FLAP DESIGN AND CONSIDERATIONS

Many variables must be considered when examining a surgical defect and considering reconstructive options. The effective restoration of soft tissue contours improves results by reducing the visual impact of the reconstructive scars. Closure options for soft tissue defects include primary closure (side-to-side repair), split- or full-thickness skin grafts, and local or distant skin flaps. For smaller and less complex defects in areas with adequate regional tissue laxity, primary closure may often be a suitable repair choice. To achieve good cosmetic results with primary closure, the surgeon must recognize the limitations of adjacent tissue reservoirs. The mobility of nearby facial structures and their tolerance for movement must be determined prior to initiating the surgical repair. Primary closure is principally used for smaller surgical defects of relatively low complexity. When the defect is too large to rely upon local tissue laxity to close the wound in a side-by-side fashion, a skin graft or flap may be considered. Both full- and split-thickness skin grafts may be used to repair cutaneous wounds in a wide variety of locations, and the uses of skin grafts are discussed elsewhere in this text. Although skin grafts, at times, may provide excellent final cosmetic results, they suffer from several limitations. To achieve excellence in cutaneous reconstruction, the surgeon must replace the missing tissue with tissue of identical or nearly identical character. When compared to the recipient site, the donor site’s skin should have a similar amount of sun damage, sebaceous glands, terminal hair, etc. Because skin grafts are usually harvested from sites not adjacent to the surgical defect, the harvested skin’s character is often dissimilar to that of the missing skin. Moreover, to ensure the survival of a full-thickness skin graft, all of the subcutaneous fat and portions of the dermis must be removed from the graft prior to its placement. The graft, therefore, may lack sufficient volume to adequately fill the surgical wound. For these reasons, flap repairs are best suited for many wounds on the face.

The flap repair of soft tissue defects is unsurpassed in its ability to provide functional preservation, contour restoration, and overall cosmetically appropriate reconstruction. A cutaneous flap is defined as a mobile attached unit of skin and soft tissue with its associated blood supply. Flaps are used extensively to repair a wide variety of soft tissue defects following skin cancer surgery in all anatomic locations. Flaps are widely used because they can often overcome many of the pitfalls seen with alternative repair options. Cutaneous flap surgery is safe¹⁰ and reproducible. Although cutaneous flaps may yield excellent results, flaps are not without the potential for some surgical risks and operative complications. It is important that the cutaneous surgeon have a firm knowledge of relevant anatomy, flap physiology, and flap design to maximize the opportunity for success. The nuances of proper surgical technique prove to significantly influence operative outcomes. Care must be extended to flap choice, flap design, incision and flap harvesting, and suture technique.

Cutaneous flaps are typically classified based upon one of two systems: either the type of principle movement (rotation, transposition, advancement, or interpolation) or blood supply (random or axial patterned).¹¹ Because the majority of flaps performed by dermatologists are random pattern cutaneous flaps, skin flaps are more commonly classified on the basis of movement. Random pattern flaps of varied design are supplied by the richly anastomotic dermal vasculature, and they lack the axial pattern flaps’ larger caliber, named vessels in their bases. When the flaps are properly designed and executed, the abundant vascular supply of the dermis affords random patterned flaps optimum chances for survival.

Advancement flaps are technically straightforward flaps that are important in cutaneous reconstruction. There are several modifications of the classical advancement flap that have expanded the flap’s utility. These include, among others, the O–T, A–T, Burow’s advancement, and island pedicle flaps (IPF). All of these flaps rely on the linear advancement of adjacent skin and soft tissue to allow surgical repair.

The subcutaneous island pedicle flap (also called a V–Y advancement flap) is a random pattern cutaneous flap that is a useful method of repairing small to medium-sized facial wounds.^12–28 The classical advancement flap recruits contiguous tissue to repair an adjacent defect by creating a flap elevated to its base after two parallel incisions are made (Figure 6.1). The traditional advancement flap, in this regard, is limited by the mechanics of the flap’s design. With the simple advancement flap, a length:width ratio of less than 3:1 must usually be followed to ensure the perfusion of the distal portion of the elevated flap. Advancement flaps designed with length:width ratios exceeding 3:1 or flaps inseted under significantly elevated wound closure tensions may be subject to inordinately high risks of distal ischemic necrosis. The IPF has surmounted this pitfall, which has, at times, limited the usefulness and success of the advancement flap. The IPF is designed so that a nutrient vascular pedicle closer to the flap’s leading edge is retained in order to provide an increased and more predictable vascular supply. The preserved central vascular pedicle significantly improves the perfusion of the flap’s anterior margin and eliminates the relative ischemia at the leading edge of the longer traditional advancement flap. Because it has an abundantly perfused central pedicle, the IPF can tolerate longer incisions and increased closure tensions than the classical advancement flap. The careful identification and preservation of a nutrient vascular pedicle in the IPF is therefore critical for the success of the flap. The classic design of the subcutaneous island pedicle flap is best used to repair defects of the upper cutaneous lip, anterior or mid-nasal ala, and brow (Figures 6.2–6.4).^{12,16,19,20,22,26} The flap may also be used to effectively repair defects of the nasal dorsum, cheek, forehead, or concha (the flip-flop flap).^24,25,27,28 Modifications including a buried island pedicle flap and transposition island flap may expand the utility of the flap and may be used to repair defects of the medial canthus, lateral ala, and other sites.

