Hydrogel-chitosan and polylactic acid-polycaprolactone bioengineered scaffolds for reconstruction of mandibular defects: a preclinical in vivo study with assessment of translationally relevant aspects.

Background: Reconstruction of mandibular bone defects is a surgical challenge, and microvascular reconstruction is the current gold standard. The field of tissue bioengineering has been providing an increasing number of alternative strategies for bone reconstruction. Methods: In this preclinical study, the performance of two bioengineered scaffolds, a hydrogel made of polyethylene glycol-chitosan (HyCh) and a hybrid core-shell combination of poly (L-lactic acid)/poly ( ε -caprolactone) and HyCh (PLA-PCL-HyCh), seeded with different concentrations of human mesenchymal stromal cells (hMSCs), has been explored in non-critical size mandibular defects in a rabbit model. The bone regenerative properties of the bioengineered scaffolds were analyzed by in vivo radiological examinations and ex vivo radiological, histomorphological, and immunohistochemical analyses. Results: The relative density increase (RDI) was significantly more pronounced in defects where a scaffold was placed, particularly if seeded with hMSCs. The immunohistochemical profile showed significantly higher expression of both VEGF-A and osteopontin in defects reconstructed with scaffolds. Native microarchitectural characteristics were not demonstrated in any experimental group. Conclusion: Herein, we demonstrate that bone regeneration can be boosted by scaffold- and seeded scaffold-reconstruction, achieving, respectively, 50% and 70% restoration of presurgical bone density in 120 days, compared to 40% restoration seen in spontaneous regeneration. Although optimization of the regenerative performance is needed, these results will help to establish a baseline reference for future experiments.

Quantitative Anatomical Comparison of Surgical Approaches to Meckel's Cave.

BACKGROUND: Meckel's cave is a challenging surgical target due to its deep location and proximity to vital neurovascular structures. Surgeons have developed various microsurgical transcranial approaches (MTAs) to access it, but there is no consensus on the best method. Newer endoscopic approaches have also emerged. This study seeks to quantitatively compare these surgical approaches to Meckel's cave, offering insights into surgical volumes and exposure areas. METHODS: Fifteen surgical approaches were performed bilaterally in six specimens, including the pterional approach (PTA), fronto-temporal-orbito-zygomatic approach (FTOZA), subtemporal approach (STA), Kawase approach (KWA), retrosigmoid approach (RSA), retrosigmoid approach with suprameatal extension (RSAS), endoscopic endonasal transpterygoid approach (EETPA), inferolateral transorbital approach (ILTEA) and superior eyelid approach (SEYA). All the MTAs were performed both with 10 mm and 15 mm of brain retraction, to consider different percentages of surface exposure. A dedicated navigation system was used to quantify the surgical working volumes and exposure of different areas of Meckel's cave (ApproachViewer, part of GTx-Eyes II, University Health Network, Toronto, Canada). Microsurgical transcranial approaches were quantified with two different degrees of brain retraction (10 mm and 15 mm). Statistical analysis was performed using a mixed linear model with bootstrap resampling. RESULTS: The RSAS with 15 mm of retraction offered the maximum exposure of the trigeminal stem (TS). If compared to the KWA, the RSA exposed more of the TS (69% vs. 46%; p = 0.01). The EETPA and ILTEA exposed the Gasserian ganglion (GG) mainly in the anteromedial portion, but with a significant 20% gain in exposure provided by the EETPA compared to ILTEA (42% vs. 22%; p = 0.06). The STA with 15 mm of retraction offered the maximum exposure of the GG, with a significant gain in exposure compared to the STA with 10 mm of retraction (50% vs. 35%; p = 0.03). The medial part of the three trigeminal branches was mainly exposed by the EETPA, particularly for the ophthalmic (66%) and maxillary (83%) nerves. The EETPA offered the maximum exposure of the medial part of the mandibular nerve, with a significant gain in exposure compared to the ILTEA (42% vs. 11%; p = 0.01) and the SEY (42% vs. 2%; p = 0.01). The FTOZA offered the maximum exposure of the lateral part of the ophthalmic nerve, with a significant gain of 67% (p = 0.03) and 48% (p = 0.04) in exposure compared to the PTA and STA, respectively. The STA with 15 mm of retraction offered the maximum exposure of the lateral part of the maxillary nerve, with a significant gain in exposure compared to the STA with 10 mm of retraction (58% vs. 45%; p = 0.04). The STA with 15 mm of retraction provided a significant exposure gain of 23% for the lateral part of the mandibular nerve compared to FTOZA with 15 mm of retraction (p = 0.03). CONCLUSIONS: The endoscopic approaches, through the endonasal and transorbital routes, can provide adequate exposure of Meckel's cave, especially for its more medial portions, bypassing the impediment of major neurovascular structures and significant brain retraction. As far as the most lateral portion of Meckel's cave, MTA approaches still seem to be the gold standard in obtaining optimal exposure and adequate surgical volumes.

