Transposition Flaps 

Updated: May 17, 2018
Author: Vandana Chatrath, MD; Chief Editor: Dirk M Elston, MD 

Overview

Background

Flaps are defined as skin and subcutaneous tissue with an intact vascular supply moved to cover an adjacent primary defect.[1]

History of the Procedure

Flaps typically are used in certain instances to take advantage of greater laxity in adjacent tissue, to change the direction of tension in the wound closure, or to camouflage a scar line. Simple linear closures are easier to perform, generally have lower complication rates than flaps and grafts, and typically leave an aesthetic linear or curvilinear scar. In addition, certain wounds (eg, those in concave areas such as the inner canthus or conchal bowl) do extremely well with second intention healing. Therefore, before the decision is made to close a surgical defect with a flap or graft, these other options must be considered. If a wound will not heal well by second intention and a linear closure will create too much tension, distort anatomic structures, or leave an unacceptable scar, flaps and grafts must be considered. Surgeons must not be too hesitant or too eager to use flaps. When used in the appropriate situation, a flap may offer the best aesthetic result.

Flap categorization

Flaps can be categorized according to several different criteria:

  • Location

    • Local flaps come from within the same or an adjacent cosmetic unit.

    • Distant flaps are transposed over intervening skin of one or more cosmetic units and, therefore, are from nonadjacent skin. These are completed in 2 stages; the pedicle is severed and returned to its initial position only when the local blood supply in the flap is developed.

    • Free flaps are a combination of flaps and grafts. They share the characteristics of both because they are excised at a distant site with a major blood supply and harvested as a graft by severing them completely from the skin. Then, the artery is anastomosed to a major vessel in the surrounding skin. Thus, although skin is separated completely from its source (as in a graft), it carries its own blood supply, analogous to a flap.

  • Blood supply

    • Axial pattern (arterial) flaps are flaps in which the blood supply to the flap is through a major vessel that is preserved when the flap is raised and the vessel is moved with it to cover the defect.

    • Random pattern (cutaneous) flaps are flaps in which the subdermal vascular plexus is the source of the blood supply to the flap; these flaps are raised below the subcutaneous fat to preserve the plexus.

  • Primary tissue movement

    Flaps. Flaps.

    See the list below:

    • Advancement flap (see image above): These are flaps that involve advancement or linear slide of adjacent tissue to cover a primary tissue defect. Classic advancement flaps have the advantage of altering the position and location of a portion of the scar that may have been produced by a linear closure.

    • Rotation flaps (see image above): These are flaps in which the tissue is rotated around a pivot point (arcuate slide) to cover a primary defect. Rotation flaps fill one defect by creating another defect that may be closed with less tension or distortion. Tension is redirected and redistributed.

    • Transposition flaps (see image above): When the flap is carried (rotated) over an intervening area of normal skin to be placed in its recipient site, it is known as a transposition flap. Like rotation flaps, transposition flaps exploit skin laxity at a site distant to the surgical defect and redirect the tension of closure. Transposition flaps are generally smaller and freer in their movement than rotation flaps.

Indications

Transposition flaps

Transposition flaps take advantage of regional laxity by mobilizing tissue from an adjacent area of excess laxity (see image below) into the area without slack.

Reservoirs of extra skin. Reservoirs of extra skin.

Transposition flaps have the following advantages:

  • They accomplish redistribution and redirection of tension.

  • They tend to be smaller in size than advancement and rotation flaps.

  • Resultant scars are geometric broken lines that may be less conspicuous and tend to be easy to hide.

Types of transposition flaps

Many different types of transposition flaps exist, with an innumerable amount of variations. The most commonly used transposition flaps include the following:

  • Classic rhombic flap, as described by Limberg in 1963

  • Modified rhombic flaps, such as the Webster 30° angle and the Dufourmentel flap

  • Banner-type flaps, such as the nasolabial transposition flap and the bilobed flap

  • Tunneled transposition flap (for deep defects of the nasal ala)

Transposition flap as a modification of island pedicle flap

Island pedicle flaps, by definition, are incised and completely separated from the surrounding skin except for the underlying pedicle that lies inferior to the flap. These closures are typically rotational or advancement in nature, which are effective for defects that are adjacent and require only sliding of the flap into place. However, for noncontiguous defects, island pedicle flaps are not an option. A modification of the island pedicle flap is a transposition movement. This enables repair of difficult and nonadjacent areas with sparing of normal tissue, allowing closure of the defect with noncontiguous but similar tissue and camouflage of scars into natural skin tension lines.