Figure 6.1 The classic advancement flap is created by two parallel incisions. The flap is then elevated and advanced to close the surgical defect.

Figure 6.2 (a, b) A small defect of the nasal ala repaired with an IPF. (c) The postoperative result with no additional revision procedures.

Figure 6.3 (a) The recruitment of cheek tissue to repair a defect of the cutaneous portion of the upper lip produces a loss of anatomic boundaries and suboptimal results. (b-d) In this separate patient, improved results are seen when the reconstruction has been restricted to the cosmetic unit with the use of an IPF.

Figure 6.4 IPF reconstruction of the eyebrow offers excellent postoperative results.

In the classic design of the IPF (Figure 6.5), the preserved nutrient vascular pedicle is directly underneath the central portion of the mobile flap. Variations of the IPF with the vascular pedicle relocated to a lateral margin, a de-epithelealized distal flap, and a flap with bi-level muscular pedicles have been previously described.^{12,15,21,24,29} However, in the author’s opinion, none of these modifications can surpass the predictably reproducible results seen with the classic design of the island pedicle flap with a central vascular pedicle.

Figure 6.5 Design of the traditional IPF.

TECHNIQUE

The proper design and execution of the island pedicle flap is obviously critical to achieving reproducible aesthetic results with minimal operative risk. Once a defect has been selected for repair with an island pedicle flap, operative consent is obtained from the patient. Routine prepping, draping, and infiltration with a local anesthetic then follow. The flap is designed as a V–Y tissue advancement. Although usually depicted as an isosceles triangle with straight edges, the flap’s long axes may be curved to place the resultant incision lines along the borders of the facial cosmetic units (for example, curvilinear incisions in the melolabial fold and along the vermilion border for an IPF used in upper lip reconstruction).

The island pedicle flap has a robust central vascular pedicle that consists of dermis, subcutaneous tissue, and underlying facial musculature. This pedicle nourishes the flap with a predictable vascular support rewarded to few other random pattern cutaneous flaps. Although categorically a random pattern cutaneous flap, the IPF has a blood supply more abundant and predictable than that of many other flap reconstructive options. This improved vascular support may be beneficial in patients with increased risks of tissue ischemia (smokers, patients with prior exposure to radiation therapy, etc). Moreover, the limited amount of required undermining and tissue mobilization associated with the proper use of the IPF may make this flap an excellent choice in patients taking anticoagulants or those with bleeding diatheses. When compared to a rotation or advancement flap used to repair similarly sized defects, the IPF typically requires less undermining, which may yield a lower risk of postoperative bleeding complications.^30,31

Following adequate tumor extirpation, the defect to be repaired with the island pedicle flap is thoroughly analyzed. The flap produces the best results when harvested from within the same cosmetic unit as the surgical wound. This, however, is not an absolute requisite for flap success. The flap is classically designed as an isosceles triangle adjacent to the primary defect (Figure 6.5). The length of the triangle is typically 3–4 times the width of the surgical defect. The apex of the triangle’s long sides is an angle of approximately 30°. After the flap is designed, the circular surgical defect is converted to a square and the beveled dermis is removed if the wound has resulted from a Mohs extirpation.³² It is the opinion of the author that a squared-off island flap inserted into a squared-off surgical defect has less of a chance of elevation (trapdooring) and resultant failure of contour restoration than a rounded flap placed into a rounded defect (Figure 6.6). The phenomenon of trapdooring is poorly understood. As a flap contracts in the postoperative period, circumferential movement of incipient scar tissue may force the flap to become elevated above the surrounding skin. Although, this elevation may prove aesthetically displeasing, it can usually be corrected with massage, intralesional corticosteroids, and simple observation, thereby avoiding the need for additional operative procedures. Despite previously published recommendations to oversize the flap, the best surgical results are obtained when the flap is slightly undersized.^32,33 For that reason, the width of the properly designed IPF is slightly smaller than the width of the primary surgical defect. Although this minimal undersizing requires some degree of secondary tissue movement from around the borders of the primary surgical defect, this undersizing reduces the risk of postoperative flap protuberance. Oversizing or equivalent sizing the island flap to the defect simply stuffs too much flap into the surgical defect, and the flap, when cicatricial forces begin to contract, decompresses anteriorly, producing an unsightly, redundant flap that will detract from the typical aesthetic success seen with the IPF.

