Skin

The nasal skin is one of the most important structures of the nose. The final result of nasal surgery will be significantly influenced by the thickness, texture and sebaceous nature of the skin. The skin is usually thinner and more loosely attached over the cartilaginous and bony framework and thicker and more adherent in the nasal tip. Thin skin has a potential to contract and make obvious the changes to the underlining framework. On the other hand, thick sebaceous skin may make it difficult to obtain the desired result of changes to the framework, especially the tip. The arterial supply of the nose comes from two sources: (1) dorsal nasal artery (anterior ethmoidal), which is a branch of the ophthalmic artery and supplies the proximal nose and subdermal plexus of the tip; and (2) two branches of the facial artery, the angular artery and superior labial artery, both of which supply the nasal tip area.

Nasal tip

The nasal tip shape, size and projection is for the most part determined by the paired (though not necessarily symmetrical) alar cartilages, each of which have medial, middle and lateral crura, and their relationship to the adjacent structures (Fig. 37.1). The medial crura consists of flared (usually) footplates and the columella segment. The middle crus is a continuation of the medial crura and joins the lateral crus. The columella lobular junction is the transition from the nasal base to the tip lobule. The middle crus extends from the columella lobular junction to the lateral crus. The tip defining points, usually at the apex of the junction of the middle crus and lateral crus (the most projecting point on each side of the tip), produces an external light reflex (Fig. 37.2). The lateral crura make up the largest part of the nasal tip and join the accessory cartilages, which join the lateral crura to the pyriform aperture. The cartilages are supported by suspensory ligaments to each other and the caudal border of the upper lateral cartilages. The caudal edge of the lateral crura of the lower lateral cartilages, the nostril sills, the membraneous septum and the alae make up the external nasal valve (Fig. 37.3).

Fig. 37.1 Diagrams of the cartilaginous and bony nose and septum.

Fig. 37.2 Tip defining points as represented by light reflection from the highest point of alar cartilage projection.

Fig. 37.3 Cartilaginous framework showing the location of internal and external valves.

Nasal tip complex

Although other factors like skin thickness do have relevance, the aesthetic appearance of the tip is in large part defined by the paired alar cartilages and their relationship with the surrounding anatomical structures. The preoperative exam should include a thorough evaluation of the shape, size, location and inherent strength of the medial, middle and lateral crura of the alar cartilages. The etiology of tip abnormalities can be attributed to abnormalities in one or more of these specific anatomic areas. Over projection of the tip, for example, may be due to elongation of the medial crura or overdevelopment of the contributing structures like the lateral crura of the alar cartilages and dorsal septum. In the case of a boxy tip the deformity is often secondary to the presence of a strong, widened lateral crura and in some cases, a wide angle between the medial crura. When considering an underprojected tip, which is due to inadequate support, surgical intervention will vary with different ideologies. A simple resection of the caudal septum to cephalically rotate the tip, a cephalic trim of the alar cartilages with transdomal suturing, the addition of a columella strut between the medial crura and an assortment of tip grafts may all address these various deficiencies that lead to an underprojected tip.

Upper lateral cartilages

The upper lateral cartilages and their attachment to the septum make up the cartilaginous mid-vault. The junction of the upper lateral cartilages with the cephalic margin of the lower lateral cartilages defines the scroll area. The angle of the junction of the septum and upper lateral cartilages at this point determine the internal valve (usually 10 to 15 degrees). The cephalic end of the upper lateral cartilages is overlapped by the nasal bones for several millimeters. This is important in maintaining mid-vault support. The junction of the upper lateral cartilages with the nasal bones and septum has a T-shaped contour and is known as the keystone area.

Nasal bones

The nasal bones vary in length and thickness and along with the ascending frontal process of the maxilla make up the bony vault. The nasal bones articulate with each other medially, the upper lateral cartilages inferiorly, the maxilla laterally, the frontal bones superiorly and the perpendicular plates of the ethmoid posteriorly. Nasal osteotomies (Fig. 37.4) are best performed through the thinner bone along the transition zone in the ascending frontal process of the maxilla that exists from the pyriform aperture to the radix.

