Transposition of temporoparietal fascia flap through lateral orbital window for anterior skull base reconstruction: A cadaveric feasibility study

Abstract

Objective

To evaluate the feasibility of utilizing a temporoparietal fascia flap (TPFF) via the lateral orbital window for anterior skull base reconstruction (ASBR) in cadavers.

Methods

Four cadavers underwent anatomical dissections on eight sides. The dissection procedure involved exposing the anterior skull base (ASB) using endoscopic endonasal techniques, dissecting the orbit, harvesting the temporalis muscle fascial flap (TPFF), and transposing the TPFF to the ASB through the lateral orbital window. The minimum required length (MRL) of the TPFF to reach the ASB and maximum harvestable length (MHL) of the flap were determined. A computed tomography (CT) scan was used to measure the dimensions of the anterior skull base defects (ASBD) in each cadaver.

Results

The harvested TPFFs successfully reached the intended ASBDs. The average MRL and MHL were 14.00 ± 1.06 and 16.45 ± 1.16 cm, respectively. The resulting ASBDs exhibited an average anterior–posterior distance, width, and area of 2.45 ± 0.42 cm, 2.46 ± 0.46 cm, and 5.17 ± 1.07 cm², respectively. Moreover, utilizing this method, the TPFF consistently reached the posterior wall of the frontal sinus in all cadavers.

Conclusions

The TPFF can be effectively utilized to cover the ASBD by passing through the lateral orbital window. The TPFF serves as a viable option for repairing defects in the posterior wall of the frontal sinus.

Level of Evidence

Level 4.

Reconstruction of the anterior skull base using the temporoparietal fascia flap via a lateral orbital window.

1. INTRODUCTION

In recent years, endoscopic surgery of the skull base has become the standard treatment for numerous skull base and intracranial conditions. The capacity to successfully reconstruct skull base defects generally determines a surgeon's ability to perform endoscopic surgery of the cranial base. Previously, the failure rate of skull base reconstruction with cerebrospinal fluid (CSF) leakage after endoscopic endonasal skull base surgery was as high as 40%. ¹ However, since the introduction of vascularized nasoseptal flap (NSF) in 2006, ² various locoregional flaps and surgical methods have been developed, leading to a dramatic reduction in the overall postoperative CSF leakage rate, which can be as low as 8.5%–11.5%. ³ , ⁴ Factors that may contribute to the successful closure of various skull base defects include low‐flow CSF leakage and the use of vascularized flaps. ³ , ⁴

The success rate of skull base defect closure is generally higher when addressing defects in the anterior skull base (ASB) compared to that when addressing defects at other locations, even when vascularized flaps are not utilized. ⁵ This may be attributed to its low‐flow leakage nature, as well as the presence of a favorable anatomical configuration. ⁵ However, it is crucial not to disregard the small number of cases in which anterior skull base reconstruction (ASBR) fails, as this could lead to a fatal outcome. Although vascularized NSFs have demonstrated excellence in addressing failure, ⁶ in numerous situations, NSF and other adjacent flaps within the nasal cavity may not be appropriate. Consequently, to maximize the probability of successful closure, skull base surgeons need to have “secondary flaps” at their disposal. Several regional flaps have been identified as suitable options for extracranial ASBR. The flaps available in this category include pericranial, paramedian forehead, temporoparietal myofascia, and temporoparietal fascia flaps (TPFF). ⁷ , ⁸ , ⁹ , ¹⁰

The TPFF, based on the superficial temporal artery (STA), is a widely recognized flap that has been applied in various head and neck surgical procedures. The TPFF is advantageous due to its consistent arterial anatomy, reliable vascular supply, wide arc of rotation, and pliability. ¹¹ , ¹² The first description of transpterygoid transposition of the TPFF for repairing skull base defects in expanded endonasal skull base surgery was documented in 2007. ¹³ The technique has subsequently been utilized by numerous authors, particularly in the treatment of middle and posterior skull base defects. ¹⁴ , ¹⁵ , ¹⁶ , ¹⁷ However, it has been challenging to achieve full closure of the ASB with the TPFF using the transpterygoid transposition method. ¹⁰

