Abstract
BACKGROUND
Skull base reconstruction following an extended endoscopic endonasal approach (EEA) is essential for preventing postoperative CSF leakage. Despite recent advancements in surgical techniques and materials, CSF leakage remains a significant complication. This report presents a rigid reconstruction technique utilizing a resorbable unsintered hydroxyapatite/poly-l-lactide (u-HA/PLLA) plate to reduce postoperative CSF leakage.
OBSERVATIONS
Between May 2024 and June 2025, this method was used in 10 cases of extended EEA involving high-flow intraoperative CSF leaks and bone defects more than 25 mm. Notably, no postoperative CSF leakage was observed following the introduction of the u-HA/PLLA plate.
LESSONS
This material offers a unique combination of flexibility and mechanical strength comparable to cortical bone, along with osteoconductivity and bioresorbability, while producing negligible interference on postoperative imaging. These properties make it a highly promising material for skull base reconstruction.
Keywords: extended endoscopic endonasal surgery, cerebrospinal fluid leakage, skull base reconstruction, resorbable artificial plate
ABBREVIATIONS: EEA = endoscopic endonasal approach, PGA = polyglycolic acid, PLLA = poly-l-lactide, u-HA = unsintered hydroxyapatite
Since the introduction of the endoscopic endonasal transsphenoidal approach,1 this procedure has been increasingly utilized and has become the standard surgical technique for sellar, suprasellar, parasellar, and midline skull base tumor surgeries, including pituitary adenomas, craniopharyngiomas, skull base meningiomas, chordomas, chondrosarcomas, and germ cell tumors. In recent years, there has been a rapid advancement in surgical techniques and materials, leading to an expanded indication for surgery. Additionally, more extensive skull base drilling has become necessary to achieve maximal resection of complex tumors. A wide opening of the skull base and dura requires proper reconstruction to prevent postoperative complications such as CSF leakage, meningitis, and visual deterioration from rare complications like optic chiasm herniation.2
The skull base reconstruction technique following endoscopic endonasal tumor removal is one of the most critical steps. As is well known, the “multilayer technique” is widely accepted and commonly used to prevent postoperative CSF leakage.3–9 However, the methods and materials vary depending on the institute or the surgeon’s preference.
We present a skull base reconstruction technique using a resorbable artificial plate composed of unsintered hydroxyapatite (u-HA) and poly-l-lactide (PLLA) (SuperFIXSORB MX40, Muranaka). This rigid reconstruction method reinforces the defective skull base, preventing arachnoid protrusion through the defect caused by brain and arachnoid pulsation, which could lead to postoperative CSF leakage.
Study Description
Methods
We performed an extended endoscopic endonasal approach (EEA) in 10 consecutive patients with intraoperative high-flow CSF leaks (Esposito grade 3)10 and bone defects more than 25 mm. Skull base repair was achieved using a u-HA/PLLA plate (Fig. 1) to cover the large skull base defect between May 2024 and June 2025.
FIG. 1.
Unsintered HA/PLLA composite and resorbable artificial plate (SuperFIXSORB MX40).
In recent years, we have encountered increasingly complex skull base tumors that require a wider opening of the skull base and dura, resulting in larger skull base defects that demand meticulous reconstruction. In most cases, autologous grafts such as nasal septum bone cannot be used to cover such extensive defects. Therefore, we have opted to use a u-HA/PLLA plate for defect reconstruction.
Since May 2024, we have been using a u-HA/PLLA plate for skull base reconstruction. First, we suture the dura with 6-0 monofilament (Johnson & Johnson) to secure the inlay fat tissue (Fig. 2A) (this step is not performed in cases of large dural defects in which the dura cannot be approximated). Next, we place the fat tissue to seal the sutured dura gap (Fig. 2B). We then cover the fat tissue with a polyglycolic acid (PGA) sheet/collagen matrix (Fig. 2C) and position the u-HA/PLLA plate (Fig. 2D). Finally, we place a nasoseptal flap (Fig. 2E) and secure it with gelatin sponge sheets (Fig. 2F).
FIG. 2.
Suture the dura to approximate the dural gap (A), place a fat tissue inlay (B), and then cover it with a PGA sheet (C). Next, insert the resorbable u-HA/PLLA plate (D), followed by positioning the nasoseptal flap (E) and packing the sphenoid sinus with gelatin sponge sheets (F)
Illustrative Case
An 8-year-old boy was incidentally diagnosed with a suprasellar lesion during CT imaging of the head conducted following a head injury. No obvious neurological abnormalities were found, and there were no episodes suggestive of diabetes insipidus. Tumor markers were within the normal range. Ophthalmological and endocrinological studies were also normal. MRI of the brain revealed a suprasellar tumor.
