Fig. 29.1
Diagram showing inlay and onlay technique of synthetic dura placement. (a) Coronal view showing how the synthetic dura is introduced above the supraorbital walls in a double layer. Arrows demonstrate how the weight of the brain keeps the graft in position. (b) Sagittal view showing graft orientation in relation to planum sphenoidale and the frontal sinus. FS frontal sinus; PS planum sphenoidale; SS sphenoid sinus (Reproduced with permission: Germani et al. [16]. Oceanside Publications)
Relative contraindications when considering any pedicled flap include conditions that directly affect the vasculature (local or systemic) or predispose the patient to thrombotic phenomena. These include granulomatous diseases such as Wegener’s granulomatosis, vasculitic diseases such as polyarteritis nodosa, or coagulopathies such as antithrombin III or protein C deficiency. Similarly, one must consider alternative reconstruction techniques in patients who have received high-dose irradiation in the area of the flap, its pedicle, or its terminal vessel.
29.3 Pedicled Flaps
An overview of mucoperiosteal and fascial vascularized flaps and their applications is provided in Table 29.1. These flaps can be further divided into intranasal and extranasal flaps. Intranasal flaps include the following:
Table 29.1
Intranasal, extranasal, and free flaps available for skull base reconstruction
Pedicled flaps | Free flaps | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|
Defect location | Intranasal | Extranasal | |||||||||
Nasoseptal flap | Inferior turbinate flap | Lateral wall posteriorly based | Lateral wall anteriorly based | Middle turbinate flap | Palatala | Transfrontal pericranial flap | Temporoparietal fascia flap | Occipital galeopericranial flapa | Facial artery myomucosal flap | ||
Anterior/cribriform | X | X | X | X | X | X | X | ||||
Planum | X | X | X | X | X | X | X | X | |||
Sella | X | X | X | X | X | X | X | X | X | ||
Clivus | X | X | X | X | X | X | X | ||||
C1–C2 | X | X | X | ||||||||
Pedicled nasoseptal flap
Reverse septal flap
Nasoseptal rescue flap
Inferior turbinate flap
Middle turbinate flap
Anteriorly based lateral nasal wall flap
Posteriorly based lateral nasal wall flap
Extranasal flaps include the following:
Transfrontal pericranial flap
Transpterygoid temporoparietal fascia flap
Occipital galeopericranial flap
Facial artery myomucosal (or mucosal) flap
Oliver-modified pedicled palatal flap
A detailed discussion of the various myofascial or myocutaneous flaps used to reconstruct the skull base is beyond the scope of this chapter; however, a concise mention is appropriate. Briefly, these include flaps comprising the following muscles: temporalis, pectoralis major, sternocleidomastoid, trapezius, and latissimus dorsi. The temporalis myofascial flap is adequate for the most lateral aspect of the anterior cranial fossa and can be extended by harvesting the temporoparietal or pericranial fascia. However, the vascular pedicles of the remaining listed muscles originate below the clavicle; therefore, their reach to the skull base is limited. Free microvascular flaps overcome this limitation, allow flexibility in flap design, are not limited by the arc of rotation of their pedicle, and are ideal to fill large dead spaces. Free flaps suitable for skull base reconstruction include the anterolateral thigh, fibula, radial forearm, rectus abdominis, serratus, scapula, gracilis, and latissimus dorsi flaps [16, 13].
29.3.1 Intranasal Flaps
29.3.1.1 Posterior Pedicle Nasoseptal Flap
The posterior pedicle nasoseptal flap (NSF), also named the Hadad-Bassagaisteguy flap, was developed at the University of Rosario, Argentina, by Hadad and Bassagaisteguy et al. and modified by Carrau et al. in a quest to design a better intranasal vascular pedicled flap to reconstruct skull base defects [17, 12].
