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J Neurosurg Case Lessons
J Neurosurg Case Lessons
J Neurosurg Case Lessons
Journal of Neurosurgery: Case Lessons
2694-1902
American Association of Neurological Surgeons

10.3171/CASE24262
CASE24262
CraniofacialCraniofacialDeformityDeformitySkull-BaseSkull BaseTechniqueTechniqueCase Lesson
A novel technique for skull base reconstruction in craniofacial fibrous dysplasia surgery using three-dimensional printing and a dental alginate mold: illustrative case
Manigos Kirby C MD 1
Navarro Joseph Erroll V MD 1
Seng Kenny S MD 1
Alcazaren Jose Carlos S MD 1
Malilay Oliver Ryan M MD 1
Rejante Tito Guillermo D MD 1
Ferraris Kevin Paul MD, MBA 1
1 Section of Neurosurgery, Department of Surgery, Jose R. Reyes Memorial Medical Center, Manila, Philippines
Correspondence Kevin Paul Ferraris: Jose R. Reyes Memorial Medical Center, Manila, Philippines. kpferraris@gmail.com.
INCLUDE WHEN CITING Published September 23, 2024; DOI: 10.3171/CASE24262.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

23 9 2024
23 9 2024
8 13 CASE2426202 5 2024
19 7 2024
© 2024 the authors
2024
the authors
https://creativecommons.org/licenses/by-nc-nd/4.0/ CC BY-NC-ND 4.0 (http://creativecommons.org/licenses/by-nc-nd/4.0/)

BACKGROUND

Fibrous dysplasia is a rare and benign skeletal lesion characterized by fibrous tissue proliferation due to an abnormal osteogenesis replacing normal bone.

OBSERVATIONS

An 18-year-old male with fibrous dysplasia of the left sphenoid, ethmoid, orbit, and frontal bones was managed with excision and skull base reconstruction. After complete removal of the tumor, skull base reconstruction was commenced by making a reverse temporalis flap and placing it over the opened paranasal sinuses for a robust vascularized graft, followed by an abdominal fat graft, and then a pedicled pericranal flap was added to complete the multilayer onlay graft. To recreate the skull base, a mirror image of the contralateral skull base was constructed using three-dimensional (3D) printing, and the 3D-printed model was sterilized prior to the surgery. Intraoperatively, the model was then pressed onto dental alginate gel to make a negative mold. This was used to make the definitive flap using polymethylmethacrylate. Temporoplasty was also performed using polymethylmethacrylate to fill the defect left by the temporalis graft. The patient recovered well following the procedure.

LESSONS

Appropriate, personalized skull base reconstruction techniques can be successfully done with 3D printing using alternative low-cost materials and implements, especially following resection of cases like craniofacial fibrous dysplasia.

https://thejns.org/doi/10.3171/CASE24262

fibrous dysplasia
skull base reconstruction
3D printing
ABBREVIATIONS

3D = three-dimensional
CSF = cerebrospinal fluid
CT = computed tomography
PLA = polylactic acid
PMMA = polymethylmethacrylate.
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pmcFibrous dysplasia is a rare, benign skeletal disorder typically seen in adolescents and young adults.1 It is distinguished by the abnormal growth of osseous tissue, which gradually replaces the normal medullary space of the affected bone with dysplastic elements.2 Craniofacial involvement can result in a variety of problems, including pain, deformation, and physical disability.3 The mainstay of treatment is controversial, encompassing a spectrum of management from close observation and monitoring of the disease to limited shaving or even removal of the affected bone. In select cases, however, surgery is essential to effectively manage the disease and restore the affected area to its normal function and appearance.1, 4 When surgery is indicated, resection of the dysplasia followed by reconstruction of the defect is the goal. The usual options for reconstruction include autologous bone grafts, bone cement, or titanium implants.5 The challenges posed by the rarity of the condition, coupled with resource constraints, make this case a compelling example of the importance of innovative and effective surgical solutions in resource-limited healthcare settings.6, 7 Herein, we present a novel, cost-effective, anatomically accurate method of skull base reconstruction using a combination of three-dimensional (3D) printing, dental alginate, and polymethylmethacrylate (PMMA) within a resource-constrained institution.