The use of the TPFF specifically for ASBR has been reported in a few studies to date. ¹⁰ , ¹⁸ , ¹⁹ , ²⁰ In 2019, Ferrari et al. ¹⁸ first reported that the TPFF could be positioned through a craniotomy to traverse the epidural space and reach the site of the defect on the ASB. In 2023, Lin et al. ¹⁰ conducted a study involving the use of a TPFF inserted via the orbit to cover defects within the ASB without performing a craniotomy. Transposing the TPFF extracranially involves passing the flap through the temporalis muscle and using the area beneath it to convey the TPFF to the ASB via the periorbital space. Theoretically, damage to the temporal muscle can occur, and the flap's pedicle may become stuck between this powerful muscle and the underlying bone, potentially compromising its blood supply and venous return.

We propose that the transposition method of the TPFF for extracranial ASBR can be modified to improve success and minimize complications. Therefore, the objective of this study was to investigate the potential of modifying the existing surgical procedure in cadaveric samples before its practical application.

2. MATERIALS AND METHODS

The research protocol was reviewed and granted an exemption by the Siriraj Institutional Review Board (SIRB Protocol No. 947/2566, December 23, 2023). All procedures involving cadaveric specimens were performed in accordance with the ethical standards of our institution and the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Four fresh‐frozen cadaver heads were utilized in this study. Dissections were performed at the Department of Anatomy, Faculty of Medicine, Siriraj Hospital, Mahidol University. Bilateral expanded endoscopic endonasal dissection was performed using standard endoscopic sinus and skull base surgical instruments. Visualization was accomplished using a 4‐mm Hopkins rod lens (0° and 30°) connected to a high‐definition camera head and monitor (Karl Storz GmbH, Tuttlingen, Germany). A bicoronal incision was created on each cadaver head and the TPFFs were raised bilaterally. Orbital dissection was performed through an upper eyelid incision with lateral extension.

2.1. Expanded endoscopic endonasal dissection

Uncinectomy, middle meatus antrostomy, frontal sinusotomy (Draf I), anterior/posterior ethmoidectomy, and sphenoidotomy were performed bilaterally. The entire anterior wall of each sphenoid sinus and the sphenoid intersinus septum was removed. The anterior–superior part of the nasal septum, floor of the frontal sinus, and bony septum between the frontal sinuses were removed to complete the Draf 3 procedure. Identification and resection of the anterior, middle (if present), and posterior ethmoid arteries were performed. The bone in the medial orbital walls was removed, sparing the parts adjacent to the ethmoid arteries. The ASB was exposed from the level of the frontal sinus posterior wall anteriorly to the posterior ethmoid arteries posteriorly and between the medial orbital walls. The bone of the ASB and the crista galli were resected to expose the dura. Finally, the durae were excised.

2.2. Harvesting the TPFF

The procedure described below was performed as previously detailed in the literature. ¹³ , ¹⁷ , ¹⁸ , ²¹ A bicoronal incision with bilateral preauricular extension was created. The subcutaneous tissue flap of the skin was lifted from the temporoparietal fascia (TPF)/galea aponeurotica, beginning above the ipsilateral zygomatic arch and to the contralateral arch. Pitanguy's line was utilized as the anterior limit of the subcutaneous skin dissection. ²² The dissection was performed approximately 5 cm behind the skin incision posteriorly. The STA and its branches were identified on the surface of the TPF. The widths of the distal parts of the TPFFs were designed to range from 3 to 8 cm, which exceeded the anterior–posterior diameter of the anticipated anterior skull base defects (ASBDs). ¹⁰ The TPFF was then harvested from the superior border of the zygomatic arch to the mid‐sagittal plane of the skull by dissecting the TPF/galea aponeurotica from the underlying pericranium and deep temporal fascia (DTF).