Indications
The posterior pedicle nasoseptal flap is a reliable flap, especially for the reconstruction of large skull base defects, as it provides an ample surface area with a superior arc of rotation. The length of the posterior pedicle nasoseptal flap is adequate to reconstruct cribriform, sella, planum sphenoidale, or clival defects [17]. The height of the septum provides enough width to cover the full width of any anterior skull base defect between the orbits. When considering posterior defects, the flap has sufficient length to cover all sellar defects and the roof or lateral walls of the sphenoid sinus, and it can cover a panclivectomy (i.e., from the posterior clinoids superiorly to the foramen magnum inferiorly) [18]. Anteriorly, the flap can cover the region extending from the posterior border of the frontal sinuses to the anterior wall of the sphenoid sinus. A single posterior pedicle nasoseptal flap, however, is not adequate to cover extensive defects involving multiple skull base locations, such as those extending from the posterior wall of the frontal sinus to the sella turcica or foramen magnum (i.e., more than two adjacent anatomical modules) [18]. Under these circumstances, bilateral posterior pedicle nasoseptal flap or a combination of different pedicled flaps or the use of free tissue grafts needs to be considered.
Contraindications
The posterior pedicle nasoseptal flap is not feasible in patients who have previously undergone procedures, which have compromised the vascular pedicle or the flap substance such as the following:
Bilateral wide sphenoidotomies, sphenopalatine artery ligations, a previous septectomy, or in those with tumor involving the septum.
A flap cannot be harvested on the side in which the tumor involves the sphenoid rostrum, lateral nasal wall, sphenopalatine foramen, or pterygopalatine fossa.
Careful consideration should be given to the use of this flap in children under 14 years of age as the impact of a posterior pedicle nasoseptal flap on facial skeletal growth in children is unknown [19]. Furthermore, the area of the septum in children under the age of 10 years may be insufficient relative to the area of the skull base; thus, a posterior pedicle nasoseptal flap in a child under this age may require supplementation with fascia or fat [19].
Anatomy
The flap consists of the mucoperiosteum and mucoperichondrium of the nasal septum and is pedicled on the posterior septal artery, a branch of the sphenopalatine artery. The posterior septal artery arises from the sphenopalatine artery in the pterygopalatine fossa, and its course is divided into three segments: the pterygopalatine, sphenoidal, and septal [20]. The posterior septal artery bifurcates into a superior and inferior branch in the sphenoidal segment, and the inferior branch is typically the larger/dominant branch [20]. The mean distance between the sphenoid ostium and the superior branch is 9.3 mm (range 5–15 mm) [21]. The branches of the posterior septal artery then form a dense network along the septum to supply the inferior two thirds of the septum and a large portion of the nasal floor [20]. The posterosuperior portion of the septum is supplied by the posterior ethmoid artery. The inferior branch of the posterior septal artery sends a branch to the incisive canal, which supplies the hard palate and anastomoses with the anterior branch of the greater palatine artery.
Technique
Several factors influence the laterality of the flap being harvested. First, tumors that invade the rostrum of the sphenoid, nasal septum, lateral pterygoid recess, or pterygopalatine fossa preclude the harvesting of the ipsilateral flap; thus, one should elevate the flap on the contralateral side. Second, when both sides of the nasal septum are available for flap harvesting, we generally prefer the right side, as it is usually easier to dissect for a right-handed surgeon, especially if a right middle turbinectomy is completed as part of the EEA. Last, the presence of nasal septal spurs or severe septal deviation increases the technical difficulty and the risk of perforation during the harvesting the flap. Thus, the contralateral side may be preferred in this instance, or a septoplasty should be performed first. If a patient has had prior sphenoidal sinus surgery, then the viability of the posterior pedicle nasoseptal flap vascular pedicle may be confirmed using an acoustic Doppler sonography with an endoscopic probe.
The posterior pedicle nasoseptal flap requires prior planning as one of its limitations is that this flap, or at least its pedicle, must be harvested at the beginning of surgery (i.e., prior to the posterior septectomy) and before the size of the skull base defect is known. Therefore, the flap dimensions must be overestimated, and the flap may require trimming to ensure it lies square against the bony rim of the resultant defect.
One advantage of the posterior pedicle nasoseptal flap is that it may be reused in cases of benign pathology such as a recurrent craniopharyngioma, incomplete pituitary adenoma resection, or in staged procedures. The flap tends to retain the shape of the defect, and, therefore, any defect that is enlarged may require additional tissue to supplement the repair.
Surgical steps to harvest the posterior pedicle nasoseptal flap are described below:
1.
