**3. Abnormal anatomy of unilateral cleft deformity: muscle imbalance, tissue hypoplasia, and skeletal asymmetry**

*"If you can articulate a problem, it is 98% solved."*

—Edwin Land

The severity of a unilateral cleft lip varies from the microform (**Figure 1A**) to a complete cleft extending into the nasal sill (**Figure 1B**). Varying degrees of nasal deformity and alveolar deficiency may also be present [5, 6]. There is varying degree of absence of central lip, philtral and nasal columella tissue [7].

The unilateral cleft typically results in a disruption of cupid's bow and the absence of one philtral column. The continuity of the orbicularis oris circumferentially is compromised, with abnormal insertions. In the lateral lip element, the upper part of cutaneous orbicularis (Pars Superficialis) inserts in the lateral aspect of the alar base and the nasolabial fold, while the lower part inserts into the nostril base periosteum of the pyriform rim. In the medial lip ele‐ ment, the cutaneous orbicularis (pars superficialis) inserts into the anterior nasal spine and columella. The deep orbicularis (pars marginalis) is simply interrupted by the cleft deficiency and results in a diminished vermillion‐cutaneous ridge at the cleft margin (**Figure 2B**).

Anatomical characteristics of unilateral cleft lip include nasal deformities of the tip, columella, nostril, alar base, septum, and skeleton. The lower lateral cartilages on the cleft side have a short medial crus, an obtuse genu, and a lateral crus that is longer and drawn into an S‐shaped fold (**Figure 3B**). The caudal septum is deviated toward the noncleft side. The nasal tip it typi‐ cally directed toward the noncleft side [8]. In addition, the columella is shorter on the cleft side with deviation toward the noncleft side due to the unopposed action of the orbicularis oris. The alar base is more horizontal on the cleft side with deviation of the nasal septum toward the noncleft side. The alar base on the cleft side is positioned laterally, inferiorly, and posteriorly.

Nasal deformities in a unilateral cleft lip‐nose arise from this cartilage deformity, muscle imbalance, and skeletal hypoplasia [5]. The various deformities are listed here:


(**Figure 3A**). The scroll area refers to the overlapping of lateral crura with the caudal edge of upper lateral cartilages. The nasalis muscle originates at the incisive fossa and inserts into four different regions. The transverse part courses past the alar base around the lateral side of the nose, and ascends medially to join procerus and the contralateral transverse fibers at midline. Fibers that course around the alar rim and above the lower lateral cartilages are the alar portion of nasalis. The columella and basal parts insert in the membranous sep‐ tum, medial crura, and nostril sill skin. The columellar part of nasalis is synonymous with

The facial artery is the main blood supply to the upper and lower lips. The facial artery travels through the cheek beneath zygomaticus major and superficial to buccinator muscles, giving rise to the inferior and superior labial arteries. Once the superior labial artery emerges from the zygomaticus major, it may dive into the substance of the orbicularis oris, giving rise to the ipsilateral columellar artery. After giving rise to the superior labial artery, the facial artery terminates as the angular artery. The lateral nasal artery is a branch of the angular artery.

**Figure 3.** (A) A schematic representation of the lower lateral cartilages demonstrating symmetry. (B) A schematic representation of the lower lateral cartilages demonstrating asymmetry: a short medial crus, an obtuse genu, and a

**3. Abnormal anatomy of unilateral cleft deformity: muscle imbalance,** 

*"If you can articulate a problem, it is 98% solved."*

—Edwin Land

**tissue hypoplasia, and skeletal asymmetry**

lateral crus that is longer and drawn into an S‐shaped fold on the cleft side.

depressor septi.

76 Designing Strategies for Cleft Lip and Palate Care