2.3. Orbital dissection

The orbital step was performed as previously described. ²³ To simulate the tissue consistency and the existing orbital space with those in actual surgery as closely as possible, water was injected into the collapsed globes of the cadaver heads to increase the orbital globe volumes. An incision was created on the upper eyelid along the skin crease, extending 1.5 cm posterolaterally. The incision on the eyelid was made through the orbicularis oculi muscle. The skin muscle flap was then raised, remaining within the preseptal area superficial to the tarsal plate/levator palpebrae superioris muscle until the superior orbital rim was reached. At this location, the periosteum/periorbita was incised, and dissection was performed between the orbital walls and periorbita. A high‐definition camera head and monitor (Karl Storz GmbH) were connected to a 0° lens, which was then inserted to visualize the subsequent procedures. A malleable retractor was inserted for traction, to safeguard the orbit. The foramen of the recurrent meningeal artery (if present), superior orbital fissure, inferior orbital fissure, optic foramen, posterior ethmoid artery, middle ethmoid artery (if present), and anterior ethmoid artery were visualized. From the intraorbital perspective, the superior and lateral orbital walls were exposed. Upon completion of the intraorbital procedure, a subperiosteal plane was created at the lateral extension of the incision to expose the lateral surface of the frontal process of the zygomatic bone and anterior edge of the temporalis muscle. To create a lateral orbital window, the bony lateral orbital wall at the frontal process of the zygomatic bone was removed using a 3‐mm high‐speed diamond burr (Medtronic, Minneapolis, MN, USA). The bone removal extended from the level of the frontozygomatic suture superiorly to that of the orbital floor inferiorly. A 2‐mm thickness of the anteriormost lateral orbital wall was preserved intact.

2.4. Creation of the temporal tunnel for flap insertion

A vertical incision was made in the DTF along the anterior aspect of the temporal fossa. The DTF was separated from the underlying temporal muscles. Subsequently, a blunt dissection was conducted deep into the DTF and periosteal layer to form a temporal tunnel that extended to the previously dissected subperiosteal space at the lateral orbital wall. Finally, the TPFF was guided through the tunnel to the orbit.

2.5. Insertion of the TPFF into the orbit and anterior skull bases

The TPFF was inserted into the orbit through the lateral orbital window. Within the orbit, the TPFF was positioned superior to the orbital globe and guided through the medial orbital window, entering the nasal cavity to reach the defect on the ASB that was created in the previous step.

2.6. Measurement

Computed tomography (CT) scans with a 0.625 mm slice thickness of the cadaver heads were performed upon completion of the dissection step. A Digital Imaging and Communications in Medicine (DICOM) viewer program (Horos v3.3.6; Horosproject.org) was utilized to process the CT scan data and measure the dimensions of the SBDs and related structures.

During dissection, the maximal length of the TPFF that could be harvested, defined as the maximum harvestable length (MHL), was measured using a ruler from the superior border of the zygomatic arch to the flap incision line at the midsagittal point of the skull. A pen was utilized to mark and measure the shortest distance from the superior border of the zygomatic arch to the point on the flap reaching the superior part of the contralateral medial orbital wall. This distance was defined as the minimum required length (MRL). ²⁴ The length and width of each lateral orbital window, which was approximately rectangular, were measured using a ruler.

The procedure is illustrated in Figure 1.

FIGURE 1.

Summary of the procedure. (A) The left temporoparietal fascia flap (TPFF) is harvested and moved (arrow) to the lateral orbital window (dashed box). (B) The left TPFF enters the orbit through a lateral orbital window (dashed box A), passing superior to the orbital content, entering the nasal cavity via a medial orbital window (dashed box B); C, minimum required length (MRL); D, maximum harvestable length (MHL).

IBM SPSS Statistics 29 software (IBM Corp., Armonk, NY, USA) was utilized for statistical calculations. The mean values of the MHL, MRL, size of the created SBDs and related structures, and size of the lateral orbital windows were calculated. The mean values of MHL and MRL were compared with those in a previous study ¹⁰ using an unpaired t‐test.

3. RESULTS

The dissection was performed on eight sides in four cadavers (Figures 2, 3, 4). Each TPFF reached the contralateral medial orbital wall. The TPFF and skull base structure measurement results are depicted in Tables 1 and 2, respectively. Statistical analysis using an unpaired t‐test revealed that the average lengths of the MRL and MHL in this study were significantly longer than the values reported in previous research ¹⁰ with mean differences of 3.025 cm (95% CI 2.081–3.969; p < .001) and 1.512 cm (95% CI 0.607–2.417; p = .0027), respectively.

FIGURE 2.