Relevant Anatomy

Uses of rhombic flap

Although each patient must be evaluated individually, rhombic transposition flaps provide outstanding cosmetic and functional reconstruction options in certain classic areas of the face.[2, 3, 4, 5]  These areas include the following (see image below):

Rhombic flap uses. Rhombic flap uses.

See the list below:

  • Dorsum of the nose and the nasal sidewall: The use of surrounding skin in transposition flaps helps maintain optimal color and texture match. Keeping the mobile free margins of the eyelid and nasal ala in mind during the planning of flaps in this area is important. Any closure that distorts these in any way is unacceptable. Tension vectors should be directed away from these areas. The nasal tip is also mobile and should be considered in the closure of nasal defects. However, the tip ptosis that frequently occurs with increasing age may be corrected aesthetically with some closures (see images below).

    Post-Mohs surgical defect over the right nasal sid Post-Mohs surgical defect over the right nasal sidewall in a 38-year-old woman.
    Reconstruction of the right nasal sidewall defect Reconstruction of the right nasal sidewall defect with a superiorly based Dufourmentel flap.
    Side view of the nose, 3 months postreconstruction Side view of the nose, 3 months postreconstruction of the right nasal sidewall defect.
    Front view of the nose with no distortion of the s Front view of the nose with no distortion of the structure and maintenance of the nasal symmetry.
  • Inner and outer canthus: Because of the proximity to neighboring mobile anatomic structures, such as the eyelids, redirection of the tension vectors by optimal orientation of the transposition flaps prevents distortion of these structures after closure of the defect. The acute angles of the folds (crow's feet) in the outer canthus offer excellent lines to hide the acute angles generated by transposition flaps.

  • Temple: Transposition flaps use the reservoir of excess skin over the cheeks, temple, and preauricular areas to repair large defects over the temple where primary closure may not be possible.

  • Cheeks: Because the skin of the cheek is richly vascular due to the favorable blood supply from the subdermal plexus, the viability of transposition flaps is less critical, which may be used to create scars as geometric broken lines that tend to be well camouflaged within the skin creases. Transposition flaps typically are designed laterally and with the redundant tissue inferior to the primary defect. This keeps the scar in a lateral position, and the inferiorly based flap maintains optimal lymphatic drainage to help prevent pin-cushioning (see images below).

    Postoperative Mohs defect on the right cheek of a Postoperative Mohs defect on the right cheek of a 69-year-old man.
    Reconstruction of the right cheek defect with a su Reconstruction of the right cheek defect with a superiorly and laterally based Dufourmentel flap.
    One-week postrepair of the right cheek defect with One-week postrepair of the right cheek defect with the resultant scar placed laterally to make it less noticeable.
    Three months postreconstruction of the right cheek Three months postreconstruction of the right cheek defect with the Dufourmentel flap.
  • Perioral: Using the laxity of the adjacent cheek and hiding scars in the various folds and normal wrinkles in this area make transposition flaps a good option (see images below).

    Postoperative Mohs defect over the left inferior a Postoperative Mohs defect over the left inferior angle of the mouth in a 60-year-old man.
    Reconstruction of the surgical defect with a super Reconstruction of the surgical defect with a superiorly based Dufourmentel flap to prevent distortion of the lower lip.
    Three months postrepair of the left inferior angle Three months postrepair of the left inferior angle of the mouth defect with the Dufourmentel flap (close-up view).
  • Chin: Transposition flaps may use neighboring areas of regional laxity and reservoirs of skin, such as the skin of the submandibular area and neck, to good advantage in the closure of selected defects (see images below).

    Postoperative Mohs surgical defect over the left c Postoperative Mohs surgical defect over the left chin in a 74-year-old woman.
    Reconstruction of the surgical defect with an infe Reconstruction of the surgical defect with an inferiorly and medially based Dufourmentel flap.
    Three months postrepair of the left chin surgical Three months postrepair of the left chin surgical defect with the resultant scar hidden well in the submental crease.
    Three months postrepair (front view) of the left c Three months postrepair (front view) of the left chin defect with no distortion of the neighboring anatomic structures and maintenance of symmetry.

A computational model of cutaneous wound closures developed by Topp et al indicated that, in rhombic transposition flaps, the extent of secondary tissue movement is determined by the width of the flap, as is the flap’s effect on surrounding tissues, while the transposition angle is responsible for the orientation at which maximal strain occurs.[6]

Banner-type transposition flaps[7]

The classic banner-type transposition flap is a finger-shaped random pattern (cutaneous) flap that makes use of areas of adjacent laxity. This flap allows for the placement of a long linear secondary scar in a skin fold or crease or along the junction of 2 cosmetic units. This type of flap most commonly is used in the following areas:

  • Ala: The classic nasolabial transposition flap is used.

