New frontiers and emerging applications of 3D printing in ENT surgery: a systematic review of the literature

The Creation of an Average 3D Model of the Human Cartilaginous Nasal Septum and Its Biomimetic Applications

The cartilaginous nasal septum is integral to the overall structure of the nose. Developing our an-atomic understanding of the septum will improve the planning and techniques of septal surgeries. While the basic dimensions of the septum have previously been described, the average shape in the sagittal plane has yet to be established. Furthermore, determining the average shape allows for the creation of a mean three-dimensional (3D) septum model. To better understand the average septal shape, we dissected septums from 40 fresh human cadavers. Thickness was measured across pre-defined points on each specimen. Image processing in Photoshop was used to superimpose lateral photographs of the septums to determine the average shape. The average shape was then combined with thickness data to develop a 3D model. This model may be utilized in finite elemental analyses, creating theoretical results about septal properties that are more translatable to real-world clinical practice. Our 3D septum also has numerous applications for 3D printing. Realistic models can be created for educational or surgical planning purposes. In the future, our model could also serve as the basis for 3D-printed scaffolds to aid in tissue regeneration to reconstruct septal defects. The model can be viewed at the NIH 3D model repository (3DPX ID: 020598, Title: 3D Nasal Septum).

3D Bioprinting in Otolaryngology: A Review

The evolution of tissue engineering and 3D bioprinting has allowed for increased opportunities to generate musculoskeletal tissue grafts that can enhance functional and aesthetic outcomes in otolaryngology-head and neck surgery. Despite literature reporting successes in the fabrication of cartilage and bone scaffolds for applications in the head and neck, the full potential of this technology has yet to be realized. Otolaryngology as a field has always been at the forefront of new advancements and technology and is well poised to spearhead clinical application of these engineered tissues. In this review, current 3D bioprinting methods are described and an overview of potential cell types, bioinks, and bioactive factors available for musculoskeletal engineering using this technology is presented. The otologic, nasal, tracheal, and craniofacial bone applications of 3D bioprinting with a focus on engineered graft implantation in animal models to highlight the status of functional outcomes in vivo; a necessary step to future clinical translation are reviewed. Continued multidisciplinary efforts between material chemistry, biological sciences, and otolaryngologists will play a key role in the translation of engineered, 3D bioprinted constructs for head and neck surgery.

3D Printing in Otolaryngology Surgery: Descriptive Review of Literature to Define the State of the Art

BACKGROUND

Three-dimensional (3D) printing has allowed great progression in the medical field. In otolaryngology practice, 3D printing can be used for planning in case of malformation/complex surgery, for surgeon training, and for recreating missing tissues. This systematic review aimed to summarize the current benefits and the possible future application of 3D technologies in the otolaryngology field.

METHODS

A systematic review of articles that discuss the use of 3D printing in the otolaryngology field was performed. All publications without the restriction of time and that were published by December 2021 in the English language were included. Searches were performed in the PubMed, MEDLINE, Scopus, and Embase databases. Keywords used were: "3D printing", "bioprinting", "three-dimensional printing", "tissue engineering" in combination with the terms: "head and neck surgery", "head and neck reconstruction", "otology", "rhinology", "laryngology", and "otolaryngology".

RESULTS

Ninety-one articles were included in this systematic review. The articles describe the clinical application of 3D printing in different fields of otolaryngology, from otology to pediatric otolaryngology. The main uses of 3D printing technology discussed in the articles included in the review were surgical planning in temporal bone malformation, the reconstruction of missing body parts after oncologic surgery, allowing for medical training, and providing better information to patients.

CONCLUSION

The use of 3D printing in otolaryngology practice is constantly growing. However, available evidence is still limited, and further studies are needed to better evaluate the benefits of this technology.

Customized Cochlear Implant Positioning in a Patient With a Low- Grade Glioma: Towards the Best MRI Artifact Management

OBJECTIVE

To report the personalized decision-making pro- cess adopted for a cochlear implant (CI) candidate requiring magnetic resonance imaging (MRI) brain surveillance.

STUDY DESIGN

Clinical capsule report.

SETTING

Tertiary academic referral center.

PATIENT

A 23-year-old man affected by posttraumatic bilat- eral profound hearing loss, already in radiological follow-up for a suspected small left cuneal low-grade glioma.

INTERVENTIONS

A multidisciplinary approach involving preoperative MRI simulations and 3D printed (3DP) models aiming to adapt the CI position to facilitate MRI brain lesion visibility.

