Utility of multimaterial 3D printers in creating models with pathological entities to enhance the training experience of neurosurgeons

3D printing for preoperative planning and surgical training: a review

Surgeons typically rely on their past training and experiences as well as visual aids from medical imaging techniques such as magnetic resonance imaging (MRI) or computed tomography (CT) for the planning of surgical processes. Often, due to the anatomical complexity of the surgery site, two dimensional or virtual images are not sufficient to successfully convey the structural details. For such scenarios, a 3D printed model of the patient's anatomy enables personalized preoperative planning. This paper reviews critical aspects of 3D printing for preoperative planning and surgical training, starting with an overview of the process-flow and 3D printing techniques, followed by their applications spanning across multiple organ systems in the human body. State of the art in these technologies are described along with a discussion of current limitations and future opportunities.

A radiation-free mixed-reality training environment and assessment concept for C-arm-based surgery

PURPOSE

The discrepancy of continuously decreasing opportunities for clinical training and assessment and the increasing complexity of interventions in surgery has led to the development of different training and assessment options like anatomical models, computer-based simulators or cadaver trainings. However, trainees, following training, assessment and ultimately performing patient treatment, still face a steep learning curve.

METHODS

To address this problem for C-arm-based surgery, we introduce a realistic radiation-free simulation system that combines patient-based 3D printed anatomy and simulated X-ray imaging using a physical C-arm. To explore the fidelity and usefulness of the proposed mixed-reality system for training and assessment, we conducted a user study with six surgical experts performing a facet joint injection on the simulator.

RESULTS

In a technical evaluation, we show that our system simulates X-ray images accurately with an RMSE of 1.85 mm compared to real X-ray imaging. The participants expressed agreement with the overall realism of the simulation, the usefulness of the system for assessment and strong agreement with the usefulness of such a mixed-reality system for training of novices and experts. In a quantitative analysis, we furthermore evaluated the suitability of the system for the assessment of surgical skills and gather preliminary evidence for validity.

CONCLUSION

The proposed mixed-reality simulation system facilitates a transition to C-arm-based surgery and has the potential to complement or even replace large parts of cadaver training, to provide a safe assessment environment and to reduce the risk for errors when proceeding to patient treatment. We propose an assessment concept and outline the steps necessary to expand the system into a test instrument that provides reliable and justified assessments scores indicative of surgical proficiency with sufficient evidence for validity.

3D printing utility for surgical treatment of acetabular fractures

INTRODUCTION

Preoperative 3D modelling enables more effective diagnosis and simulates the surgical procedure.

MATERIAL AND METHODS

We report twenty cases of acetabular fractures with preoperative planning performed by pre-contouring synthesis plates on a 3D printed mould obtained from a computarized tomography (CT) scan. The mould impression was made with the DaVinci 1.0 printer model (XYZ Printing). After obtaining the printed hemipelvis, we proceeded to select the implant size (pelvic Matta system, Stryker^®) that matched the characteristics of the fracture and the approach to be used.

RESULTS

Printing the moulds took a mean of 385minutes (322-539), and 238grams of plastic were used to print the model (180-410). In all cases, anatomic reduction was obtained and intra-operative changes were not required in the initial contouring of the plates. The time needed to perform the full osteosynthesis, once the fracture had been reduced was 16.9minutes (10-24). In one case fixed with two plates, a postoperative CT scan showed partial contact of the implant with the surface of the quadrilateral plate. In the remaining cases, the contact was complete.

CONCLUSIONS

In conclusion, our results suggest that the use of preoperative planning, by printing 3D mirror imaging models of the opposite hemipelvis and pre-contouring plates over the mould, might effectively achieve a predefined surgical objective and reduce the inherent risks in these difficult procedures.

Making data matter: Voxel printing for the digital fabrication of data across scales and domains

We present a multimaterial voxel-printing method that enables the physical visualization of data sets commonly associated with scientific imaging. Leveraging voxel-based control of multimaterial three-dimensional (3D) printing, our method enables additive manufacturing of discontinuous data types such as point cloud data, curve and graph data, image-based data, and volumetric data. By converting data sets into dithered material deposition descriptions, through modifications to rasterization processes, we demonstrate that data sets frequently visualized on screen can be converted into physical, materially heterogeneous objects. Our approach alleviates the need to postprocess data sets to boundary representations, preventing alteration of data and loss of information in the produced physicalizations. Therefore, it bridges the gap between digital information representation and physical material composition. We evaluate the visual characteristics and features of our method, assess its relevance and applicability in the production of physical visualizations, and detail the conversion of data sets for multimaterial 3D printing. We conclude with exemplary 3D-printed data sets produced by our method pointing toward potential applications across scales, disciplines, and problem domains.

Use of a life-size three-dimensional-printed spine model for pedicle screw instrumentation training

Background

Training beginners of the pedicle screw instrumentation technique in the operating room is limited because of issues related to patient safety and surgical efficiency. Three-dimensional (3D) printing enables training or simulation surgery on a real-size replica of deformed spine, which is difficult to perform in the usual cadaver or surrogate plastic models. The purpose of this study was to evaluate the educational effect of using a real-size 3D-printed spine model for training beginners of the free-hand pedicle screw instrumentation technique. We asked whether the use of a 3D spine model can improve (1) screw instrumentation accuracy and (2) length of procedure.

Methods

Twenty life-size 3D-printed lumbar spine models were made from 10 volunteers (two models for each volunteer). Two novice surgeons who had no experience of free-hand pedicle screw instrumentation technique were instructed by an experienced surgeon, and each surgeon inserted 10 pedicle screws for each lumbar spine model. Computed tomography scans of the spine models were obtained to evaluate screw instrumentation accuracy. The length of time in completing the procedure was recorded. The results of the latter 10 spine models were compared with those of the former 10 models to evaluate learning effect.

