Staged Interpolation Flaps

Indication

The PFF is a workhorse in facial reconstruction. Although it may close any wound on the central face, its best application is to the distal nose (tip, ala, and columella), where tissue thickness and sebaceous quality are closely matched by forehead skin. The PFF is ideal for recreating the convexity and projection of the nasal tip. Subtotal nasal tip and/or alar defects may be candidates for the PFF. Proximal wounds on the nasal dorsum, sidewall, nasal root, and medial canthus have inherently thinner skin and may be incongruous for the much thicker PFF, unless a substantially deep defect is present.

Anatomy

The primary and secondary vascular supply to the PFF is the supratrochlear (internal carotid system) and dorsal nasal artery (external carotid system), respectively. The supratrochlear artery (SA) is reliably located at the medial border of the eyebrow, on average 10.9 mm from the facial midline. At the medial eyebrow, a glabellar crease (if present) delineates where the SA crosses the superior orbital rim to enter the forehead ( Fig. 8.1 ). Below the orbital rim, the SA lies deep to the periorbital muscles (orbicularis oculi and frontalis) just above the periosteum. Above the rim, however, the SA pierces the corrugator supercilii muscle at 15–25 mm above the supraorbital rim and ascends superficially into the forehead, sandwiched between the frontalis muscle below and the subcutis above. Consequently, to preserve the SA near the orbital rim, dissection must be below the frontalis muscle and deep fascia. Transection of the SA during surgery is not always disastrous. The robust arterial perforators are often sufficient to nourish the flap. Indeed, histologic studies suggest that the PFF is sometimes a random pattern flap, with no discernible high caliber artery within the pedicle.

Flap Design

The ideal PFF is an aesthetic covering that restores normal contour and symmetry without creating a shapeless blob. Table 8.1 discusses the critical design issues in a PFF. The covering provided by a PFF requires a stable nasal infrastructure (cartilage support and mucosal lining). Structural cartilage grafts (SCGs) to prevent nasal valve collapse and alar rim contraction are usual considerations in PFF repairs. More neglected, however, are SCGs that restore contour to the nasal supratip. Contour grafts should be considered in patients that have thick nasal tip skin and supratip defects ( Fig. 8.2 ). Without a contour graft in these patients, a PFF alone may be insufficient to restore normal tip projection.

Measurements of the defect must be accurate—neither oversized nor undersized for the wound. The PFF template should be measured after the residual subunit has been outlined, but prior to the excision of any remaining skin ( Fig. 8.3 ). This avoids an artificially enlarged dimension from a retracted wound edge. A template should also reflect the three-dimensional nature of the nose, especially if a defect extends to the infratip, columella, and ala ( Fig. 8.4 ). If the vestibular mucosa is missing, the PFF may be extended and turned down to provide nasal lining. The thin soft nasal triangle is difficult to rebuild. Either second intention healing or a finely thinned PFF are options for this thin, concave area. Whenever possible, the unaffected contralateral side should be used as a template to restore symmetry. A right-sided nasal tip and ala wound, for example, should be repaired based on the normal left tip and ala.

The vertical height of the forehead (from orbital rim to anterior frontal hairline) will determine the potential reach of this flap. If the vertical length is inadequate (short forehead height relative to distal defect), then the modifications listed in Table 8.2 will significantly extend a flap's distal reach.

Design considerations for the pedicle include its position and width. Identifying the SA pedicle may be done clinically, by using the anatomic landmarks mentioned earlier, or definitively by confirming with a manual Doppler (8–10 MHz frequency). However, 8% of supratrochlear arteries cannot by detected by Doppler. Alternatively, PFF may be designed as a random flap based on the complex vascular plexus of the corrugator complex and frontalis. The pedicle width therefore rarely needs to be greater than 1.5 cm. Wider pedicles, in fact, are counterproductive and restrict flap mobility as well as vascular integrity (by increasing torque and compression on the artery during flap rotation). This author routinely develops a pedicle base of 1–1.5 cm. The glabellar frown line may be used as an anatomic landmark, with flap borders placed 8–9 mm lateral and 2–3 mm medial. Another option is to base the template on a vertical line directly above the medial canthus, since the supratrochlear vascular pedicle has been shown to lie no more than 3 mm lateral or medial to the medial canthus. The lateral pedicle incision stops at the eyebrow, whereas the medial incision should extend longer, often into the nasal root, to incorporate branches from the dorsal nasal artery (see Fig. 8.1 ). Traditionally the pedicle position is on the opposite side of where the defect is located. A left nasal tip defect, for example, would have been closed by a PFF based on the right SA. This concept applied when pedicles were much wider, to minimize twisting and tension. With more narrow pedicles (1.5 cm), there is less twisting during movement, and PFFs may be ipsilateral to the defect. Same side flaps are shorter in length than contralateral designs and conserve significant tissue.

Anesthesia

The PFF may be safely performed as an outpatient procedure under local anesthesia (LA). LA should be injected in stages. If a patient needs a CG and a PFF, then consider anesthetizing the ear and forehead first. Begin anesthetizing the nose when the forehead flap is incised. By administering LA in a stepwise fashion, the patient will be kept comfortable. Tumescent anesthesia (TA) is useful by rapidly anesthetizing large areas with minimal patient discomfort. With TA, however, waiting (at least 20 minutes) for the swelling to subside is advisable, as there is a pseudotension in tissue movement when it is edematous. LA may be supplemented by nerve blocks, oral benzodiazepines (lorazepam, midazolam), and oral analgesics. Rarely, conscious sedation may be needed and can be safely performed by dermasurgeons. Appropriate credentialing for advanced cardiac life support and sedation are essential for the latter modalities.

