Acquired nasal defects are difficult problem to manage secondary to the topography of the nose.An aesthetically pleasing result depends on the match of the color and texture of the donor site as well as the ability for the donor site to be closed adequately. All this should be accomplished while maintaining adequate nasal function.
Nasal reconstruction began approximately 2000 B.C. in India during which time the Indian culture believed in punishment of adultery by amputation of the nasal tip. It was not until 600 B.C. when the Sushruta Samihta documented the first facial flap for reconstruction of the nose, through the use of the midline forehead flap, or "Indian" flap. The "Indian" flap remains the workhorse of nasal reconstruction today.
Gonzalez-Ulloa first described the face in terms of aesthetic units - one of which is the nose. The convexities and concavities of the nose play with light and shadow to create visual patterns. Knowledge of these visual patterns allows one to hide the scars of reconstructive surgery by blending these scars into the subunit borders. These patterns divide the nose into 9 topographical subunits. Five of the subunits are convex : the tip, dorsum, columella, and paired ala - nostril sills. Four concave units are: the paired sidewalls and soft triangles. When presented with a given defect, attempts should be made to make the defect fit the subunit or subunits in which it is contained. It may be necessary to advance nearby skin or excise surrounding normal tissue.
Of primary concern when determining the goals of surgery, one must consider what the patient desires. When the goal becomes reconstruction of an aesthetically appealing nose, it should be thought of as three dimensional. The normal nose is composed of a vascular lining, support structures and a covering. Nasal lining is best reconstructed from an intranasal donor sites. The structural support and the vascular lining are interdependent - the lining depends on the cartilage for support and the cartilage depends on the lining for its vascular supply. The support structures consist of sculptured cartilage and bone grafts. Coverage consist of only a thin layer of skin and subcutaneous fat that conforms to the underlying structural support.
For defects involving all 3 dimensions one should begin with harvest of lining flaps. The blood supply for the intranasal lining flaps can arise from several sources with the main source being the septal branch of the superior labial artery. Replacement of nasal lining can impair nasal function if not done correctly. Usually this is seen when tissues such as skin grafts, local nasal skin and composite auricular grafts are used for lining.
Keeping this in mind, the goal for reconstruction of the lining is threefold:
1) the flap should be thin, preventing both distortion of the outer contour of the nose or nasal obstruction
2) the flap should be soft in order to conform to the desired contour
3) the flap should have a vascular supply to nourish the cartilage grafts.
The intranasal donor sites are best which includes septal, midvault and vestibule mucosa. The bipedicle vestibule flap and septal mucoperichondrial flap are utilized most often. The septal mucoperichondrial flap is based on a 1 - 1.2 cm pedicle and is raised as a mucoperichondrial flap, with or without cartilage, unilateral or bilateral. The donor defect becomes resurfaced with transitional respiratory epithelium.
Septum and conchal cartilage are the most readily available and widely used tissues for reconstruction of the subsurface framework. Providing support in reconstruction requires replacement of cartilage in the areas where structure is lost, as well as providing support in areas where there was previously no structural support, such as the nasal ala and soft triangles.
General guidelines in reconstruction of the subsurface framework include:1) Creation of a nasal tip with projection and length
2) You should provide support against gravity and contraction
3) Reduce the dimensions by 2 -3 mm to attain the desired size of the nose
4) Each graft is carved to resemble a subsurface unit
5) The graft is best placed at the initial construction in order to prevent the blob appearance.
Options for coverage depend on the defect size, skin thickness and any structural abnormalities. Small surface defects are those that measure less than 1.5 cm and have and underlying intact periosteum/ perichondrium. Surface defects are divided with regard to the zones of skin thickness. Thin smooth skin is located on the dorsum, nasal sidewalls, columella, alar margins and soft triangles. Thick pitted skin is located along the alar grooves, extends above the supratip down to include tip in this area. The problem occurs with small defect involving thick skin. Do these warrant an axial flap? Lesser attempts produce divots from skin grafts, and local flaps, such as the dorsal nasal or single lobed, tend to produce dog ears and increased scar.
Options for thin skin defects are:
1) Preauricular full thickness skin graft
2) Single lobed transposition flaps of the flag , banner, rhomboid types.
Options for thick skin regions include:
1) Single lobed transposition flaps
2) Dorsal nasal flap of Reiger and the frontonasal flap
3) Bilobed flap of Zitelli
The bilobed flap of Zitelli is the workhorse flap for these defects less than 1.5 cm of thick skin. Creation of this flap requires the diameter of the first lobe to be equal to that of the defect with the diameter of the second lobe is reduced to ease donor site closure. The flap is undermined widely in the submuscular plane. There should be no greater than 50 degrees of rotation for each lobe with the total arc of 100 degrees. Lateral based flaps are performed for tip work and a medial based flap for ala work.
The superiorly based nasolabial flap is good for reconstruction of the entire ala subunit, the 2 - 3 mm on the lower sidewall, and to repair the premaxillary soft tissue on which the alar base sits. This flap is not good for reconstruction of the tip, dorsum, or large unilateral defects covering the lower 1/2 of the nose. The flap is a random flap with an axial nature based on the facial artery perforators through the levator labii in the region of the nasolabial fold. Thus a subcutaneous base is used and a wide skin pedicle is not required. This flap has variations based inferiorly and medially.
The forehead is an excellent donor site for nasal defects, with good match for color and texture, reliable blood supply and minimal donor site deformity. Thus, the paramedian forehead flap is used for most aesthetic reconstructions of the tip, ala and lower dorsum. Disadvantages include a forehead scar, limitations in length, and a second operation is required for pedicle division.
To create this flap you first must identify the extent of the nasal defect and repair any structural deficiencies. The axial blood supply is based on the vertically oriented supratrochlear artery which is identified with the doppler located near the corrugator frown crease. The proximal pedicle may be narrowed to measure 1.1 -1.5 cm, which allows easy rotation and transposition of the flap with tension-free closure. The flap can be extended across the orbital rim, or into the hairline, to gain extra length.
Improved results in the forehead defect are achieved by elevation of the forehead and scalp tissues in the loose areolar plane for 7 cm in all directions. Vertical fasciotomies ease closure. Often the upper 1/3 of the wound cannot be closed, thus it is covered with petrolatum dressing. Scar contracture produces a satisfactory forehead wound within 7 weeks.
Intermediary or secondary operations are performed to add contour to the flap prior to the division of the pedicle. This is usually performed 3 weeks postoperatively. Once the flap is detached it can be defatted or cartilage may be placed to obtain better tip projection.
The pedicle of the paramedian forehead flap can be sectioned as early as 10 to 14 days based on vascular efficiency of the flap. However, most advocate allowing it to remain attached for at least 3 weeks to allow for tensile strength to increase. After pedicle division, no further contouring surgery may be performed for 4 months due to risk of devascularization.
Some helpful hints regarding the paramedian forehead flap include:1) Thinning and depilation should be performed at a later date in smokers, due to the compromised vascular supply
2) Skin grafts are not necessary for the forehead flap donor site, except in cases where the defect is greater than 4.5 cm
3) Tissue expanders are to be avoided because it delays reconstruction by months, it is discomforting, it causes social isolation, skin is subject to shrinkage upon transfer, a rind develops which does not conform well to the defect and excision of the rind jeopardizes the flap vascularity
4) Pedicles greater than 1.5 cm in width may cause strangulation of the flap.
In summary, the 3 dimensional nature of the nose makes for a complex reconstruction.
Preserving function is paramount while maintaining the normal appearance of the nose. The subunit principle hides the scar in the natural boundaries of nose.