  • Superior helix

    • The banner flap is taken behind the superior aspect of the ear. Reconstruction of the upper one third of the ear may be achieved using several strategies such as full-thickness skin grafts, wedge resection with subsequent primary closure, helical advancement flaps, multistage preauricular or postauricular tubed flaps, and one-stage preauricular or postauricular transposition flaps.[8, 9]

    • When defects are smaller than 1.5 cm, wedge conversion of the defect followed by primary closure is aptly suited without distortion of the anatomy. However, when the defect is 1.5-2.5 cm, the best choice is helical advancement flap. For helical defects greater than 2.5 cm, a multistaged tubed flap (anterior or posterior) is considered.

    • To reconstruct a similarly sized defect, a postauricular transposition flap can be performed as a single-stage procedure. The anterior edge of the flap is cut along the retroauricular sulcus. The flap is designed to have a length-to-width ratio of 1:4 (exceeding the length of the defect). A burrow triangle is added to the flap to allow easy closure of the secondary defect by tapering the tip of the secondary defect. Because the postauricular skin is thin, undermining should be done with care. After trimming the flap to fit the defect, the first suture is placed at the tip of the flap and secured to the remaining helix with a vertical mattress suture to allow good eversion and avoid notching of the rim. The rest of the flap is then sewn into place with routine simple interrupted sutures.

    • A cartilage graft may be harvested from the opposite ear to re-form the rim if there is significant cartilage loss in the primary defect. The possibility of a trapdoor deformity may be desired here to some extent because it would help to recreate the natural helical rim contour. Therefore, an anteriorly or posteriorly placed transposition flap can be effectively used for reconstruction of superior helical rim defects located proximally, enabling a single-stage procedure in place of a multistage interpolation flap.

  • Medial anterior ear (ie, concha, tragus, crus of the helix): The banner flap is taken in the preauricular area (see images below).

    Postoperative Mohs defect in the right concha of a Postoperative Mohs defect in the right concha of a 58-year-old man.
    Reconstruction of the right conchal surgical defec Reconstruction of the right conchal surgical defect with a Banner transposition flap.
    Three months postrepair of the right conchal surgi Three months postrepair of the right conchal surgical defect with no distortion of the structure of the ear.
    Three months postrepair of the right conchal surgi Three months postrepair of the right conchal surgical defect (close-up view).

Bilobed flap

The bilobed flap is a double-lobed modification of the banner transposition flap described above. The principle of transposing skin from an area of laxity remains the same; however, the transfer of tissue is in 2 steps and allows the donor skin to be at a greater distance from the recipient area.[10, 11, 12, 13, 14, 15]

The basic motion of the flap is that of rotation. Each lobe of the flap is tethered to a cutaneous pedicle, which creates the same pivotal restraint on the movement of the flap as a rotation flap.

There are 2 important variables in the construction of a bilobed flap, namely, the flap length and the flap angle, which relate to each other directly. Greater angles of rotation require longer flaps to overcome the pivotal restraint. Typically, the first lobe of the flap is designed to be equal to the width of the original defect. If the location of the primary defect is in an area that allows secondary motion, the first lobe may be designed up to 20% smaller than the primary defect. The primary lobe can be thinned if bulky; however, deepening the defect may be preferable to thinning the lobe, thus increasing the risk of flap necrosis.

The second lobe also may be designed smaller because tension can be shared by closure of the defect created by the second lobe. In addition, the second lobe of the flap is constructed with an elliptical tip to facilitate side-to-side closure of the tertiary defect. The movement of the flap is facilitated through wide undermining around the flap, especially at the pedicle. The undermining is deep and wide just above the level of the perichondrium or periosteum. In this way, the muscle remains attached to the base of the pedicle ensuring a rich vascular supply (see image below).

Bilobed flap. Bilobed flap.

A modification of the original bilobed flap was described by Zitelli in 1988 (see image below) and is the most used design of the bilobed flap.[16]

Bilobed flap evolution. Bilobed flap evolution.

In this, a triangle or a dog-ear cone is designed along one side of the circular defect, orienting the line of closure along the resting skin tension lines or a cosmetic unit junction line without the distortion of neighboring free margins. This has the advantage of maintaining a rich vascular supply to the flap because this does not cut into the base of the defect. Also, it prevents a secondary procedure to remove the standing cutaneous deformity (dog-ear) that occurs at the point of rotation.

An arc is then extended from the defect tip up to 90°, and the 2 lobes of the flap are drawn along this arc (see image below).