A posterior pedicle nasoseptal flap may be designed based on the anticipated size and shape of the defect. In our practice, however, we harvest its maximum surface area, which spans from the vomer posteriorly to the mucocutaneous junction of the columella anteriorly and from the floor of the nasal cavity to 1–2 cm below the olfactory cleft (to preserve the olfactory epithelium). Anterior to the anterior head of the middle turbinate, where there is no significant olfactory epithelium, we harvest the entire height of the nasal septum.
2.
First, the nasal cavity is decongested and prepared as previously described.
3.
To facilitate the visualization of the nasal septum and surgical field, and, therefore, the harvesting of the flap, the inferior turbinates and the left middle turbinate are out-fractured bilaterally and the right middle turbinate is removed.
4.
The inferior third of the right superior turbinate is removed using a microdebrider or the straight tru-cut forceps, and the sphenoid ostium is identified.
5.
To harvest the posterior pedicle nasoseptal flap, we incise the mucosa with a monopolar electrocautery equipped with an extended insulated needle tip bent at 90° (Arthroscopic hook electrode; Valley Lab, Boulder, CO) set at 15 W.
6.
Two posterior incisions encompass the pedicle. The superior incision begins at the level of the natural ostium of the sphenoid sinus. The inferior incision starts at the junction of the superior border of the choana and lateral nasal wall, anterior to the torus tubarius.
7.
The inferior incision of the pedicle is extended along the posterior choana toward the nasal septum medially. This incision is then continued anteroinferiorly following the free edge of the posterior nasal septum toward the junction of the nasal crest of the palatine bone and the vomer. At this point it continues as a sagittally oriented incision along the junction between the nasal crest of the palatine bone/maxilla and the vomer/nasal cartilage. The incision continues toward the columella and ceases at its mucocutaneous junction.
8.
The superior incision extends from the superior aspect of the sphenoid ostium (incorporating the ostium into the incision) and crosses the rostrum of the sphenoid toward the septum. This incision continues sagittally following an imaginary line drawn to spare the olfactory epithelium. The olfactory epithelium can be identified as a raised, yellowish area with vertical striations over the most cephalic 1–2 cm of the nasal septum in the region posterior to the head of the middle turbinate.
9.
At the level of the head of the middle turbinate, the incision is extended vertically to the most superior aspect of the septum. This incision is then carried anteriorly toward the mucocutaneous junction of the columella.
10.
These two sagittally oriented incisions traverse the entire length of the septum and are connected at their most anterior aspect by a vertical incision that follows the mucocutaneous junction of the columella (Fig. 29.2).
Fig. 29.2
Outline of incisions for a posterior pedicle nasoseptal flap. 1. Superior incision parallel to the skull base and below the olfactory epithelium. 2. Vertical anterior incision from the nasal dorsum to meet the inferior incision on the floor of the nose. 4. Posterior incision along the posterior septum to the junction of the palatine crest and vomer (Reproduced with permission: Peris-Celda et al. [22]. Thieme Publishers)
11.
These incisions can be modified to suit specific areas and needs of the reconstruction or to ensure a complete resection with adequate oncologic margins. The flap may be extended laterally onto the floor of the nose and into the inferior meatus. This adds 20 mm and 774 mm2 of surface area to the posterior pedicle nasoseptal flap [22].
12.
A Cottle dissector is used to elevate the mucoperichondrium and mucoperiosteum of the flap from anterior to posterior. If the flap has been extended onto the nasal floor, care must be taken during elevation of the mucoperichondrium and mucoperiosteum along the nasal floor as a strong matrix of collagenous fibers (Sharpey’s fibers) connecting the periosteum and bone exists in this location. Sharp dissection reduces the risk of tearing the flap during its elevation in this location.
13.
Once harvested, the nasoseptal flap may be stored in the nasopharynx, or inside the maxillary sinus, or against the lateral nasal wall to avoid injury during the extirpative surgery. During any clival or nasopharyngeal surgery pathology, we often prefer to place the posterior pedicle nasoseptal flap along the lateral nasal wall after placing a suture through its anterior border. This avoids congestion of the flap. The suture is brought out through the nostril and clamped with a hemostat, which is allowed to hang freely from the nostril. The hemostat provides a counterweight that maintains the flap in an extended position along the lateral nasal wall and, thus, out of the way of any instrumentation. If the flap is on the right lateral nasal wall, then the endoscope shaft will displace it and keep it out of the way. If the flap is on the left, the endoscope should be used to guide any instrumentation into the nasal cavity to avoid injury to the flap.
