala are preferably repaired with skin from the melolabial fold. This is usually accomplished by use of an interpolated cheek flap that crosses the alar-facial sulcus and requires subsequent detachment of the flap’s pedicle. Crossing over rather than through the sulcus maintains a perfectly natural alar-facial sulcus, an important facial aesthetic boundary.

Local cutaneous flap classification and terminology are discussed in detail in Chapter 6, but a brief summary here is helpful in understanding the mechanisms of movement of flaps harvested from the melolabial fold. Classification of flaps by method of transfer, which is to say by tissue movement, is usually the most convenient way of discussing flaps relative to their use in repair of facial cutaneous defects.^4–6 It also contributes to the understanding of where standing cutaneous deformities develop and where the maximum wound closure tension occurs during wound repair. By use of this classification, melolabial flaps may be categorized as pivotal, advancement, and hinge. Melolabial hinge flaps are rarely used and are not discussed in this chapter. Advancement in the majority of situations depends on stretching the flap skin in the direction of flap movement. Such flaps are subjected to an increase in wound closure tension. In contrast, pivotal flaps rotate about a point at their base and in their purest form are not stretched. Thus, they are not subjected to wound closure tension greater than the natural tension of the remaining facial skin, although the repair of the donor site of the flap is subjected to increased tension. There are three types of pivotal flaps: rotation, transposition, and interpolated. Transposition and interpolated flaps may be transferred on a cutaneous pedicle or subcutaneous tissue pedicle. In the latter case, the flap is referred to as an island flap because it has no cutaneous connection to the donor site. Island transposition pivotal flaps are occasionally harvested from the melolabial fold but are uncommonly used and are not discussed. Rotation flaps are pivotal flaps with a curvilinear configuration. They must be designed immediately adjacent to the defect and are best used to close triangular defects. In the author’s practice, local flaps in the form of rotation are rarely designed in the area of the melolabial fold because their curvilinear incision frequently creates a scar that crosses the melolabial crease perpendicular to relaxed skin tension lines (RSTLs). For this reason, rotation flaps are not discussed.

In contrast to rotation flaps, which must be designed adjacent to the defect, transposition flaps provide the surgeon the ability to construct a flap at some distance from the defect with its axis independent of the linear axis of the defect. The only requirement is that the base of the flap be contiguous with the defect the flap is designed to repair. This is one of the greatest advantages of transposition flaps. This fact enables the surgeon to recruit skin from the melolabial fold that may be a considerable distance from the defect. Skin elasticity and redundancy are greater in the area of the melolabial fold than in any other location on the face, providing a resource for harvesting sizable flaps. The linearity of transposition flaps can be designed so that they parallel the melolabial fold, and this in turn enables the donor site to be closed parallel to or in the melolabial crease. Because of these advantages, transposition is the most common design of local flaps harvested from the area of the melolabial fold.

The interpolated flap, like the transposition flap, is transferred by pivotal movement and has a linear configuration so that it can be designed to conform to the linear axis of the melolabial fold. Interpolated flaps differ from transposition flaps in that their bases are not contiguous with the defect. Thus, the pedicle must cross over or under intervening tissue. If the pedicle passes over intervening tissue, the flap must subsequently be detached from its donor site in a second surgical procedure. This is the greatest disadvantage of such flaps. On occasion, the pedicle can be de-epithelialized or reduced to subcutaneous tissue only (island flap) and brought under the intervening skin to allow a single-stage reconstruction. Passing flaps through a subcutaneous tunnel may compromise the vascularity of the pedicle or create a contour deformity along its path. The major advantage of interpolated flaps compared with transposition flaps is the ability to recruit skin for construction of the flap at a site that is more removed from the facial defect. The interpolated melolabial flap is frequently used for nasal reconstruction because of the proximity of the melolabial fold to the nose and its similar color and texture to the skin of the nose.

Melolabial Transposition Flaps

Transposition flaps are the most common type of melolabial flaps used in facial reconstruction. Transposition flaps are pivotal flaps with a linear configuration. They may be based inferiorly or superiorly and have a number of different configurations; however, their linear dimension is always longer than their width. Typically, the linear axis of a melolabial transposition flap is oriented directly above and parallel to the linear axis of the angular artery. Although the flap is rarely elevated as a true axial flap incorporating the angular artery, many small peripheral branches of the artery are probably included in the base of melolabial flaps.

