The upper lip poses challenges during reconstruction. Distortion of well-defined anatomic structures, including the vermilion border, oral commissures, Cupid’s bow, and philtrum, leads to noticeable deformities. Furthermore, maintenance of upper and lower lip function is essential for verbal communication, facial expression, and controlled opening of the oral cavity.
Similar to a prior review focused on the lower lip,1 we conducted a review of the literature using the PubMed database (1976-2017) and the following search terms: upper lip, lower lip, anatomy, comparison, cadaver, histology, local flap, and reconstruction. We reviewed studies that assessed anatomic and histologic characteristics of the upper and the lower lips, function of the upper lip, mechanics of local flaps, and upper lip reconstruction techniques including local flaps and regional flaps. Articles with an emphasis on free flaps were excluded.
The initial search resulted in 1326 articles. Of these, 1201 were excluded after abstracts were screened. Full-text review of the remaining 125 articles resulted in exclusion of 85 papers (9 foreign language, 4 duplicates, and 72 irrelevant). Among the 40 articles eligible for inclusion, 12 articles discussed anatomy and histology of the upper lip, 9 examined function of the upper lip, and 19 reviewed available techniques for reconstruction of the upper lip.
In this article, we review the anatomy and function of the upper lip as well as various repair techniques to provide the reconstructive surgeon with greater familiarity with the local flaps and an algorithmic approach for upper lip reconstruction.
Anatomic Characteristics of the Upper Lip
The muscular component of the upper lip primarily is comprised of the orbicularis oris (OO) muscle divided into 2 distinct concentric components: pars peripheralis and pars marginalis.2,3 It is discontinuous in some individuals.4 Although OO is the primary muscle of the lower lip, the upper lip is remarkably complex. Orbicularis oris and 3 additional muscles contribute to upper lip function: depressor septi nasi, the alar portion of the nasalis, and levator labii superioris alaeque nasi (LLSAN).5
The modiolus, a muscular structure located just lateral to the commissures, serves as a convergence point for facial muscle animation and lip function while distributing contraction forces between the lips and face.6 It is imperative to preserve its location in reconstruction to allow for good functional and aesthetic outcomes.
The upper lip is divided into 3 distinct aesthetic subunits: the philtrum and 1 lateral subunit on each side.7,8 Its unique surface features include the Cupid’s bow, vermilion tubercle, and philtral columns. The philtral columns are created by the dermal insertion on each side of the OO, which originates from the modiolus, decussates, and inserts into the skin of the contralateral philtral groove.2,9-11 The OO has additional insertions into the dermis lateral to the philtrum.5 During its course across the midline, it decreases its insertions, leading to the formation and thinness of the philtral dimple.9 The philtral shape primarily is due to the intermingling of LLSAN and the pars peripheralis in an axial plane. The LLSAN enters superolateral to the ipsilateral philtral ridge and courses along this ridge to contribute to the philtral shape.2 Formation of the philtrum’s contour arises from the opposing force of both muscles pulling the skin in opposite directions.2,5 The vermilion tubercle arises from the dermal insertion of the pars marginalis originating from the ipsilateral modiolus and follows the vermilion border.2 The Cupid’s bow is part of the white roll at the vermilion-cutaneous junction produced by the anterior projection of the pars peripheralis.10 The complex anatomy of this structure explains the intricacy of lip reconstructions in this area.