14.
Prior to placement of the posterior pedicle nasoseptal flap over the defect, the mucosa of the surrounding bone is removed to ensure no mucosa is buried beneath the flap. This prevents the development of a mucocele. Subsequently, the nasoseptal flap is positioned over the defect ensuring its full contact against the surrounding denuded bone. It must overlap the bone to allow for any retraction of the flap (potentially up to 20 %). One should note that if the periosteal side of the pedicle is exposed to air, it would heal by secondary intention leading to contraction. Abdominal free fat maybe used to obliterate any dead space, a bony tunnel (e.g., after a transclival or transodontoid approach), or the sphenoid sinus when appropriate so that the periosteal side is against fat and not exposed to air.
15.
Others apply a biologic glue to further fix the flap (optional). However, we have abandoned this practice as we feel its value is questionable. Subsequently, nonadherent nasal packing materials, such as Nasopore (Polyganics, Groningen, the Netherlands), and expandable sponges (Merocel, Medtronic Corporation; Jacksonville, Florida) are inserted under direct endoscopic visualization to bolster the flap against the defect.
16.
If a perforation is accidentally made in the flap at any stage during the surgery, the surgeon may align the flap so that the perforation does not directly overlay the defect. If this is not possible, then the hole may be sutured, bolstered with collagen matrix, or plugged with fat [23].
29.3.1.2 Reverse Flap
Indications
This flap was described by Caicedo et al. in 2010 and is also known as the Caicedo reverse rotation flap [24]. The reverse flap is harvested as part of the posterior pedicle nasoseptal flap to avoid crusting on the exposed cartilage of the denuded anterior septum donor site, which can persist for 3–6 months postoperatively [12]. Nasal crusting leads to nasal obstruction, an offensive smell, halitosis, and olfactory dysfunction. The reverse flap has been shown to reduce crusting of the donor site to 1–2 weeks [25]. Any crusting after the reverse flap most commonly occurs at the site of the sutures, and patients should be warned about this to avoid any attempts to digitally remove the crusts.
Anatomy
This flap is based on branches of the anterior ethmoid artery (a branch of the ophthalmic artery), the greater palatine artery (a branch of the internal maxillary artery), and alar branches of the facial artery.
Technique [24, 25]
1.
After the posterior pedicle nasoseptal flap is harvested and placed in the nasopharynx, along the lateral nasal wall, or in the maxillary sinus, the contralateral septal mucoperichondrium and mucoperiosteum is elevated. A posterior septectomy, removing the posterior septal cartilage and portions of the vomer and perpendicular plate of the ethmoid bone, creates a single cavity that can be approached through either nostril. Intraoperative image guidance may be used to ensure that the septectomy does not include the structural support of the nasal septum (that portion inferior to the nasal bones and resting over the premaxilla), thus avoiding a saddle nose deformity.
2.
An extended, insulated needle tip electrocautery is used to make the three incisions. Prior to making these incisions, cottonoids are placed in the left nostril between the septum and the inferior and middle turbinates to protect them from any injury due to the cautery.
3.
Superior and inferior incisions are made in a similar fashion to those of the posterior pedicle nasoseptal flap except that the inferior incision is made approximately 1 cm above the level of the floor of the nose. They are brought to the level of the remaining cartilaginous septum anteriorly.
4.
A posterior vertical incision is made at the level of the rostrum of the sphenoid, joining the superior and inferior incisions and completing the anteriorly based flap (Fig. 29.3).
Fig. 29.3
Right nasal cavity after endoscopic endonasal approach shows right maxillary antrostomy, vascular pedicled nasoseptal flap positioned in the nasopharynx, posterior septectomy with preservation of opposite nasal septal mucosa (reverse rotation flap). Black dotted line demonstrates incisions for the reverse flap on opposite nasal septal mucosa. Gray arrow indicates the direction of flap transposition (Reproduced with permission: Caicedo-Granados et al. [24]. Wiley and Sons)
5.
The posterior edge of the flap is then grasped with a Blakesley forceps and brought anteriorly to cover the denuded septal cartilage (Fig. 29.4).