Bilobed flap modification. Bilobed flap modification.

The 2 lobes should be separated by an angle of 30-45° to limit the size of the dog-ear and to reduce the risk of pin-cushioning (see images below).

Post-Mohs surgical defect over the right nasal sid Post-Mohs surgical defect over the right nasal sidewall in a 66-year-old man.
Reconstruction of the left nasal sidewall surgical Reconstruction of the left nasal sidewall surgical defect with a bilobed flap (Zitelli modification).

Because some degree of pivotal restraint is created by the motion of rotation and the lobes may be shortened slightly in the rotation, the first lobe of this flap may be designed to extend beyond the arc (see image below).

Bilobed flap modification. Bilobed flap modification.

Thus, as the flap is rotated and transposed into position, the lengthened lobe fits into the primary defect without any tension (see images below). The lobes should be inset or flush with the adjacent skin. A tacking suture may be placed in the defect to the underside of the primary lobe to avoid trapdooring. A study by Grieco et al found good aesthetic and functional outcomes in patients who, following treatment for skin cancer of the nose, underwent nasal reconstruction with the Zitelli bilobed flap. Although 12 of 86 patients (14%) ended up with small alar rim distortions, these individuals were still pleased with the cosmetic result.[17]

Bilobed flap with the first and second lobe coveri Bilobed flap with the first and second lobe covering the primary and secondary defect respectively after side-to-side closure of the tertiary defect.
Completed bilobed flap for reconstruction of the l Completed bilobed flap for reconstruction of the left nasal sidewall defect with no distortion of the ala.

The bilobed flap is particularly suited for reconstruction of the defects located over the following areas (see image below):

Anatomic areas where a bilobed flap may be used. Anatomic areas where a bilobed flap may be used.

See the list below:

  • Nasal tip and supra-tip (see images below)

    Postoperative Mohs defect over the left tip of the Postoperative Mohs defect over the left tip of the nose in a 71-year-old man.
    Reconstruction of the left nasal tip surgical defe Reconstruction of the left nasal tip surgical defect with a bilobed flap to provide a good texture and color match.
    Three months postrepair of the left nasal tip. Three months postrepair of the left nasal tip.
    Three months post repair (front view) with no dist Three months post repair (front view) with no distortion of the tip.
    Three months postrepair with a well-blended scar l Three months postrepair with a well-blended scar line (side view).
  • Nasal sidewall (see images below)

    Postoperative Mohs defect over the left nasal side Postoperative Mohs defect over the left nasal sidewall in a 45-year-old woman with a bilobed transposition flap marked for repair.
    Three months postreconstruction of the surgical de Three months postreconstruction of the surgical defect over the left nasal sidewall with a bilobed transposition flap
  • Medial nasal ala

  • Auricular helix (see images below)

    Postoperative Mohs defect over the helix of the ri Postoperative Mohs defect over the helix of the right ear in a 59-year-old man.
    Reconstruction of the right helical surgical defec Reconstruction of the right helical surgical defect with a bilobed flap exploiting the laxity of the postauricular skin.
    Three months postrepair of the right helical surgi Three months postrepair of the right helical surgical defect with the bilobed flap.
    Three months postrepair of the right helical surgi Three months postrepair of the right helical surgical defect showing intact helical rim with no distortion of the structure of the ear.
  • Posterior ear

A retrospective study by Kelly-Sell et al indicated that substituting a superiorly based bilobed flap for a laterally based one has advantages in nasal reconstruction, observing that use of the laterally based flap to repair larger, more cephalic, or more lateral nasal defects carries the risk of lower nasal distortion. In the study, superiorly based bilobed flaps were employed following tumor extirpation via Mohs micrographic surgery, with more than half of the tumors situated on the nasal dorsum and the median of the longest postsurgical tumor axis being 1.4 cm. The investigators found no instances of infection, hematoma, or full-thickness necrosis.[18]

Transposition island pedicle flap

This is best used over the following areas:

  • Nasal side wall

  • Nasal ala

  • Alar grooves

Extranasal applications of the bilobed flap

The novelty of the bilobed flap as it is used for extranasal reconstruction is that the surgeon has some degree of variance in designing the size of the individual lobules of the flap, with a lower risk of secondary tissue distortion. The flap must be carefully designed to place the incision lines as closed to the relaxed skin tension lines as possible, and a meticulous suture technique is important for camouflaging the complex suture line of this flap. Importantly, keep in mind that the extranasal bilobed flap's vascular support may be reduced compared with nasal sites. The extranasal sites where the bilobed flap may be used are as follows:

  • Lower lip

  • Chin: Particular attention must be given to avoiding damage to the marginal mandibular nerve during execution of this reconstructive technique.