Results

A total of 37/200 screws (18.5%) perforated the pedicle cortex with a mean of 1.7 mm (range, 1.2–3.3 mm). However, the latter half of the models had significantly less violation than the former half (10/100 vs. 27/100, p < 0.001). The mean length of time to complete 10 pedicle screw instrumentations in a spine model was 42.8 ± 5.3 min for the former 10 spine models and 35.6 ± 2.9 min for the latter 10 spine models. The latter 10 spine models had significantly less time than the former 10 models (p < 0.001).

Conclusion

A life-size 3D-printed spine model can be an excellent tool for training beginners of the free-hand pedicle screw instrumentation.

Clinical 3D printing: A protected health information (PHI) and compliance perspective

Advanced manufacturing techniques such as 3-dimensional (3D) printing, while mature in other industries, are starting to become more commonplace in clinical care. Clinicians are producing physical objects based on patient clinical data for use in planning care and educating patients, all of which should be managed like any other healthcare system data, except it exists in the "real" world. There are currently no provisions in the Health Insurance Portability and Accountability Act (HIPAA) either in its original 1996 form or in more recent updates that address the nature of physical representations of clinical data. We submit that if we define the source data as protected health information (PHI), then the objects 3D printed from that data need to be treated as both (PHI), and if used clinically, part of the clinical record, and propose some basic guidelines for quality and privacy like all documentation until regulatory frameworks can catch up to this technology. Many of the mechanisms designed in the paper and film chart era will work well with 3D printed patient data.

Feasibility of Clinician-Facilitated Three-Dimensional Printing of Synthetic Cranioplasty Flaps

BACKGROUND

Integration of three-dimensional (3D) printing and stereolithography into clinical practice is in its nascence, and concepts may be esoteric to the practicing neurosurgeon. Currently, creation of 3D printed implants involves recruitment of offsite third parties. We explored a range of 3D scanning and stereolithographic techniques to create patient-specific synthetic implants using an onsite, clinician-facilitated approach.

METHODS

We simulated bilateral craniectomies in a single cadaveric specimen. We devised 3 methods of creating stereolithographically viable virtual models from removed bone. First, we used preoperative and postoperative computed tomography scanner-derived bony window models from which the flap was extracted. Second, we used an entry-level 3D light scanner to scan and render models of the individual bone pieces. Third, we used an arm-mounted, 3D laser scanner to create virtual models using a real-time approach.

RESULTS

Flaps were printed from the computed tomography scanner and laser scanner models only in a ultraviolet-cured polymer. The light scanner did not produce suitable virtual models for printing. The computed tomography scanner-derived models required extensive postfabrication modification to fit the existing defects. The laser scanner models assumed good fit within the defects without any modification.

CONCLUSIONS

The methods presented varying levels of complexity in acquisition and model rendering. Each technique required hardware at varying in price points from $0 to approximately $100,000. The laser scanner models produced the best quality parts, which had near-perfect fit with the original defects. Potential neurosurgical applications of this technology are discussed.

Novel Biomaterials Used in Medical 3D Printing Techniques

The success of an implant depends on the type of biomaterial used for its fabrication. An ideal implant material should be biocompatible, inert, mechanically durable, and easily moldable. The ability to build patient specific implants incorporated with bioactive drugs, cells, and proteins has made 3D printing technology revolutionary in medical and pharmaceutical fields. A vast variety of biomaterials are currently being used in medical 3D printing, including metals, ceramics, polymers, and composites. With continuous research and progress in biomaterials used in 3D printing, there has been a rapid growth in applications of 3D printing in manufacturing customized implants, prostheses, drug delivery devices, and 3D scaffolds for tissue engineering and regenerative medicine. The current review focuses on the novel biomaterials used in variety of 3D printing technologies for clinical applications. Most common types of medical 3D printing technologies, including fused deposition modeling, extrusion based bioprinting, inkjet, and polyjet printing techniques, their clinical applications, different types of biomaterials currently used by researchers, and key limitations are discussed in detail.

Three-Dimensional Physical Model-Assisted Planning and Navigation for Laparoscopic Partial Nephrectomy in Patients with Endophytic Renal Tumors

Resection of completely endophytic renal tumors is a huge challenge for surgeons due to a lack of definite visual clues, especially in the laparoscopic approach. Three-dimensional (3D) kidney models, which can illustrate the clear relationship between renal masses and surrounding health tissues, were considered as reliable tools for understanding renal tumor characteristics in previous studies. We hypothesized that 3D kidney models can be used not only for planning but also for navigating laparoscopic partial nephrectomy (LPN) in patients with completely endophytic renal tumors. In this study, we successfully constructed five cases of 3D kidney models for assisted planning and navigation for LPN in endophytic renal tumors. The renal masses and surrounding normal parenchyma of the patient-specific 3D models were dyed by different colorants for clear illustration. All patients experienced acceptable perioperative outcomes, and no patient suffered serious relative complications. The 3D kidney models were considered as a reliable tool based on clinical outcome and postoperative questionnaire results. This study is the first report of 3D kidney models for patients with completely endophytic tumors. 3D kidney models can aid surgeons in understanding the characteristics of renal tumors and potentially support assisted planning and performance of LPN in endophytic tumor cases.

Current status of 3D printing in spine surgery

Three-dimensional printing (3DP) is one of the latest tools in the armamentarium of the modern spine surgeon. The yearning to be more precise and reliable whilst operating on the spine has led to an interest in this technology which has claimed to achieve these goals. 3D printing has been used pre-operatively for surgical planning and for resident or patient education. It has also found its way to the operation theatre where it is used to fabricate customized surgical tools or patient-specific implants. Several authors have highlighted significant benefits when 3D printing is used for specific indications in spine surgery. Novel applications of this technology in spine surgery have also been described and though still in a nascent stage, these are important for this technology to sustain itself in the future. However, major limitations have also come to light with this technology in use. This article seeks to review the current status and applications of 3D printing in spinal surgery and its major drawbacks while briefly describing the essentials of the technology. It is imperative that the modern spine surgeon knows about this important innovation and when and how it can be applied to improve surgical outcomes.

