Design

The classic rhombic flap was first described by Limberg in 1963¹ and was designed to create a secondary defect perpendicular to the primary defect that, when closed, would not only provide tissue to close the primary defect, but would also redirect the tension vector 90°.² This traditional flap design allows the primary defect to be closed under almost no wound tension.³ Subsequent design modifications by DuFourmental and Webster enabled more tension sharing between the primary and secondary defects because the angles and sizes of the flaps’ primary lobes were reduced.⁴

In planning a classic Limberg rhombic flap, the surgeon converts the primary defect into a four-sided parallelogram with each side of equal length and tip angles equal to 60° and 120°.⁵ This basic shape, the rhombus, forms the recipient site for the flap as well as the template upon which the required incisions are planned. In this classic design (Figure 7.1), the flap’s incision lines are drawn by extending a line (line AB) outward from one of the obtuse tips for a length equal to that of one side of the rhombus. From the free end of the extending line (line AB), a second line (line BC) is drawn parallel to and equal in length to one of the near sides of the rhombus. The tip angle of the flap’s primary lobe in this configuration is 60°. The incised flap is then lifted and transposed into place. The vector of maximal wound closure tension is thus redirected from that of closing the primary defect to that of closing the new secondary defect created in the execution of the flap. This allows for an effective 90° redirection of the tension vector.

Figure 7.1 The classic rhombic flap.

Though the classic rhombic transposition flap can be designed and executed off of the long axis of the rhombus, there are two advantages to designing it off of the short axis of the defect.⁶ First, this design keeps the flap as small as possible while filling the primary defect completely. Second, the design also minimizes the arc through which the flap must rotate to reach the defect.^7,8 There are four possible flap designs off of the short axis for any rhombic defect (Figure 7.2). Which of these four flap configurations is chosen by the surgeon depends on several factors that affect the final outcome. These factors include the adjacent anatomic structures, the adjacent skin type, and where the resulting scar line will be best hidden.

Figure 7.2 Four possible configurations of rhombic flaps drawn off of the short axis of the rhombus-shaped defect.

Extrapolation of Rhombic Flap Principles to Round Defects

Most defects encountered in dermatologic surgery are not rhombic in shape. Rather, defects resulting from extirpation of tumors are generally round because of the radial growth patterns of most tumors. The principles described for repair of rhombic defects may also be used to reconstruct circular defects. In fact, applying these principles to a round defect affords even greater flexibility in transposition flap design and orientation.⁸ A rhombic design can be drawn around the round defect in a favorable orientation, keeping in mind the optimal flexibility of the surrounding tissue and adjacent anatomic structures (Figure 7.3). The optimal placement of the flap’s closure lines can also be planned according to the adjacent relaxed skin tension or cosmetic unit junction lines. Since the majority of the wound closure tension is placed on the closure of the secondary defect, the secondary defect’s closure is usually designed to be aligned with the relaxed skin tension lines.

Figure 7.3 Options for optimal placement of rhombic flaps.

When designing the flap from a circular defect, the length of the line extending from the defect should be designed longer than the diameter of the circular wound because this diameter is actually shorter than the short axis of the rhombus that could be drawn around the circular defect (Figure 7.1). After the initial line is drawn extending from the circular wound, a second line of the same length is drawn to meet this initial line, keeping a tip angle of 60° or less to complete the flap. The tissue redundancy at the base of the primary defect created by the rotation of the transposition flap is removed with trimming of a triangle in the area of the flap’s pivot point. The tip of the transposed tissue may be rounded to fit the circular defect, or the defect may be squared off to accommodate the angular flap. This choice can be made based upon which option is likely to yield the optimal aesthetic result.

A thorough understanding of the forces of wound closure tension is essential to the planning, execution, and outcome of any closure. The primary tension component of a classic rhombic flap occurs with the closure of the secondary defect. A second set of tension forces is generated at the tip of the flap when it is moved into the primary defect. These forces are due to resistance to movement at the flap pedicle as well as effective shortening of the length of the flap during the rotation into the recipient site. Dzubow has described these forces as pivotal restraint.⁹ Securing the flap tip to the far end of the recipient site under inappropriately high tension can lead to tip ischemia and necrosis. There are two modifications of flap design that can be used in certain situations to minimize the shortening of the flap and reduce or eliminate the potential tension at the flap tip.