After a 2-year follow-up, the patient developed bitemporal hemianopia. Subsequent MRI showed an increase in the size of the cystic component, which was compressing the optic nerves and optic chiasm (Fig. 3A). CT imaging of the brain revealed calcification within the tumor. Additionally, a well-pneumatized sphenoid sinus was observed (Fig. 3B). As a result, the patient was referred to our institute for surgical treatment.
FIG. 3.
A: Preoperative sagittal MR image of the brain obtained in an 8-year-old boy, identifying a suprasellar tumor compressing the optic nerve and optic chiasm. B:Preoperative sagittal CT scan of the brain, revealing a calcified suprasellar tumor. C: Postoperative sagittal MR image revealing no evidence of residual tumor, with no noticeable artifact from the u-HA/PLLA plate. D: Postoperative sagittal CT scan of the brain demonstrating the integrity of the u-HA/PLLA plate (P) coverage from the anterior to the posterior aspect of the skull base defect.
The tumor was resected via an extended EEA, with skull base drilling performed at the planum sphenoidale, tuberculum sellae, and sellar floor. The drilling was extended to the dorsum sellae, including posterior clinoidectomy and upper clivus resection (Video 1).
VIDEO 1. Video clip illustrating the key surgical steps of EEA for resection of a craniopharyngioma, including skull base drilling, dural opening, tumor removal, and multilayer reconstruction using a u-HA/PLLA plate to reinforce the defect. The final segment demonstrates preparation of the u-HA/PLLA plate. Click here to view.
Following complete tumor resection, a large skull base and dural defect required reconstruction (Fig. 4A). We began by suturing the dura using 6-0 monofilament and then placed fat tissue to seal the dural defect (Fig. 4B), followed by covering it with a PGA sheet. Next, we measured the skull base defect (Fig. 4C) and cut the u-HA/PLLA plate to the appropriate size (Fig. 4D). The plate was then inserted between the dura and the defective bone edge (Fig. 4E). Finally, we positioned the nasoseptal flap (Fig. 4F) and secured it with gelatin sponge sheets. No lumbar drainage was used, and no evidence of postoperative CSF leakage was observed. Pathological examination confirmed the diagnosis of adamantinomatous craniopharyngioma.
FIG. 4.
A: Large skull base and dural defect following tumor resection. B: Suture the dura and place a fat graft as an inlay layer to cover the dural defect. C: Measure the skull base defect. D: Then cut the u-HA/PLLA plate to the desired size. E: Next, insert the u-HA/PLLA plate between the dura and the defective bone edge. F: In the final step, position a nasoseptal flap to cover the plate.
Postoperative MRI revealed no evidence of residual tumor, with no noticeable artifact from the u-HA/PLLA plate on MRI (Fig. 4C). Postoperative CT imaging demonstrated that the u-HA/PLLA plate completely covered the defect from the anterior to the posterior aspect of the skull base (Fig. 4D).
Results
We utilized a u-HA/PLLA plate for rigid skull base reconstruction following an extended EEA in 10 consecutive patients with Esposito grade 3 CSF leaks and bone defects more than 25 mm between May 2024 and June 2025. The mean patient age was 52.2 years (range 4–80 years), with 30.0% male and 70.0% female. Reoperations were performed in 2 cases (20.0%).
Histological diagnoses included craniopharyngioma in 5 cases (50.0%) and meningioma in 5 cases (50.0%). The mean skull base bony defect after tumor removal was 32.1 mm (range 25–50 mm). Dural suturing was performed in 7 cases (70.0%), and a nasoseptal flap was utilized in all patients. Notably, lumbar drainage was not used in any case.
Since adopting the u-HA/PLLA plate for coverage and reinforcement of large skull base defects, we have observed no postoperative CSF leakage or other complications following surgery (Table 1).
TABLE 1.
Clinical data and patient outcomes
| Value | |
|---|---|
| Demographic & treatment data | |
| Age, yrs | 52.2 (4–80) |
| Sex | |
| Male | 3 (30.0) |
| Female | 7 (70.0) |
| Prior EEA | 2 (20.0) |
| Intraop large CSF leak (Esposito grade 3) | 10 (100) |
| Skull base bony defect after tumor removal, mm | 32.1 (25–50) |
| Pathology | |
| Craniopharyngioma | 5 (50.0) |
| Meningioma | 5 (50.0) |
| Skull base reconstruction technique | |
| Dural suture | 7 (70.0) |
| Nasoseptal flap | 10 (100) |
| Lumbar drainage | 0 (0) |
| Postop CSF leak | 0 (0) |
Values are given as number of patients (%) or mean (range).