  • Medial cheek: To eliminate the transfer of hair into a reconstructed surgical wound, the surgeon may thin the flap and destroy the hair bulbs at the time of flap insertion; to avoid flap necrosis, avoid excessively thinning the distal portion of the flap.

  • Ear lobule

  • Dorsum of the hand: The secondary lobule of the flap in this case may be somewhat undersized compared with the design of the flap used in nasal reconstruction.

Tunneled transposition flap

The tunneled transposition flap is a single-staged flap for the repair of deep defects of the nasal ala that do not lend themselves to skin graft repairs. When a decision is made by the surgeon to use this particular flap, 2 important considerations must be addressed. First, the defect should be limited to the nasal ala entirely in order to achieve a good aesthetic outcome, because recreating the alar crease is impossible with this flap. Second, the alar defect must be deep because this flap requires a pedicle, and, if the depth of the defect is not enough to fit the pedicle, the result would be a pin-cushion deformity. Additionally, if an attempt is made to thin the pedicle in order to fit the defect, the blood supply to the flap may be compromised. Therefore, if the alar defect is shallow, a full-thickness skin graft is the ideal choice or else the defect has to be deepened.

The flap is planned such that it lies along the melolabial fold so that the secondary defect is closed along a natural cosmetic line. The major advantage of this flap over a banner-type flap is that with the tunneling, the alar crease is entirely preserved.

Contraindications

Smoking, aspirin, and anticoagulant use are relative contraindications to the use of transposition flaps because they interfere with the healing of the flaps and, therefore, increase the incidence of flap necrosis. Herbal supplements containing such substances as gingko biloba also have some anticoagulant activity. The use of these substances should be addressed at the time of preoperative evaluation so that they may be discontinued a few weeks prior to surgery if it needs to be performed.

 

Treatment

Intraoperative Details

Surgical approaches are described for the classic rhombic flap and for rhombic flap modifications.

Classic rhombic flap

The classic rhombic flap is constructed around a defect that is converted into a geometric 4-sided defect (rhombus) with equal side length and tip angles equal to 60° and 120°. It classically is designed by extending the short diameter of the defect (X) beyond the flap for a length equivalent to one of the sides (see image below).

Classic rhombic flap. Classic rhombic flap.

Then, the flap is created by drawing a line from the free end of the extended short diameter parallel to one of the sides of the existing rhombus (see image below).

Classic rhombic flap. Classic rhombic flap.

When designed in this manner, the tip angle is 60°. The flap typically is designed off the short axis of the defect to keep the flap as small as possible (see image below).

Classic rhombic flap. Classic rhombic flap.

A flap can be constructed in 4 possible directions for any rhomboid defect off its short axis (see image below). The optimal flap is chosen out of the 4 possibilities, keeping in mind the considerations outlined below.

Classic rhombic flap. Classic rhombic flap.

Best tension distribution

The flap uses the area of maximum tissue laxity with no effect on the surrounding anatomic structures when the flap is closed with no distortion of free margins (see image below).

Classic rhombic flap. Classic rhombic flap.

Best scar line

Orient the flap such that most of the resultant scar line lies along relaxed skin tension lines (see image below) or at the junction of 2 cosmetic units. In addition, if all else is equal, the scar should be placed in a lateral position.

Optimal placement. Optimal placement.

When patients look in a mirror and when they have face-to-face communication, a laterally placed scar is hidden much better than a medially placed scar (see images below).

Post-Mohs surgical defect over the left angle of t Post-Mohs surgical defect over the left angle of the mandible in a 63-year-old man.
Post-Mohs defect reconstructed with a classic rhom Post-Mohs defect reconstructed with a classic rhombic flap based superiorly and laterally.
Three months postreconstruction of the left angle Three months postreconstruction of the left angle of the mandible in a 63-year-old man.

Flap dynamics

The flap is designed (see section A of image below) and cut along the incision lines. It is undermined widely and rotated into the defect (see section B of image below). The secondary defect is closed with the first tension-bearing suture. However, even after the donor defect is closed, the flap is not completely tension free.

Classic rhombic flap. Classic rhombic flap.

Some shortening in the length of the flap occurs because of the restraint at the pivot point of the pedicle. Therefore, the leading flap tip does not quite meet the recipient tip. For the tips to meet, there must be some movement of the recipient tissue toward the flap and/or some degree of flap advancement (see section C of the image above). If this does not occur, the forceful pulling of the tip carries the risk of tip ischemia and necrosis. If no movement is possible in this direction, the flap may be oversized to compensate.