[Additive technologies in neurosurgery]

Modern achievements of technical progress, in particular additive technologies (ATs) and three-dimensional printing, have been increasingly introduced in neurosurgical practice. The increasing complexity of surgical interventions requires thorough planning of surgery and a high level of training of young neurosurgeons. Creation of full-scale three-dimensional models for planning of surgery enables visualization of the anatomical region of interest. Additive technologies are especially extensively used in reconstructive surgery of skull defects. ATs enable fast and efficient solving of the following tasks: - generation of accurate models of the skull and an implant; - development and fabrication of individual molds for intraoperative formation of implants from polymeric two-component materials (e.g., PMMA); - fabrication of individual implants from titanium alloys or polyetheretherketone (PEEK) for further use in surgery.

Evaluation by medical students of the educational value of multi-material and multi-colored three-dimensional printed models of the upper limb for anatomical education

For centuries, cadaveric material has been the cornerstone of anatomical education. For reasons of changes in curriculum emphasis, cost, availability, expertise, and ethical concerns, several medical schools have replaced wet cadaveric specimens with plastinated prosections, plastic models, imaging, and digital models. Discussions about the qualities and limitations of these alternative teaching resources are on-going. We hypothesize that three-dimensional printed (3DP) models can replace or indeed enhance existing resources for anatomical education. A novel multi-colored and multi-material 3DP model of the upper limb was developed based on a plastinated upper limb prosection, capturing muscles, nerves, arteries and bones with a spatial resolution of ∼1 mm. This study aims to examine the educational value of the 3DP model from the learner's point of view. Students (n = 15) compared the developed 3DP models with the plastinated prosections, and provided their views on their learning experience using 3DP models using a survey and focus group discussion. Anatomical features in 3DP models were rated as accurate by all students. Several positive aspects of 3DP models were highlighted, such as the color coding by tissue type, flexibility and that less care was needed in the handling and examination of the specimen than plastinated specimens which facilitated the appreciation of relations between the anatomical structures. However, students reported that anatomical features in 3DP models are less realistic compared to the plastinated specimens. Multi-colored, multi-material 3DP models are a valuable resource for anatomical education and an excellent adjunct to wet cadaveric or plastinated prosections. Anat Sci Educ 11: 54-64. © 2017 American Association of Anatomists.

An Assembled Prototype Multimaterial Three-Dimensional-Printed Model of the Neck for Computed Tomography- and Ultrasound-Guided Interventional Procedures

A low-cost, semirealistic, multimaterial prototype phantom of the neck was developed for computed tomography- and ultrasound-guided interventions, using three-dimensional (3D) printing with a variety of materials as well as through molding techniques. This dual-modality phantom can be used by trainees for practicing procedures and can also serve as a prototype for developing more complex and realistic 3D-printed models, particularly with the continued development and advancement in multimaterial 3D printing technologies.

Three-Dimensional Printed Modeling of Diffuse Low-Grade Gliomas and Associated White Matter Tract Anatomy

BACKGROUND

Diffuse low-grade gliomas (DLGGs) represent several pathological entities that infiltrate and invade cortical and subcortical structures in the brain.

OBJECTIVE

To describe methods for rapid prototyping of DLGGs and surgically relevant anatomy.

METHODS

Using high-definition imaging data and rapid prototyping technologies, we were able to generate 3 patient DLGGs to scale and represent the associated white matter tracts in 3 dimensions using advanced diffusion tensor imaging techniques.

RESULTS

This report represents a novel application of 3-dimensional (3-D) printing in neurosurgery and a means to model individualized tumors in 3-D space with respect to subcortical white matter tract anatomy. Faculty and resident evaluations of this technology were favorable at our institution.

CONCLUSION

Developing an understanding of the anatomic relationships existing within individuals is fundamental to successful neurosurgical therapy. Imaging-based rapid prototyping may improve on our ability to plan for and treat complex neuro-oncologic pathology.

Three-dimensional reconstructions in spine and screw trajectory simulation on 3D digital images: a step by step approach by using Mimics software

There is a rapidly increasing amount of literature outlining the use of three-dimensional (3D) reconstruction and printing technologies in recent years. However, precise instructive articles which describe step-by-step methods of reconstructing 3D images from computed tomography (CT) or magnetic resonance imaging (MRI) remain limited. To address these issues, this article describes a detailed protocol which will allow the reader to easily perform the 3D reconstruction in their future research, to allow investigation of the appropriate surgical anatomy and allow innovative designs of novel screw fixation techniques or pre-operative surgical planning.

Increasing the safety of surgical treatment for complex Cranio-vertebral anomalies using customized 3D printed models

Surgery for the Cranio-vertebral (CV) junction anomalies using top loading subocciput (C0)/C1-C2 screws is difficult and requires high level of skill and expertise. This is because of complex abnormal anatomy in that region and other issues including the instrumentation. Thorough knowledge of the 3D anatomy of the Craniovertebral junction of the patient is essential for favourable outcome. The customised 3D printed model of CV junction region of the patient can be used for studying the anatomy and relationship of vertebral artery to the C1-C2 joint before the actual surgery. Thirteen patients (includes twelve males and one female) of congenital CV junction anomalies having AAD with or without BI (Basilar Invagination) were included in the study. For all thirteen patients, customised 3D models of CV junction were made based on their CT scan data. The rehearsal of surgical procedure on the model was done a day before the actual surgery. Post surgery, twelve out of thirteen patients showed significant clinical and radiological improvement. We did not had any misplaced screws or vertebral artery injury. 3D models can improve decision making and planning of the surgical procedure in the CV junction region. It unmasks abnormal bony & vascular anatomy effectively. Moreover the rehearsal of the surgical procedure enables the surgical team to be more confident & familiar with the anatomy during the actual surgery.