The majority of melolabial transposition flaps are designed as a rectangle, parabola, or rhombus. The axes of these flaps are usually oriented along or are parallel to the axis of the melolabial fold (Fig. 12-1). Closure of the flap donor site is within or parallel to the melolabial crease. The flap may be lengthy relative to its width, which facilitates closure of the donor defect without excessive wound closure tension. Melolabial transposition flaps used to repair small (2 cm or less) cutaneous defects of the medial cheek may be based superiorly or inferiorly. However, transposition flaps used to repair medial cheek defects larger than 3 cm should be based superiorly because there is more redundancy of facial skin in the inferior cheek, in the region of the jowl. In older patients, this redundancy can provide a source for a large flap and still enable primary closure of the donor site. Flaps should be designed so that whenever possible, closure of the donor site is in the melolabial and labial mandibular creases. When superiorly based melolabial transposition flaps are used, the standing cutaneous deformity is removed just medial or lateral to the superior border of the defect, depending on whether the flap is pivoted medially or laterally.

Transposition flaps are pivotal flaps, and the greater the arc of pivotal movement, the greater will be the size of the standing cutaneous deformity and the less will be the effective length of the flap (see discussion in Chapter 8). The reduction in effective length must be accounted for in designing melolabial transposition flaps so that greater pivoting requires a longer design of the flap. To limit this restricting factor, whenever possible, melolabial transposition flaps should be designed to pivot no more than 90°.

Melolabial Advancement Flaps

Advancement flaps have a linear configuration and are moved by sliding toward the defect. This involves stretching the skin of the flap. Thus, advancement flaps work best in areas of greater skin elasticity and redundancy, like the melolabial fold. The most basic advancement flap is the simple linear layered closure, which involves undermining and direct side-to-side advancement of tissue to close the defect primarily. Sizeable (3 cm) skin defects of the medial cheek can be closed this way by advancing skin from the melolabial region in such a fashion that the resulting standing cutaneous deformities can be excised parallel to the melolabial crease. However, the term advancement flap usually refers to a flap created by incisions that allow a sliding movement of tissue. Tissue transfer is achieved by moving the flap on its pedicle in a single vector. The greatest wound closure tension is perpendicular to the distal border of the flap. Advancement flaps may be categorized as unipedicle, bipedicle, V-Y, Y-V, and island. Only unipedicle and island advancement flaps are discussed in this chapter because they are the most common melolabial advancement flaps used in facial reconstruction.

Melolabial Interpolated Subcutaneous Tissue Pedicle Flaps

Melolabial transposition flaps have frequently been used for reconstruction of the ala and nasal sidewall. They have the advantage of maintaining a lymphatic drainage route through the pedicle of the flap, which remains in continuity with cheek skin. They also avoid a circumferential scar, which in part accounts for trap-door deformity. Why not use a transposition flap instead of an interpolated flap for ala repair? Both flaps have the advantage of using skin with color, texture, sebaceous glandularity, and thickness similar to those of the natural skin of the ala. Both flaps leave an acceptable donor scar in the depth of the melolabial crease. The main reason for not using a melolabial transposition flap is that it deforms the alar-facial sulcus and lateral portion of the alar groove. A portion of the flap by necessity must pass through the superior aspect of the alar-facial sulcus, which represents an important topographic junction between the facial aesthetic regions of the nose, cheek, and upper lip. Whenever possible, local flaps should be designed so that they do not cross borders that separate aesthetic regions. This is especially true if the border has a concave topography, like that of the alar-facial sulcus.⁹ Too often, this sulcus has been violated by transposition flaps harvested from the cheek to reconstruct lower lateral nasal defects. The flap passes through the sulcus, obliterating the valley between the ala and cheek. When this happens, it is extremely difficult to restore the valley to a completely natural contour. For this reason, an interpolated melolabial flap is recommended for reconstruction of the ala. The pedicle of the flap does not extend through the alar-facial sulcus, it crosses over the sulcus. The pedicle may consist of skin and subcutaneous fat or subcutaneous fat only and is detached from the cheek 3 weeks after the initial transfer to the nose. Although 3 weeks is a lengthy period for the patient to endure the deformity caused by the attachment of the flap’s pedicle to the cheek, this interval enables the surgeon to thin and sculpt the subcutaneous tissues of the distal flap at the time of flap transfer and the proximal portion of the flap at the time of pedicle detachment and flap inset. On inset of the flap, the patient is left with a completely natural alar-facial sulcus because no incision or dissection has been performed in this region. Because of this advantage, I recommend the choice of an interpolated design when a pivotal cheek flap is planned for reconstruction of a defect of the ala and the defect does not extend laterally to the alar-facial sulcus (Fig. 12-4).¹⁰

The nasal-alar unit is highly contoured, has a free margin, and functions as the external nasal valve. In reconstructing the ala, consistent results require a cartilage subsurface framework to resist the forces of scar contraction, to provide a stable external valve, and to serve as a scaffold for contour. The framework in the form of a cartilage graft must be used at the time of the initial reconstructive procedure and requires vascularized tissue superficial and deep to the graft, totally enveloping the cartilage. Adequate function of the nose requires a thin internal layer most appropriately supplied by vascularized mucosa.¹¹ The external covering flap is provided by an interpolated cheek or forehead flap. Lining flaps and structural grafts for defects of the nose are discussed in detail in Chapter 18.