When the leading edge and the secondary limb of the flap’s primary lobe are extended/lengthened, the flap is slightly enlarged (Figure 7.4). This lengthening can compensate for the inevitable shortening that results from pivotal restraint at the flap’s base. Lengthening the flap by this method will help to ensure that flap rests in the primary defect without undue tension at its tip.

Figure 7.4 Lengthening the flap is one option for planning a closure with minimal tip tension.

An alternate method to lengthen the flap and minimize tip tension at closure is to design the flap with a slightly more obtuse angle (greater than 120°) at the flap’s origination point (Figure 7.5). This design decreases the degree of rotation necessary during flap execution and subsequently reduces pivotal restraint. Wide undermining around the flap also assists in the redistribution of tension vectors and contractile forces during the healing phase.

Figure 7.5 Increasing the angle of the flap also acts to minimize tension and lengthen the flap.

Modified Rhombic Flaps

DuFourmental Flap

This modification of the classic rhombic transposition flap narrows the angle of the tip of the secondary defect and creates a shorter arc of rotation for the flap. This allows easier closure of the secondary defect and some sharing of the tension between the primary and secondary defects. As in the classic rhombic flap, the DuFourmental variant of the rhombic flap is designed by extending the first line from the short axis of the rhombic defect (Figure 7.6). However, the angle at which the first line is extended from the rhombus differs from the classic rhombic flap in that it bisects the angle formed by the first line of the classic rhombic flap (which extends straight from the short axis of the rhomboid defect) and the line formed by extending one of the sides of the rhomboid from the same corner. The length of the first line is equal to that of a side length of the rhomboid. The second line originates from the free end of the first line, and is drawn parallel to the long axis of the rhomboid. This second line’s orientation results in a slightly widened pedicle base, a decrease in the tip volume of the flap, a decrease in the amount of movement necessary to execute the flap, and the introduction of some degree of tissue advancement along the long axis of the rhomboid defect. In most cases, a tissue redundancy at the base of the leading edge of the flap is generated; this should be removed by excising a slightly larger “dog-ear” at the base of the flap.

Figure 7.6 The DuFourmental flap. Note the narrowed tip angle and more obtuse leading edge angle compared to the classic rhombic flap.

The oblique orientation of the leading edge of the DuFourmental flap relieves some of the pivotal restraint at the flap’s base, resulting in additional lateral tip tension instead of vertical tip tension seen with the classic rhombic flap design. This allows use of the DuFourmental flap in situations where lateral tension is more acceptable than vertical tension.

Webster 30° Angle Flap

The Webster modification of the rhombic transposition flap makes the angle of the flap even more acute than the DuFourmental variant and allows for even greater tension sharing between the primary and secondary defects.¹⁰ A Webster 30° angle flap is planned similarly to the DuFourmental flap, with the exception that the distal tip of the flap is designed to have an angle of 30° (Figure 7.7). This more acute angle produces a slimmer design and narrower pedicle. The Webster design of the rhombic flap also frequently incorporates a m-plasty in the closure of the Burow’s triangle excision at the flap’s base. The flap width is approximately 50% of that of the defect, thus the flap only relieves about half of the tension from the primary defect. Closure of the flap is therefore partially dependent upon secondary motion at the site of the surgical defect. This design modification is used in situations where some laxity exists in the horizontal axis of the rhombic-shaped defect. Given that more tension is placed on the primary defect with this design, care must be taken not to distort adjacent anatomic structures.

Figure 7.7 The Webster modification to the rhombic flap.

Double 30° Angle Flap

Another variation of the rhombic transposition flap uses two flaps to borrow laxity from either side of a defect. Essentially resembling a series of Z-plasties, the double 30° angle flap is planned by drawing two 30° angle flaps, one from each short axis of the rhombus and in opposite directions (Figure 7.8).

Figure 7.8 Note the two flaps designed to fill the single defect, thus effectively sharing the tension.

