Introduction
The pericranial flap has been used for/in many different surgical applications since first described by Wolfe in 1978, 1 due to its excellent vascularity and strength. 2 These applications include closure of the skull-base and orbital defects, 3, 4, 5 closure of sinus fistula and frontal sinus obliteration, 6, 7, 8 and support for scalp and skin reconstruction. 9, 10, 11, 12 The use of the pericranial flap in total septum perforation repair surgery is not well documented in the literature. There is one case report 13 that basically outlines the surgical technique but does not study the consequences or the possibility of applying this technique in other patients. There is another article in the literature, 14 which describes a pericranial flap and calvarial bone grafts for septal reconstruction; however, these were not total septal perforations and the technique was used only in cadaver. This surgical method offers us an approach to solving total septum perforation, which has had no effective solution until now.
21.2 Surgical Anatomy
21.2.1 Scalp Anatomy
A good knowledge of the anatomy of the scalp and its layers is essential for a clear understanding of the pericranial flap. The scalp is made up of five tissue layers.
Skin.
Subcutaneous tissue/connective tissue.
Aponeurotic layer/galeal layer includes the frontalis muscle anteriorly, the occipitalis muscle posteriorly, the galea that connects both of them, and the temporoparietal fascia laterally.
Loose areolar tissue/subgaleal layer is composed of a central dense collagenous layer surrounded by vascularized areolar tissue. The subgaleal fascia is usually included in pericranial flaps, which are often based beyond the periosteum. The loose areolar tissue is continuous with the temporalis fascia laterally. 2
Pericranium layer is the periosteum of the skull bones and in temporal area joins to the deep temporalis fascia, which overlies the temporalis muscle.
The pericranial flap is formed by the union of the pericranium layer and most of the subgaleal layer 15 ( ▶ Fig. 21.1).
Fig. 21.1 Exits of the supraorbital (SO) and supratrochlear (ST) arteries at the level of the orbital rim. The pericranial flap is composed of the pericranium and the loose areolar tissue; on the other side, the frontalis muscle is covered by the subcutaneous tissue and the skin of the scalp.
21.2.2 Blood Supply
The anterior part of the scalp, where you can harvest the pericranial flap, is supplied mainly by two supraorbital (SO) and two supratrochlear (ST) arteries, one of each on each side (see ▶ Fig. 21.1). Both arteries are branches of the ophthalmic artery that is a branch of the internal carotid artery. 16 These arteries enter into the scalp just below the orbital roof and divide either near or above the SO rim into both superficial and deep branches. The superficial branches run through the galea-frontalis layer of the scalp, and the deep branches ascend supplying the pericranium. 17 These arteries anastomose with each other and with the superficial temporal artery laterally, communicating the external and internal carotid systems. 15
The SO artery, which is the main supply of the pericranial flap, crosses the orbital rim beside the SO notch (or through the foramen), approximately 30 mm from the midline, 18 and divides at this level into superficial and deep branches in 80% of cases. 17 The SO notch is more common than the foramen, being present in approximately 70% of cadaveric specimens. 19
The ST artery, which is smaller and more medial than the SO artery, emerges through the frontal notch or foramen as part of the neurovascular pedicle, approximately 22.2 mm from the midline. 19 The division into superficial and deep branches occurs at the level of SO rim or below in 92% of the cases. 17
Although the division of the SO and ST arteries into superficial and deep branches occurs in most cases at the level of the orbital rim or below, in some cases it occurs above that level. Therefore, it is recommended avoiding extending the separation of the pericranial flap from the galea-frontalis muscle layer into the 10 mm above the orbital rim, to prevent injury to the vascular supply. 17
21.2.3 Sensory Innervation to Scalp
The sensory innervation of the scalp comes from the SO and the ST nerves. Both are branches of the ophthalmic division of the trigeminal nerve, which divides within the orbit to give rise to these branches. Both of them usually emerge from the superior orbital rim with the arteries of the same name, the SO and the ST arteries, respectively. The ST branch is a small nerve that supplies the anterior midline forehead to the hairline. The SO nerve divides into a superficial branch and a deep branch, and provides the most of sensation in the scalp, from the forehead to the vertex. 20
21.3 Indications
It has been well established that intranasal vascularized flaps are the best reconstructive options in small-medium septal perforations. However, these flaps are not always available or not large enough to close a septal perforation. The indications could be summarized as
Large septal perforations, for example in cases of near total septal perforation after surgery, trauma, or drug abuse.