MAIN OUTCOME MEASURES

MRI visibility and surgical approach.

RESULTS

Preoperative MRI scans with the placement of an Ultra 3D CI were performed simulating different implant location to assess the brain lesion visibility in MRI. CI was positioned 9 cm away from the external auditory canal with an angle of 90 degrees. To assess the technical feasibility of the surgical procedure, a patient-specific 3DP head model was produced preoperatively. The postoperative course was uneventful, the patient showed a significant benefit from CI, and the brain lesion was highly visible at the MRI follow-up.

CONCLUSIONS

The employment of strategies aimed at improving the MRI quality in CI recipients still represents a topic requiring attention. Thanks to multidisciplinary team collaboration, in our case, the CI position was successfully determined to allow unhindered MRI visibility of a specific intracranial structure.

The cutting edge of customized surgery: 3D-printed models for patient-specific interventions in otology and auricular management-a systematic review

PURPOSE

3D-printing (three-dimensional printing) is an emerging technology with promising applications for patient-specific interventions. Nonetheless, knowledge on the clinical applicability of 3D-printing in otology and research on its use remains scattered. Understanding these new treatment options is a prerequisite for clinical implementation, which could improve patient outcomes. This review aims to explore current applications of 3D-printed patient-specific otologic interventions, including state of the evidence, strengths, limitations, and future possibilities.

METHODS

Following the PRISMA statement, relevant studies were identified through Pubmed, EMBASE, the Cochrane Library, and Web of Science. Data on the manufacturing process and interventions were extracted by two reviewers. Study quality was assessed using Joanna Briggs Institute's critical appraisal tools.

RESULTS

Screening yielded 590 studies; 63 were found eligible and included for analysis. 3D-printed models were used as guides, templates, implants, and devices. Outer ear interventions comprised 73% of the studies. Overall, optimistic sentiments on 3D-printed models were reported, including increased surgical precision/confidence, faster manufacturing/operation time, and reduced costs/complications. Nevertheless, study quality was low as most studies failed to use relevant objective outcomes, compare new interventions with conventional treatment, and sufficiently describe manufacturing.

CONCLUSION

Several clinical interventions using patient-specific 3D-printing in otology are considered promising. However, it remains unclear whether these interventions actually improve patient outcomes due to lack of comparison with conventional methods and low levels of evidence. Further, the reproducibility of the 3D-printed interventions is compromised by insufficient reporting. Future efforts should focus on objective, comparative outcomes evaluated in large-scale studies.

Properties of CAD/CAM 3D Printing Dental Materials and Their Clinical Applications in Orthodontics: Where Are We Now?

In the last years, both medicine and dentistry have come across a revolution represented by the introduction of more and more digital technologies for both diagnostic and therapeutic purposes. Additive manufacturing is a relatively new technology consisting of a computer-aided design and computer-aided manufacturing (CAD/CAM) workflow, which allows the substitution of many materials with digital data. This process requires three fundamental steps represented by the digitalization of an item through a scanner, the editing of the data acquired using a software, and the manufacturing technology to transform the digital data into a final product, respectively. This narrative review aims to discuss the recent introduction in dentistry of the abovementioned digital workflow. The main advantages and disadvantages of the process will be discussed, along with a brief description of the possible applications on orthodontics.

Fabrication of 3D Models for Microtia Reconstruction Using Smartphone-Based Technology

OBJECTIVE

Microtia reconstruction is technically challenging due to the intricate contours of the ear. It is common practice to use a two-dimensional tracing of the patient's normal ear as a template for the reconstruction of the affected side. Recent advances in three-dimensional (3D) surface scanning and printing have expanded the ability to create surgical models preoperatively. This study aims to describe a simple and affordable process to fabricate patient-specific 3D ear models for use in the operating room.

STUDY DESIGN

Applied basic research on a novel 3D optical scanning and fabrication pathway for microtia reconstruction.

SETTING

Tertiary care university hospital.

METHODS

Optical surface scanning of the patient's normal ear was completed using a smartphone with facial recognition capability. The Heges application used the phone's camera to capture the 3D image. The 3D model was digitally isolated and mirrored using the Meshmixer software and printed with a 3D printer (Monoprice^TM Select Mini V2) using polylactic acid filaments.

