Upper Lip Anatomy, Mechanics of Local Flaps, and Considerations for Reconstruction

Function of the Upper Lip

Although the primary purpose of OO is sphincteric function, the upper lip’s key role is coverage of dentition and facial animation.¹² The latter is achieved through the relationship of multiple muscles, including levator labii superioris, levator septi nasi, risorius, zygomaticus minor, zygomaticus major, levator anguli oris, and buccinator.^7,13-17 Their smooth coordination results in various facial expressions. In comparison, the lower lip is critical for preservation of oral competence, prevention of drooling, eating, and speech due to the actions of OO and vertical support from the mentalis muscle.^1,18-22

Reconstructive Methods for the Upper Lip

Multiple options are available for reconstruction of upper lip defects, with the aim to preserve facial animation and coverage of dentition. When animation muscles are involved, restoring function is the goal, which can be achieved by placing sutures to reapproximate the muscle edges in smaller defects or anchor the remaining muscle edge to preserve deep structures in larger defects, respecting the vector of contraction and attempting simulation of the muscle function. Additionally, restoration of the continuity of OO also is important for good aesthetic and functional outcomes.

Janis²³ proposed the rule of thirds to approach upper and lower lip reconstruction. Using these rules, we briefly analyze the available flaps focusing on animation, OO restoration, preservation of the modiolus position, and sensation for each (eTable).

The perialar crescentic flap, an advancement flap, can be utilized for laterally located partial-thickness defects affecting up to one-third of the upper lip, especially those adjacent to the alar base, as well as full-thickness defects affecting up to two-thirds of the upper lip.^7,24 The OO continuity and position of the modiolus often are preserved, sensation is maintained, and muscles of animation commonly are unaffected by this flap, especially in partial-thickness defects. In males, caution should be exercised where non–hair-bearing skin of the cheek is advanced to the upper lip region. Other potential complications include obliteration of the melolabial crease and pincushioning.⁷

Nasolabial (ie, melolabial) flaps are suggested for repair of defects up to one-third of the upper lip, especially when the vermilion is unaffected, or in lateral defects with or without commissure involvement.^7,24-28 This flap is based on the facial artery and may be used as a direct transposition, V-Y advancement, or island flap with good aesthetic and functional outcomes (Figure 1).^29,30 There is limited literature regarding the effects on animation. However, it may be beneficial in avoiding microstomia, as regional tissue is transferred from the cheek area, maintaining upper lip length. Additionally, the location of the modiolus often is unaffected, especially when the flap is harvested above the level of the muscle, providing superior facial animation function. Flap design is critical in areas lateral to the commissure and over the modiolus, as distortion of its position can occur.²⁶ Similar to crescentic advancement, it is important to exercise caution in male patients, as non–hair-bearing tissue can be transferred to the upper lip. Reported adverse outcomes of the nasolabial flap include a thin flat upper lip, obliteration of the Cupid’s bow, and hypoesthesia that may improve over time.³⁰

Figure 1. A, A patient with a 2.6×2-cm wound of the right upper lip following Mohs micrographic surgery stage 1. B, The defect was repaired using a 17.5-cm2 advancement flap with musculocutaneous pedicle.

The Abbe flap is suitable for reconstruction of upper lip defects affecting up to two-thirds of the upper lip and lateral defects, provided the commissure or philtrum is unaffected.^7,8 It is a 2-stage lip-switch flap based on the inferior labial artery, where tissue is harvested and transferred from the lower lip (Figure 2).^23,31 It is particularly useful for philtral reconstruction, as incision lines at the flap edges can recreate the skin folds of the philtrum. Moreover, incision lines are better concealed under the nose, making it favorable for female patients. Surgeons should consider the difference in philtral width between sexes when designing this flap for optimal aesthetic outcome, as males have larger philtral width than females.²¹ The Abbe flap allows preservation of the Cupid’s bow, oral commissure, and modiolus position; however, it is an insensate flap and does not establish continuity of OO.²³ For central defects, the function of animation muscles is not critically affected. In philtral reconstruction using an Abbe flap, a common adverse outcome is widening of the central segment because of tension and contraction forces applied by the adjacent OO. Restoration of the continuity of the muscle through dissection and advancement in small defects or anchoring of muscle edges on deeper surfaces may avoid direct pull on the flap. In larger central defects extending beyond the native philtrum, it is important to recreate the philtrum proportional to the remaining upper and lower lips. The recommended technique is a combination of a thin Abbe flap with bilateral perialar crescentic advancement flaps to maintain a proportional philtrum. Several variations have been described, including 3D planning with muscular suspension for natural raised philtral columns, avoiding a flat upper lip.⁵

Figure 2. An Abbe flap. A, Design. Obtains blood supply from the ipsilateral artery. B, Flap inset with pedicle in place. It is divided 14 to 21 days later. Illustrations courtesy of Joshua P. Hays, MD (Houston, Texas).