33.6.3 Bilobed Flap

The bilobed flap used today is a highly evolved transposition flap. The bilobed flap was first described by Esser in 1918. It became a workhorse flap only after the modifications described by Zitelli were published in 1989 (Fig. 33.16) [21]. The design of the bilobed flap actually consists of two transposition flaps executed in succession which follow the same direction of rotation over intervening tissues. The basic premise of this flap is to fill the defect with the primary lobe, while filling the secondary defect with the secondary lobe, leaving a triangular-shaped tertiary defect to be closed primarily. This series of transposition flaps allow the surgeon to further the reach of the flap and borrow laxity from donor sites at a greater distance from the defect while decreasing the arc of rotation of the pedicle.

The Zitelli modification of the bilobed flap is designed by placing the lobes over a 90° arc from the center of the defect, with the primary lobe rotating from a pivot point that is created by removing a Burow’s triangle at one pole of the defect [21]. The width of the primary lobe should be equal to the width of the defect and should be long enough to just extend past the edge of the defect. The secondary lobe must be trimmed to match the secondary defect left by the transposition of the primary lobe.

As with the rhombic flap, the bilobed flap redirects the principal tension vector and takes advantage of tissue laxity of the donor site. This flap is predominantly used for smallto medium-sized defects of the lower nose as the tension is redirected to a near vertical vector, preventing distortion of the alar rim (Fig. 33.17). The

bilobed flap works especially well when the Burrow’s triangle falls along the alar crease.

Summary: Interpolation Flaps

•Interpolation flaps import pedicled tissue from a site distant to the defect. These are axial flaps that can support a larger mass of tissue than random flaps. Because the flap is used to repair defects distant from the donor site, the vascular pedicle must temporarily be left in place to ensure adequate blood supply, requiring more than one stage to complete the repair. Types of interpolation flaps include paramedian forehead, nasolabial, Abbé, and retroauricular flaps.

33.7Interpolation Flaps

Interpolation flaps are more complex repairs that import pedicled tissue from a site distant to the defect. They are typically utilized on defects that are either too wide or too deep to reconstruct with local flaps or grafts. Many interpolation flaps may be classified as axial flaps if their vascular pedicle is based on a large, named artery. They are also commonly referred to as staged flaps as more than one stage is required to complete the repair. Interpolation flaps require careful planning and significant, albeit temporary, disfigurement of the patient.

The first stage of on interpolation flap involves the design and creation of the flap, including repair of the secondary defect. The flap is designed around a substantial artery and therefore is able to support a larger mass

of tissue than random flaps. Because the flap is used to repair defects distant from the donor site, the vascular pedicle must temporarily be left in place to ensure adequate blood supply. The distal end of the flap is thinned to match the depth of the defect and sutured in place. The area is bandaged and kept moist. The second stage generally takes place 2–3 weeks later, by which time the flap has established a local blood supply from the donor site. The pedicle is then divided from the donor site and the proximal portion of the flap is secured into the original defect. Due to granulation tissue formation, this portion of the flap may need to be thinned out subcutaneously to approximate the depth of the defect. The pedicle is

also separated from the donor site which will then require further steps for complete repair.

33.7.1 Paramedian Forehead

The paramedian forehead flap is useful to repair large, deep nasal defects that may or may not require cartilage grafts. Tissue is mobilized from the forehead, based on one of the supratrochlear arteries, and transposed to repair large distal nasal defects with the pedicle remaining attached in the glabellar region (Fig. 33.18). The supratrochlear artery is located at the

medial border of the eyebrow, approximately 1.5–2 cm from the midline.

The aesthetics of the repair is often improved when the defect is enlarged to include the total cosmetic subunit. The portion of the flap that will fill the defect is the superior portion closest to the hairline; the width here should be equal to the widest portion of the defect, although the pedicle itself need be no wider than 1–1.5 cm. Its height must be equal to the distance from the base of the flap to the distal edge of the defect. In designing the flap, it is important that the vertical height of the forehead be able to accommodate the necessary length of the flap. The tissue is rotated approximately 180° around its pedicle and should be rotated medially as to minimize obscuration of the medial visual field of the ipsilateral eye; therefore, the flap will require less rotation if it is harvested from the forehead supplied by the supratrochlear artery contralateral to the defect.

The donor site is undermined and closed primarily as far superiorly as it will close resulting in a long linear scar. The donor site is repaired with a side-to-side closure, The superior portion of the defect will be the widest, as it is here that the width of the defect must be accommodated, and thus, generally this portion of the wound is too tight to be closed and is left to heal by secondary intention. The distal aspect of the flap is debulked to the depth of the defect and secured at the distal margin with sutures. The proximal margin, by design, cannot be secured until the pedicle is divided. The pedicle should be circumferentially wrapped with Vaseline or Xeroform gauze or Surgicel to prevent desiccation.

The second stage takes place 3 weeks subsequently. The pedicle is separated from the brow, the wound edges are freshened, and the donor defect is closed. After the pedicle is separated from the defect, the tissue is further debulked and trimmed, and the remaining edge is secured.

33.7.2 Nasolabial Interpolation

This flap is utilized to repair complex defects of the ala, particularly in instances when cartilage grafting is also required to restore the structural integrity of the alar rim. The flap is harvested from the medial cheek and nasolabial fold and is based on branches of the angular artery (Fig. 33.19).

The aesthetics of the repair is often improved when the defect is enlarged to include the entire alar lobule. The flap is designed around a pedicle that will be placed

at the alar groove, extending as an ellipse that will be easily closed in the nasolabial fold. Through-and- through nasal defects will require the repair of the mucosa, and thus, the width of the flap must take this into account. This myocutaneous flap is dissected from the donor site, rotated downwardly, debulked and trimmed, and secured to the widely undermined defect.

As with the paramedian forehead flap, the pedicle may be wrapped with Vaseline or Xeroform gauze or Surgicel. Three weeks later, the pedicle is separated, the wound edges are freshened, and the donor defect is closed. After the pedicle is separated from the defect, the tissue is further debulked and trimmed, and the remaining edge is secured.

The reverse nasolabial flap, also known as a Spear’s flap, is employed when the defect involves the alar groove. The motion of this flap is an upward rotation, opposite of the traditional nasolabial interpolation flap.

33.7.3 Abbé

The Abbé flap is also known as the lip-switch flap and is reserved for repair of large, deep defects, typically of the upper lip. It is particularly useful for defects that involve up to half of the lip without crossing the midline and those that penetrate into the muscularis. The Abbé flap is harvested from the ipsilateral lower lip and is based on the inferior labial artery. This artery is located deep to or within the orbicularis oris muscle and runs along the mucosal aspect of the vermillion border [22].

The vermillion border and flap design must be properly marked out. The defect should be full thickness (including muscularis and oral mucosa) and may be enlarged to encompass the total cosmetic unit which includes the ipsilateral upper cutaneous lip. The flap, also designed to be full thickness to fill the enlarged defect, is rotated upon a vascular pedicle that makes up the lateral aspect of the flap. The inferior labial artery will be visualized as it is transected at the mobilized (medial) edge of the flap. The pedicle itself should be about 1 cm thick, containing the robust blood supply.

The donor site is undermined and closed first to facilitate the movement of the flap. It should be closed in layers as in the repair of a lip wedge resection: mucosa, muscularis, subcutaneous, then cutaneous. The flap is rotated superiorly and also inset with a layered closure. Careful attention should be given to aligning the vermillion borders at the donor site and defect.