The classic rhombic flap has 2 major tension sites. The first and primary tension site is at the closure of the secondary defect, and the second site is at the closure of the leading tip. To ensure success of the flap, the surgeon must understand and plan for these tension forces. The tension may be minimized by the following modifications:

  • Lengthening the leading edge of the rhombic flap and elongating the secondary limb of the flap enlarges the flap while ensuring that the flap tip meets the recipient tissue without tension (see image below).

    Classic rhombic flap. Classic rhombic flap.
  • The leading tip may be made to reach the recipient tip in a tension-free environment if the flap angle is made slightly more obtuse, ie, greater than 120° (see image below).

    Classic rhombic flap. Classic rhombic flap.

Rhombic flap modifications

Webster flap[19]

In this modification of the rhombic flap, the tension is not fully displaced but rather shared by the lax adjacent tissue. It is designed by decreasing the flap tip angle to 30°, and the base of the flap is only half the length of the recipient defect (see image below).

Webster flap. Webster flap.

This narrows the flap pedicle and increases the side-to-side tension on the flap as the defect is closed. By doing so, the tension is shared between the area of the defect and the adjacent tissue where the flap is harvested. This additional tension, if too great, may increase the risk of flap ischemia or necrosis.

This flap most commonly is used when 2 flaps must draw from different tension vectors such that each flap closes one half of the defect, reducing the angle from 60° to 30°.

Dufourmentel flap[20, 21, 22]

This is a modification of the rhomboid transposition flap. The flap is designed by extending one line from the short axis to a length equivalent to the side lengths, similar to a classic rhombic flap, and another line is drawn by extending the side adjacent to the lower angle to a similar length (see image below).

Classic rhombic flap. Classic rhombic flap.

However, the incision is made along a line that bisects these 2 extended lines (see image below).

Classic rhombic flap. Classic rhombic flap.

A second incision is made along a line that is dropped from the end of the bisected line parallel to the long axis of the rhombic defect to complete the flap (see image below).

Classic rhombic flap. Classic rhombic flap.

By using a line drawn parallel to the long axis instead of one of the sides of the rhombic defect, the pedicle is widened but the movement is inhibited. Therefore, for the flap to rotate to its receptor angle completely, some degree of upward advancement is essential.

A key feature of the flap is the obtuseness of the leading angle. This relieves the pivotal restraint to some extent and results in more lateral tip tension compared to more vertical tip tension in a classic rhombic flap. Therefore, the Dufourmentel flap is useful in areas where lateral tension is acceptable and vertical pull is not.

Although this article deals with the construction of transposition flaps for rhomboid-shaped defects, the same principles may be used to reconstruct a circular defect. For this, the defect remains circular, and a rhombic design is drawn around it. With a circular defect, the flap may be designed in any direction, keeping in mind the optimal flexibility of the surrounding tissue and adjacent anatomic structures. The optimal closure lines are determined according to the resting skin tension lines or cosmetic unit junction lines and are transposed to the circular defect axis (the diameter of the circular wound). See image below.

Optimal placement of rhombic flaps. Optimal placement of rhombic flaps.

The length of the line extended beyond the defect is longer than the circular diameter because this diameter is shorter than the short axis of the rhomboid drawn around the circular defect. A second line of the same length is drawn, keeping a tip angle of 60° to complete the flap (see image above). The tissue redundancy created by the rotation of the transposition flap is removed with trimming of a triangle at the pivot point. The transposed tissue may be rounded to fit the circular defect, or the defect may be squared off to accommodate the angular flap. The surgeon may determine which of these modifications will yield the best aesthetic result.

Banner-type transposition flap

The finger-shaped flap is designed with a width that is 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 (see image below). The flap rotates in an arc about the pivot point. Although theoretically the flap can move through an arc of 180°, this is difficult to perform.

Banner transposition flap. Banner transposition flap.

Unless the flap is based on an artery, this movement of 180° may produce a kink at the base of a random pattern flap that decreases the perfusion of the tip. Therefore, the flap typically is designed to rotate through an angle of 60-120° (see image above). As the flap is rotated and transposed, a protrusion often forms at the base of the flap (see image below).

Banner transposition flap. Banner transposition flap.

This tissue redundancy (dog-ear) generated by the rotating motion should be removed. Care should be taken to remove the redundant tissue in a direction away from the pedicle of the flap such that the narrowing of the base of the flap does not compromise the blood flow to the flap, thereby affecting its viability (see images below).

