Forehead flaps are 2-stage tissue flaps in which a forehead-based pedicle flap is used to repair more distal nasal defects. The first crude forms of this flap were described in India in about 600 BC. More narrow, paramedian flaps have replaced the broad, mid-forehead pedicles used in the past. This is a common form of interpolation flap in which a vascular pedicle of the flap bridges over an intervening area of normal skin to reach the defect. The pedicle is removed in a subsequent procedure after the flap has established vascularity in the wound base.
The paramedian forehead flap is an axial flap based on the supratrochlear artery, although more recent studies have suggested that it can survive as a random flap due to the vast network of vascular anastomoses in the mid-forehead area. Cadaver studies have shown that the supratrochlear artery exits the orbit 1.7 to 2.2 cm from the midline, passing deep to the orbicularis oculi muscle and ascending superficial to the corrugator supercilii muscle. It then passes medial to the eyebrow and through the frontalis muscle ascending superiorly in the subcutaneous tissue, 1.5 to 2 cm from the midline. It has been found that the supratrochlear artery runs toward the scalp within 3 mm of a line drawn up from the medial canthus. Other authors have demonstrated the safety of simply taking a pedicle from the glabellar midline to 1.2 cm lateral to the midline.
The forehead flap is used to repair more extensive defects on the nasal tip and ala (and occasionally nasal lining) when simpler techniques cannot provide adequate coverage. Deep wounds of the distal nose often consist of exposed cartilage that cannot well support the vascular requirements of a skin graft and even when there is a vascular base; a sustainable graft may not be of sufficient to provide proper contour. Adjacent flaps can provide their vascular supply and thickness, but very large wounds can exceed the limits of mobility and size, especially on the nose. If structural stability is compromised in a wound, it is also possible to combine a cartilage graft with a forehead flap.
The use of PFF is contraindicated in patients who are unwilling or unable to tolerate multiple-staged surgical procedures, or in patients who cannot leave their surgical sites undisturbed. The actively infected skin should not be covered with a flap or used to form a flap. With a forehead of low vertical height, a variation of the forehead flap or another repair method may be required. Smoking is a relative contraindication for the PFF because it increases the risk of flap necrosis, but these flaps can usually be performed safely if thinning is not performed too aggressively. Also, it is best to avoid the use of previously radiated skin or scar tissue, unless no better repair options are available. Interpolation flaps should be performed carefully in patients who are receiving anticoagulant therapy or in patients with bleeding disorders, and consultation with the physician who prescribed the medication is prudent before discontinuing any anticoagulant therapy; however, the author rarely discontinues warfarin, clopidogrel or aspirin before skin surgery. Contacting consulting physicians is appropriate before operating on individuals with bleeding dyscrasias.
Items required preoperatively include:
Intraoperatively, the following sterile items are required:
After completion of the flap, dressing materials and wound care may include:
The surgery can be performed by one physician with one surgical assistant if performed on an outpatient basis.
The procedure must be explained to the patient, preferably with illustrations or with actual patient photos. They must understand that the flap will appear as a trunk for two weeks or more, and a second surgical stage is required to separate the flap. Also, one or more additional stages may be required to revise the flap. The patient must be able and willing to leave the flap undisturbed until it is time for division and inset. Bleeding is common in the first 24 to 48 hours, especially at the base of the flap pedicle, and the patient should be prepared for this occurrence with gauze to reinforce the dressing. Phone numbers should be given to contact in case the bleeding is heavy or cannot be stopped. Smoking should be stopped as long as possible prior to surgery and for the duration of healing. Patients should also be asked about any upcoming events or trips, as it is not uncommon to forget to divulge this information until after surgery. They should also be prepared to avoid any strenuous or other activities that would increase the risk of bleeding. We do not, however, discontinue anticoagulants that have been prescribed. The risk of adverse events by stopping anticoagulants is greater and more serious than that due to the effects of those agents on the surgery.