3D printing materials and their use in medical education: a review of current technology and trends for the future

3D printing is a new technology in constant evolution. It has rapidly expanded and is now being used in health education. Patient-specific models with anatomical fidelity created from imaging dataset have the potential to significantly improve the knowledge and skills of a new generation of surgeons. This review outlines five technical steps required to complete a printed model: They include (1) selecting the anatomical area of interest, (2) the creation of the 3D geometry, (3) the optimisation of the file for the printing and the appropriate selection of (4) the 3D printer and (5) materials. All of these steps require time, expertise and money. A thorough understanding of educational needs is therefore essential in order to optimise educational value. At present, most of the available printing materials are rigid and therefore not optimum for flexibility and elasticity unlike biological tissue. We believe that the manipuation and tuning of material properties through the creation of composites and/or blending materials will eventually allow for the creation of patient-specific models which have both anatomical and tissue fidelity.

3D-printed phantom study for investigating stent abutment during gastroduodenal stent placement for gastric outlet obstruction

Background

Placing a self-expandable metallic stent (SEMS) is safe and effective for the palliative treatment of malignant gastroduodenal (GD) strictures. SEMS abutment in the duodenal wall is associated with increased food impaction, resulting in higher stent malfunction and shorter stent patency. The desire to evaluate the mechanism and significance of stent abutment led us to design an in vitro experiment using a flexible anthropomorphic three-dimensional (3D)-printed GD phantom model.

Results

A GD phantom was fabricated using 3D printer data after performing computed tomography gastrography. A partially covered (PC) or fully covered (FC) stent was placed so that its distal end abutted onto the duodenal wall in groups PC-1 and FC-1 or its distal end was sufficiently directed caudally in groups PC-2 and FC-2. The elapsed times of the inflowing of three diets (liquid, soft, and solid) were measured in the GD phantom under fluoroscopic guidance. There was no significant difference in the mean elapsed times for the liquid diet among the four groups. For the soft diet, the mean elapsed times in groups PC-1 and FC-1 were longer than those in groups PC-2 and FC-2 (P = 0.018 and P < 0.001, respectively). For the solid diet, the mean elapsed time in group PC-1 was longer than that in group PC-2 (P < 0.001). The solid diet could not pass in group FC-1 due to food impaction. The mean elapsed times were significantly longer in groups FC-1 and FC-2 than in groups PC-1 and PC-2 for soft and solid diets (all P < 0.001).

Conclusions

This flexible anthropomorphic 3D-printed GD phantom study revealed that stent abutment can cause prolonged passage of soft and solid diets through the stent as well as impaction of solid diets into the stent.

Comparison of the Conventional Surgery and the Surgery Assisted by 3d Printing Technology in the Treatment of Calcaneal Fractures

PURPOSE

This study was aimed to compare conventional surgery and surgery assisted by 3D printing technology in the treatment of calcaneal fractures. In addition, we also investigated the effect of 3D printing technology on the communication between doctors and patients.

METHODS

we enrolled 75 patients with calcaneal fracture from April 2014 to August 2016. They were divided randomly into two groups: 35 cases of 3D printing group, 40 cases of conventional group. The individual models were used to simulate the surgical procedures and carry out the surgery according to plan in 3D printing group. Operation duration, blood loss volume during the surgery, number of intraoperative fluoroscopy and fracture union time were recorded. The radiographic outcomes Böhler angle, Gissane angle, calcaneal width and calcaneal height and final functional outcomes including VAS and AOFAS score as well as the complications were also evaluated. Besides, we made a simple questionnaire to verify the effectiveness of the 3D-printed model for both doctors and patients.

RESULTS

The operation duration, blood loss volume and number of intraoperative fluoroscopy for 3D printing group was 71.4 ± 6.8 minutes, 226.1 ± 22.6 ml and 5.6 ± 1.9 times, and for conventional group was 91.3 ± 11.2 minutes, 288.7 ± 34.8 ml and 8.6 ± 2.7 times respectively. There was statistically significant difference between the conventional group and 3D printing group (p < 0.05). Additionally, 3D printing group achieved significantly better radiographic results than conventional group both postoperatively and at the final follow-up (p < 0.05). However, No significant difference was noted in the final functional outcomes between the two groups. As for complications, there was no significant difference between the two groups. Furthermore, the questionnaire showed that both doctors and patients exhibited high scores of overall satisfaction with the use of a 3D printing model.

CONCLUSION

This study suggested the clinical feasibility of 3D printing technology in treatment of calcaneal fractures.

The application of 3-dimensional printing for preoperative planning in oral and maxillofacial surgery in dogs and cats

OBJECTIVE

To describe the application of 3-dimensional (3D) printing in advanced oral and maxillofacial surgery (OMFS) and to discuss the benefits of this modality in surgical planning, student and resident training, and client education.

STUDY DESIGN

Retrospective case series.

ANIMALS

Client-owned dogs (n = 28) and cats (n = 4) with 3D printing models of the skulls.

METHODS

The medical records of 32 cases with 3D printing prior to major OMFS were reviewed.

RESULTS

Indications for 3D printing included preoperative planning for mandibular reconstruction after mandibulectomy (n = 12 dogs) or defect nonunion fracture (n = 6 dogs, 2 cats), mapping of ostectomy location for temporomandibular joint ankylosis or pseudoankylosis (n = 4 dogs), assessment of palatal defects (n = 2 dogs, 1 cat), improved understanding of complex anatomy in cases of neoplasia located in challenging locations (n = 2 dogs, 1 cat), and in cases of altered anatomy secondary to trauma (n = 2 dogs).

CONCLUSION

In the authors' experience, 3D printed models serve as excellent tools for OMFS planning and resident training. Furthermore, 3D printed models are a valuable resource to improve clients' understanding of the pet's disorder and the recommended treatment.

CLINICAL RELEVANCE

Three-dimensional printed models should be considered viable tools for surgical planning, resident training, and client education in candidates for complex OMFS.

Training in Cerebral Aneurysm Clipping Using Self-Made 3-Dimensional Models

INTRODUCTION

Recently, there have been increasingly fewer opportunities for junior surgeons to receive on-the-job training. Therefore, we created custom-built three-dimensional (3D) surgical simulators for training in connection with cerebral aneurysm clipping.