Figure 6.6 (a) A surgical defect following Mohs surgery. (b) The IPF is designed to repair the skin and soft tissue defect. (c) The surgical wound is converted from a circle to a square. (c) The IPF is incised. (d) The flap is elevated and undermined to leave a central nutrient vascular pedicle. (e) The flap is advanced to fill the surgical defect, and the key suture is placed. (f) The flap sutured into place. Note the preservation of the melolabial fold, as this portion of the flap was not undermined.

After the flap has been designed with attention to anatomic boundaries and flap geometry, the flap is sharply incised. The margins of the flap’s donor area are then undermined to facilitate flap advancement and donor site closure. It is important to recognize the degree of secondary tissue movement that will be required in all cases in order to avoid unwanted anatomic distortion. The primary defect’s peripheral margins are also undermined at an identical depth. Undermining the island pedicle flap itself presents the most risky portion of the reconstruction. If inadequate undermining is done, the flap will prove difficult to mobilize and thus may require excessive tensions for closure. These inappropriately elevated tensions increase the risk of flap ischemia and produce associated anatomic distortion. Conversely, if the flap is undermined without careful attention to the preservation of the central vascular pedicle, insufficient vascular supply may fail to nourish the nascent flap. Although facial flaps may have a greater and more predictable vascularity than similarly designed flaps in other locations, the facial island pedicle flap must still be executed with careful attention to surgical detail. A central pedicle of 40–50% of the flap’s area is typically adequate to ensure the flap’s survival. A significant restriction to the linear advancement of the flap may originate at the narrow apex (tail) of the flap. The apex of the flap may be incised and elevated to increase the forward sliding motion of the flap. This undermining and elevation of the flap’s tail greatly improve the flap’s mobility, but they should be limited to the exact extent necessary to advance the flap. Increasing the extent of undermining reduces the size of the nutrient vascular pedicle and therefore increases the risk of ischemic flap necrosis. The advancing margin of the flap is also undermined several millimeters, principally to assist with accurate wound edge reapproximation. This small amount of undermining also significantly improves flap movement, particularly when the tail of the flap has also been liberated from its underlying attachments.

After undermining of the recipient site, donor site, and the anterior and posterior margins of the flap, the flap and surrounding skin are elevated and hemostasis is achieved. After achieving adequate hemostasis, the flap is advanced in a V–Y manner to fill the surgical defect. The initial suture (the key stitch) is placed at the midpoint of the flap’s anterior margin to a corresponding point along the opposite margin of the primary surgical defect. This suture is placed with particular care to ensure that the flap is carefully aligned to minimize the risk of subsequent anatomic distortion. Suture technique is critical to achieve operative success. To compensate for the inevitable wound contraction seen in the postoperative period, the flap must be sutured into place with care. Buried vertical mattress sutures of absorbable material are placed in the mid-dermis. If placed correctly, each successively placed buried suture will lower the central portion of the slightly undersized island pedicle flap. At the completion of the buried suture placement, the center of the flap should be depressed 2–3 mm below the surrounding skin. This slight flap recession is important to provide a well-contoured flap after wound healing has been completed, as the flap will inevitably rise to a small extent as wound contraction occurs at the flap’s bed in the early postoperative period.³³ The author has never observed a recessed flap that failed to eventually elevate to a proper position.

After the flap has been secured with properly placed buried sutures, the epidermis is then reapproximated with a running cuticular suture. Drains are infrequently used, even with larger flap procedures. Tip stitches at the apex of the flap are not typically required. The wound is bandaged and wound care instructions are provided to the patient. Oral antibiotics may be prescribed as needed. The sutures are removed at an appropriate postoperative interval, typically at 5–7 days for facial flaps. The IPF repair infrequently needs any postoperative refinement such as scar revision, debulking, or dermabrasion.