Video-assisted microsurgical transoral approach to the craniovertebral junction: personal experience in childhood.

PURPOSE: This paper outlines the perspectives of transoral craniosurgery for anterior craniovertebral junction (CVJ) compressive abnormalities in the specific subset of paediatric patients. In particular we analyzed the opportunity for endoscopic video-assisted approach to the CVJ along with neuronavigation for anterior decompression by the transoral approach in paediatric patients. METHODS: Among 30 patients ranging 6-78 years undergoing CVJ decompressive procedures, we operated transorally 3 paediatric patients (ranging 11-15 years) by using open access, microsurgical technique, neuronavigation, and endoscopy. RESULTS: The microscope was the main stone of the transoral procedure; a complete CVJ decompression was accomplished in all the cases by using the 30-degree endoscope that allowed to identify residual compression not clearly visible by using the microscope alone. The use of an angled-lens endoscope can significantly improve the exposure of the clivus without splitting the soft palate. CONCLUSIONS: Endoscopically assisted transoral surgery represents an emerging alternative to the standard microsurgical approach to the anterior CVJ. Used in conjunction with traditional microsurgery and intraoperative fluoroscopy, endoscopy provides information for a better decompression with a reduced need for extensive soft-palate splitting, no need for hard-palate resection, or extended maxillotomy. Transoral video-assisted microsurgical approach should be considered the gold standard especially in the paediatric patient.

Anterior superior alveolar nerve injury after extended endoscopic medial maxillectomy: a preclinical study to predict neurological morbidity.

BACKGROUND: Endoscopic medial maxillectomies (EMMs) are used to optimize exposure of the maxillary sinus and retromaxillary areas. Although in type D EMM (Sturmann-Canfield procedure) the anterior superior alveolar nerve (ASAN) is always at risk of injury, only 29% of patients complained of alveolar process and dental anesthesia. The purpose of this anatomical study is to assess the neural anastomotic network of the ASAN (ASAN-NAN) and describe different extensions of type D EMMs in a preclinical setting. METHODS: The ASAN and its medial anastomotic branches (MABs) and lateral anastomotic branches (LABs) were evaluated by cone-beam computerized tomography (CBCT). Five different extensions of type D (D1 to D5) EMMs were identified and nerves at risk of injury in each type were assessed by CBCT. Moreover, quantification of surgical corridors was performed on cadaver heads with a neuronavigation system. RESULTS: Fifty-seven CBCT scans were analyzed. The ASAN would be spared in 16.3% of cases with a type D1 EMM, while it would be injured in the majority of type D2 to D5 resections. At least 1 nerve of the ASAN-NAN was spared in 96.6%, 93%, 74.6%, 0%, and 65.8% of type D1 to D5 EMMs, respectively. Two cadaver heads were dissected and the incremental volume and number of maxillary subsites exposed was assessed in type D1 to D5 EMMs. CONCLUSION: ASAN function impairment is probably compensated by LABs and MABs. If this hypothesis will be validated in a prospective study on patients, preoperative CBCT evaluation could predict neurological morbidity after type D EMM, and allow tailoring the procedure to minimize impairment of the ASAN-NAN.

Modular Endoscopic Medial Maxillectomies: Quantitative Analysis of Surgical Exposure in a Preclinical Setting.