METHODS

Three patient-specific models were composed of a trimmed skull, retractable brain, and a hollow elastic aneurysm with its parent artery. The brain models were created using 3D printers via a casting technique. The artery models were made by 3D printing and a lost-wax technique. Four residents and 2 junior neurosurgeons attended the training courses. The trainees retracted the brain, observed the parent arteries and aneurysmal neck, selected the clip(s), and clipped the neck of an aneurysm. The duration of simulation was recorded. A senior neurosurgeon then assessed the trainee's technical skill and explained how to improve his/her performance for the procedure using a video of the actual surgery. Subsequently, the trainee attempted the clipping simulation again, using the same model. After the course, the senior neurosurgeon assessed each trainee's technical skill. The trainee critiqued the usefulness of the model and the effectiveness of the training course.

RESULTS

Trainees succeeded in performing the simulation in line with an actual surgery. Their skills tended to improve upon completion of the training.

CONCLUSION

These simulation models are easy to create, and we believe that they are very useful for training junior neurosurgeons in the surgical techniques needed for cerebral aneurysm clipping.

Three-dimensional printing of X-ray computed tomography datasets with multiple materials using open-source data processing

Advances in three-dimensional (3D) printing allow for digital files to be turned into a "printed" physical product. For example, complex anatomical models derived from clinical or pre-clinical X-ray computed tomography (CT) data of patients or research specimens can be constructed using various printable materials. Although 3D printing has the potential to advance learning, many academic programs have been slow to adopt its use in the classroom despite increased availability of the equipment and digital databases already established for educational use. Herein, a protocol is reported for the production of enlarged bone core and accurate representation of human sinus passages in a 3D printed format using entirely consumer-grade printers and a combination of free-software platforms. The comparative resolutions of three surface rendering programs were also determined using the sinuses, a human body, and a human wrist data files to compare the abilities of different software available for surface map generation of biomedical data. Data shows that 3D Slicer provided highest compatibility and surface resolution for anatomical 3D printing. Generated surface maps were then 3D printed via fused deposition modeling (FDM printing). In conclusion, a methodological approach that explains the production of anatomical models using entirely consumer-grade, fused deposition modeling machines, and a combination of free software platforms is presented in this report. The methods outlined will facilitate the incorporation of 3D printed anatomical models in the classroom. Anat Sci Educ 10: 383-391. © 2017 American Association of Anatomists.

Current and emerging applications of 3D printing in medicine

Three-dimensional (3D) printing enables the production of anatomically matched and patient-specific devices and constructs with high tunability and complexity. It also allows on-demand fabrication with high productivity in a cost-effective manner. As a result, 3D printing has become a leading manufacturing technique in healthcare and medicine for a wide range of applications including dentistry, tissue engineering and regenerative medicine, engineered tissue models, medical devices, anatomical models and drug formulation. Today, 3D printing is widely adopted by the healthcare industry and academia. It provides commercially available medical products and a platform for emerging research areas including tissue and organ printing. In this review, our goal is to discuss the current and emerging applications of 3D printing in medicine. A brief summary on additive manufacturing technologies and available printable materials is also given. The technological and regulatory barriers that are slowing down the full implementation of 3D printing in the medical field are also discussed.

Three-dimensional printing: technologies, applications, and limitations in neurosurgery

Three-dimensional (3D) printers are a developing technology penetrating a variety of markets, including the medical sector. Since its introduction to the medical field in the late 1980s, 3D printers have constructed a range of devices, such as dentures, hearing aids, and prosthetics. With the ultimate goals of decreasing healthcare costs and improving patient care and outcomes, neurosurgeons are utilizing this dynamic technology, as well. Digital Imaging and Communication in Medicine (DICOM) can be translated into Stereolithography (STL) files, which are then read and methodically built by 3D Printers. Vessels, tumors, and skulls are just a few of the anatomical structures created in a variety of materials, which enable surgeons to conduct research, educate surgeons in training, and improve pre-operative planning without risk to patients. Due to the infancy of the field and a wide range of technologies with varying advantages and disadvantages, there is currently no standard 3D printing process for patient care and medical research. In an effort to enable clinicians to optimize the use of additive manufacturing (AM) technologies, we outline the most suitable 3D printing models and computer-aided design (CAD) software for 3D printing in neurosurgery, their applications, and the limitations that need to be overcome if 3D printers are to become common practice in the neurosurgical field.

Fabrication of cerebral aneurysm simulator with a desktop 3D printer

Now, more and more patients are suffering cerebral aneurysm. However, long training time limits the rapid growth of cerebrovascular neurosurgeons. Here we developed a novel cerebral aneurysm simulator which can be better represented the dynamic bulging process of cerebral aneurysm The proposed simulator features the integration of a hollow elastic vascular model, a skull model and a brain model, which can be affordably fabricated at the clinic (Fab@Clinic), under $25.00 each with the help of a low-cost desktop 3D printer. Moreover, the clinical blood flow and pulsation pressure similar to the human can be well simulated, which can be used to train the neurosurgical residents how to clip aneurysms more effectively.

The utility of 3D printing for surgical planning and patient-specific implant design for complex spinal pathologies: case report

OBJECTIVE

There has been a recent renewed interest in the use and potential applications of 3D printing in the assistance of surgical planning and the development of personalized prostheses. There have been few reports on the use of 3D printing for implants designed to be used in complex spinal surgery.

METHODS

The authors report 2 cases in which 3D printing was used for surgical planning as a preoperative mold, and for a custom-designed titanium prosthesis: one patient with a C-1/C-2 chordoma who underwent tumor resection and vertebral reconstruction, and another patient with a custom-designed titanium anterior fusion cage for an unusual congenital spinal deformity.

RESULTS

In both presented cases, the custom-designed and custom-built implants were easily slotted into position, which facilitated the surgery and shortened the procedure time, avoiding further complex reconstruction such as harvesting rib or fibular grafts and fashioning these grafts intraoperatively to fit the defect. Radiological follow-up for both cases demonstrated successful fusion at 9 and 12 months, respectively.