Postoperative Mohs defect over the right ala and n Postoperative Mohs defect over the right ala and nasal sidewall in a 42-year-old man.
Reconstruction of the right alar and nasal sidewal Reconstruction of the right alar and nasal sidewall surgical defect with a nasolabial transposition flap (Banner).
Three months postrepair of the right alar and nasa Three months postrepair of the right alar and nasal sidewall defect with the Banner transposition flap (side view).
Three months postrepair showing intact alar rim an Three months postrepair showing intact alar rim and patency of the nares.
Three months postrepair (front view) showing intac Three months postrepair (front view) showing intact symmetry of the nose a well-hidden scar within the cosmetic junction unit line (nasolabial fold).

Transposition island pedicle flap[23]

The design of the transposition island pedicle flap with a melolabial cheek donor site is such that a template is made of the defect and transposed onto the lower melolabial cheek. The distance between the lateral border of the defect and the template serves as the length of the island pedicle and should not be more than the defect width. If the length is longer, it impairs flap movement due to excess tissue at the point of transposition. The intervening skin between the flap and the template is excised partially, leaving a pedicle of subcutaneous tissue.

At the distal end of the flap, a full-thickness Burrow triangle is removed to facilitate closure of the donor area. Proximally, the pedicle is created, incorporating the subcutaneous tissue, deep muscle fibers, and vessel perforators to ensure flap survival through good vascular supply. The island flap is then transposed onto the defect by reflecting back the cheek skin at the point of transposition. The cheek skin is advanced medially and closed, eliminating the need to remove the proximal Burrow triangle.

For nasal sidewall and nasal ala defects, the sidewall acts as a donor site; the Burrow triangles are designed along the superior and inferolateral aspects of the defect. The island pedicle is created with the inclusion of the nasalis fibers to ensure vascularity. The secondary defect is closed by cheek advancement and primary closures of the Burrow triangles.

The major advantage of the transposition island pedicle flap is excellent color and texture match. The disadvantage, however, is the high incidence of trapdooring because, in these flaps, the proximal Burrow triangle is not excised and this may result in constriction of the surrounding flap causing the resultant trapdooring. This can be minimized to some extent by undermining the recipient site and placing tacking sutures if possible.

Subcutaneous pedicle Limberg flap[24, 25, 26]

This is an innovative refinement to the Limberg transposition flap that eliminates the dog ear and is useful in a variety of benign and malignant lesions of the face. The Limberg flap is designed near the defect with a 30-45°, and the width of the flap is approximately four fifths of the width of the defect. The distal part of the flap is elevated at the subcutaneous plane but over the mimetic muscle, and the proximal pedicle is then created as usual, incorporating the deep muscle fibers and vessel perforators.

A V-shaped incision limited to the immediate subdermis is performed at the pedicle of the flap, and this modification makes the Limberg flap a subcutaneous pedicle flap. The V-shaped incision is designed with a 45-60° angle so that this part of the donor site can also be sutured directly. In addition, further undermining around the V-shaped incision at the subdermal level, leaving the thick subcutaneous pedicle underneath, increases the mobility of the flap. This modified flap is of particular use in younger patients with restricted laxity of surrounding tissue.

Tunneled transposition flap[27]

This flap has 3 parts: (1) the inferior Burrow triangle, which is removed as a full-thickness, single-standing cone; (2) the donor site, which is to be completely matched to the primary defect; and (3) the superior Burrow triangle, which is excised to the dermis only because the underlying muscle and fat form the pedicle of the flap (see image below).

Tunneled transposition flap. Tunneled transposition flap.

As with all transposition flaps, ensuring that the flap and the pedicle are of appropriate length is important. Therefore, the distance from the tip of the superior Burrow triangle to the end of the donor site is 5 mm greater than the distance from the tip of the superior Burrow triangle to the end of the defect (see image above). If the flap is taken more superiorly from the melolabial fold, then the pedicle will twist as it tunnels into the defect and compromise the blood supply to the flap; additionally, if it is taken too inferiorly, then a bulge would develop in the flap owing to the increased length of the flap.

The first step in the execution of the flap is to remove the superior Burrow triangle up to the dermis. Then, the inferior Burrow triangle and the flap donor site are separated from the surrounding skin and lifted at the level of the subcutaneous fat. The pedicle is then dissected such that the pedicle consists of the deep subcutaneous fat and the muscle fiber of the levator labii superioris alaeque nasi. The proximal portion of the pedicle should be thicker than 3-4 mm to ensure a good blood supply to the flap, and the distal portion should be up to 3-4 mm and not more, because this is the part of the pedicle that passes through the tunnel of the melolabial fold and the alar crease.

