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Nasal anatomy
Under the skin of the nose lie soft tissue layers, a muscle and fascia layer called the nasal SMAS, and a framework of bone above and cartilage below. Rhinoplasty raises the soft tissue off this framework and reshapes the framework.
Outside to inside
Skin and soft tissue thickness is measured at the nasion, rhinion, supratip and tip. In a 35-patient ultrasound study, swelling at the rhinion was greater early in thin skin and lasted longer in thick skin. In a 57-patient randomized trial, taping for 2 or 4 weeks reduced skin thickness in thick-skinned patients and had no effect in thin skin.[1][2]
A 1988 study of 30 noses found five soft tissue components under the dermis: a superficial fatty layer, a fibromuscular layer, a deep fatty layer, a longitudinal fibrous sheet and an interdomal ligament. The nasal SMAS is part of the SMAS of the face, and raising the envelope beneath the nasal muscles keeps these layers intact. A 2008 study of 30 cadavers found the nasal SMAS divides at the nasal valve into deep and superficial layers, and cutting their medial expansions allows the tip to rotate upward.[1][2]
The paired nasal bones form the upper third of the nose. In CT scans of 600 patients from six populations, the ethmoidal point lay on average 10.1 mm above the rhinion, and in most patients the hump had no ethmoid bone under it and its peak sat over septal cartilage. Surgeons shape the bony vault with saws, chisels, osteotomes and rasps, or with piezoelectric instruments.[1][2]
The upper lateral cartilages form the middle third and join the nasal bones at the keystone area. The internal nasal valve, bounded by the septum, the lower edge of the upper lateral cartilage and the inferior turbinate, lies about 1.3 cm inside the nose at an angle of 10 to 15 degrees in Caucasian noses.[1]
The lower lateral cartilages shape the tip and nostrils. In 20 cadavers, the lateral crura averaged 23.4 mm long and 0.5 mm thick and 11.1 mm wide at their turning point, and a chain of accessory cartilages continued from them in every dissection. Lateral crural strut grafts sutured to their deep surface treat a boxy tip, malpositioned crura and alar rim retraction or collapse.[1][2]
The septum divides the nose and supports the dorsum and tip. Surgeons keep an L-strut of at least 1 cm of dorsal and caudal septum to avoid tip collapse and saddle deformity. Septal cartilage is the most common source of graft material. Maurice Cottle taught that as the septum goes, so goes the nose.[1][2][3]