The classically designed island pedicle flap is a hearty flap that may be used to repair a wide variety of facial defects with elegance and minimal procedural morbidity. The flap repairs wounds with skin of excellent color and textural match. The advancement island pedicle flap should be viewed as an ideal reconstructive choice for soft tissue defects of the cutaneous lip, eyebrow, and medial cheek. Although previous authors have championed the flap as a viable reconstruction choice for distal nasal defects, the flap may prove problematic on the lower nose if the mobility of the nasal skin is limited or misjudged.¹⁵ In such a case, prominent nasal distortion may result after inadequate flap advancement because a reliance on secondary tissue movement to close the primary surgical defect is required. For small to medium-sized distal nasal wounds, alternative reconstructive choices (the bilobed and other flaps) may prove to be superior selections.

MODIFICATIONS

When preoperative assessment predicates that a central pedicle may limit the flap’s movement, lateral pedicles may be used to increase flap movement and maintain adequate flap perfusion. This design modification may prove to be important in certain anatomic areas (the temple, for example). Alternative modifications may also increase the usefulness of the IPF. The advancing margin of the island pedicle flap may be de-epithelealized and buried in yet another variation of the flap.²⁴ This removal of the distal flap’s epidermis may provide a soft tissue platform upon which to reconstruct a nasal sill or medial canthus.

Modifications of the island pedicle flap’s design may improve the versatility of the flap and allow the island flap to be used with larger facial wounds and in less traditional locations such as the upper nose and lateral ala. With large facial and non-facial wounds, dual island pedicle flaps may be useful. These double island flaps may be of equal or unequal sizes. The dual flaps are designed, elevated, and mobilized with the identical techniques previously described for the single island pedicle flap.

A significant variation of the island pedicle flap is the previously described transposition island pedicle flap.²¹ With this flap design, the flap is modified to recruit tissue from a donor site near to, but not contiguous with, the primary defect. This modification of the IPF’s design may prove to be an ideal solution to the reconstruction of lateral nasal ala or upper nasal dorsum wounds. In both areas, the design of the transposition island flap is similar. The wound’s template is transferred to a nearby reservoir of matching skin (usually located at a distance of 1–1.5 times the diameter of the surgical defect from the wound) (Figure 6.7). The template is then placed over the donor site, and it is confirmed that adequate tissue laxity exists to allow interpolation of the flap. The design of the flap can be conceptually compared to the design of the melolabial interpolation or paramedian forehead flap. However, the epidermis from the proximal portion of the flap (from the flap’s origin to the superior margin of the placed template) is removed with particular attention to ensure that the subcutaneous tissue with its vascular supply is preserved.³⁴ The standing cutaneous deformity distal to the template is then removed. The island flap is then elevated with care to protect the deep, proximal vascular pedicle. The flap is then transposed and inset into the primary surgical defect. The proximal portion of the pedicle, lacking an overlying epidermis, is buried and covered with the repair. The donor site of the flap is then repaired. This one-stage repair of defects that have been traditionally repaired with two-stage flaps may prove useful in certain clinical circumstances such as a patient who is a poor candidate for staged reconstructive efforts or who lives a long distance from the treating physician. However, because the burying of this flap’s pedicle can occasionally cause a significant elevation/deformity near the flap’s pivot point near the medial cheek, this modification of the island pedicle flap is unlikely to entirely replace the more classically designed interpolation flaps that retain a vascular pedicle that is removed in a second surgical procedure performed several weeks after the initial creation of the flap. This fullness near the flap’s pivot point typically subsides with time and with the use of intralesional corticosteroids, but the shadowing and elevation of the medial cheek near the flap’s donor site may prove persistently troubling to the aesthetically demanding patient. Some authors advocate removing subcutaneous tissue and creating a tunnel to lay the pedicle in to reduce the bulking effect.

Figure 6.7 A moderately sized defect of the medial canthus. An IPF with a de-epithelealized proximal pedicle is harvested from the forehead. The flap is then tunneled through the intact skin of the glabella in order to repair the defect.

The de-epithelealizing of the proximal pedicle of this transposition-type IPF may introduce a significant operative risk of necrosis to the distal portion of the flap. Additionally, an unintentionally incomplete resection of all the pedicle’s epidermis may result in the postoperative development of an epidermal inclusion cyst at the flap’s donor site. Though a novel modification of the IPF, the transposition variant of the flap has significant limitations that may limit its usefulness.