Fig. 29.4
Right nasal cavity after reverse rotation flap is positioned against the contralateral septum (Reproduced with permission: Caicedo-Granados et al. [24]. Wiley and Sons)
6.
The flap can then be trimmed to size and is sutured to the columella with a 4-0 absorbable suture such as chromic.
7.
Quilting transmural absorbable 3-0 or 4-0 sutures are then used to appose the flap against the septum.
8.
The remaining inferior mucosa is incised vertically at its posterior and anterior borders, extending the incisions down to the floor of the nose. This creates an inferiorly based flap that can be placed/folded over the maxillary crest to avoid further crusting in this region.
9.
Silicone splints are then cut to size and sutured to the remnant septum using a nonabsorbable suture, i.e., 3-0 Nylon. These splints protect the flap from the trauma caused by the repeated passage of instruments during surgery.
29.3.1.3 Rescue Flap
Indications
This technique is a modification of the original posterior pedicle nasoseptal flap that involves the elevation and preservation of its pedicle, while the flap paddle remains attached anteriorly. This flap is indicated when a CSF leak is not anticipated in any expanded endonasal approach, such as in routine pituitary surgery.
Technique
1.
First, the nasal cavity is decongested and prepared as previously described (see Reconstruction technique).
2.
Superior and inferior incisions are made with the needle tip electrocautery as described in the posterior pedicle nasoseptal flap. However, unlike the posterior pedicle nasoseptal flap, these incisions are not extended anteriorly to the mucocutaneous junction. Instead, the superior and inferior incisions are brought to a level that is just anterior to the head of the middle turbinate.
3.
Using a Cottle dissector and a ball-tipped seeker probe, the mucoperiosteum is elevated from the septum toward the pedicle. This creates a bi-pedicled flap with attachments at the lateral nasal wall and nasal septum.
4.
The bi-pedicled flap is then pushed inferiorly enough to allow a Frazier suction tip to sit under the choana without compromising the flap.
5.
Dissection of the sphenoid sinus can then proceed without risk to the flap. However, surgeons must be wary of the flap during dissection as an unprotected drill shaft may inadvertently injure the flap and/or pedicle.
6.
At the end of the procedure, if a posterior pedicle nasoseptal flap was not required, the rescue flaps are transposed posteriorly to cover the denuded floor of the sphenoid sinus. Silicone splints are placed along the septum and sutured with a nonabsorbable suture. These are generally removed at 1–2 weeks postoperatively.
29.3.1.4 Inferior Turbinate Flap
Indications
Contraindications
An inferior turbinate flap is contraindicated in any patient who has undergone an ipsilateral sphenopalatine artery ligation. Prior inferior turbinectomy or turbinate surgery may reduce the surface area and pliability of the flap, limit its ability to mold to the shape of the defect, and may also compromise its blood supply.
Anatomy
The inferior turbinate flap is based on the inferior turbinate arterial branch of the posterior lateral nasal artery, a branch of the sphenopalatine artery. The posterior lateral nasal artery branches from the sphenopalatine artery and runs in an inferolateral direction along the perpendicular plate of the ascending process of the palatine bone and sends a branch to the middle turbinate medially. The inferior turbinate branch enters the inferior turbinate on the anterior aspect of its lateral attachment, 1.0–1.5 cm from its posterior border [26]. It runs inside the bone 50 % of the time, through soft tissue in 14 % and in a mixed pattern in 36 % [27]. The artery runs through the soft tissue on the medial aspect of the bone for a mean of 1.2 cm before piercing the soft tissue and bone and dividing into up to six branches [27]. Of note, the artery increases in size as it moves anteriorly, possibly due to contributions from the angular artery, a branch of the facial artery, which could be considered the anterior vascular pedicle to the inferior turbinate [28]. The dominant blood supply to the inferior turbinate is the inferior turbinate artery, however [29]. The inferior turbinate flap provides a surface area of approximately 4.97 cm2 [28]. To enlarge this surface area, bilateral flaps may be harvested for larger defects.
Technique [9, 30]
1.
First, the nasal cavity is decongested and prepared as previously described (see Reconstruction technique).
2.
It is important to avoid disruption to the nasolacrimal duct by sharply dissecting its attachment during flap harvest.
3.
Next the inferior turbinate is medialized in such a way that the medial surface of the inferior turbinate is well visualized. Steps 4–6 are performed to identify the pedicle of the inferior turbinate flap.
