3D printing in neurosurgery – our experience

Overview

Aim: The aim of this work was to evaluate our experience with the 3D printing method in neurosurgery. In addition to the well-known utilization of cranial implants, a significant use of this modern, rapidly developing technology is possible.

Methods: We present and evaluate the series of our ten patients, which we operated on using 3D printing methods. In the field of vascular neurosurgery, four cases involved a brain aneurysm model and one arteriovenous malformation model. In two patients, this method contributed to the closure of the skull base defect with a custom-shaped cranial grid and in neuro-oncology, it improved the visualization of skull base tumors in two patients. In one patient, the 3D model of the C2 vertebra allowed the choice of the optimal trajectory of the fixation material. Results: In the mentioned cases, the desired result was achieved and the 3D printing method was adapted to the correct treatment in all patients.

Conclusion: Based on our experiences, we can claim that the 3D printing method, in addition to the already commonly used 3D implantology, also presents a new and interesting modality in the field of neurosurgical planning, simulation and training. We assume that it will be increasingly used in many areas of neurosurgery.

Keywords:

neurosurgery – 3D printing – 3D imaging – neurosurgical planning – neurosurgical simulation – neurosurgical training

This is an unauthorised machine translation into English made using the DeepL Translate Pro translator. The editors do not guarantee that the content of the article corresponds fully to the original language version.

Introduction

Current practice in neurosurgical planning depends largely on the surgeon's imagination. In this process, the surgeon relies on the data that current imaging techniques, especially MR, CT, digital subtraction angiography (DSA) and their software modalities, are able to deliver. This is always a two-dimensional view, even in the case of graphic three-dimensional reconstructions. The actual spatial image of the problem is only really formed in the brain of the operator. The degree of this skill is conditioned by long-term practice and acquired experience, while training the surgeon to the appropriate level is a demanding and lengthy process. A realistic three-dimensional visualization of the problem using 3D printing technology should be an asset in this area. This is one of the most progressive technologies of this millennium. It involves the rapid and precise manufacture of a product of complex shapes from a variety of materials, which can also be used to change the functional properties of the final model. In the medical field, this technology enables non-invasive visualization and subsequent fabrication of anatomical or pathological structures. In contrast to conventional radiological imaging methods, the model not only provides the user with different viewing angles but also an important tactile experience, thus expanding the user's imagination [1]. In the past, several studies have been published in neurosurgery with the clinical use of this technology [2]. In principle, these can be divided into the following two main areas: the creation of specific anatomical models with regard to surgical planning and the design of individual implants "tailored" to each patient. In the first group, this mainly involves the implementation of 3D printed models of tumors, cranial bone defects, spinal pathologies or vascular brain lesions (aneurysms, arteriovenous malformations [AVMs]) based on the patient's radiological data [3-9]. The key parameters for this type of application are mainly geometric accuracy, speed of fabrication and the type of material used. In the second group, cranioplasties made for the needs of a specific patient are mainly used, which, due to their simplicity, were one of the first applications of 3D printing in clinical practice in the world and in our country and are currently part of routine practice with very good results [10-14]. Although abroad 3D printing in neurosurgery is in many respects already a routine practice, this is not yet the case in the Czech Republic. In the following paper, the authors want to present their own experience with the use of 3D printing in neurosurgery.