Intranasal flaps are not available, for example when vascular supply to intranasal flaps has been compromised.
The use of the pericranial flap would be contraindicated in patients who have suffered previous forehead surgery with likely interruption of the blood supply of the flap or in case of orbital rim fractures.
21.4 Surgical Steps
At the beginning of surgery, the nasal cavity is decongested with cottonoids impregnated with a solution of adrenalin 0.001% with lidocaine 2%. This aids with hemostasis throughout the surgery. The edges of the septal perforation are refreshed to improve their binding to the flap. 15, 21
To introduce the pericranial flap into the nasal cavity, an osteotomy of frontal sinus is needed, which requires a Draf III frontal sinusotomy, as described previously by Draf in 1991. 22 This procedure involves removal of the interfrontal septum, the superior part of the nasal septum, and the frontal sinus floor until the orbit laterally.
A standard coronal incision at the vertex of the scalp is made to start harvesting the pericranial flap. It would be advisable to be careful with the superficial temporal artery. This artery runs 16.68 mm in front of the tragus and divides into frontal and temporal branches above the zygomatic arch in 74% of specimens. 23
It is important to make the incision from one ear to the other to improve the mobility of the superficial layers of the scalp and facilitate the harvest of the pericranial flap and help its introduction into the nasal cavity. At the level of the temporal line, the incision has to continue down until the superficial layer of the deep temporal fascia, which is continuous with the periosteal layer of the cranium. 15, 21
If additional length of the pericranial flap posterior to the coronal incision is needed, care must be taken in making the coronal incision to ensure that the pericranium is not divided. Extend the incision down between galeal layer and loose areolar tissue, and identify this plane of dissection.
Scalp incisions can be made using electrocautery, which is associated with decreased operative times and reduced blood loss, and without increased complications such as alopecia, infection, and dehiscence of the incisions. 24
Dissect down along the skull and elevate the galeal fascia and the subcutaneous tissue anteriorly. This dissection is superficial to the loose areolar tissue that is a component of the pericranial flap. 15
As it is explained in the section of anatomy, one must be careful at the level of the orbital rim because the deep branches of the SO and the ST arteries could arise from these main trunks 1 cm above the orbital rim. To prevent injury of these neurovascular pedicles, it is highly recommended that dissecting the first centimeter above the orbital rim is avoided. 17
Posteriorly the periosteum is incised according to the tissue required for a complete closure of septal perforation. Laterally it is incised along the temporal lines. Later on, the pericranial flap is elevated to approximately 1 cm above the SO rims. Care must be taken not to damage the deep branches of the SO and ST arteries, as previously explained. 15, 21
The flap is folded back on itself, in its most distal area, for greater thickness of new nasal septum, suturing with dissolvable stitches ( ▶ Fig. 21.2).
The upper margin of the frontal sinus was localized through sinus transillumination; then the anterior plate of the upper portion of the frontal sinus was drilled to ensure a 30-mm width and 10-mm height frontal osteotomy. We recommend not making a small osteotomy to avoid causing vascularity problems in the flap in its introduction ( ▶ Fig. 21.3).
With an endoscopic view, the pericranial flap would be introduced into the nasal cavity through the osteotomy of the frontal sinus and rotated laterally 90 degrees to be in a sagittal plane like the nasal septum. Before that, it would be advisable to mark the extremes of the flap with stitches to facilitate insertion into the nasal ( ▶ Fig. 21.2, ▶ Fig. 21.4).
The flap is sutured anteriorly to the edge of the perforation and inferiorly to the mucosa of the floor of the nasal cavity with absorbable stitches. In its most posterior portion, a suture passing through the soft palate is performed. It is anchored to the sphenoid rostrum with two stitches that pass through two holes made in the sphenoid rostrum, above the choana, thus creating a new septum made of two layers of pericranial flap ( ▶ Fig. 21.5, ▶ Fig. 21.6, ▶ Fig. 21.7, ▶ Fig. 21.8).
It would be advisable to place nasal packing during 48 to 72 hours, as well as silicone nasal splints anchored in the most anterior region of the remains of the nasal septum.
Fig. 21.2 This picture shows how to fold back the flap on itself to maximize the thickness of new nasal septum and how to mark the extremes of the flap with stitches to facilitate insertion into the nasal cavity.
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