4.
The natural ostium of the ipsilateral maxillary sinus is identified after performing an uncinectomy.
5.
The maxillary sinus ostium is enlarged posteriorly toward the posterior maxillary sinus (antral) wall.
6.
Submucoperiosteal elevation from the ascending process of the palatine bone allows the identification of the crista ethmoidalis and the sphenopalatine foramen, thus identifying the sphenopalatine artery and its terminal branches. There is significant anatomical variation of the sphenopalatine artery branches, and the posterolateral nasal artery may be anterior to the posterior wall of the maxillary antrum [31, 32]. It is important to recognize this anatomic variation during the maxillary antrostomy and mucoperiosteal elevation so as not to injure the vascular pedicle.
7.
Once the vascular pedicle is well defined, two sagittal incisions are made to define the superior and inferior limits of the flap (Fig. 29.5).
Fig. 29.5
Left lateral inferior turbinate flap incisions. Shaded area nasoantral window opened to facilitate identification of the sphenopalatine artery (SPA) and the posterior lateral nasal artery (PLNA) (Reproduced with permission: Fortes et al. [9]. Wiley and Sons)
8.
A posterior to anterior incision is made along the superior sagittal plane of the inferior turbinate.
9.
An inferior sagittal incision is made along the caudal margin of the inferior turbinate.
10.
A vertical incision is made at the head of the inferior turbinate at its attachment at the pyriform aperture joining the two sagittal incisions.
11.
A periosteal elevator (Freer dissector or Cottle elevator) is used to raise the mucoperiosteum off the inferior turbinate in an anterior to posterior direction both medially and laterally to the inferior turbinate bone. Elevation has to be done in a submucoperiosteal plane to prevent injury to the vascular supply.
12.
Care is taken not to injure the vascular pedicle as it enters the turbinate at the superior aspect of its lateral attachment, 1–1.5 cm from its posterior aspect.
13.
The inferior turbinate bone is kept in situ until the flap is elevated. The bone is then taken down once the flap is elevated using true-cutting forceps.
14.
The flap is then rotated into the skull base defect and secured in place.
29.3.1.5 Middle Turbinate Flap
Indications
Contraindications
This is a technically difficult flap to elevate due to its thin mucoperiosteum that is firmly attached to the multiple pits and crevices of the middle turbinate bone. In addition there is some risk to avulse the bony attachments of the middle turbinate to the cribriform plate, resulting in a CSF leak. This flap is especially difficult to harvest in any patient who has a destabilized middle turbinate, concha bullosa, paradoxical middle turbinate, and unilateral hypoplasia of the middle turbinate or in patients who have undergone previous surgery involving the middle turbinate. The middle turbinate flap is contraindicated in any patient who has undergone a sphenopalatine artery ligation on the involved side.
Anatomy
The middle turbinate flap comprises the mucoperiosteum of the middle turbinate and is based on the middle turbinate branch of the posterior lateral nasal artery, a branch of the sphenopalatine artery. This artery is located inferiorly in the middle turbinate and has anterior and posterior branches, which supply the lateral and medial mucosa of the turbinate, respectively [35]. See Sect. 29.3.1.4 for a further description of the vascular anatomy.
Technique [34]
1.
First, the nasal cavity is decongested and prepared as previously described.
2.
A vertical incision is made along the anterior face of the middle turbinate head using a 15 blade scalpel (Fig. 29.6a), a straight Beaver blade (Beaver-Visitec International Inc., Waltham, MA, USA), or monopolar electrocautery equipped with an extended insulated needle tip bent at 90° (Arthroscopic hook electrode; Valley Lab, Boulder, CO). Care must be taken not to injure the pedicle during this incision.
Fig. 29.6
(a) Endoscopic photograph of a cadaveric dissection demonstrating the anterior vertical incision of the middle turbinate flap. Asterisk septum; dashed arrow inferior turbinate; white arrow middle turbinate. (b) Endoscopic photograph of a cadaveric dissection demonstrating the removal of the middle turbinate bone. White arrow medial limb of flap; white dashed arrow lateral limb of flap; asterisk middle turbinate bone with concha bullosa. (Reproduced with permission: Prevedello et al. [34]. Wiley and Sons)
3.