CONCLUSIONS

These cases demonstrate the feasibility of the use of 3D modeling and printing to develop personalized prostheses and can ease the difficulty of complex spinal surgery. Possible future directions of research include the combination of 3D-printed implants and biologics, as well as the development of bioceramic composites and custom implants for load-bearing purposes.

En Bloc Resection of Primary Malignant Bone Tumor in the Cervical Spine Based on 3-Dimensional Printing Technology

OBJECTIVE

To investigate the feasibility and safety of en bloc resection of cervical primary malignant bone tumors by a combined anterior and posterior approach based on a three-dimensional (3-D) printing model.

METHODS

Five patients with primary malignant bone tumors of the cervical spine underwent en bloc resection via a one-stage combined anteroposterior approach in our hospital from March 2013 to June 2014. They comprised three men and two women of mean age 47.2 years (range, 26-67 years). Three of the tumors were chondrosarcomas and two chordomas. Preoperative 3-D printing models were created by 3-D printing technology. Sagittal en bloc resections were planned based on these models and successfully performed. A 360° reconstruction was performed by spinal instrumentation in all cases. Surgical margins, perioperative complications, local control rate and survival rate were assessed.

RESULTS

All patients underwent en bloc excision via a combined posterior and anterior approach in one stage. Mean operative time and estimated blood loss were 465 minutes and 1290 mL, respectively. Mean follow-up was 21 months. Wide surgical margins were achieved in two patients and marginal resection in three; these three patients underwent postoperative adjuvant radiation therapy. One vertebral artery was ligated and sacrificed in each of three patients. Nerve root involved by tumor was sacrificed in three patients with preoperative upper extremity weakness. One patient (Case 3) had significant transient radiculopathy with paresis postoperatively. Another (Case 4) with C 4 and C 5 chordoma had respiratory difficulties and pneumonia after surgery postoperatively. He recovered completely after 2 weeks' management with a tracheotomy tube and antibiotics in the intensive care unit. No cerebrovascular complications and wound infection were observed. No local recurrence or instrumentation failure were detected during follow-up.

CONCLUSION

Though technically challenging, it is feasible and safe to perform en bloc resection of cervical primary bone tumors. This is the most effective means of managing cervical spine tumors. Preoperative 3-D printing modelling enables better anatomical understanding of the relationship between the tumor and cervical spine and can assist in planning the surgical procedure.

Bismuth Infusion of ABS Enables Additive Manufacturing of Complex Radiological Phantoms and Shielding Equipment

Radiopacity is a critical property of materials that are used for a range of radiological applications, including the development of phantom devices that emulate the radiodensity of native tissues and the production of protective equipment for personnel handling radioactive materials. Three-dimensional (3D) printing is a fabrication platform that is well suited to creating complex anatomical replicas or custom labware to accomplish these radiological purposes. We created and tested multiple ABS (Acrylonitrile butadiene styrene) filaments infused with varied concentrations of bismuth (1.2-2.7 g/cm³), a radiopaque metal that is compatible with plastic infusion, to address the poor gamma radiation attenuation of many mainstream 3D printing materials. X-ray computed tomography (CT) experiments of these filaments indicated that a density of 1.2 g/cm³ of bismuth-infused ABS emulates bone radiopacity during X-ray CT imaging on preclinical and clinical scanners. ABS-bismuth filaments along with ABS were 3D printed to create an embedded human nasocranial anatomical phantom that mimicked radiological properties of native bone and soft tissue. Increasing the bismuth content in the filaments to 2.7 g/cm³ created a stable material that could attenuate 50% of 99mTechnetium gamma emission when printed with a 2.0 mm wall thickness. A shielded test tube rack was printed to attenuate source radiation as a protective measure for lab personnel. We demonstrated the utility of novel filaments to serve multiple radiological purposes, including the creation of anthropomorphic phantoms and safety labware, by tuning the level of radiation attenuation through material customization.

Creation and Validation of a Simulator for Neonatal Brain Ultrasonography: A Pilot Study

RATIONALE AND OBJECTIVES

Historically, skills training in performing brain ultrasonography has been limited to hours of scanning infants for lack of adequate synthetic models or alternatives. The aim of this study was to create a simulator and determine its utility as an educational tool in teaching the skills that can be used in performing brain ultrasonography on infants.

MATERIALS AND METHODS

A brain ultrasonography simulator was created using a combination of multi-modality imaging, three-dimensional printing, material and acoustic engineering, and sculpting and molding. Radiology residents participated prior to their pediatric rotation. The study included (1) an initial questionnaire and resident creation of three coronal images using the simulator; (2) brain ultrasonography lecture; (3) hands-on simulator practice; and (4) a follow-up questionnaire and re-creation of the same three coronal images on the simulator. A blinded radiologist scored the quality of the pre- and post-training images using metrics including symmetry of the images and inclusion of predetermined landmarks. Wilcoxon rank-sum test was used to compare pre- and post-training questionnaire rankings and image quality scores.

RESULTS

Ten residents participated in the study. Analysis of pre- and post-training rankings showed improvements in technical knowledge and confidence, and reduction in anxiety in performing brain ultrasonography. Objective measures of image quality likewise improved. Mean reported value score for simulator training was high across participants who reported perceived improvements in scanning skills and enjoyment from simulator use, with interest in additional practice on the simulator and recommendations for its use.

CONCLUSIONS

This pilot study supports the use of a simulator in teaching radiology residents the skills that can be used to perform brain ultrasonography.

Three-Dimensional Printing of a Hemorrhagic Cervical Cancer Model for Postgraduate Gynecological Training

INTRODUCTION

A realistic hemorrhagic cervical cancer model was three-dimensionally (3D) printed and used in a postgraduate medical simulation training session.