The paramedian forehead flap is an axial flap based on the supratrochlear artery, although more recent studies have suggested that it can survive as a random flap due to the vast network of vascular anastomoses in the mid-forehead area. Cadaver studies have shown that the supratrochlear artery exits the orbit 1.7 to 2.2 cm from the midline, passing deep to the orbicularis oculi muscle and ascending superficial to the corrugator supercilii muscle. It then passes medial to the eyebrow and through the frontalis muscle ascending superiorly in the subcutaneous tissue, 1.5 to 2 cm from the midline. It has been found that the supratrochlear artery runs toward the scalp within 3 mm of a line drawn up from the medial canthus. Other authors have demonstrated the safety of simply taking a pedicle from the glabellar midline to 1.2 cm lateral to the midline. If more than 50% of an anatomic subunit is involved in the surgical defect, it is often preferable to remove the remainder of the subunit. A template of the defect is made, and then tubed gauze or similar material is used to measure needed pedicle length to reach the defect from the pedicle base. The tube gauze is rotated to the forehead, and the inverted template pattern is marked at the uppermost aspect of the pedicle. From that area, a pedicle of 1 to 1.5 cm width is drawn down to the planned pedicle base.
The flap is then mobilized with its base situated at the inferior aspect of the forehead and often around the orbital rim. The forehead donor site is closed primarily, and the wider portion of that defect on the upper forehead may be allowed to heal secondarily. Alternatively, that portion of the donor site may be repaired with a full-thickness skin graft, but final cosmetic results are less optimal. The flap is then thinned distally and secured in the nasal defect with simple interrupted sutures. Hemostasis in the exposed pedicle stalk is controlled with precise electrocoagulation, hemostatic gauze and aluminum chloride or Monsel's ferric subsulfate may even be applied. The pedicle is then loosely wrapped in a nonadherent dressing such as petrolatum-impregnated gauze. Fluffed gauze is then applied for absorption and gentle pressure, and it is secured with hypoallergenic tape. Extra gauze may be applied at the base of the pedicle, as bloody oozing is a regular occurrence, especially in the first 24 to 48 hours. Patients should be apprised of this expectation and given extra gauze to apply pressure. If bleeding is heavy or uncontrollable, patients are instructed to call the physician.
The initial dressing can safely be left in place for one week, although some surgeons prefer to see the patient back in 1 to 2 days to examine the site and provide a new dressing. In 2 to 3 weeks, the pedicle trunk can safely be excised. The base of the pedicle stalk is excised in a fusiform manner to allow primary closure. Another option to leave a portion of the stalk and then close the defect as an inverted "V," but this method is more prone to thickening, or "pincushioning." The incised portion of the nasal flap is then thinned, excess granulation tissue is resected, and skin edges are "freshened" prior to the inset of the proximal flap into the defect.
Minor revision procedures may be preferable in the coming weeks, and it is best to discuss these revisions as expected parts of the procedure before starting this flap. It is also wise to have photos from one or more prior patients, showing all stages of the procedure, revisions and postoperative progression. Examples can also be found in textbooks and online. Dermatologic surgeons most often perform this procedure under local anesthesia, sometimes with concious sedation, while physicians in other specialties often do this under general anesthesia.
Bleeding, scar and infection represent the most common potential complications with paramedian forehead flaps. Careful hemostasis and proper surgical dressings can decrease the risk of significant postoperative bleeding, as can patient avoidance of strenuous activities. Moderate oozing is common from the base of the flap in the first 48 hours, but can usually be controlled with pressure. Scar formation is unavoidable, but it can be minimized with appropriate surgical technique. The skin should be precisely approximated, and the flap should be sized and thinned appropriately. Use of the anatomic subunit principle can improve the aesthetic appearance as well. One or more revisions may be required, and the patient should be told this prior to the surgery. Sterile technique and preoperative antibiotic administration can minimize the risk of infection. Necrosis of the flap may rarely occur and is usually due to smoking, overaggressive thinning of the flap, too narrow pedicle or patient manipulation of the flap.
The paramedian forehead flap provides a well-vascularized option for covering distal nasal and intranasal surgical defects that are too extensive or deep to be repaired with local flaps or skin grafts. It is highly useful alone or in combination with other techniques to repair select defects.