A periosteal elevator is used to raise the mucoperiosteum of the middle turbinate in a superior to inferior direction both medially and laterally to the middle turbinate bone. Care must be taken not to destabilize the middle turbinate during dissection or to fracture the ethmoid sinus cells resulting in a CSF leak.
4.
The thin bone of the middle turbinate is removed from the inner aspect of the flap in a piecemeal fashion using true-cutting forceps (Fig. 29.6b).
5.
Once the middle turbinate bone has been removed, the middle turbinate mucoperiosteum is detached from the lateral nasal wall and the skull base. This is done by making a horizontal cut through the axilla (Fig. 29.7) and following it posteriorly in a sagittal plane to the posterior pedicle yielding a posterior pedicle flap. Caution must be taken not to enter the skull base.
6.
Identification of the pedicle is key, and following it to the sphenopalatine foramen allows for an increased length and a better arc of rotation.
Fig. 29.7
Endoscopic photograph of a cadaveric dissection demonstrating the medial horizontal incision of the middle turbinate flap. Scissors are angled to avoid injury to the septum or skull base. White arrow medial limb of flap; white asterisk skull base; white dashed arrow septum
7.
The flap is then rotated into the skull base defect and secured in place.
29.3.1.6 Anteriorly Based Lateral Nasal Wall Flap
Indications
This flap, also known as the Hadad-Bassagaisteguy 2 or HB2 flap, is amenable to cover defects in the region from the frontal sinus to the tuberculum sella and from orbit to orbit [36]. An HB2 flap is designed based on the anticipated size and shape of the defect. The width of the flap can be extended to the nasal septum as required or can be combined with a nasoseptal flap to reconstruct very large skull base defects. Unfortunately, this flap tends to have “memory” for the original shape of the inferior turbinate [36].
Contraindications
Any patient who has undergone surgery that may compromise the blood supply or the tissue comprising the flap such as an anterior ethmoid artery ligation, previous facial fractures (particularly those involving the frontal, maxillary, ethmoid, or nasal bones) or orbital fractures, neck dissections, excision of the submandibular gland, or inferior turbinate surgery. It is also uncertain if the pedicle of this flap can withstand postoperative radiotherapy. Vascularity of the flap can be assessed preoperatively using contrast imaging or a Doppler.
Anatomy
The inferior turbinate receives a dual blood supply, from the inferior turbinate branch of the posterolateral nasal artery posteriorly, and the angular artery branch of the facial artery anteriorly [36]. The anteriorly based lateral nasal wall flap, also known as the Haddad-Bassagaisteguy (HB2) flap, is based on the facial (angular and lateral nasal branches) and anterior ethmoidal arteries.
Technique [36]
1.
First, the nasal cavity is decongested and prepared as previously described (see Reconstruction technique).
2.
To facilitate the visualization of the surgical field and harvesting of the flap, the middle turbinate ipsilateral to the flap is usually removed.
3.
A monopolar electrocautery equipped with an extended insulated needle tip bent at 90° (Arthroscopic hook electrode; Valley Lab, Boulder, CO) is used to harvest the flap.
4.
The pedicle of the flap is aligned vertically in the sagittal plane and extends from the roof of the nasal cavity, just anterior to the middle turbinate, to the head of the inferior turbinate. Its anterior incision follows the anterior border of the ascending maxillary process. Its posterior incision follows the uncinate process and extends over the superior aspect of the inferior turbinate. Although technically difficult, this incision can be extended superiorly to incorporate the fontanelle of the maxillary sinus (to increase the width of the flap) (Fig. 29.8).
Fig. 29.8
Incisions for a right anterior pedicle lateral nasal wall flap. IT inferior turbinate, MT middle turbinate, ST superior turbinate. Curved arrows demonstrate the pedicle base and blood flow. White arrow points to the incision over the head of the middle turbinate. Black arrow extension of the incision over the nasal floor (Reproduced with permission: Hadad et al. [36]. Wiley and Sons)
5.
The sphenopalatine neurovascular bundle will be encountered at the most posterior aspect of the incision and needs to be controlled either by clipping or cauterization.
6.
A perpendicular incision starting at the most posterior aspect of the incision over the lateral nasal wall travels medially to cross the floor of the nose and to reach the inferior border of the septum.
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