BACKGROUND: The nomenclature adopted for endoscopic medial maxillectomies (EMMs) is exceedingly heterogeneous. The aim of this study was to objectively measure surgical exposure in a preclinical anatomic setting to validate a classification for modular EMMs. MATERIALS AND METHODS: Computed tomography was used to scan 6 cadaver heads, and images were uploaded on dedicated software. A neuronavigation system was used to measure areas and volumes of surgical corridors during dissection. Differences of >10% of area exposed and >3 cm3 of volume were considered to define incremental types of EMM. Specific anatomic targets were assessed on the axial and sagittal planes. Influence of anatomic variants on surgical exposure was evaluated. RESULTS: There were 4 types of EMMs (A-D), with a transseptal variant for each, identified. In the axial plane, type A exposed the vidian canal and foramen rotundum, type B exposed the foramen ovale and foramen spinosum, and transseptal type C or type D exposed the coronoid process. In the sagittal plane, type A exposed the vidian canal, and type B exposed the foramen ovale and styloid process. Transseptal type C exposed the pterygomaxillary fissure, and type D exposed the inferior border of the lateral pterygoid plate. The nasal floor limits the downward angle in transseptal approaches. The width of the piriform aperture independently influenced surgical volume of types B and C. CONCLUSIONS: This modular classification of EMMs, based on quantitative analysis in a preclinical setting, should allow for better personalized preoperative surgical planning and provides standardization of nomenclature.

The Inferolateral Transorbital Endoscopic Approach: A Preclinical Anatomic Study.

BACKGROUND: In recent years, transorbital endoscopic approaches are increasing in popularity as they provide several corridors to reach lateral areas of the ventral skull base through the orbit. The aim of this study is to investigate the feasibility of the inferolateral transorbital endoscopic approach (ILTEA) by detailing the step-by-step dissection, anatomic landmarks, and target anatomic areas. METHODS: Seven cadaveric specimens (14 sides) were dissected in the Laboratory of Endoscopic Anatomy of the University of Brescia. Step-by-step dissection of ILTEA was performed to identify the main anatomic landmarks and corridors. Skin incision, dural incision, and boundaries of craniectomy were measured. Neuronavigation was used to check landmarks, track boundaries of surgical volumes, and measure orbital dislocation. RESULTS: The study on the 14 ILTEAs defined 1 anatomic area ("waterline door") that leads to 4 corridors: Meckel's cave corridor, carotid foramen corridor, petrous corridor, and transdural middle fossa corridor. Crucial anatomic landmarks were identified and analyzed. Orbital dislocation was <10 mm. CONCLUSIONS: ILTEA provides the surgeon with a direct route to the region of the "waterline door," lateral areas of the ventral skull base, and middle cranial fossa. In addition, it allows an optimal view of the intracranial and extracranial portions of the maxillary and mandibular nerves. Further anatomic and clinical studies are needed to validate ILTEA in surgical practice.

Microscopic and endoscopic extracranial approaches to the cavernous sinus: anatomic study.

OBJECTIVE: In the past 2 decades, various extracranial approaches to the cavernous sinus (CS), using either microscopic or endoscopic techniques, have been described. The aim of this study was to describe the distinctive anatomic features of these approaches and compare their efficacy in exposing the sella and parasellar areas. METHODS: Ten adult cadaver heads with red latex injected in the arterial system were used. Five different approaches were performed: 1) endonasal microscopic transsphenoidal approach; 2) sublabial microscopic transsphenoidal approach, including its variation described by Fraioli et al. ; 3) transmaxillary microscopic approach; 4) paraseptal endoscopic transsphenoidal approach; and 5) transethmoid-pterygoid-sphenoidal endoscopic approach. The CS exposition was evaluated for each approach and a grading system, which considers surgical maneuverability as well as visualization, was used. RESULTS: The medial CS compartment is well exposed with all endoscopic and microscopic transsphenoidal approaches, but it is insufficiently exposed with the transmaxillary approach. The variation to the sublabial microscopic approach suggested by Fraioli et al. allows its widest microsurgical exposure. The lateral compartment is well visualized with the transmaxillary microscopic and the endoscopic approaches. The major anatomic structures that can limit exposure of the CS lateral compartment are the posterior ethmoid and medial pterygoid process. CONCLUSION: The sublabial transsphenoidal microscopic approach, with its variations, allows the most versatile extracranial microscopic exposure of the sella and CS. The paraseptal, binostril endoscopic approach allows a very good exposure of the CS; the transethmoid-pterygoid-sphenoidal endoscopic approach achieves the best maneuverability in the lateral compartment of the CS.