Bilobed Flaps - Indications, Contraindications, and Procedure

Introduction

Human skin has a natural repairing system. Any damage or break in the tissue or skin is repaired sequentially by the body cells. There are various causes of such damage to the human skin, such as a cut, injury, trauma, and burn. Some damages are large, and some are small. When the damages are large and severe, they do not heal on their own; they become a defect or deformity. Large defects in the skin require special support for healing. It means a healthy piece of the skin or tissue should be transplanted into the defect for healing. These pieces of tissue can be a skin graft or a flap.

In severe nasal defects, for example, special skin flaps are used to restore and reconstruct the shape of the nose. A bilobed flap is one such flap that is commonly used in nasal reconstruction procedures. A piece of adjacent tissue, along with a fat layer and intact blood vessels, is transplanted into the defect, and it becomes a flap. A bilobed flap is commonly used in oval or round-shaped defects.

What Are Bilobed Flaps?

These are double transposition flaps with a joint base meaning that two tissues are attached on a tissue bridge. Each lobe has a separate spindle that creates a separate, individual cutaneous deformity.

What Is a Transposition Flap?

These flaps are taken from a donor site and are transferred to the defect area. The skin, mucosa, and blood supply remain intact and are transplanted for treatment procedures. These are also called lifting flaps.

What Are the Commonly Used Transposition Flaps?

These are commonly used in cutaneous surgery that includes:

• Bilobed Transposition Flaps - These are double transposition flaps with a joint base meaning that two tissues are attached on a tissue bridge.

• Rhombic Transposition Flaps - These are used in rhombic-shaped defects.

• Nasolabial Transposition Flaps - These are versatile flaps used in various nose-related reconstructive procedures such as nasal tips.

• Z-Plasty - These are triangular-shaped double transposition flaps used to improve the appearance of the scar.

What Is the History of the Bilobed Flap?

• It was first described by Esser in 1918 and used for nose tip defects. The 180 degrees angle transportation and placement of the second flap over the primary flap towards the glabellar region resulted in undesirable outcomes such as deformities.

• Zimany, in 1953, described the use of the second and third lobes as smaller than the first lobe.

• McGregor and Soutar, in 1980, reduced the pivot angle to reduce the complications.

• Zitelli, in 1989, modified the arc angle between 90 to 110 degrees. This modification is most commonly used.

What Are the Uses of Bilobed Flaps?

Bilobed flaps are helpful in:

• Cheek reconstruction procedures to repair large defects.

• Repairing central and lateral cheek defects.

• Nasal reconstruction to repair the tip of the nose.

• Repairing small to medium-sized defects.

• Repairing the lower third part of the nose.

• Repairing defects in the neck, eyelids, ears, feet, or hands.

What Is the Anatomy of Bilobed Flaps?

• Position: There are two lobes attached to a common base. When the bilobed flap is placed over a defect, the first lobe fills the primary defect, and the second lobe fills the space or remaining defect left by the first lobe - the secondary defect. The first, or the original flap, uses a rotational arc of 180 degrees, and the second lobe is placed superior to the first lobe.

• Blood Supply: The blood supply of these flaps comes from the subdermal plexus - a junction between the deep layer of the skin and fat tissue. This creates a random pattern of the blood supply which is different from the other blood supply from a blood vessel - the axial blood supply.

• Placement: Most of these flaps are placed in the subdermal region while filling the defect. This ensures the blood supply from the subdermal plexus is intact.

Which Bilobed Flap Is Most Commonly Used?

Zitelli’s modified bilobed flap at 45 degrees angle is a commonly used variant over other bilobed flap variants, such as Esser’s design which uses 90 degrees angle.

What Is the Surgical Technique for Using Bilobed Flaps?

Before placing a flap to fill the defect, it is important to remove all the damaged tissues. The technique to place a bilobed flap includes:

• The defect shape must be oval or round-shaped.

• A central point is selected from the defect edges, and tangent lines are drawn toward the edges of the circle or defect. This prevents a dog-ear formation (which is formed when wounds on opposite sides of the ear are uneven and the skin can get distorted with the simple closure of the adjacent skin) of defective edges.

• The first of the primary lobe is drawn at 45 degrees angle from the central or pivot point. The length of the flap is similar to or larger than the defect dimensions.

• If the skin is non-elastic, for example, the tip of the nose, then the flap or lobe size must be larger than the defect. If the skin is elastic, then the flap or lobe size must be smaller than the defect to cover up to 80 % of the area.

• The second lobe or secondary lobe is created at 90 degrees angle from the central point.

• Ideally, the size of the second lobe should be longer than the first lobe and narrow at the base such that it is half of the diameter of the primary lobe. However, some doctors suggest that the width of the primary defect, primary lobe, and secondary lobe should be equal in size to minimize distortion, But some doctors may also suggest that both primary and secondary lobes should be small-sized.

• The secondary lobe should be excised with a cone-shaped or triangular tip. This creates a linear or straight scar at the donor site.

• After the flap excision, the donor site and the defect site must be undermined, meaning that the edges must be loosened.

• After the excision, the flap should be rotated at 45 degrees. This ensures that the primary lobe covers the defect and the secondary lobe covers the left-out spaces.

• The donor site is closed with sutures, and the primary lobe is sutured into the defect.

• The secondary flap is trimmed and sutured into the left-out defect.

• After the defect is closed, the bilobed flaps resemble the shape of a heart’s upper part or semi-circles.

• Propylene dressing with adhesive tape should be placed for at least one week.

What Are the Complications of Bilobed Flap Surgery?

The possible complications include:

• Pain.

• Swelling.

• Scar formation.

• Flap necrosis.

• Bleeding.

• Trapdoor effect which means the flap is elevated above the surrounding tissues because of undermining of the flap, larger flap size, excessive fat in the flap tissue, or insufficient flap contact at the base of the defect.

• Pincushing deformity may also develop due to subdermal tissue construction, which can be overcome by reducing the tension at closure.

What Are the Contraindications of the Bilobed Flap?

The bilobed flap surgery should be done in:

• Patients with smoking habits.

• Patients who have peripheral vascular disease near the defect (narrowed blood vessels that reduce the blood flow in limbs).

• Patients who take anticoagulant medications.

• Patients with a history of infection, radiation, or allergic reactions.

• Patients have a history of cardiovascular diseases and malignant hyperthermia.

What Is the Geometric Description of Bilobed Flaps?

The geometric measurements of the bilobed flap can be difficult because of the angles and varying contours of the nose from patient to patient. In general, the design includes:

1. Measure the diameter of the defect size.

2. The distance of the bilobed flap should be equal to the radius of the defect. If the central or pivot point is away, then the flap should be large.

3. At an angle of 45 degrees, a concentric circle is drawn with the diameter of the defect and the distance of the flap from the defect. The primary lobe is taken from here.

4. At an angle of 90 degrees from the central point, the secondary lobe is taken.

5. A dog-ear excision shape is marked from the pivot point to the defect.

Conclusion:

Bilobed flaps are two lobes attached to a common base. When the bilobed flap is placed over a defect, the first lobe fills the primary defect, and the second lobe fills the empty space or remaining defect left by the first lobe - the secondary defect. The geometric construction of this flap is difficult because it is made with 45 and 90-degree angles. The placement of the flap with a precise angle plays an important role in the success of the bilobed flap technique. The doctor should inform the patient beforehand that the suture lines can be significantly longer than the actual defects. In addition, they must also inform the patient that the procedure might be multi-stage and they may have to undergo various types of surgical interventions, such as intralesional steroid injection.