RESULTS

The 3D model of the ear served as a helpful intraoperative reference and an adjunct to the traditional 2D template. Collectively, time for imaging acquisition, editing, and fabrication was approximately 3.5 hours. The upfront cost was around $210, and the recurring cost was approximately $0.35 per ear model.

CONCLUSION

A novel, low-cost approach to fabricate customized 3D models of the ear is introduced. It is feasible to create individualized 3D models using currently available consumer technology. The low barrier to entry raises the possibility for clinicians to incorporate 3D printing into various clinical applications.

Objective structured assessment of technical skill in temporal bone dissection: validation of a novel tool

OBJECTIVE

This study developed an assessment tool that was based on the objective structured assessment for technical skills principles, to be used for evaluation of surgical skills in cortical mastoidectomy. The objective structured assessment of technical skill is a well-established tool for evaluation of surgical ability. This study also aimed to identify the best material and printing method to make a three-dimensional printed temporal bone model.

METHODS

Twenty-four otolaryngologists in training were asked to perform a cortical mastoidectomy on a three-dimensional printed temporal bone (selective laser sintering resin). They were scored according to the objective structured assessment of technical skill in temporal bone dissection tool developed in this study and an already validated global rating scale.

RESULTS

Two external assessors scored the candidates, and it was concluded that the objective structured assessment of technical skill in temporal bone dissection tool demonstrated some main aspects of validity and reliability that can be used in training and performance evaluation of technical skills in mastoid surgery.

CONCLUSION

Apart from validating the new tool for temporal bone dissection training, the study showed that evolving three-dimensional printing technologies is of high value in simulation training with several advantages over traditional teaching methods.

3D printed temporal bone as a tool for otologic surgery simulation

PURPOSE

In this face validity study, we discuss the fabrication and utility of an affordable, computed tomography (CT)-based, anatomy-accurate, 3-dimensional (3D) printed temporal bone models for junior otolaryngology resident training.

MATERIALS AND METHODS

After IRB exemption, patient CT scans were anonymized and downloaded as Digital Imaging and Communications in Medicine (DICOM) files to prepare for conversion. These files were converted to stereolithography format for 3D printing. Important soft tissue structures were identified and labeled to be printed in a separate color than bone. Models were printed using a desktop 3D printer (Ultimaker 3 Extended, Ultimaker BV, Netherlands) and polylactic acid (PLA) filament. 10 junior residents with no previous drilling experience participated in the study. Each resident was asked to drill a simple mastoidectomy on both a cadaveric and 3D printed temporal bone. Following their experience, they were asked to complete a Likert questionnaire.

RESULTS

The final result was an anatomically accurate (XYZ accuracy = 12.5, 12.5, 5 μm) 3D model of a temporal bone that was deemed to be appropriate in tactile feedback using the surgical drill. The total cost of the material required to fabricate the model was approximately $1.50. Participants found the 3D models overall to be similar to cadaveric temporal bones, particularly in overall value and safety.

CONCLUSIONS

3D printed temporal bone models can be used as an affordable and inexhaustible alternative, or supplement, to traditional cadaveric surgical simulation.

Anatomic variations of the round window niche: radiological study and related endoscopic anatomy

PURPOSE

In the last decades, literature has shown an increasing interest in round windows (RW) anatomy due to its pivotal role in deafness surgery. The high variability of this anatomical region, with particular regard to the round windows niche (RWN), has been studied by several authors through different methods of investigation. The aim of the present research was to radiologically examine the morphological variability of the RWN and to link the imaging findings to the endoscopic view.

METHODS

High-resolution CT scans of 300 temporal bones without neuro-otological pathologies were retrospectively reviewed by 2 neuroradiologist and 1 ENT surgeon who independently evaluated the RWN morphological variations. To link the radiological to the endoscopic data, 45 cadaveric human temporal bones were submitted to a radiological evaluation and to an otoendoscopy conducted through a posterior tympanotomy approach.

RESULTS

Three variants of the RWN were detected on coronal CT scan reconstructions: 155 "cylindrical-type", 97 "j-type" and 48 "truncated cone-type". For each radiological type the endoscopic findings showed a specific endoscopic position of the RW chamber, which results in different degrees of RW membrane visibility when analysed through a posterior tympanotomy approach.

CONCLUSIONS

To the best of our knowledge, this is the first description of the above-mentioned RWN radiological variations supported by endoscopic data. This study suggests an additional anatomical evaluation that could be useful to predict the RW membrane visibility through a posterior tympanotomy approach. Further studies are required to support the clinical implications of our observations.