Key points
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Bilobed flaps are excellent local reconstructive options for nasal dorsum, tip, and sidewall defects.
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The bilobed flap can be applied to other areas of the face and enlarged considerably because it is similar in concept to the cervicofacial advancement flap.
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Wide undermining of adjacent skin, thinning of the flap at the initial inset, and use of angled incisions can help minimize the incidence and severity of a trapdoor deformity.
Introduction
Local tissue rearrangement and flap reconstruction of the head and neck have a long and storied history. Much interest has been placed on selecting and executing the appropriate flap to reconstruct an ablative defect. Bilobed flaps are among the many techniques available to a surgeon. They are double transposition flaps that share a single base. The flaps move around pivotal points located at the base. This naturally creates a standing cutaneous deformity and a reduction in length as the flap pivots. Most often these flaps are random cutaneous and thus subjected to the restrictive parameters (length-to-width ratios) required by this type of flap.
Historically, the first description of a bilobed flap was in 1918. Esser described the pedicled bilobed flap for nasal tip reconstruction, which draws on tissue that is adjacent to the skin defect, allowing for excellent texture and color match. Esser described a double transposition of 2 equal-sized flaps with a 180º total arc of rotation, which ultimately harvested skin from the glabellar region. The tension from such a large arc of rotation, however, increased the risk of flap necrosis and created unwanted cosmetic outcomes, such as dog-ears and pin-cushioning. Subsequently, several modifications have been described in the literature that aimed to minimize these complications. In 1953, Zimany modified the flap to use successively smaller lobes, allowing for a more esthetic closure without excessive tissue harvesting. In 1989, Zitelli decreased the total rotational arc to 90° to 100°. The smaller rotational arc helps to reduce tension, which improved the cosmetic result. This is the modification used most often today. Application of the bilobed flap has expanded beyond nasal reconstruction to include repair of other locations in the face like the cheek, ear, upper lip, zygoma, and orbit.
Bilobed flaps for smaller-sized defects have shown acceptable esthetic outcomes and low rates of complications. Salgarelli and colleagues reported their experience with the use of 285 consecutive Zitelli bilobed flaps used for facial reconstruction of various sites. They examined these flaps after the resection of basal cell carcinomas or squamous cell carcinomas, with defect sizes between 1 cm and 4 cm. They reported a 3.6% postoperative complication rate, with 2 cases of local infection, 1 complete flap necrosis, and 7 cases of partial necrosis requiring partial revision.
Although bilobed flaps traditionally have been utilized for smaller reconstructive defects around the face and neck, Mourad and colleagues demonstrated their utility in reconstruction of various larger defects. A total of 23 giant bilobed flaps were used, with the average-sized defect 27.2 cm. All closures were achieved in a single stage without the need for tissue expanders, free tissue transfers, or skin grafts. They reported acceptable cosmetic outcomes with no wound complications or flap breakdowns. In these cases, the bilobed flap functions much like a very large cervicofacial advancement flap because skin laxity from the neck and even chest can function as a double transposition flap with primary closure of the donor site. Moore and colleagues illustrated the great versatility of local double transposition flaps for large head and neck defects in a 33 patient series. Although limited by the small number of the series, the investigators found no detrimental impact of prior smoking, prior radiation, or medical comorbidities, illustrating the robust nature of these flaps and their applications for patients unfit for free tissue transfer.
Nasal anatomy
The nose can be divided into 3 zones, each with different tissue characteristics. Zone 1 includes the upper half the nose and is made of thin, movable tissue. Zone 2, which includes the ala and tip, is made of skin that is sebaceous, thick, and less movable. Zone 3 has tissue characteristics that are similar to those of zone 1 and includes the columella and infratip lobule. There is a rich blood supply to the skin of the nose that comes laterally via tributaries of the angular artery and from the columellar artery as a branch of the superior labial artery. The dorsal nasal artery and infraorbital artery also contribute to the vascular supply of the nose and have multiple anastomoses, with the branches of the angular artery giving the nose a rich blood supply for local flap reconstruction.
Surgical technique
See Figs. 1–3 .
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Circumscribe the skin defect in a circular fashion.
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Note the center of the defect and measure the radius, “r”.
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Next, determine the pivot point, also known as the base. The pivot point is marked 1r length, perpendicularly from the edge of the defect, typically placed lateral to the defect. The region approximately 90° from the lesion about this pivot point should be an area with sufficient tissue laxity to accommodate transposition.
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Mark a line from the pivot point that is 90° – 110° to the line created between center of the lesion and the pivot point. The angle created is the total axis of rotation for the entire flap.
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To plan for the donor site design, 2 concentric 90° arcs are drawn with the pivot point as the center.
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The first arc is drawn 2r from the pivot point, and the second arc is drawn 3r from the pivot.
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The first lobe, that is, the primary donor site, is drawn as a circle adjacent to the defect, with its center 45° from the center of the lesion, about the pivot point (P). The width of this circle should be approximately equal to the width of the defect, but no bigger. As such, the radius of this lobe is 1r and should reach the outermost arc. In tissues with more laxity than nasal skin, the width of primary donor site can be 1/2r of the defect because undermining allows closure of the wound.
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The second lobe is approximately triangular in shape, with its center 45° from the center of the first lobe. The second lobe is drawn adjacent to the first lobe, with its base corner at the previously drawn inner arch, adjacent to the base of the first donor site. The width of the base should be slightly smaller than the width of defect. The apex of this triangle should extend just beyond the outer arc to complete the outline of the bilobed flap.
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To allow for rotation of the flap into the defect, draw 2 tangent lines from the pivot point to the skin defect. The resulting V-shaped tracing (also known as the Burow triangle) is excised to allow for rotation of the flap.
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The flaps are elevated in a supra-perichondrial plane.
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The surrounding tissue is elevated in a supra-periosteal and supra-perichondrial plane or in a submuscular plane in laterally based flaps.
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Remember that the thickness of the transposed flap depends on the depth of the defect. As such, the subcutaneous tissues should be trimmed accordingly.
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The terminal donor site is closed primarily.
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The lobules are inset with deep, 5-0 absorbable monofilament sutures in a horizontal mattress technique, and the skin is closed with meticulous care in the surgeon’s preferred method.
