# Introduction

The reconstruction of upper lip defects in dermatologic surgery presents a number of notable challenges, particularly. When the defects are located next to or on the mucosal junction [1]. Common therapeutic options often involve sacrificing the unaffected orbicularis oris muscle, which can have significant functional implications. Although simple transposition flaps represent a potential alternative, they may result in muscle winding with intraoral protrusion [2,3]. The use of multiple transposition flaps for the repair of extensive mid-upper lip defects has been documented in the literature and it appears to be a promising approach [4,5]. We address these challenges using a birhombic flap technique specifically designed to avoid these pitfalls [6,7].

# Methods

This retrospective study included all birhombic flap procedures conducted between September 2022 and December 2023 in our dermatology department. Informed consent was obtained from all patients, and pre-, peri-, and post-operative photographs were systematically taken. The data set comprised information derived from medical records and photographic documentation, including patient age, histologic classification of the treated lesion, type of anesthesia administered, defect size, location, and the potential for complications to occur. Esthetic and functional evaluations were collected from patients and rated on a scale from 0 to 5 (0 = not satisfied, 5 = very satisfied).

We utilized an inferiorly based birhombic flap having the following specifications (Fig. 1
                     ):
                        
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                           The starting point for the first lobe was established at either 11o’clock or 1 o’clock depending on the side of the wound (outward) corresponding to the superior border of the defect.
                        
                        
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                           The primary limb extended along the axis of the radial folds of the lip, with a length equal to that of the cutaneous lip defect (vermilion defect excluded), similarly to a Limberg or Dufourmentel flap.
                        
                        
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                           The apical angle was set at 60°, and the length of the primary limb was maintained.
                        
                        
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                           To improve flap mobility, a second lobe was designed as a Z-plasty from 60° to 120° to the outer limb, maintaining a 60° apical angle. The flap could be directed into the lip or cheek, maintaining a perpendicular orientation relative to the melolabial fold.

The overall design of the flap resembled a capital letter M.

Subsequently, a flap incision was made, and undermining was performed above the orbicularis oris muscle until the vermilion was reached. The flap was then rotated, transposed, and advanced to close the cutaneous portion of the wound using a running suture with 5–0 polyglactin 910, extending from the third defect to the primary defect. The observed flap movement resulted in the formation of a standing-cone deformity (SCD) at the base of the primary defect. Subsequently, the cutaneous portion of the SCD was excised by means of a triangular incision along the vermilion. The vermilion part of the defect was treated either by direct closure or using a rhombic transposition flap. The rhombic transposition flap was created by making an incision at a 90° angle from the lower border of the defect into the labial mucosa of the mouth, with a 60° apical angle. The flap was undermined above the muscle and subsequently advanced into position.

# Results

The study cohort comprised 15 patients, with an age range of 50 to 91 years (mean age 75 years). Tumors were predominantly basal cell carcinoma (n = 12) and squamous cell carcinoma (n = 3). All, but one procedure, were conducted under local anesthesia. Demographic and surgical data are detailed in Table 1
                     . The mean defect length was 1.76 cm (range: 1.4 cm to 2.3 cm). Eight cases exhibited a vermilion defect, and one patient underwent a mucosal transposition flap procedure to repair the vermilion defect. No complications were documented. The mean scores for the esthetic and functional evaluations were 4.36 (range: 2–5) and 4.15 (range: 2–5), respectively. Three patients reported mild labial stiffening.

# Discussion

In our series, the skin defects were situated next to or beyond the vermilion. The use of rotation flaps in this area necessitates the sacrifice of muscle tissue, which may subsequently result in functional impairment [8]. The advancement of perialar crescentic cheek flaps has been seen to result in the obliteration of the nasolabial fold [9,10]. The use of island flaps warrants enlargement of the defect to the full height of the lip, thereby avoiding the formation of an unsightly horizontal scar. These procedures necessitate the extensive undermining of tissue and result in prolonged edema [10]. While simple transposition is an interesting possibility, the closure of the donor site could result in a profound muscular protrusion. To circumvent this issue, the introduction of a second lobe to displace the pivot point outside the lip appears to be a promising solution. The use of the bilobed flap technique in the reconstruction of upper lip defects has been shown to yield favorable outcomes. The M−shaped design, which incorporates a Z-plasty for enhanced flap mobility, allows for versatile application in a range of defect sizes and locations.

Three distinct defect locations and flap designs were identified:
                        
                           1-
                           Defect on the middle third of the hemi lip, along or on the vermilion border. The second lobe was either totally or partially in the cheek, perpendicular to the melolabial fold. This defect was observed in eight cases (Fig. 2
                              ).
                        
                        
                           2-
                           Small size (≤ 1.5 cm) on or close to the philtrum, along or on the vermilion border, treated by means of an infralabial flap (3 cases) (Fig. 3
                              ).
                        
                        
                           3-
                           Large size (>1.5 cm) extending completely or almost completely over the entire length of the lip, close to the philtrum, with the first lobe raised from the perialar triangle and the second lobe from the cheek perpendicular to the melolabial fold (4 cases) (Fig. 4
                              ).

The standing cone deformity must be corrected as required along the vermilion border by trimming excess skin in order to achieve a precise fit. The absence of reported complications indicates that the birhombic flap technique is safe and feasible. The use of angulated repair lines often results in the formation of scars that are not readily discernible. A potential complication of transposition flaps is pincushioning. This early hypertrophy scarring can be treated by prompt injection of corticosteroids. In our series, we did not use this option, as spontaneous resolution commonly occurs [11]. The results of the esthetic and functional evaluations indicated a high level of patient satisfaction, with mean scores of 4.36 (range: 2–5) and 4.15 (range: 2–5), respectively. These findings highlight the effectiveness of the technique in addressing both cosmetic and functional goals.

In conclusion, the bilobed flap appears to be a viable option for consideration in the treatment of lateral upper lip defects, particularly when lesions are situated near or on the vermilion border.

# Funding sources

None.