Auricular defects may also represent significant operative challenges. The three-dimensional complexity of the ear and its aesthetic prominence may obviate simpler repair options such as primary closure. Although second intention healing and skin grafting may afford good postoperative results, larger and more significant surgical wounds may require flap closures to achieve aesthetic and functional success. The island pedicle flap has been previously described to serve as a reconstructive method for conchal or scaphoid fossa defects (Figure 6.8).^27,28 An appropriate donor site overlying the mastoid is selected. A template of the wound is transferred to this mastoid skin, and an island pedicle flap is incised and elevated as previously described. The flap, with its preserved vascular pedicle, is then passed through a full-thickness defect in the ear. The flap is then inserted into the wound located on the anterior aspect of the ear (the flip-flop flap). The inclusion of musculature in the flap’s base significantly improves the flap’s vascularity. The flap’s donor site may be allowed to granulate or may be repaired with a full-thickness skin graft. Like more traditional island pedicle flaps, this one-stage repair offers excellent postoperative results when used for appropriate surgical defects.

Figure 6.8 An IPF from the skin overlying the mastoid process is elevated and mobilized. The flap is then advanced through a full-thickness defect in the ear to repair a moderately sized operative defect of the anterior ear (the “pull through” or “flip-flop” flap).

In summary, the random pattern island pedicle flap is a robust and versatile cutaneous flap for regional reconstruction. The well-preserved vascular pedicle provides durability and predictability to the flap. The classically designed advancement island pedicle flap with a central pedicle provides unsurpassed results for reconstructing variably sized defects of the upper cutaneous lip, brow, and medial cheek. Modifications of the island pedicle flap’s design may expand the flap’s ability to repair defects of the nose, ear, and other locations.

The island pedicle flap’s carefully identified and dissected vascular supply makes flap necrosis unlikely. The flap is a bulky flap that may be subject to pin-cushioning. If the flap is designed and executed with care, this is a very uncommon problem. If the skin’s mobility near the flap’s origination or insertion points is misjudged, excessive secondary tissue movement may result in anatomic distortion and aesthetically inferior results. Even with its limited shortcomings, the island pedicle flap should occupy a significant place in the reconstructive surgeon’s armamentarium.

COMPLICATIONS

The classic IPF design preserves a central pedicle that allows predictable nutritional support to the flap. However, this central pedicle may not only limit forward movement but may also increase the bulkiness of the flap. Others have described the relocation of the flap’s pedicle from a central location to a bipedicled lateral vascular supply. In this technique, the central portion of the flap is elevated to improve movement with the two lateral pedicles supplying the perfusion to the nascent flap.

Although an excellent choice for repairing medial cheek defects, the IPF may at times prove problematic. Figure 6.9a shows a moderately sized defect of the medial cheek. Reconstructive choices include repair with one local flap, repair of the individual cosmetic units, secondary intention healing, and skin grafting. In this circumstance, reconstruction of the wound with a local flap will likely yield the best functional and aesthetic results. In this case, an inferior IPF with a central pedicle was incised and advanced to fill the defect with no distortion of the nearby mobile ala, eyelid, or lip (Figure 6.9b). The postoperative result with no additional procedures is seen in Figure 6.9c. The flap has provided effective functional reconstruction but has failed to meet the physician’s and the patient’s cosmetic expectations. The lack of exact contour restoration has limited the success of the flap. The flap’s imperfect initial design was the principal error. Because of the IPF’s inherent bulkiness, the flap must be slightly undersized to compensate for the postoperative flap elevation that inevitably accompanies wound contraction. In this case, the flap was not adequately undersized, and too much flap was “stuffed” into the surgical defect. This has resulted in persistent flap elevation. An improved result would have been obtained by undersizing the flap enough to avoid excessive tissue advanced into the primary surgical wound. Importantly, excessive undersizing of the flap must also be avoided, as too small a flap will rely on secondary tissue movement to close the primary defect. This movement will result in excessive risk of anatomic distortion. A bilateral pedicled flap with the central flap elevated may have increased the effective movement of the flap, leading to lower closure tensions and improved results. In this example, the best result would have likely been achieved with the repair of the individual cosmetic units (a flap to repair the cheek defect and a full-thickness graft to repair the nasal defect). The use of a single flap to fill a defect bridging two cosmetic units should be avoided, if possible. In this case, the oversized flap has elevated with postoperative wound contraction, and the flap has not only provided poor contour restoration but has also softened the distinction of the anatomic border separating the nose and cheek.

Figure 6.9 (a) A moderately sized defect of the medial cheek. (b) An inferior IPF with a central pedicle was incised and advanced to fill the defect with no distortion of the nearby mobile ala, eyelid, or lip. (c) The postoperative result with no additional procedures.