Steps of the dissection. (A) A bicoronal incision (1) was curved slightly backward to increase the area of the flap that could be harvested posterior to the Pitanguy's line (2) to avoid injury to the frontal branch of the facial nerve. The flap was harvested superior to the superior border of the zygomatic arch (3). (B) The temporoparietal fascia flap (TPFF) was harvested superficial to the deep temporal fascia (DTF). The flap was wide at the distal region and narrow at the proximal end. (C) An upper eyelid incision with a 1.5‐cm posterolateral extension was marked. (D) After creating an upper eyelid incision, the dissection was performed in the left orbit to obtain a superior orbital space for flap insertion: ON, optic nerve; OR, orbital roof; PEA, posterior ethmoid artery; SOF, superior orbital fissure.

FIGURE 3.

Steps of the dissection. (A) A medial orbital window was created in the left orbit as a corridor to insert the TPFF into the nasal cavity. OR, orbital roof. (B) The frontal process of the left zygomatic bone (FZ) was exposed. A lateral orbital window would be created on this bone anterior to the temporalis muscle (TM). (C) A lateral orbital window (arrow) was created. (D) A straight incision was made in the anterior part of the temporal fossa, on the deep temporal fascia (DTF). The temporalis muscle (arrow) is deep in the DTF.

FIGURE 4.

Steps of the dissection. (A) An arterial clamp was inserted into the previously made incision, and a temporal tunnel, deep to the plane of the DTF and periosteum, was created by blunt dissection. (B) The TPFF (arrow) was inserted through the lateral orbital window. (C) The left temporoparietal fascia flap (TPFF) was placed on the created skull base defect. The tip of the flap was positioned along the medial side of the right orbit. (D) The left temporoparietal fascia flap (TPFF) could be rotated to the frontal sinus, easily reaching the level of the frontal sinus roof (FSR); dashed polygon = created skull base defect.

TABLE 1.

Measurement of the TPFF parameters and lateral orbital windows.

	MHL in cm (N = 8)	MRL in cm (N = 8)	Lateral orbital window in cm (N = 8)
			Width	Length
Mean	16.45	14.00	0.950	1.825
Std. error of mean	0.41144	0.37559	0.0327	0.0590
Std. deviation	1.16374	1.06234	0.0926	0.1669
Minimum	15.0	12.40	0.8	1.6
Maximum	18.0	15.50	1.1	2.0

Abbreviations: MHL, maximum harvestable length; MRL, minimum required length.

TABLE 2.

Skull base and frontal sinus measurements.

	Interorbital distance in cm (N = 4)	AP diameter of the ASBD in cm (N = 4)	Defect area in cm2 (N = 4)	Length of the posterior wall of the frontal sinus in cm a (N = 4)
Mean	2.4555	2.4528	5.1705	3.1308
Std error of mean	0.23081	0.20809	0.53345	0.07701
Std deviation	0.46162	0.41617	1.06690	0.15402
Minimum	1.92	2.08	4.07	2.94
Maximum	3.05	2.94	6.49	3.30

Abbreviations: AP, anterior to posterior; ASBD, anterior skull base defect.

^a Measured from the level of floor to the roof of the frontal sinus at the position of the intersinus septum.

Several TPFFs with distal widths ranging from 3 to 8 cm were harvested. The minimum distal width required to fully cover the SBD in the anterior–posterior dimension was 4 cm. The TPFF, with an 8 cm distal width, could be easily inserted through the lateral orbital window and manipulated to pass into the nasal cavity; however, substantial force was necessary to push the orbit down. Flaps with a distal width ≤7 cm were readily manipulated within the orbit and nasal cavity. TPFFs with distal widths measuring 5 and 6 cm were the most suitable options due to their ease of manipulation and ability to effectively cover skull base defects. These observations suggest that flaps with large distal tips are impractical.

All TPFFs were conveniently rotated into the frontal sinus cavity and effectively covered most of the posterior frontal sinus wall, extending to the roof of the sinus cavity. Manipulation of the flap to cover the posterior frontal sinus wall was facilitated by the absence of gravitational resistance.

A temporal tunnel can be easily created by spreading an arterial clamp under the DTF and periosteum of the zygomatic bone. The tunnel was observed to be spacious, with minimal risk of flap compression.

