Tip Support Mechanisms
Understanding major and lesser tip support mechanisms plays an all-important role in executing tip incisions in tip-contouring procedures. These support mechanisms consist of the contour, size, and strength of the lateral crura, the attachment of the medial crural footplates to the caudal septum, along with the size and strength of the medial crura, the attachment of the caudal edge of the upper lateral cartilage to the cephalic edge of the alar cartilages.
Of lesser but still of vital importance to tip support include the nasal tip ligamentous aponeurosis, the cartilaginous dorsum, the nasal spine, the strength and resilience of the medial crura and the thickness of the tip skin and subcutaneous tissues, and the supportive strength of the alar sidewalls.
In every surgical procedure of the nasal tip, the operation will ultimately result in either preservation of tip projection or an increase of tip projection or a decrease in tip projection. Anatomic situations will be regularly encountered in a diverse rhinoplasty practice such as Dr. Sam Rizk's where he sees many different ethnicities from around the world. In the majority of rhinoplasties, however, it is critical to preserve and maintain the already existing tip projection, while favorably altering the contour and attitude of the alar cartilages and avoiding at all costs the loss of vital tip support with consequent potential decrease in projection (tip ptosis). Respecting tip support mechanisms results in a predictable outcome.
Therefore, it can be assumed that the appropriate incisions should be followed to preserve as many tip support mechanisms as possible. Alar sculpturing techniques should likewise respect theis principle by conserving the volume and integrity of the lateral crus, while maintaining an intact complete caudal strip of alar cartilage. With these precepts in mind, the appropriate incisions, approaches, and tip sculpturing techniques will be discussed.
Incisions are only a method to gain access to the underlying cartilaginous and soft tissue substructures of the nose. Sculpturing of the tip cartilages, suture techniques and grafting techniques can create changes in contour, projection of the nasal tip, and projection/rotation of the nasal tip by changing the position of the alar cartilages (lower lateral cartilages) and their relationship to other structures including the caudal nasal septum. The choice of incisions depends on the anatomy of the tip and its related nasal structures. Less invasive incisions are preferred since they result in greater control of a more rapid healing process.
The incisions selected to gain access to the nasal tip should provide unobstructed visualization and access to the alar cartilages, preserve whenever possible the important tip support mechanisms, avoid interference with other incisions contemplated in the same area, and lend itself well to healing without contracture or scarring. The different alar cartilage incisions to gain access to the nasal tip through the endonasal rhinoplasty approach include the intercartilaginous, transcartilaginous, and marginal (rim) incisions. Both the intercartilaginous and the transcartilaginous incisions may be used as the only incisions to approach the alar cartilages, especially when a volume reduction of the medial cephalic portion of the lateral crus is desired. This one incision creates less trauma and a more rapid recovery rhinoplasty with less scarring and more control. Through the intercartilaginous incision, a retrograde, or eversion, approach may be accomplished. The cartilage splitting approach is carried out through the transcartilaginous incision. Although both the intercartilaginous and transcartilaginous incisional approaches may be used, it is important to emphasize that these incisions divide and ultimately eliminate one of the vital major tip support mechanisms: the attachment between the caudal aspect of the upper lateral cartilage and the cephalic aspect of the alar cartilages (lower lateral cartilages).
Although the marginal (rim) incision may be used alone, especially to correct minor tip asymmetries in revision tip surgery, it classically is combined with the intercartilaginous incision in the delivery approach to the alar cartilages, creating a bilateral chondrocutaneous flap that is delivered from the nostril for direct vision modeling and refinement. Ideally, the marginal incision is positioned 1mm inside (cephalic to) the palpable caudal margin of the lateral crus, to allow ease of incision closure and further protection of the soft tissue alar margin. As the marginal incision is carried medially into the area of the soft triangle and facets, care must be taken to maintain complete precision of the cut along the caudal edge of the lateral crus, dome, and upper medial crus where the incision courses close to the alar and columella margins.
The septal transfixion incisions assist in exposing the nasal tip structures as well and may be either complete or partial (limited). The complete transfixion incision, ordinarily a continuation of the intercartilaginous or transcartilaginous incision, separates the caudal end of the septum from the membranous septum and medial crura. If truly complete (complete transfixion incision), a major tip support mechanism is interrupted, and creates a major loss of tip support. This complete transfixion incision can be used to the surgeon's advantage if a nose requires deprojection (bringing it closer to the face) in over projected noses. This retropositioning of the over projecting nasal tip can be a very desirable effect. When limited access to the nasal tip and nose will be sufficient, a limited partial transfixion is preferred, preserving the major tip support mechanisms while allowing adequate exposure.
When combined with the intercartilaginous or transcartilaginous incisional approaches, the partial transfixion may be limited to one side only, exposing the septal angle and the supratip dorsum by extending the transcartilaginous or intercartilaginous incisions medially to encounter the partial transfixion. Exposure is adequate, scarring is diminished, and controlled rapid recovery healing is facilitated in this limited minimally invasive rhinoplasty. A hemitransfixion incision is created unilaterally at the junction of the caudal nasal septum and columella, particularly in procedures where the caudal septum is deviated or requires resection modification for tip rotation or columellar adjustment. Another preferred approach to the septal region is a vertical incision 2-3 mm proximal to the mucocutaneous junction near the caudal septum. This approach facilitates identification and rapid elevation of the mucoperichondrial septal flap, is easily repaired when no longer required, and eliminates any possible vertical contracture during healing. The high septal transfixion incision is a useful alternative to septorhinoplasty incisional approaches. Tip support mechanisms are preserved and incisions in vestibular skin are minimized. Tip rotation and nasal shortening of the central component of the nose is facilitated without altering the relationships of the caudal septum to the columella and nasal tip structures. Tip support remains undisturbed by the incision.
Marginal columellar incisions may be created high or low at the columella. If carefully done, and limited in length, the cartilage-splitting nature of this approach enhances delicate repair of the incision, actually splinting it while healing progresses. Cartilage tip grafts, columellar struts or battens, and augmenting "plumping" grafts positioned at the nasolabial angle may be secured in the precise pockets provided through these marginal columellar incisions. Midline skin incisions in the caudal columella are best avoided in favor of lateral marginal incisions, however, they are not objectionable and camouflage favorably if carefully executed and repaired. In selected patients, the external rhinoplasty approach may be useful to expose the tip and superstructure of the nose through an irregular inverted v incision on the caudal columella and connect with the marginal alar cartilage incision on either side.