Lip reconstruction

Cosmetic goals

Cosmetic goals of lip reconstruction involve restoration of the natural anatomy, of which there are several subunits ( Fig. 11.1 ). The primary difference between the anatomy of the upper and lower lips is the presence of the philtrum and associated Cupid’s bow of the upper lip, which divide the upper lip into its subunits. The philtral columns, created by contralateral orbicularis oris fibers that attach to the underlying dermis, extend from the vermilion to the nasal base. At the inferior extent of these columns lies Cupid’s bow, so named because of its resemblance to the god of love’s weapon. Inferior to that structure are the three tubercles of the upper lip, one centrally and two laterally. This differs from the lower lip, which only contains two symmetric tubercles and lacks any significant defining features on its cutaneous portion. Laterally, the oral commissure is the junction between the upper and lower lips and presents a difficult reconstructive challenge when violated. Not only is the commissure and its underlying fibrous modiolus, which serves as a site for intersecting muscle attachment, a distinct anatomic feature of the lip, it also plays a key role by preventing the spillage of oral contents out of the corner of the mouth.

A crucial component of lip reconstruction is the precise alignment of the vermilion border, or mucocutaneous ridge. This well-vascularized structure lacks minor salivary glands and has a thin overlying epithelial layer. The red vermilion represents the transition from its external keratinized squamous epithelium to the non-keratinized squamous epithelium of the oral mucosa. Regarding the white roll surrounding the vermilion, its contour and color is created by the pars marginalis fibers of the orbicularis oris. As little as a 1 mm misalignment of this junction between the cutaneous and vermilion red lip can be noticeable at conversation distance. Both the vermilion and the white roll are widest at the central lip, gradually tapering laterally. In order to reapproximate the white roll, techniques such as intraoperative methylene blue tattooing of the respective edge may be employed to ensure those points are precisely aligned.

The restoration of the normal harmonious contour of the lips is also an important cosmetic consideration. On profile, the upper lip protrudes anteriorly relative to the lower lip, and in both lips there is a slight Indentation beyond the vermilion borders. When this harmony is lost, particularly in patients with cleft lip deformity and in some burn patients with severe contractures and lip ectropion, obvious and marked deformity results. Finally, in the male, the restoration of hair-bearing skin components of the lip is also an important cosmetic consideration when planning reconstruction.

Functional goals

While normal appearance of the lip is ideal, the primary objective of lip reconstruction is the restoration of a functional oral sphincter with adequate oral aperture to enable proper feeding and speech. Appropriate oral aperture and adequate depth of the lip sulci are important, particularly in the lower lip, in maintaining proper oral and dental hygiene, preventing drooling, and allowing patients to wear dentures or other removable prostheses. A secondary goal accomplished in the restoration of this sphincter and the surrounding musculature is the ability to animate the lips for the expression of emotion.

These goals are satisfied by careful reapproximation of the orbicularis oris, which is composed of two layers. The pars marginalis lies anterior beneath the vermilion and functions to protrude the lips outward. The deeper pars peripheralis extends to the cutaneous lip from an area deep to the pars marginalis and brings the lips in toward the maxillary and mandibular arches. When combined, this creates the “pucker” motion.

The remainder of the musculature in this region primarily serves the purpose of facial expression ( Fig. 11.2 ). Upper lip elevators are innervated by buccal branches of the facial nerve and include, from medial to lateral, the levator labii superioris alaeque nasi, levator labii superioris, zygomaticus minor, zygomaticus major, and risorius. Depressors of the inferior lip include the depressor labii medially and the depressor anguli oris laterally, which are innervated by mandibular branches of the facial nerves. The depressors and levators intersect just lateral to the commissures at the fibrous modiolus. This structure can often be marked by a dimple, which represents the center of the dermal insertion of the two heads of the zygomaticus major. The platysma extends superiorly from the neck and may also play a role in lower lip depression. Conversely, the mentalis muscle contracts against the mandible, raising the lower lip to create a “pout”. Posteriorly, the buccinator and pharyngeal constrictors insert on the lip to force it posteriorly against the intraoral sulci.

Blood supply to the upper and lower lip is provided by the superior and inferior labial arteries, respectively, which originate from the external carotid artery via the facial artery, which branches approximately 1.5 cm lateral to the oral commissure. While the anatomy is variable, these typically course between the lip mucosa and orbicularis oris and anastomose at the midline, although the inferior labial artery has been shown to have various branching patterns. Venous drainage does not follow the arterial pattern, but a dense venous syncytial plexus exists in the lips, which eventually empties into the facial vein located more laterally in the cheek and lateral to the facial artery.

Sensory innervation to the upper and lower lip is provided via the maxillary and mandibular divisions of the trigeminal nerve, respectively. Loss of sensory innervation can eliminate the ability to distinguish hot versus cold during oral intake, or the ability to sense inadvertent trauma to the lip during mastication. Motor innervation to the orbicularis oris and all surrounding muscles of facial expression is controlled by the buccal and marginal mandibular branches of the facial nerve, with potential contributions from the cervical branch to the lip depressors. All of these muscles are innervated on their deep surface, with the exception of the mentalis, levator anguli oris, and buccinator. Disruption of motor innervation can be a particularly devastating consequence, as this compromises the functional oral sphincter, diminishing or potentially eliminating the ability to perform actions such as speaking, eating, drinking, and sucking.

Etiology of the defect

Lip defects fall into three major etiologic classes: traumatic, malignant, and congenital. Traumatic defects can present secondary to any of a variety of mechanisms, from motor vehicle collisions to animal bites. As with all lip defects, they should be assessed to determine the structures involved that require reconstruction. While these injuries often appear large on initial assessment, the tissue edges tend to gape due to the sphincteric forces of the orbicularis oris and typically do not have loss of tissue once the wound is cleaned and thoroughly examined.

In terms of malignant lesions, the vast majority of cancers of the lip occur on the lower lip, likely due to its increased sun exposure. Squamous cell carcinoma is the most common overall, while basal cell carcinoma is the most common on the upper lip. Defects may also be congenital in nature, such as in patients with cleft lip and palate, although the unique reconstructive methods utilized in their repair is beyond the scope of this topic.