Creation of the lateral orbital window was most effectively accomplished using a high‐speed drill. Due to the thickness of the bone in this region, the procedure required a considerable amount of time to complete. Additional drilling could be conducted on the lower section of the lateral orbital window near the zygomatic body because this area was broader and more distant from the base of the skull. The remaining strip of bone measuring 2 mm at the anterior portion of the lateral orbital window appeared sufficiently robust to maintain the lateral orbital rim and was unlikely to fracture.

4. DISCUSSION

Resection of the ASB, whether for tumor removal or to create a surgical pathway for addressing intracranial conditions, invariably leads to cranial base defects that require secure reconstruction to separate the intracranial space from the nasal cavity and paranasal sinuses. In endoscopic transnasal skull base surgery, if vascularized tissue coverage of a skull base defect is required, the primary option should be intranasal pedicle flaps due to their reliability and proximity to the surgical area. However, these flaps are often unavailable or unsuitable in many situations, such as when the desired flap is affected by tumors, becomes compromised during the surgical procedure, or has been previously utilized. If local flaps cannot be used, regional flaps should be considered. Several extranasal pedicled regional flaps, whether feasible or not, have been documented for closing skull base defects through extracranial pathways. These include the transfrontal‐pericranial, occipital, palatal, temporoparietal myofascial, paramedian forehead, facial buccinator, pedicled buccal fat pad, and salpingopharyngeus flaps. ⁷ , ⁹ , ²⁵ , ²⁶ The transfrontal‐pericranial flap and TPFF are the most frequently utilized and documented flaps for endoscopic endonasal ASBR among these flap options. ¹⁰ , ¹³ , ¹⁴ , ¹⁷ , ²⁷ , ²⁸ , ²⁹ , ³⁰

The pericranial flap, supplied by the supratrochlear and supraorbital arteries, has been extensively utilized for skull base reconstruction even before the era of endoscopic skull base surgery. ³¹ To perform skull base reconstruction using the endoscopic endonasal extracranial technique, the flap is obtained and subsequently placed into the nasal cavity through the frontal sinus, either via the upper part of the frontal sinus anterior wall or through the nasion. ²⁷ , ²⁹ , ³⁰ The pericranial flap is capable of covering the entire ASB and has the potential to extend its coverage further posteriorly to the level of the craniovertebral junction. ²⁹ , ³⁰ Reliable blood supply, structural integrity, a large area/length that can be harvested, and a simple harvesting procedure are among the advantages of this flap. ³² , ³³

In certain extreme situations where other locoregional flaps are unavailable, the TPFF may be considered for skull base reconstruction. This is particularly relevant when the area requiring reconstruction is located posteriorly or when microvascular free tissue transfer is not a feasible option. The TPFF has primarily been utilized to close the middle and posterior skull bases by inserting the flap through the infratemporal fossa and posterior wall of the maxillary sinus. ¹³ , ¹⁴ , ¹⁷ , ²⁸ As previously stated, it was recently demonstrated that the TPFF could reach and cover the ASBD by passing through the temporalis muscle and orbit. The authors reported that using this method, a TPFF of at least 10.98 ± 0.83 cm in length was required to cover the ASBD. When using the unpaired t‐test for comparison, the TPFF's MRL of 14.0 ± 1.06 cm observed in this current study is significantly longer than the measurement found in previous research. ¹⁰ Although the difference in MRL may be considered questionable owing to the small sample size, it appears logical that our technique would lead to a longer MRL, considering the flap's longer travel distance from its origin, bypassing the temporalis muscle to reach the intended target. However, rather than harvesting at the MRL, it would be more prudent to harvest the TPFF at its maximum length, thereby ensuring adequacy of the flap and accounting for any postoperative tissue retraction.