Illustrative Case

Clinical Details

An 18-year-old male presented with a 5-year history of frequent frontal headaches and a progressively enlarging left fronto-orbital mass, resulting in obvious and bothersome facial asymmetry. He did not have any signs or symptoms suggestive of a possible associated endocrinopathy. The neurological examination was unremarkable. Fundoscopy did not reveal signs of optic neuropathy. His computed tomography (CT) scan showed an expansile, well-defined, bony lesion with a ground-glass appearance involving the left sphenoid, ethmoid, orbit, and frontal bones, leading to a diagnosis of monostotic craniofacial fibrous dysplasia. The lesion did not involve the optic canal or any other major foramina. Because of the deformity coupled with the headaches, excision of the affected bones followed by cranial reconstruction was offered. The procedure, including its risks and benefits, was explained thoroughly to the patient and his relatives.

Surgical Technique

A bicoronal incision was utilized, and a pedicled pericranium was prepared at the start of the surgery. Intraoperatively, the affected bones were observed to be expanded with a thinned cortex, along with a tan-gray, fibrous, and gritty intramedullary lesion. All the affected bones were removed using a high-speed drill and rongeurs, exposing the left periorbita and frontal, ethmoid, and sphenoid sinuses, as well as part of the infratemporal fossa (Fig. 1). The dura was not violated during the procedure. Skull base reconstruction was commenced by creating a reverse temporalis muscle flap, as described by Kim and Park,8 and placing it over the open paranasal sinuses to provide a robust, vascularized graft to the anterior cranial fossa floor. Subsequently, a generous amount of abdominal fat graft was placed over it to obliterate the remaining space in the postresection cavity as a filler for dead space and as an added hydrophobic layer for preemptive management of cerebrospinal fluid (CSF) leakage. Finally, the pedicled pericranium was added to form a multilayer onlay graft for the skull base (Fig. 2). FIG. 1. Left: Preoperative CT reconstructions of the skull revealing the left fronto-orbital lesion. Right: Postexcision photograph showing extensive disease involvement of the skull base, leaving a sizable defect on the anterior and middle fossa after diseased bone removal.

FIG. 2. Recreated anterolateral skull base as shown on the patient’s postsurgery CT reconstruction (A). Photographs (B) depict the multilayer onlay graft of the skull base, which commenced with the placement of the reverse temporalis flap (left) as the initial layer. Next, a substantial quantity of fat graft (center) was introduced to fill the void within the postresection cavity. The sequence culminated with the addition of the pericranial graft (right) as the topmost layer of the onlay graft. The final step in the skull base reconstruction (C) involved positioning the customized bone graft over the defect, secured in place with titanium implants and screws. Additionally, PMMA was applied over the temporal fossa for the temporoplasty.

Prior to the surgery, a model of the patient’s skull base was created from the imaging study files. To maintain exactitude, a mirror image of the contralateral skull base was 3D printed using a PRUSA i3 MK3S+ 3D printer (Prusa Research) and using the patient’s preoperative CT scan as a guide. The 3D-printed model was made from polylactic acid (PLA), a common 3D-printing material that is inexpensive and biodegradable and has good tensile strength. While its physical qualities are suitable as a cranial graft, its compatibility as a human biomaterial remains to be proven; hence, it can only be used as a guide in creating the actual cranial graft made from PMMA.9, 10 The 3D-printed model was then sterilized for use during the surgery. Intraoperatively, this 3D-printed model was pressed into an alginate mixture made by mixing Makintal High Precision Alginate (PGO Dental) and normal saline solution to create a negative mold. This mold was then used to fashion a suitable flap using NTCem PMMA (Meta Biomes), prepared by mixing its two parts: the liquid monomer and a powder copolymer (Fig. 3). The hardened PMMA was then placed and secured into the defect using titanium cranial plates and screws. Temporoplasty was also performed to fill the void in the temporal fossa left by the reverse temporalis flap to mitigate postoperative temporal hollowing.11 FIG. 3. Intraoperative photographs showing recreation of the skull base. The 3D-printed model was modularized (A) to produce a more detailed mold using the dental alginate mixture (B). The 3D models were then pressed onto the dental alginate to create a negative mold for the PMMA (C). The PMMA accurately replicated the mold, resulting in the final orbital bar graft precisely mirroring the model (D).

