Nasal Osteotomies

Nasal Analysis

Achieving success in rhinoplasty is based on careful preoperative planning and assessment. The relationship of the nose to the face has been studied for centuries. Objective measurements of contour, angles, and proportions have been proposed and accepted to help provide the facial plastic surgeon with guidelines that define ideal standards of beauty and aesthetic facial harmony. One of these guidelines states that the aesthetically pleasing face can be divided equally into vertical fifths, with the nasal base width equal to the intercanthal distance. The width of the upper two thirds of the nose should be approximately 75% of the width of the nasal base ( Figure 10-1 ). The nasal dorsum should also follow a gentle curvilinear path from the medial brow to the nasal tip. The dorsum should also be perpendicular to a line drawn vertically from the midglabella to the menton ( Figure 10-2 ). The external contour of the upper third of the nose is defined by the two side walls: the dorsum and the nasofrontal angle. The nasofrontal angle is the external landmark identifying the deepest or most posterior portion of the nasal dorsum, and by this definition is synonymous with the radix, or soft tissue nasion. The bony nasion is the junction between the frontal and nasal bones. The rhinion is the osseocartilaginous junction of the nasal bones inferiorly with the superior edge of the upper lateral cartilages. The bony nasal vault and its intimate attachment to the upper lateral cartilages make it the main determinant of nasal width of the upper and middle third of the nose. Precise manipulation of the bony pyramid is essential to provide balance with any nasal tip work and create overall aesthetic harmony. Failure to complete proper osteotomies can negate the effects of intricate tip maneuvers and leave the patient with a “washed-out” or poorly defined nose on frontal view, even though the patient may have an improvement on profile and oblique views.

Pertinent Nasal Anatomy

The nasal bones are paired structures that attach superiorly to the frontal bone and laterally to the nasal process of the maxillary bones. Together, these bones form the bony nasal vault. The perpendicular plate of the ethmoid, a portion of the bony septum, attaches to the undersurface of the nasal bones in the midline. The nasal bones are thin inferiorly and become thick superiorly. Figure 10-3 demonstrates this by transillumination of the skull. The variable thickness of the bony structures of the nose will influence osteotomy placement. The nasal septum supports the nose along its entire length. The septum serves to support the dorsal profile, and loss of this structure can result in the classic saddle-nose deformity. Preservation of adequate (>1 cm) dorsal and caudal septal struts is necessary to preserve support after any nasal surgery. The anterior nasal spine supports the caudal septum and the feet of the medial crura. When excessive in size, the nasal spine may actually blunt the nasolabial angle.

The paired upper lateral cartilages are triangular and fused medially to the dorsal septum. The cartilages attach to the undersurface of the nasal bones at their superior extent and are connected to the frontal process of the maxilla by dense fibrous connective tissue. The paired lower lateral cartilages support the nasal lobule and nostrils. This fibrocartilaginous arch is supported medially by the caudal septum and nasal spine. Laterally, the arch is supported by the lateral crura and a variable number of small accessory cartilages between the lateral crura and pyriform aperture.

Dorsal Hump Reduction

Prior to instituting maneuvers to mobilize and shift the bony nasal vault, it is critical to evaluate the contribution of the dorsal hump to the nasal profile and whether a hump reduction will be required. To gain proper access to this area, sharp dissection of the midline raphe of decussating periosteal fibers should be completed up to the level of the nasofrontal angle. Care should be taken to stay midline to avoid lateral disruption of supportive soft tissue attachments to the nasal skeleton. It is also important to consider the variation of thickness of the skin soft tissue envelope over the nasal dorsum. The skin is thickest in the nasion and supratip areas and thinnest over the rhinion; therefore, resection of the dorsal hump at the rhinion should be performed with extreme care ( Figure 10-4 ). In fact, to achieve a straight soft tissue profile, the cartilaginoskeletal framework at the rhinion should be kept slightly convex.

Several techniques are available to reduce the bony dorsum. An osteotome or a rasp can be used, depending on the surgeon's experience and preference. Most surgeons use an osteotome for larger humps and a rasp for smaller reductions and refinements. The dorsal septum and upper lateral cartilages can be reduced sharply with a scalpel. For removing larger humps, a conservative correction is performed with an osteotome (often double-guarded) and refinements are then made with a tungsten carbide pull rasp or scalpel. It is critical not to violate the attachments of the upper lateral cartilages to the undersurface of the caudal margin of the nasal bones as lack of support of the cartilages may lead to inferomedial collapse and cause an inverted-V deformity ( Figure 10-5 ).

The orientation of the bony vault must be considered and evaluated before dorsal hump removal. If the vault is shifted toward one side, the hump removal should not be symmetric. Less bone should be excised from the side of the deviation ( Figure 10-6 ). Performing a hump reduction with this technique more closely approximates a midline vertical orientation of the lateral nasal bones and prevents excessive reduction in their height. Dorsal hump reduction may lead to an open roof deformity that sets the stage for osteotomies.