Rhombic Flap Execution: Flap Mobilization and Key Sutures

As with all reconstructive procedures, transposition flaps should be designed while patients are in upright (or near upright) positions. This places the forces of gravity on the face in the typical resting position, allowing more appropriate flap planning. In addition, the defect and the designed flap should not be overly distorted with too much local anesthetic. The tissue surrounding the defect is then manipulated with a probing hand, and a determination of the local tissue laxity and the adjacent anatomic structure mobility is made. The most appropriate flap is drawn out on the skin with a sterile surgical marker. Even the most experienced surgeons typically mark their lines of incision prior to reconstruction. The old carpentry adage holds true in reconstructive surgery: “measure twice, cut once.”

After designing the flap, anesthetizing the area, and prepping and draping, skin incisions oriented directly perpendicular to the surface of the skin are made along the flaps proposed lines to the depth of the subcutaneous tissue. It is very important to make certain that all skin edges are squared off prior to closure. Leaving beveled tissue at the corners or edges places unnecessary force on the tissue edges during closure and prevents proper wound edge eversion. In most cases, it is preferable to remove the redundant Burow’s triangle at the pivot point of the flap prior to insetting the flap. Although there are certain cases where the exact position of the redundant triangle is not as important, this triangle is usually designed to lie in a predetermined location to optimize the final aesthetic result.

The flap is raised at the desired plane with sharp dissection. The plane of dissection is based upon both the anatomic location and the depth of the primary defect. The defect, flap, and undermined tissue should all be of the same relative thickness. The proper undermining plane may vary from the superficial subcutaneous fat to just above the periosteum, depending on wound size and anatomic location. The entire area surrounding the flap and the primary defect is undermined widely to fully mobilize the borrowed tissue and to dissipate contractile forces over a wider area during the healing phase. Failing to insufficiently undermine concentrates the forces of contracture during wound healing on the scar itself, and this may result in depressed wound edges and/or pin-cushioning of the flap.

After undermining, the entire defect, the adjacent undermined zone, and the underside of the flap should be visually inspected for hemorrhage. This may be facilitated with the use of a skin hook, which assists in reflecting the flap and free edges without introducing unnecessary trauma to the epidermis. To better visualize bleeding at the recesses of the undermined tissue, the surgeon should push the skin beyond the wound’s edge back towards the defect with the fourth finger of the hand holding the skin hook. It is obviously important to get sufficient and precise hemostasis. Postoperative bleeding and hematoma formation can often result in an unfavorable aesthetic result. Similarly, excessive use of tissue cautery, especially at the wound edges, may necrose tissue and produce widened scars. A fine Bishop-Harmon forceps may be used to grasp any visualized bleeding vessel and serve as an appropriate conductor for a very short burst of electrocautery current. This maneuver helps minimize necrosis of the surrounding area by eliminating widespread, indiscriminate use of electrocautery. Charred tissue needlessly increases healing time and may serve as a nidus for infection.

After hemostasis has been achieved, the flap is lifted and transposed over the intervening skin into the primary defect. At this point, the secondary defect can be closed by approximating the dermal edges with a tension-bearing stitch. This stitch is executed by placing a buried vertical mattress suture using a slowly dissolving suture material such as Vicryl®. Proper suturing technique cannot be stressed enough. Undyed suture material is usually selected to minimize visibility in the event that the suture is placed too superficially or is brought to the surface during the healing phase as a “spitting suture.”

Obtaining good wound eversion and wound edge approximation is absolutely critical in achieving aesthetic results. Without these, closures have little chance of being relatively imperceptible after healing has been completed. The optimal time to obtain proper wound eversion is during the placement of the subcutaneous sutures. A properly placed buried vertical mattress suture is one of the skilled reconstructive surgeon’s best tools. It everts the closure line and takes the pressure off the healing wound edge, placing it in the dermis slightly distant to the edge. This allows the wound to heal under little tension and leaves the thinnest possible scar line. Once the wound has been everted and closed under minimal tension, cutaneous sutures are meticulously placed to keep the wound edges fully approximated during the initial healing phase. These cutaneous sutures may be fast-absorbing or nonabsorbable materials. If nonabsorbable suture material is used, the sutures, when used in areas of the head and neck, should be examined and removed at five to seven days following the procedure.