Clinical Outcome

The patient's postsurgery recovery was uneventful, and he was discharged on the 7th day following the operation. The diagnosis was confirmed with histopathological analysis of the surgical specimen. During the follow-up at 8 weeks postsurgery, the swelling had subsided, and the patient reported no complications. The patient expressed satisfaction with the aesthetic outcome during the outpatient follow-up. He resumed school during the 5th week after the operation.

Patient Informed Consent

The necessary patient informed consent was obtained in this study.

Discussion

The diagnosis of craniofacial fibrous dysplasia is based on history, examination, and imaging studies and is confirmed on pathological study when submitted for surgery. Craniofacial fibrous dysplasia is unique in that it is considered monostotic despite involving several bones of the skull base, for example, in contrast to polyostotic forms that are also associated with other diseases including Jaffe-Lichtenstein syndrome, McCune-Albright syndrome, and Mazabraud syndrome. Malignant degeneration into sarcomatous forms has been estimated to have a rate between 0.5% and 4% but is most common in polyostotic forms of the disease, usually heralded by the new onset of pain or tenderness, sensory changes, and changes in imaging characteristics.1 It is difficult to ascertain the appropriate management of a patient with this illness, but the decision typically factors in symptoms, natural history, and a nuanced discussion with the patient about the benefit-risk ratio, taking into consideration the psychosocial implications as well. While conservative management is an option for the asymptomatic or mildly asymptomatic patient,12 surgery is often indicated for patients with facial deformity, visual compromise, and nasal obstruction and for those with signs of local pain or even increased intracranial pressure.13–15

Observations

When it comes to diagnosing, treating, and even performing surgeries in low-income countries and resource-challenged settings, a unique set of challenges emerges.16 These challenges encompass limited access to specialized medical care, financial constraints, and equipment limitations, all of which impact both the neurosurgeon and the patient involved. While the removal of diseased bones is a crucial aspect of the procedure, the subsequent reconstruction of the surgical defect poses its own set of challenges. Traditional reconstruction methods typically involve the utilization of autologous bone grafts or even the reshaping and reuse of the excised fibrous dysplastic bone after thinning and contouring.17, 18 Additionally, materials such as titanium and similar alternatives have been documented.7, 19 The proliferation of commercial 3D printers worldwide makes the case for their widespread adoption, thereby improving the availability and accessibility of customized surgical implants. In the case herein, our approach utilized an innovative method by incorporating PMMA in conjunction with 3D printer–assisted mold creation using an inert and unassuming material, which is dental alginate. The utility of 3D printing technology as an adjunct to craniofacial surgery has been previously highlighted, yielding patient-specific guides that facilitate intraoperative tissue contouring.20–22 The use of 3D printing improves cosmetic outcomes, such as symmetry to the contralateral side of surgery, with a close-to-perfect cranial index of symmetry for calvarial bone flaps in the convexity based on an investigation by Tan and colleagues.23 On this basis, it is conceivable that even for skull base locations, better patient satisfaction and cosmetic outcomes can be achieved. As with many novel ideas, however, this technique is not without possible complications, including postoperative infection, CSF fistulas even with the robust flap, and PMMA graft fixation failure.

Lessons

Our case demonstrates the successful use of a novel, simple, anatomically accurate technique for skull base reconstruction by way of 3D printing, using materials such as a dental alginate mold and PMMA in a patient with craniofacial fibrous dysplasia. The technique outlined herein offers a simple solution to reconstruction and stands as a practical alternative to conventional approaches. This technique can also be replicated for skull base diseases other than fibrous dysplasia that require extensive reconstruction.

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: Manigos, Navarro, Seng, Malilay, Rejante. Acquisition of data: Manigos, Malilay. Analysis and interpretation of data: Manigos, Navarro, Malilay. Drafting the article: Manigos, Navarro, Seng, Malilay. Critically revising the article: Ferraris, Manigos, Navarro, Alcazaren, Malilay. Reviewed submitted version of manuscript: Ferraris, Navarro, Seng, Alcazaren, Malilay. Approved the final version of the manuscript on behalf of all authors: Ferraris. Administrative/technical/material support: Ferraris, Navarro, Rejante. Study supervision: Navarro, Malilay.

Correspondence

Kevin Paul Ferraris: Jose R. Reyes Memorial Medical Center, Manila, Philippines. kpferraris@gmail.com.
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