Fig. 37.4 Nasal bone anatomy in relationship to cartilaginous framework.

Nasal profile

The nasal profile (Fig. 37.5) is dictated by the osteocartilaginous vault and its relationship to the alar cartilages. Understanding this relationship is important when one considers reducing the dorsal hump (which is often more cartilage than bone). The amount of resection should be guided by the amount of tip projection, the nasal frontal angle and the supratip break on the lateral views. Tip projection is the distance the nose projects from the face, or more anatomically defined as the distance from the tip of the nose to the most posterior point of the nose-cheek junction. The nasal frontal angle, which approximates 115 to 130 degrees, its location and depth, will dictate if it should be left alone, lowered, augmented or if the dorsal hump should be reduced. Similarly, if the nose lacks tip projection, increasing tip projection (tip augmentation, strut graft) may alleviate the need for, or influence the amount of dorsal hump reduction.

Fig. 37.5 An ideal profile.

Columella and nasolabial angle

In the lateral view the preferred appearance of the columella is a slow curving structure traveling from the nasal tip to the base of the nose with a slight overhang in comparison to the alar base. In the basal view, a 2 : 1 ratio of the length of the columella to the length of the lobule is desirable (Fig. 37.6) and the base should be slightly wider than the confluence of the columella with the tip. In patients with a deficient columella, one will find a disruption of the length ratio between the columella and the lobule along with a distortion or the flaring of the alae. This is a common finding in some ethnic noses such as African and Asian. A retracted columella may occur in isolation or in combination with other abnormalities like a plunging tip. Even though the medial crura, the membraneous septum and the caudal septum all contribute to the shape of the columella, augmentation of the medial crura with a cartilage graft is the most common option for correction of a retracted columella. In comparison, an overhanging columella can often be corrected by a simple trim of the caudal septum or a reduction of the most caudal edge of the medial crura.

Fig. 37.6 A–C, Lobule–columella ratio is corrected following strut graft.

Patients may also present with a widened columella base secondary to enlarged or widened feet of the medial crura. This is commonly addressed with a direct resection, or in less severe cases with suture plication. The nasolabial angle influences the appearance of the columella. Commonly 90 to 95 degrees in men and 90 to 100 degrees in woman, this angle determines the degree direction of tip rotation required in a specific case. If the tip is over rotated cephalically, then elongated spreader grafts may be used to rotate the tip in a caudal direction. In comparison, if the tip is over-rotated caudally, then an oblique caudal septal resection, transection of the depressor septi nasi muscles or a columella strut graft can all change the angle and rotate the tip in the cephalic direction.

Alar shape and alar base width

Alar shape and alar base width vary depending on the patients’ racial characteristics. An important standard to consider in evaluation is that the alar base width should approximate the intercanthal distance. This is useful when evaluating patients that have a perceived flaring of the nostrils. Operative planning of any type of alar resection must be a process that considers symmetry, patients’ ethnic characteristics and placement of resulting scars. It is imperative to avoid iatragenic disproportion of the lobule and nostril; a conservative section is recommended.

Nasal deviation

External deviation is primarily a result of deformities present in the nasal bones, cartilaginous septum or the nasal tip. A thorough pre-operative exam that evaluates the dorsal lines (Fig. 37.7) will help define the anatomic areas where the deviation occurs (upper, middle or lower third of the nose). The dorsal lines begin in the infra-brow area, curving gently, to converge at the level of the medial canthus, then diverge slightly at the keystone area and continue to diverge slightly as they continue down to the tip defining points. With this information the deviation can be addressed at different steps of the procedure: Infracture of asymmetric nasal bones for an upper third deviation, septoplasty and/or placement of unilateral spreader grafts for middle third deviations and revision of tip asymmetry or nasal spine repositioning for lower third deviation. Even in cases without deviations, the location of the nasal bones in reference to the nasal base width will dictate whether infracture is necessary. In most instances a wide nasal base, which is greater than 80% of the alar base width, will require infracture to improve the frontal view proportions.

Fig. 37.7 Dorsal lines begin at the infrabrow area and extend to tip defining points.