Applications of the Rhombic Flap

Rhombic transposition flaps are very versatile and may be used to reconstruct a variety of defects. Transposition flaps are generally used when there is insufficient laxity in the immediate surrounding area of closure or when the tension vectors need to be redirected.¹¹ This is particularly important when repairing defects near free margins such as the eyelids and nose. The most common areas where rhombic flaps are employed include the nasal dorsum and sidewalls, the medial and lateral canthi, the lateral forehead, temple, cheek, the perioral region, the inferior chin, and the dorsal hand (Figure 7.9).

Figure 7.9 Common locations, noted with shading, for the use of rhombic flaps.

The following is a brief review of the rationale for choosing a rhombic flap in the locations.

Dorsum of the nose and the nasal sidewall (Figure 7.10)

The use of surrounding skin in transposition flaps helps maintain optimal color and texture match when repairing defects of the nasal dorsum or sidewall. Transposition flaps are more spatially confined than most other closures. On the dorsal nose, they may be used to keep the closure within a single cosmetic unit. In this area, the free margins of the lower eyelid and nasal ala are particularly susceptible to distortion from adjacent forces. Keeping this in mind during the planning of repairs in these areas is essential. Tension vectors should be directed away from the free margins of these structures, as distortion can lead to functional and aesthetic compromise. The mobility of the nasal tip should also be considered when repairing nasal defects. Occasionally, a favorable effect on the nasal tip can be achieved by correcting age-associated nasal tip ptosis during the repair of nasal defects. This is done by planning a repair where some of the tension produced by the repair is in a vertical orientation. In order to be aesthetically successful, the elevation of the nasal tip must be strictly vertical, which is often difficult to achieve if a rhombic flap is used off the nasal midline. Too much tip elevation and any lateral deviation are obviously cosmetically undesirable.

Figure 7.10 Use of a rhombic flap on a circular defect with an excellent result. (a) Intraoperative markings around the defect. (b) At the time of closure. (c, d) Appearance 3 months after closure.

Medial and Lateral Canthi (Figure 7.11)

The medial and lateral canthi are located near the highly mobile free margins of the eyelids. Care must be taken to redirect tension vectors to ensure that distortion of these structures does not occur after closure of the defect. Patients with lid margin laxity are particularly prone to distortion, which can lead to functional impairment of the eyelid. In addition, because some wound contraction inevitably occurs along the long axis of any wound, closures should be designed to minimize lines going across the concave contours of the inner canthus. The prominent lines of the crow’s feet of the lateral canthi offer an excellent hiding places for the acute angles generated by transposition flaps.

Figure 7.11 An example of the use of the rhombic flap in the canthal area. (a) Intraoperative markings around the defect. (b) At the time of closure. (c) Appearance 3 months after closure.

Cheeks (Figure 7.12)

Although most small and medium-sized defects on the cheeks may be closed primarily, transposition flaps can be used on larger defects or can even be used on smaller defects to leave geometric broken line scars instead of long linear scars. Transposition flaps are generally designed laterally, with the redundant tissue inferior to the primary defect. Positioning the scar laterally tends to make the scar less visible to the patient and observers. An inferiorly based flap provides better lymphatic drainage and may minimize the risk of flap engorgement and subsequent pin-cushioning.

Figure 7.12 Repairing a cheek defect with a transposition flap. (a) Intraoperative markings around the defect. (b) At the time of closure. (c) Appearance 3 months after closure.

Perioral (Figure 7.13)

Transposition flaps may also be a good option for repairing some perioral defects. The adjacent skin folds as well as wrinkles in various orientations provide camouflage for the geometric scars of transposition flaps. The medial cheek often provides a good reservoir of lax skin. Care must be taken to properly orient the flap to ensure that the closure of the secondary defect does not result in any tension that may distort the lip.

Figure 7.13 Repair of a perioral defect using a transposition flap. (a) Intraoperative markings around the defect. (b) At the time of closure. (c, d) Appearance 3 months after closure.

Chin (Figure 7.14)

When repairing defects of the lateral and inferior chin, one may take advantage of the laxity of the medial cheek and submandibular area as well as the many natural lines in this area to hide the resulting scar. Care should be taken to minimize lines across the convex contour where the chin and neck meet, as scars in such situations tend to be quite visible and prone to hypertrophy.