Patients and methods and results

In the period 01/2022--12/2022, 10 patients were operated on at our department, for whom a model of the pathological situation was created in advance using 3D printing to improve the surgeon's imagination (Table 1). In the field of vascular neurosurgery, four cases involved models of complex aneurysms and one AVM. The three-dimensional visualization contributed to information about the size of the aneurysm, the width and position of the neck and the trunk arteries, and also helped in planning the access side and the final closure of the aneurysm (shape and position of the clips) (Figure 1). In the case of AVM, it showed the exact position of the supplying arteries relative to the nidus and contributed to the choice of resection strategy. In two patients, we used the anterior skull base model to prepare a titanium mesh cover, which could be pre-shaped according to the bone defect model and directly applied after sterilization (Figure 2). In one case, the defect was a defect after a comminuted base fracture, in the other a defect after resection of a Wegener's granuloma. For two skull base tumors (petroclival meningioma, chordoma of the clivus), 3D technology allowed us to plan the position and extent of the approach and obtain the optimal view corridor to allow their radical removal (Figure 3). In the spinal problem, we used the printing of the fractured C2 vertebra to select and determine the trajectory of the fixation material. The creation of virtual models is performed by a now standardized method from native CT (MR) data, i.e., segmentation in a specialized program such as 3D Slicer (The Slicer community, BSD - style), in which anatomical structures of interest are selected. Subsequently, an algorithm is used to create a spatial virtual model, which must be cleaned of structures that are redundant for the actual planning. In the case of cancer, bone structures are preferably reconstructed from CT data and soft tissues from MR data. The virtual models are then collapsed using anatomically significant points (landmarks). In the case of small anatomical structures (e.g. aneurysms), we additionally create models enlarged at a scale of 2:1. Currently, we use both FDM (fused filament fabrication) printing technology (AzteQ, Trilab Prusa Research s. r. o., Prague, Czech Republic) and stereolithography (SLA) printing technology (XiP Nexa 3D, ITS s. r. o., Brno, Czech Republic). These two printers allow us both volumetric variability of the models as well as speed and accuracy of the prints. For FDM technology we primarily use ASA filament (Prusa Research, Prague, Czech Republic), 0.15 mm layer height and 20% fill. In case of aneurysms, it is possible to use e.g. tree supports. We do not sterilize these models. When using SLA technology we use autoclavable KeyGuide material (KeyStone Industries, Singen, Germany). The time required for printing is variable and varies according to the size of the model volume and the technology used. The specific times are shown in Table 1.

Discussion

While the utility of 3D printing in implantology is now well established and its use is widespread, its benefits in preoperative planning are still a matter of debate. From our point of view, the situation needs to be considered on several levels. In the case of experienced neurosurgeons, the interest so far seems to be rather marginal, and only in the most complex cases is three-dimensional modelling seen as a practical complement to other examinations, slightly expanding the surgeon's understanding of the pathology in question. On the other hand, for neurosurgeons with less experience, this technology allows a more accurate and faster orientation in the problem to be solved, allowing in many ways to accelerate the learning curve and to start performing more complex operations. For novice neurosurgeons, 3D printing also represents an opportunity to obtain high-quality anatomical educational material. In our experience, from the moment a neurosurgeon first applies this method in practice, he or she quickly becomes aware of its potential and begins to give further suggestions for its wider application and, above all, its improvement. And the possibilities of improving the methodology are quite undoubted in the future, given the rapid software innovations and technological progression of 3D printers. It can also be assumed that the economics of the process will also become increasingly acceptable and less restrictive. We have exploited the possibilities of 3D modelling on a diverse patient population at our institution and will undoubtedly further develop and apply the clinical themes in wider practice based on our positive experiences. In particular, we foresee the testing of additional printable substances with different material properties (softer - blood vessels, harder - bone, etc.), which will make it possible to bring the model even closer to clinical practice with the possibility of simulating the actual procedure (clip loading, screw insertion, etc.). In addition to the practical cases mentioned above, we also used 3D printing to produce a special splitter for minimally invasive access to the lumbar spine.

Conclusion

Although three-dimensional printing is now a readily available technology that has found widespread use in many technical professions and in some branches of medicine, it is still minimally used in neurosurgery. We have presented the possibilities of its application in clinical practice on the presented patient cohort and we believe that this communication will contribute to its popularization and wider use.

Ethical aspects

The work was carried out in accordance with the Helsinki Declaration of 1975 and its revisions in 2004 and 2008. The study is not subject to ethics committee approval

Financial support

The contribution was made with the financial support of the Regional Hospital Liberec, a. s. (internal grant VR220303).

Conflict of interest

The authors declare that they have no conflict of interest in relation to the subject of the study.

Tables

Table 1: List of patients, 3D printing usage and printing time.