Now, both the donor and recipient site of the flap should be extensively undermined, which allows the secondary defect to be closed easily and it creates the tunnel between the primary and secondary defects. After this, the flap and the pedicle pass through the tunnel that was created. Sometimes it may be necessary to remove some fat from the tunnel for the pedicle to pass more easily and without compression. The donor site is closed primarily along the melolabial fold, and the inferior Burrow triangle is trimmed so as to suture the flap into the defect. This enables a pleasing aesthetic outcome because the alar crease is completely preserved.

Complications

Dehiscence

Primary dehiscence is due to incorrect construction of the flap such that there is excessive tension along the lines of closure. Secondary dehiscence is due to postoperative infection or bleeding (unrelated to the flap design or construction).

Flap necrosis

Flap necrosis may occur for a variety of reasons (eg, excessive tension, postoperative infection or bleeding, desiccation). Understanding the essential design and the pivotal restraining forces of transposition flaps is necessary to avoid problems. When the flap dynamics are understood and modifications are used to reduce tension on the tip, when required, complications are minimal.

Pincushioning, or the trapdoor phenomenon[28, 29]

This refers to the puffing up or out-pouching of a flap or graft above the surrounding skin surface and may occur in transposition flaps (see image below). It is seen more commonly with curvilinear flaps, such as the traditional banner and the double banner (bilobed) transposition flaps, because these allow more peripheral contraction than geometric flaps. Trapdooring also may occur because of such factors as excess subcutaneous fat under the flap, lymphedema (inferiorly based flaps offer better lymphatic drainage), oversized flaps, and a lack of contact inhibition (ie, failure to establish contact between the undersurface of the flap and the recipient bed), which allows contraction of the sides only and not the base, thereby pushing up the flap center.

Transposition flap used for the reconstruction of Transposition flap used for the reconstruction of a Mohs defect over the left ala showing trapdooring (puffing up) of the flap.

The most important factor may be the process of scar contraction and maturation, which occurs at the periphery and base of the flap (see image below). If only the flap base contracts, the flap tissue is forced upward, creating pincushioning. The risk of puffing up or trapdooring can be minimized by avoiding the factors that may lead to it during the reconstruction of the flap.

Trapdoor phenomenon. Trapdoor phenomenon.

See the list below:

  • Use straight lines and geometric angles and avoid curvilinear lines wherever possible to minimize scar contraction.

  • Undermine widely beyond the base of the flap. This cannot be emphasized enough. Wide undermining creates a uniform plane of scar contraction and, therefore, does not push the flap tissue up.

  • Undersize the flap enough to prevent bunching up of the flap but not enough to cause tension on the line of closure because of the risk of flap necrosis.

  • Maintain contact of the flap base with the recipient base to cause contact inhibition of flap contraction. If necessary (eg, if covering a concavity), this may be facilitated by the use of an absorbable suture from the base of the flap to the recipient bed oriented parallel to the direction of the blood flow.

  • Orient or position the flap to allow good lymphatic drainage to prevent lymphedema. Inferiorly based flaps allow favorable lymphatic drainage.

  • Use Z-plasty at the base of a transposition flap, such as rhombic flap, to enhance flap mobility, especially on the nose to prevent nasal tip and alar rim distortion.[30]

Minor corrections can be made through intralesional steroid injections, but surgical debulking is needed for major trapdooring.

A study by Lindsay and Morton of 21 patients indicated that alar wounds left by excision of small, penetrating carcinomas can be successfully repaired, and pincushioning avoided, by combining a skin graft with a subcutaneous fat transposition flap from the adjacent cheek.[31]

Outcome and Prognosis

In conclusion, many variations and modifications of transposition flaps exist. Similar to other flaps, transposition flaps may be further modified and adjusted to accommodate individual situations. They may be lengthened or shortened, and their angles may be altered depending upon the availability and laxity of surrounding skin.

Future and Controversies

No single flap can be used to reconstruct all defects. Each patient must be treated with a unique strategy. A 2-dimensional picture of a given defect may seem to indicate a certain type of repair. This may or may not be the optimal repair for that given patient. Only by feeling the skin in the area around the defect may the best option for repair be determined.

Transposition flaps dissipate tension away from the flap apex and distribute it proximally, thus redirecting the tension lines and reducing the likelihood of anatomic distortion in the reconstructed area; this is a major advantage offered by the use of these types of flaps. Flaps designed in this manner allow improved contour by avoiding webbing, tenting across concavities, and bunching of skin laterally.

A significant degree of artistic ability and individual modification is required to consistently obtain optimal aesthetic and functional result.