Execution

Prior to the first incision, all design elements should be measured and remeasured, and anesthesia must be complete. The execution sequence for this author is (1) cartilage support and nasal lining restoration (if needed), (2) flap harvesting and pedicle mobilization, (3) defect preparation, (4) flap preparation and inset, (5) donor site closure, and (6) postoperative care.

Suturing intranasally can be difficult both ergonomically and visually and is facilitated by Loupe magnification, a headlamp, Castroviejo needle drivers, Castroviejo delicate tissue forceps, or bayonet forceps.

Cartilage and Lining Restoration

CG and nasal lining are essential ingredients for a stable nasal architecture. CG are either structural (native cartilage present but additional CG needed for support; Fig. 8.5 ) or restorative (replacing missing cartilage). SCG serve to (1) support heavy flap tissue, (2) maintain airway patency of the internal nasal valve (priority in nasal reconstruction), (3) minimize scar contraction, and (4) restore contour projection (nasal tip). CG may be auricular (antihelix or concha; Fig. 8.6 ), nasal (septum), or costal in nature. Auricular cartilage harvest is easiest and may be performed from an anterior or posterior approach. Anterior incisions are more accessible, but scars are more visible than posterior incisions. Postauricular access often yields a larger cartilage piece than an anterior approach. The antihelix yields cartilage that is long but thin, ideal for alar support. The concha offers thick, curved, and large grafts that may be sculpted and divided into multiple grafts, ideal for the PFF. The subject of nasal lining is beyond the scope of this chapter. General options, however, for smaller mucosal defects (<1 cm) include (1) turnover hinge flap, (2) turndown of a forehead flap extension, (3) full-thickness skin graft (FTSG), and (4) bipedicle vestibular skin advancement flap. Larger lining restoration may require (1) turnover forehead flap, (2) septal mucoperichondrial hinge flap, (3) composite septal chondromucosal pivotal flap, or (4) larger FTSG vascularized by an overlying PFF.

Flap Harvesting and Pedicle Mobilization

The PFF may be mobilized at its superior edge to include just the skin and subcutis or down to underlying galea. The former approach facilitates flap debulking during inset but results in greater bleeding. A subcutaneous level is preferred if the flap is in the hair-bearing scalp, to expose terminal hair bulbs for depilation. The level of undermining, however, delves deeper into the subgaleal plane as one approaches the eyebrow to preserve the SA. The transition from subcutis to subgalea should occur at least 3 cm above the orbital rim. Undermining past the orbital rim should be under direct visualization, as the SA is at risk of transection. Occasionally, subperiosteal release of the arcus marginalis and brow complex is required to enhance flap extension (see Table 8.2 ). The PFF should now overlie the defect without tension ( Fig. 8.7 ).

Flap Preparation and Inset

Prior to any suturing, the flap thickness must be revised to fit the defect. Aggressive debulking except for a thin subdermal layer is possible because of the excellent vascularity of the SA ( Fig. 8.8 ). Constant reference to the defect is mandatory to prevent excessive thinning. Flap inset begins with interrupted epidermal sutures to secure its leading edge with the defect. If dermal-buried sutures are placed, this author prefers Poliglecaprone 25 (Monocryl, Ethicon) because of its minimal tissue reaction, a desirable feature on the sebaceous nasal tip. Dermal sutures contribute to flap security and minimize incision line separation. The proximal flap as it abuts the nasal dorsum is not sutured until pedicle division.

Donor Site Closure

Donor areas are approximated as much as possible, and any remaining wound heals by second intention ( Fig. 8.9 ). Patients may be reassured that this open portion will be significantly smaller because of inevitable wound contraction ( Fig. 8.10 ). Tissue expansion and complex scalp flaps should be avoided, as they often lead to excessive morbidity on both donor and recipient tissue without cosmetic benefits. At most, unilateral or bilateral W-plasties along the frontal hairline may be considered for complete closure of the forehead wound, but excessive tension should be avoided. Forehead tension (forced donor site closure) often leads to severe headache and nausea postoperatively.

Postoperative Care

Postoperative bleeding at the sides of the exposed pedicle is common and may be prevented with meticulous electrocoagulation. Bovine collagen matrix (BCM) may be sutured with 5-0 fast absorbing plain gut onto the exposed pedicle, followed by petrolatum gauze application. BCM is also applied to any remaining secondary defect at the forehead to aid second intention healing. BCM seals the exposed tissue, facilitates hemostasis, and is incorporated into the pedicle as an epithelial covering. Alternatively, the exposed pedicle may be wrapped with Surgicel or Surgicel Nu-Knit. This oxidized cellulose gauze promotes hemostasis and its removal causes less discomfort than Vaseline gauze. Visual fields are blocked with pressure dressings, and the wearing of glasses is usually not possible without preoperatively customized devices. An optometrist may adjust the frame to temporarily fit over the dressing.

Postoperative observation for several hours is advisable, especially for patients at risk of bleeding. Hospitalization is not necessary, although patients must stay locally in the charge of a caretaker. Postoperative prescriptions include antibiotics (optional), analgesics, and antiemetics as needed. Wound care for the PFF may be intimidating and patients often express fear of detaching the pedicle. Detailed guidance with the first dressing change and the availability of a wound-dressing video will preempt much anxiety. A telephone call from the surgeon in the immediate perioperative period can also provide reassurance.