Figure 7.14 Repair of a chin defect with a transposition flap. (a) Intraoperative markings around the defect. (b) At the time of closure. (c, d) Appearance 3 months after closure.

Banner Type Flaps

Banner type flaps are random pattern, finger-shaped flaps that, like other transposition flaps, tap into adjacent skin to borrow laxity and cover a defect. Banner transposition flaps produce longer, linear secondary scars typically placed at the junction of two cosmetic units, allowing the surgeon to optimally camouflage a long scar.¹²

The fundamental design of the banner flap consists of a finger-shaped flap drawn with a width equal to the width of the defect and a length equal to the distance from the pivot point to the far edge of the defect (Figure 7.15). The flap is transposed and rotated in an arc around the pivot point to fill the defect. Because the banner flap is a long random pattern flap with a narrow pedicle, the risk of vascular compromise may be high if the flap is too long or if it is harvested from an area of minimal vascularity. Unless the flap is based on a particular larger caliber artery, the flap is typically designed to rotate through an angle of 60°–120° instead of the originally described 180°. In either scenario, a tissue redundancy (dog-ear) is generated by the rotational motion of the flap. When removing this redundancy, the excision should be designed in a direction away from the pedicle of the flap in order to avoid narrowing the pedicle of the flap even further. This will minimize the risk of compromising the blood flow to the flap and maximize its viability.

Figure 7.15 Examples of banner flaps. Note the greater redundancy at the pivot point of the flap with the larger angle.

Banner Transposition Flap Mobilization and Application

Typical locations for use of the banner flap include the nasal ala, the superior helix of the ear, and the medial anterior ear. At the nasal ala and inferior lateral side wall, a classic nasolabial transposition flap, a variant of a banner flap, can be designed, with the resulting scar hidden within the nasolabial fold (Figure 7.16). Although this flap has been maligned for blunting the nasofacial groove, when used properly in the appropriate patient, it offers an excellent reconstructive option for some nasal defects. The flap should be designed so the closure of the secondary defect is hidden in the nasolabial fold but does not come too close to the inferior lateral ala, where blunting of the isthmus (the triangle of flat skin where the upper lip, ala, and nasolabial fold meet) could occur. The redundant Burow’s triangle superior to the primary defect should be designed to leave the resultant scar on the lateral nasal sidewall. When the flap is raised, the cheek donor site should be widely undermined. Care should be taken not to harvest more adipose tissue than necessary. If too much adipose is taken while harvesting the flap, the nasolabial fold can be flattened, resulting in cheek asymmetry. When the flap is transposed into place, it should be anchored to the nasal sidewall with a periosteal suture. This will help reduce tension on the flap. In addition, a tacking suture from the underside of the flap to the area where the alar crease is located on the recipient bed helps recreate the alar groove. The flap is then appropriately trimmed and thinned to match the defect. If this is done prior to the tacking sutures, it is easy to trim too much off the end, not taking into account the extra length required to recreate the alar crease. Conversely, not trimming and thinning the flap enough may lead to pin-cushioning.

Figure 7.16 An example of a banner type flap harvested from the nasolabial fold to repair a defect of the nasal ala. (a) Intraoperative markings around the defect. (b) At the time of closure. (c-e) Appearance 3 months after closure.

To repair defects of the superior helix, a banner flap can be taken from behind the superior aspect of the ear. The secondary defect is closed along the postauricular sulcus and the flap is transposed into place along the helix. As with any repair of the helix, it is important to remember the convex nature of the area and to allot enough tissue to recreate this. A simple flat measurement across the defect will not give the true volume of tissue required for reconstruction. By using a slightly wider (but not thicker) flap, the forces of contraction during healing will usually elevate the flap slightly in the middle and recreate the convex nature of the helix. Attaining proper wound edge eversion with well-placed buried subcutaneous mattress sutures is critical at the distal aspect of the flap where it joins the helix. If this edge is not everted properly, it will usually contract and appear as a noticeable notch on the helix.