The porous and sebaceous nature of medial cheek skin closely resembles that of the caudal third of the nose, so an interpolated melolabial flap is generally the preferred covering flap for alar reconstruction. The flap is based superiorly on the rich vascular supply in the region of the alar-facial sulcus described by Herbert.¹² At this location, perforating branches from the angular artery penetrate the levator labii muscle. Other perforating vessels on both borders of the midportion of the zygomatic major muscle assist in supplying the cheek skin adjacent to the ala. The flap may be designed as a peninsular flap based superiorly on a cutaneous pedicle or as an island based on a subcutaneous tissue pedicle. In most circumstances, I prefer to design the flap as a crescent-shaped island of skin based on a subcutaneous tissue pedicle. The superior extent of the island remains 5 mm below the alar-facial sulcus, preserving this important aesthetic area.⁹

An exact template of the alar unit is made from the contralateral normal side with a malleable material such as foil or a thin sheet of foam rubber. The template is reversed to design the interpolated cheek flap. When the defect extends beyond the confines of the ala into another nasal aesthetic unit, the template is designed slightly smaller than the defect to accommodate the phenomenon of distraction of wound margins, which creates an open wound that is larger than the surface area of the skin removed. If excision of additional skin is indicated to resurface an adjacent nasal aesthetic unit, the template is fashioned before the remaining skin is removed because of this same phenomenon. Alternatively, the contralateral intact nasal aesthetic unit can be used to design the template.

When the ala is reconstructed with a melolabial flap, the entire ala is resurfaced with the cheek flap, except for 1 mm of alar skin just anterior to the alar-facial sulcus (see Fig. 12-4). This small skin tag preserves the alar-facial sulcus and often provides a better scar than when the flap extends to the sulcus. This approach is similar to the method recommended by Sheen and Sheen¹³ for performing a type II Weir excision to reduce the size of the nasal base. Maintaining the excision outside of the alar-facial sulcus lessens the risk for development of a depressed scar. This approach also avoids the technically challenging requirements of integrating the flap into the nasal sill at the time of flap inset. When using cheek flaps for repair, I often delay excision of the extreme lateral portions of the residual alar skin until the time of pedicle detachment and flap inset. This delay reduces the wound tension on the flap at the time of initial transfer.

The fashioned template is placed on the melolabial fold so that the center of the flap is positioned 1 cm above the horizontal plane of the oral commissure. The template is positioned so that the medial border of the designed flap lies in the melolabial crease. This arrangement ensures that the flap is harvested from the cheek, not the lip, and that the donor site wound closure will lie within the melolabial crease, providing maximum scar camouflage. The flap is designed to pivot 90° toward the midline in a clockwise direction when it is harvested from the left cheek and counterclockwise when it is harvested from the right cheek. Thus, the template is positioned to design the flap with a specific orientation. As the flap is pivoted and transferred to the recipient site, the medial border of the in situ flap is sutured to the cephalic border of the nasal defect. This in turn causes the inferior border of the in situ flap to join the anterior border of the defect. The lateral border of the in situ flap becomes the inferior border of the reconstructed ala (see Fig. 12-4).

A tracing is made around the template. A triangle of skin is marked superior and inferior to the tracing to fashion a crescent-shaped island of skin. The two triangles extending from the template tracing represent standing cutaneous deformities that will form when the cheek donor site is closed. The lower triangle of skin is excised and discarded at the time of flap transfer, and the upper triangle is transferred with the skin of the flap and is discarded at the time of pedicle detachment and inset of the flap. The superior triangle of skin is minimized to reduce loss of tissue from the upper melolabial fold where the fold is well developed. Removal of skin from the upper portion of the fold may result in considerable asymmetry of the medial cheeks.

The flap is incised, and the distal portion is elevated in the subcutaneous plane. The distal third of the flap is thin, leaving 1 to 2 mm of subcutaneous fat attached to the undersurface. As the dissection proceeds superiorly, the plane extends deeper to facilitate development of the subcutaneous tissue pedicle. The pedicle of fat is freed from the surrounding cheek fat by incising through the borders of the pedicle perpendicular to the surface of the skin. The depth of the incision is carried to the level of the superficial surface of the zygomatic major and levator labii muscles. On reaching the zygomatic major muscle, blunt dissection continues upward on the surface of the muscle, releasing the attachments of the pedicle to deeper structures until the flap can reach the recipient site without undue tension. To aid in reducing tension, it is sometimes helpful to place a 4-0 polypropylene suture between the superior skin edge of the donor incision and the alar base. This has the effect of pulling the pedicle upward toward the ala without the need to place additional traction on the subcutaneous tissue pedicle. The suture is released when the pedicle is divided at the time of flap inset.