MATERIALS AND METHODS

Computer-assisted design (CAD) software was the platform of choice to create and refine the cervical model. Once the prototype was finalized, another software allowed for the addition of a neoplastic mass, which included openings for bleeding from the neoplasm and cervical os. 3D printing was done using two desktop printers and three different materials. An emergency medicine simulation case was presented to obstetrics and gynecology residents who were at varying stages of their training. The scenario included history taking and physical examination of a standardized patient. This was a hybrid simulation; a synthetic pelvic task trainer that allowed the placement of the cervical model was connected to the standardized patient. The task trainer was placed under a drape and appeared to extend from the standardized patient's body. At various points in the simulation, the standardized patient controlled the cervical bleeding through a peripheral venous line. Feedback forms were completed, and the models were discussed and evaluated with staff.

RESULTS

A final cervical model was created and successfully printed. Overall, the models were reported to be similar to a real cervix. The models bled well. Most models were not sutured during the scenarios, but overall, the value of the printed cervical models was reported to be high.

DISCUSSION

The models were well received, but it was suggested that more colors be integrated into the cervix in order to better emphasize the intended pathology. The model design requires further improvement, such as the addition of a locking mechanism, in order to ensure that the cervix stays inside the task trainer throughout the simulation. Adjustments to the simulated blood product would allow the bleeding to flow more vigorously. Additionally, a different simulation scenario might be more suitable to explore the residents' ability to suture the cervical models, as cervical suturing of a neoplasm is not a common emergency department procedure.

CONCLUSION

3D-printed cervical models are an economical and anatomically accurate option for simulation training and other educational purposes.

3D printing in neurosurgery: A systematic review

BACKGROUND

The recent expansion of three-dimensional (3D) printing technology into the field of neurosurgery has prompted a widespread investigation of its utility. In this article, we review the current body of literature describing rapid prototyping techniques with applications to the practice of neurosurgery.

METHODS

An extensive and systematic search of the Compendex, Scopus, and PubMed medical databases was conducted using keywords relating to 3D printing and neurosurgery. Results were manually screened for relevance to applications within the field.

RESULTS

Of the search results, 36 articles were identified and included in this review. The articles spanned the various subspecialties of the field including cerebrovascular, neuro-oncologic, spinal, functional, and endoscopic neurosurgery.

CONCLUSIONS

We conclude that 3D printing techniques are practical and anatomically accurate methods of producing patient-specific models for surgical planning, simulation and training, tissue-engineered implants, and secondary devices. Expansion of this technology may, therefore, contribute to advancing the neurosurgical field from several standpoints.

Influence of Contrast Agent Dilution on Ballon Deflation Time and Visibility During Tracheal Balloon Dilation: A 3D Printed Phantom Study

PURPOSE

To determine the effect of contrast medium dilution during tracheal balloon dilation on balloon deflation time and visibility using a 3-dimensional (3D) printed airway phantom.

MATERIALS AND METHODS

A comparison study to investigate balloon deflation times and image quality was performed using two contrast agents with different viscosities, i.e., iohexol and ioxithalamate, and six contrast dilutions with a 3D printed airway phantom.

RESULTS

Compared to 1:0 concentration, 3:1, 2:1, 1:1, 1:2, and 1:3, contrast/saline ratios resulted in a 46% (56.2 s), 59.8% (73.1 s), 74.9% (91.6 s), 81.7% (99.8 s), and 83.5% (102 s) reduction for iohexol, respectively, and a 51.8% (54.7 s), 63.8% (67.6 s), 74.7% (79.2 s), 80.5% (85.3 s), and 82.4% (87.4 s) reduction for ioxithalamate, respectively, in the mean balloon deflation time, although at the expense of decreased balloon opacity (3.5, 6.9, 11.1, 12.4, and 13.9%, for iohexol, respectively, and 3.2, 6, 9.6, 10.8, and 12.4%, for ioxithalamate, respectively).

CONCLUSIONS

Use of a lower viscosity contrast agent and higher contrast dilution is considered to be able to reduce balloon deflation times and then simultaneously decrease visualization of balloons. The rapid balloon deflation time is likely to improve the safe performance of interventional procedures.

A combination of three-dimensional printing and computer-assisted virtual surgical procedure for preoperative planning of acetabular fracture reduction

OBJECTIVE

Treatment of acetabular fractures remains one of the most challenging tasks that orthopaedic surgeons face. An accurate assessment of the injuries and preoperative planning are essential for an excellent reduction. The purpose of this study was to evaluate the feasibility, accuracy and effectiveness of performing 3D printing technology and computer-assisted virtual surgical procedures for preoperative planning in acetabular fractures. We hypothesised that more accurate preoperative planning using 3D printing models will reduce the operation time and significantly improve the outcome of acetabular fracture repair.

METHODS

Ten patients with acetabular fractures were recruited prospectively and examined by CT scanning. A 3-D model of each acetabular fracture was reconstructed with MIMICS14.0 software from the DICOM file of the CT data. Bone fragments were moved and rotated to simulate fracture reduction and restore the pelvic integrity with virtual fixation. The computer-assisted 3D image of the reduced acetabula was printed for surgery simulation and plate pre-bending. The postoperative CT scan was performed to compare the consistency of the preoperative planning with the surgical implants by 3D-superimposition in MIMICS14.0, and evaluated by Matta's method.

RESULTS

Computer-based pre-operations were precisely mimicked and consistent with the actual operations in all cases. The pre-bent fixation plates had an anatomical shape specifically fit to the individual pelvis without further bending or adjustment at the time of surgery and fracture reductions were significantly improved. Seven out of 10 patients had a displacement of fracture reduction of less than 1mm; 3 cases had a displacement of fracture reduction between 1 and 2mm.

CONCLUSIONS

The 3D printing technology combined with virtual surgery for acetabular fractures is feasible, accurate, and effective leading to improved patient-specific preoperative planning and outcome of real surgery. The results provide useful technical tips in planning pelvic surgeries.

Stereolithographic models in the interdisciplinary planning of treatment for complex intracranial aneurysms

BACKGROUND

Treatment of complex intracranial aneurysms requires strategic pre-interventional or preoperative planning. In addition to modern three-dimensional (3D) rotational angiography, computed tomography angiography (CTA) or magnetic resonance angiogram (MRA), a solid, tangible 3D model may improve anatomical comprehension and treatment planning. A 3D rapid prototyping (RP) technique based on multimodal imaging data was evaluated for use in planning of treatment for complex aneurysmal configurations.