A banner flap may also be employed to correct defects of the medial anterior ear, such as the concha, tragus, or crus of the helix (Figure 7.17). Tissue is harvested from the preauricular area and transposed into the defect. This donor area typically provides ample tissue laxity. Since it is a cosmetic unit junction area (like the melolabial fold and postauricular sulcus), the preauricular area offers an excellent location for placing a minimally visible linear or curvilinear scar.

Figure 7.17 Repair of a conchal bowl ear lesion with a banner type transposition flap.

The Bilobed Flap

The bilobed flap commonly used today is a highly evolved transposition flap. Its design actually consists of two transposition flaps, used in succession, which follow the same direction of rotation over intervening tissues.^13,14 The flap allows the surgeon to extend the reach of the transposition flap and borrow laxity from donor sites at a greater distance from the defect. The second lobe also decreases the degree of the arc through which the pedicle moves to borrow from the distal site.

The bilobed flap was first described for use in nasal reconstruction by Esser in 1918,¹⁵ where he designed a flap with each lobe traveling 90°, resulting in a significant dog-ear at the proximal advancing border of the primary lobe. When this type of closure is attempted in the highly sebaceous, thick zones of the lower nose, distortion of the alar rim is inevitable. The bilobed flap became a workhorse flap in nasal reconstruction after Zitelli published several design modifications to it in 1989.¹⁶ His modifications corrected the original flap’s two major drawbacks, large angles of flap transposition and the production of a dog-ear deformity that typically needs a revision procedure. This produced an excellent reconstructive option for the very unforgiving, sebaceous terrain of the lower nose. Zitelli’s modifications are illustrated in Figure 7.18.

Figure 7.18 The evolution of the Bilobed flap. (a) Original bilobed flaps. (b) Bilobed flap using Zitelli’s modification.

When executed, a bilobed flap resembles the motion of a rotation flap. The modified bilobed flap is designed by drawing the two lobes along a 90° arc off of the tip of the center of the primary defect. Unlike the original bilobed flap, the pivot point of this arc extends beyond the width of the defect, incorporating the dog-ear at one side of the circular defect. This is essential to avoiding a large, tissue-distorting standing cone. With the larger radius of the arc, the lobes travel through fewer degrees of rotation, minimizing the large degree of pivotal restraint seen in the original bilobed design. The standing cone should be oriented in an attempt to place this scar in a well-hidden location, such as the alar crease.¹⁷

The modified bilobed flap calls for the primary lobe to have a width equal to the width of the primary defect. In cases where there is some degree of laxity in the skin surrounding the primary defect, the primary lobe can be designed up to 20% narrower than the width of the primary defect. Subsequently, the second lobe can also be designed with a smaller width if there is sufficient tissue laxity in the areas of the secondary and tertiary defects. The second lobe, which creates the tertiary defect, should be designed at a 90° angle to the midline of the redundant Burow’s triangle at the pivot point of the flap. Since the majority of the tension is in the closure of the tertiary defect, it should be oriented in such a manner as to not distort any nearby free margins. For example, it is typically oriented perpendicular to the nasal ala when the bilobed flap is used in distal nasal reconstruction.

Some shortening of the lobes of the flap should still be anticipated because of the pivotal restraint through the arc of flap rotation. To compensate for this, the first lobe may be drawn to extend slightly beyond the edge of the primary defect. The angle of separation between the primary and secondary lobes should be drawn to 30°–45°. This minimizes both the surgical effort needed to execute the flap and the tension on the edges of the flap once it is in place.

The bilobed flap may be designed in several different directions on the nose. In general however, more medial defects are usually closed with laterally based bilobed flaps, whereas more lateral defects are closed with medially based bilobed flaps.

Application of the Bilobed Flap

The bilobed flap is most often selected for reconstruction of defects located over the nasal tip and supra-tip, the distal nasal sidewall, the medial nasal ala, the auricular helix, and the posterior ear (Figure 7.19). These are areas with little local tissue laxity and high potential for distortion with side-to-side closure. In fact, the bilobed flap is often described as the flap of choice for repair of defects of the lower one-third of the nose. Since this is an area where skin cancers typically occur, familiarity with the bilobed flap and its modifications is essential for surgeons treating nonmelanoma skin cancers.

Figure 7.19 Potential zones for use of the bilobed flap.