3D printed headholder for use in neurosurgical cadaver training: Technical note.

Introduction: Headholders or skull clamps serve as indispensable tools in neurosurgery, facilitating the precise positioning and stabilization of the head for surgery. The realm of neurosurgical training in cadaver labs presents a clear challenge due to the lack of suitable non-clinical headholders. Research question: We describe a 3D printed stainless-steel headholder for use in neurosurgical cadaver lab training. Material and methods: Computer-aided design software was used to design a headholder, utilizing a three-pin skull fixation. Through an iterative process involving a plastic 3D printed prototype, ultimately a robust model was manufactured using a 3D stainless-steel printer. Results: The headholder was fixed to a multi-angle adjustable vise, enabling optimal positioning to support simulation of neurosurgical approaches and dissection training by neurosurgical residents and staff in the cadaver lab. Discussion and conclusion: This custom-made headholder offers an effective solution for secure fixation of cadaver skulls during neurosurgical training, contributing to practicality and efficiency in cadaver dissection. Despite the lack of evidence-based guidelines for neurosurgical headholder use, this device provides a valuable tool for neurosurgical trainees to practice proper placement, understand associated complications, and improve their hands-on skills. The digitally available 3D model can be optimized, shared, and further improved by other neurosurgical units and trainees, fostering collaborative advancements in neurosurgical training.

Detection of Bone Marrow Edema Pattern With Dual-Energy Computed Tomography of the Pig Mandible Treated With Radiotherapy and Surgery Compared With Magnetic Resonance Imaging.

OBJECTIVE: The aim of the study was to investigate the accuracy of dual-energy computed tomography (DECT) compared with magnetic resonance (MR) imaging for the detection of edema of the mandible. MATERIALS AND METHODS: Fifteen adult Göttingen mini pigs received irradiation to the mandible with an equivalent dose of 0, 25, 50, or 70 Gy. Six months after irradiation, all animals underwent DECT and MR imaging of the mandible. Magnetic resonance short tau inversion recovery (STIR) was used for the grading of the bone marrow edema (0-3). Dual-energy CT (80 and 140 kVp) was performed, and virtual noncalcium (VNCa) images were calculated. RESULTS: Increased signal intensity at STIR was found in the higher radiation groups. An increase of signal intensity in MR imaging was accompanied by a significant increase in the Hounsfield unit value of the VNCa images of the bone marrow (STIR: 0, 1, 2, 3; mean Hounsfield unit: -103, -90, -76, -34, respectively; P < 0.05; R = 0.388). CONCLUSIONS: The VNCa images derived from DECT are able to demonstrate bone marrow edema in radiation-induced bone changes in the mandible.

The histological and histomorphometric changes in the mandible after radiotherapy: An animal model.

PURPOSE: Approximately 5% of irradiated head and neck cancer patients develop osteoradionecrosis of the mandible. The current non-surgical treatment options for osteoradionecrosis have limited effects and are based on a small number of studies. Therefore, we aimed to enhance the understanding of the pathophysiology of osteoradionecrosis by investigating changes induced by external irradiation in mini-pigs. METHODS: Sixteen Göttingen mini-pigs were divided into four groups for the application in two fractions with total equivalent radiation dosages of 25, 50, 70 Gray, and one group served as control. Thirteen weeks after irradiation, the left lateral teeth the mandible were removed and implants were placed. The pigs were sacrificed twenty-six weeks after irradiation, and the bone samples were stained with Masson's trichrome. RESULTS: The amount of fibrosis, resorption lacunae, necrosis, and the woven/lamellar bone ratios were increased after higher radiation dosages. The diameter of the lumen of the inferior alveolar artery was reduced depending on the irradiation dosages. The rate of bone remodeling decreased after irradiation. CONCLUSION: Both surgery and increasing irradiation dosages cause architectural bone changes and damage the vascularization. This might result in a chronic hypoxic state of the mandibular bone. In general, the bone formation rate was markedly decreased after radiotherapy.

Radiological changes with magnetic resonance imaging and computed tomography after irradiating minipig mandibles: The role of T2-SPIR mixed signal intensities in the detection of osteoradionecrosis.

PURPOSE: Radiotherapy in the head and neck can induce several radiologically detectable changes in bone, osteoradionecrosis (ORN) among them. The purpose is to investigate radiological changes in mandibular bone after irradiation with various doses with and without surgery and to determine imaging characteristics of radiotherapy and ORN in an animal model. MATERIALS AND METHODS: Sixteen Göttingen minipigs were divided into groups and were irradiated with two fractions with equivalent doses of 0, 25, 50 and 70 Gray. Thirteen weeks after irradiation, left mandibular teeth were removed and dental implants were placed. CT-scans and MR-imaging were made before irradiation and twenty-six weeks after. Alterations in the bony structures were recorded on CT-scan and MR-imaging and scored by two head-neck radiologists. RESULTS: Increased signal changes on MR-imaging were associated with higher radiation doses. Two animals developed ORN clinically. Radiologically mixed signal intensities on T2-SPIR were seen. On CT-scans cortical destruction was found in three animals. Based on imaging, three animals were diagnosed with ORN. CONCLUSION: Irradiation of minipig mandibles with various doses induced damages of the mandibular bone. Imaging with CT-scan and MR-imaging showed signal and structural changes that can be interpreted as prolonged and insufficient repair of radiation induced bone damages.

Osseointegration and implant stability of extraoral implants in Göttingen minipigs after irradiation.