METHODS

Six patients with complex aneurysms were selected for 3D RP based on CTA and 3D rotational angiography data. Images were segmented using image-processing software to create virtual 3D models. Three-dimensional rapid prototyping techniques transformed the imaging data into physical 3D models, which were used and evaluated for interdisciplinary treatment planning.

RESULTS

In all cases, the model provided a comprehensive 3D representation of relevant anatomical structures and improved understanding of related vessels. Based on the 3D model, primary bypass surgery with subsequent reconstruction of the aneurysm was then considered advantageous in all but one patient after simulation of multiple approaches.

CONCLUSIONS

Preoperative prediction of intraoperative anatomy using the 3D model was considered helpful for treatment planning. The use of 3D rapid prototyping may enhance understanding of complex configurations in selected large or giant aneurysms, especially those pretreated with clips or coils.

Cost-Benefit Analysis of Three-Dimensional Craniofacial Models for Midfacial Distraction: A Pilot Study

OBJECTIVE

Patient-specific three-dimensional (3D) models are increasingly used to virtually plan rare surgical procedures, providing opportunity for preoperative preparation, better understanding of individual anatomy, and implant prefabrication. The purpose of this study was to assess the benefit of 3D models related to patient safety, operative time, and cost.

DESIGN

Retrospective review.

SETTING

Academic, tertiary care hospital.

PATIENTS, PARTICIPANTS

Midfacial distraction was studied as a representative craniofacial operation. A consecutive series of 29 patients who underwent a single type of midfacial distraction was included.

INTERVENTION

For a subset of patients, computed tomography-derived 3D models were used to study patient-specific anatomy and precontour hardware.

MAIN OUTCOME MEASURES

Complications, operative time, blood loss, and estimated cost.

RESULTS

Twenty patients underwent midfacial distraction without and nine with preoperative use of a 3D model. Seven complications occurred in six patients without model use, including premature consolidation (3), cerebrospinal fluid leak (2), and hardware malfunction (2). No complications were reported in the model group. Controlling for surgeon variation, model use resulted in a 31.3-minute (7.8%) reduction in operative time. Time-based cost savings were estimated to be $1036.

CONCLUSIONS

Three-dimensional models are valuable for preoperative planning and hardware precontouring in craniofacial surgery, with potential positive effects on complications and operative time. Savings related to operative time and complications may offset much of the cost of the model.

Design and Fabrication of Kidney Phantoms for Internal Radiation Dosimetry Using 3D Printing Technology

Currently, the validation of multimodal quantitative imaging and absorbed dose measurements is impeded by the lack of suitable, commercially available anthropomorphic phantoms of variable sizes and shapes. To demonstrate the potential of 3-dimensional (3D) printing techniques for quantitative SPECT/CT imaging, a set of kidney dosimetry phantoms and their spherical counterparts was designed and manufactured with a fused-deposition-modeling 3D printer. Nuclide-dependent SPECT/CT calibration factors were determined to assess the accuracy of quantitative imaging for internal renal dosimetry.

METHODS

A set of 4 single-compartment kidney phantoms with filling volumes between 8 and 123 mL was designed on the basis of the outer kidney dimensions provided by MIRD pamphlet 19. After the phantoms had been printed, SPECT/CT acquisitions of 3 radionuclides (^99mTc, ¹⁷⁷Lu, and ¹³¹I) were obtained and calibration constants determined for each radionuclide-volume combination. A set of additionally manufactured spheres matching the kidney volumes was also examined to assess the influence of phantom shape and size on the calibration constants.

RESULTS

A set of refillable, waterproof, and chemically stable kidneys and spheres was successfully manufactured. Average calibration factors for ^99mTc, ¹⁷⁷Lu, and ¹³¹I were obtained in a large source measured in air. For the largest phantom (122.9 mL), the volumes of interest had to be enlarged by 1.2 mm for ^99mTc, 2.5 mm for ¹⁷⁷Lu, and 4.9 mm for ¹³¹I in all directions to obtain calibration factors comparable to the reference. Although partial-volume effects were observed for decreasing phantom volumes (percentage difference of up to 9.8% for the smallest volume [8.6 mL]), the difference between corresponding sphere-kidney pairs was small (<1.1% for all volumes).

CONCLUSION

3D printing is a promising prototyping technique for geometry-specific calibration of SPECT/CT systems. Although the underlying radionuclide and the related collimator have a major influence on the calibration, no relevant differences between kidney-shaped and spherically shaped uniform-activity phantoms were observed. With comparably low costs and submillimeter resolution, 3D printing techniques hold the potential for manufacturing individualized anthropomorphic phantoms in many clinical applications in nuclear medicine.

The Future of Plastic Surgery Resident Education

The challenge of the current graduate medical education environment requires in plastic surgery acceptance of those contemporary pressures that cannot be substantially modified and address of those that can be successfully met. To do so implies an examination of conference didactics, intraoperative teaching, and a valid assessment of resident performance.

Current Applications and Future Perspectives of the Use of 3D Printing in Anatomical Training and Neurosurgery

3D printing is a form of rapid prototyping technology, which has led to innovative new applications in biomedicine. It facilitates the production of highly accurate three dimensional objects from substrate materials. The inherent accuracy and other properties of 3D printing have allowed it to have exciting applications in anatomy education and surgery, with the specialty of neurosurgery having benefited particularly well. This article presents the findings of a literature review of the Pubmed and Web of Science databases investigating the applications of 3D printing in anatomy and surgical education, and neurosurgery. A number of applications within these fields were found, with many significantly improving the quality of anatomy and surgical education, and the practice of neurosurgery. They also offered advantages over existing approaches and practices. It is envisaged that the number of useful applications will rise in the coming years, particularly as the costs of this technology decrease and its uptake rises.