Informed Consent
The necessary informed consent was obtained in this study.
Discussion
Observations
Skull base reconstruction following an extended EEA is a crucial step in preventing postoperative complications. Over the past decade, advancements in surgical techniques and materials have enabled more complex skull base tumor resections via the EEA. However, the risk of postoperative CSF leakage remains, with reported incidence rates of 2.8%–4.7% in recent years.11–13
Prior to implementation of the u-HA/PLLA plate for rigid skull base reconstruction at our institute, the postoperative CSF leakage rate was 2.3% between November 2018 and March 2021, with 1 case requiring additional surgical repair. Furthermore, intraoperative findings during reoperations revealed delayed healing of the nasoseptal flap, likely due to compromised vascularity.14 A prolonged healing process was observed in some patients, particularly in patients who underwent reoperation. These observations suggest that rigid reconstruction may provide structural support to the repaired layer during the extended healing phase.
Theoretically, rigid reconstruction may yield better results than soft reconstruction, as the pulsation of the brain and arachnoid can potentially disrupt the repaired layer, especially in cases of delayed healing. Since adopting the u-HA/PLLA plate for rigid skull base reconstruction in May 2024, we have not encountered any cases of postoperative CSF leakage.
Various types of autologous and allogenic bone grafts have been used by different authors to cover the skull base defects.15–17 Some authors have utilized autologous bone, such as nasal septum bone, for rigid skull base reconstruction following EEA. However, in cases of extended EEA with large skull base defects, autologous bone may not adequately fit the defect. Therefore, our institute uses u-HA/PLLA plates for rigid reconstruction, which offer several beneficial properties.
SuperFIXSORB MX40 (Fig. 1) consists of 0.3-mm-thick sheets made of u-HA/PLLA composite. This material has been used in maxillofacial and orthopedic surgery for many years.18–20 Its properties include being a resorbable biomaterial with high mechanical strength and bioactive osteoconductivity, which promotes postoperative bone healing, as demonstrated in multiple studies.18–20
This material is soft and flexible, minimizing the risk of injury to surrounding structures. It is sufficiently large to provide complete coverage for skull base defects, even in cases with extensive defects, and is easy to cut to the desired size. Additionally, it can be positioned between the dura and the defective bone edge with ease. Furthermore, it retains mechanical strength comparable to cortical bone for approximately 25 weeks.
Since adopting this u-HA/PLLA plate, we have encountered 1 case requiring reoperation due to tumor recurrence. We found that the u-HA/PLLA plate served as a useful landmark during the reoperation, as it caused no adhesion and facilitated identification of the surgical plane. This plate is also easy to crush into small pieces and remove with ease.
Another advantage of the u-HA/PLLA plate is its partial radiopacity, which enables postoperative visualization on CT imaging (Fig. 3D) while minimizing artifacts on MRI (Fig. 3C). This feature is particularly valuable for follow-up assessments, facilitating the precise detection of small residual or recurrent tumors.
Lessons
In recent years, the incidence of postoperative CSF leakage following extended EEAs has decreased but remains a concern. We have reported use of the u-HA/PLLA plate for rigid skull base reconstruction following extended EEA to prevent postoperative complications.
This material offers several advantages; it is soft and flexible and resorbable, yet it maintains strength comparable to cortical bone for 6 months. It is easy to use and exhibits osteoconductive properties that accelerate bone healing. Additionally, its partial radiopacity enables postoperative imaging without significant artifact, facilitating accurate follow-up assessments. These properties make the u-HA/PLLA plate a promising option for rigid skull base reconstruction. Since implementing this material, no cases of postoperative CSF leakage have been encountered.
Acknowledgments
Video narration was created by ondoku3.com.
Disclosures
The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.
Author Contributions
Conception and design: Morisako, Manthawornsiri, Nagahama, Ikegami, Goto. Acquisition of data: Morisako, Manthawornsiri, Nagahama, Ikegami, Hazunga. Analysis and interpretation of data: Morisako, Manthawornsiri. Drafting the article: Morisako, Manthawornsiri. Critically revising the article: Morisako, Manthawornsiri, Hazunga, Liew. Reviewed submitted version of manuscript: Morisako, Manthawornsiri, Hazunga, Liew. Approved the final version of the manuscript on behalf of all authors: Morisako. Administrative/technical/material support: Ikegami. Study supervision: Goto.
Supplemental Information
Videos
Video 1. https://vimeo.com/1115854504
Correspondence
Hiroki Morisako: Osaka Metropolitan University Graduate School of Medicine, Osaka, Japan. hmorisako@omu.ac.jp.
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