OBJECTIVES: The aim of this study was to compare the influence of implant surface treatment and irradiation dose on implant stability and osseointegration of 144 extraoral implants in irradiated frontal bone of minipigs. MATERIAL AND METHODS: 144 implants with 3 different surface treatments (machined, etched and HAVD-coated) were implanted in the frontal bone of 16 Göttingen minipigs. Three groups of four pigs received radiation with equivalent doses of 25, 50 and 70 Gy, and one group served as control. Resonance frequency analysis (RFA) was performed recording Implant Stability Quotients (ISQ) at implant placement and 3 months thereafter. Removal torque was measured whilst removing specific implants after 3 months. In addition, the bone-to-implant contact (BIC) was analyzed. RESULTS: Evaluation of ISQ, BIC-values showed no significant difference between the different surface treatments in irradiated and non-irradiated bone. Removal torque revealed statistically significant differences between machined and HAVD-coated implants in the irradiated bone. CONCLUSIONS: Implant stability and osseointegration, based on Removal Torque showed significant higher results for the HAVD-coated implants. No significant difference was observed between the irradiated and non-irradiated animals. This study shows that HAVD-coated extraoral implants can potentially be used for craniofacial rehabilitation in non-irradiated and irradiated bone.

Assessment of local blood flow with laser Doppler flowmetry in irradiated mandibular and frontal bone, an experiment in Göttingen minipigs.

PURPOSE: The aim of this study was to investigate local blood flow changes in the mandibular bone compared to the os frontale after irradiation in various doses. MATERIALS AND METHODS: This study used an animal experiment with 16 female Göttingen minipigs. Three groups of four animals were irradiated with equivalent doses of 25, 50 or 70 Gray on the mandible and os frontale and four animals served as control. Three months after irradiation laser Doppler flowmetry (LDF) was used to record local blood flow on the left mandible and in the irradiated area on the os frontale. At 6 months measurements were repeated. Descriptive and univariate analyses were conducted and p-values lower than 0.05 were considered statistically significant. RESULTS: Local blood flow measurements in the mandible were significantly higher compared to the os frontale. In the os frontale and mandible there was no significant change in the measurements with increasing irradiation dose. CONCLUSION: We found a non-significant decrease in LDF values with an increase in radiation dose in the mandible and non-significant changes in the os frontale at 3 and 6 months. We consider this to represent the process of on-going fibrosis affecting the local blood flow in the mandible.

Does a change in bone mineral density occur in the mandible of Göttingen minipigs after irradiation in correlation with radiation dose and implant surgery?

PURPOSE: To date, studies have not agreed on the effects of irradiation on bone mineral density. The aim of our study was to investigate the changes in mandibular bone mineral density after irradiation at various doses with and without surgery. MATERIALS AND METHODS: We implemented a descriptive animal experiment. The sample included 16 female Göttingen Minipigs, randomly assigned to 4 groups and irradiated with equivalent doses of 0, 25, 50, and 70 Gy to the mandibular region. At 3 months after irradiation, the mandibular left premolars and molars were removed, and dental implants were placed. Computed tomography scans were taken before and 6 months after irradiation. The measured bone density was related to a bone phantom to calculate the bone mineral density quotient (BMDQ). The outcome variable was the BMDQ. Other study variables were the radiation dose and surgery. Descriptive and univariate analyses were computed, and significance was set at P ≤ .05. RESULTS: In the left hemimandible, compared with the control group, a significant decrease in BMDQ was observed: 0.01 at 0 Gy, -0.01 at 25 Gy, -0.06 at 50 Gy, and -0.11 at 70 Gy (P = .023). The right hemimandible compared with the control group also showed a significant decrease in BMDQ: -0.02 at 0 Gy, -0.08 at 25 Gy, -0.09 at 50 Gy, and -0.11 at 70 Gy (P = .007). CONCLUSIONS: The present study used a large animal model to simulate the tissue reactions induced by various radiation doses in the mandible. We found a significant decrease in the BMDQ after irradiation, but no significant correlation could be found between the irradiation dose and a decrease in the BMDQ.

Reconstruction of a maxillary defect with a fibula graft and titanium mesh using CAD/CAM techniques.

We present a case of maxillary and orbital floor reconstruction with a microvascular fibula graft and an individualized titanium mesh. Both were planned virtually; templates were made by rapid prototyping. The postoperative computer tomography scans showed that the planned positions were achieved correctly. This case report illustrates maxillary reconstruction performed with a special template technique and demonstrates the possibilities of computer aided design/computer aided manufacturing (CAD/CAM) applications in reconstructive surgery.

Sensory testing of inferior alveolar nerve injuries: a review of methods used in prospective studies.

PURPOSE: The inferior alveolar nerve (IAN) can be injured during trauma or surgery. So far there is no consensus for evaluating IAN injury. This study aimed to identify a testing method suitable for daily clinical practice which allows us to identify nerve injury, grade its severity, and monitor its recovery. MATERIALS AND METHODS: Covering a 20-year period, prospective studies on sensory changes after mandibular procedures were reviewed regarding sensory testing methods; 75 studies on third molar removal, osteotomy, fracture, and implants were included. RESULTS: These studies reported varying incidences. In third molar removal and implant studies, a limited number of sensory tests were used, whereas in osteotomy and fracture studies more detailed testing was performed, using reproducible tests like light touch test with Semmes-Weinstein monofilaments and 2-point discrimination. CONCLUSIONS: Sensory function was not uniformly tested and presented, making a comparison of data impossible and highlighting the need for uniform testing methodology. Based on the results of this review, the light touch test with Semmes-Weinstein monofilaments for grading is recommended, using a grid and control site describing unilateral or bilateral nerve injury. Additionally, a visual analog scale-based questionnaire should be used to evaluate subjective sensibility. Using this method to test IAN injuries will allow comparison of future studies and provide valuable insight in the severity and prognosis of IAN injuries.