When the TPFF is inserted into the nose, its length determines whether the flap can reach the skull base defect, whereas its distal width determines the extent to which the target area is covered anteriorly to posteriorly. In theory, the distal end of the TPFF could be customized to fit the size of the skull base defect. ¹⁰ However, in this study, when using the superior orbital route to access the ASB, having a TPFF distal width of 8 cm made it challenging to maneuver the flap inside the orbit, necessitating significant orbital traction that could potentially lead to orbital injury. We found that a distal width of 5–6 cm was the most suitable for fully covering the skull base defect and facilitating flap manipulation. In addition to reconstructing the cribriform area, passing the TPFF through the orbit effectively covered the posterior wall of the frontal sinus. This process was easily accomplished, as gravity naturally directed the flap toward the sinus wall. In all cadavers, the width of the flap adequately covered a substantial portion of the posterior frontal sinus wall and its length could reach the roof of the sinus cavity. These findings indicate that TPFF may be an appropriate choice for reconstructing skull base defects involving the frontal sinus.

Complications specific to this surgical procedure pertain to those that may occur at the donor site, the creation of the flap tunnel, and the orbital step. Alopecia and scalp skin necrosis, which could occur at the donor site, are preventable by ensuring that the dissection when raising the skin‐subcutaneous flap is not too superficial. Although blunt dissection under the DTF and periosteum carries no risk of facial nerve injury because the nerve runs superficial to these structures, there remains the possibility of hematoma or seroma formation. These postoperative events can be mitigated by implementing precise hemostatic techniques and utilizing surgical drains. The creation of a lateral orbital window poses a risk of CSF leakage if the upper part of the window is drilled too high. Furthermore, the size of the lateral orbital window should not be too small, as the flap can swell and get constrained at this point during the initial days after surgery. When manipulating the flap within the orbit, excessive traction on the globe can lead to injury to the globe itself and to the supplying nerves. To prevent orbital complications, it is advisable to employ gentle retraction, periodically release the traction instruments, and design an appropriate distal flap width. Levator palpebrae superioris muscle function impairment can be minimized by performing tissue reapproximation accurately. Given that the TPFF is thin and is placed outside the periorbita, it is unlikely to significantly interfere with the action of the superior rectus muscle.

The procedure utilized in this study possesses three main disadvantages: the arc of rotation, twisted flap, and long MRL. When used for ASBR, the TPFF pedicle needs to be rotated by nearly 90°, which could potentially compromise the arterial supply and venous return compared with a lesser rotation. Although the lateral orbital window is adequately sized, the flap may undergo twisting in this area, resulting in the aforementioned effects. Finally, the long MRL of the TPFF, approximately 85% of the MHL, may lead to reduced blood supply at the tip of the flap.

5. CONCLUSION

Reconstruction of the ASBD around the cribriform area is feasible using a TPFF passing through the lateral orbital window. As the flap is distant from the ASB and nasal cavity/paranasal sinuses, the TPFF is likely to remain unaffected by the disease and treatment procedures, making the flap generally available. Furthermore, as the flap traverses outside the temporalis muscle, the flap pedicle is not compressed by this muscular structure, and the likelihood of injury to the muscle is low. Limitations of this procedure include a high arc of flap rotation, potential flap twisting, long MRL, and possible complications in the temporal area and orbit. This surgical approach can be regarded as the final option for ASBR before proceeding to microvascular‐free tissue transfer. The feasibility of this technique in clinical scenarios has yet to be validated. Finally, although this research indicates that the TPFF can be used to cover defects at the posterior frontal sinus wall, further studies, particularly concerning the quantitative measurement of the flap dimensions, are required.

FUNDING INFORMATION

No funding was received for conducting this study.

CONFLICT OF INTEREST STATEMENT

Financial interests: Pongsakorn Tantilipikorn has received research grants from ALK‐Abbott/AstraZeneca and has received a speaker honorarium from GSK/Abbott/Menarini. Non‐financial interests: Pongsakorn Tantilipikorn has served on advisory boards for Menarini and Viatris. The remaining authors have no relevant financial or non‐financial interests to disclose.

Lumyongsatien J, Durongphan A, Tritrakarn S, Tantilipikorn P. Transposition of temporoparietal fascia flap through lateral orbital window for anterior skull base reconstruction: A cadaveric feasibility study. Laryngoscope Investigative Otolaryngology. 2025;10(2):e70067. doi: 10.1002/lio2.70067

DATA AVAILABILITY STATEMENT

The experimental data of this study are available in Figshare with the identifier https://doi.org/10.6084/m9.figshare.26804686.v1.