Cranioplasty prosthesis manufacturing based on reverse engineering technology

Three-dimensional analysis of reconstructed skulls using three different open-source software versus commercial software

This study aimed to compare the 3D skull models reconstructed from computed tomography (CT) images using three different open-source software with a commercial software as a reference. The commercial Mimics v17.0 software was used to reconstruct the 3D skull models from 58 subjects. Next, two open-source software, MITK Workbench 2016.11, 3D Slicer 4.8.1 and InVesalius 3.1 were used to reconstruct the 3D skull models from the same subjects. All four software went through similar steps in 3D reconstruction process. The 3D skull models from the commercial and open-source software were exported in standard tessellation language (STL) format into CloudCompare v2.8 software and superimposed for geometric analyses. Hausdorff distance (HD) analysis demonstrated the average points distance of Mimics versus MITK was 0.25 mm. Meanwhile, for Mimics versus 3D Slicer and Mimics versus InVesalius, there was almost no differences between the two superimposed 3D skull models with average points distance of 0.01 mm. Based on Dice similarity coefficient (DSC) analysis, the similarity between Mimics versus MITK, Mimics versus 3D Slicer and Mimics versus InVesalius were 94.1, 98.8 and 98.3%, respectively. In conclusion, this study confirmed that the alternative open-source software, MITK, 3D Slicer and InVesalius gave comparable results in 3D reconstruction of skull models compared to the commercial gold standard Mimics software. This open-source software could possibly be used for pre-operative planning in cranio-maxillofacial cases and for patient management in the hospitals or institutions with limited budget.

Accuracy of virtual rhinomanometry

Introduction: This paper describes the results of research aimed at developing a method of otolaryngological diagnosis based on computational fluid dynamics, which has been called Virtual Rhinomanometry.

Material and methods: Laboratory studies of airflows through a 3D printed model of nasal cavities based on computed tomography image analysis have been performed. The CFD results have been compared with those of an examination of airflow through nasal cavities (rhinomanometry) of a group of 25 patients.

Results: The possibilities of simplifying model geometry for CFD calculations have been described, the impact of CT image segmentation on geometric model accuracy and CFD simulation errors have been analysed, and recommendations for future research have been described.

Conclusions: The measurement uncertainty of the nasal cavities’ walls has a significant impact on CFD simulations. The CFD simulations better approximate RMM results of patients after anemization, as the influence of the nasal mucosa on airflow is then reduced. A minor change in the geometry of the nasal cavities (within the range of reconstruction errors by CT image segmentation) has a major impact on the results of CFD simulations.

Characterisation of Selected Materials in Medical Applications

Tissue engineering is an interdisciplinary field of science that has developed very intensively in recent years. The first part of this review describes materials with medical and dental applications from the following groups: metals, polymers, ceramics, and composites. Both positive and negative sides of their application are presented from the point of view of medical application and mechanical properties. A variety of techniques for the manufacture of biomedical components are presented in this review. The main focus of this work is on additive manufacturing and 3D printing, as these modern techniques have been evaluated to be the best methods for the manufacture of medical and dental devices. The second part presents devices for skull bone reconstruction. The materials from which they are made and the possibilities offered by 3D printing in this field are also described. The last part concerns dental transitional implants (scaffolds) for guided bone regeneration, focusing on polylactide-hydroxyapatite nanocomposite due to its unique properties. This section summarises the current knowledge of scaffolds, focusing on the material, mechanical and biological requirements, the effects of these devices on the human body, and their great potential for applications.

Development of an Automatic Robotic Procedure for Machining of Skull Prosthesis

The project presented in this paper develops within the field of automation in the medical-surgical sector. It aims at automating the process for the realization of prosthetic devices for the skull in cranioplasty, following a craniotomy intervention for brain tumor removal. The paper puts emphasis on the possibility to create the prosthetic device in run-time during the surgery, in order to ease the work that surgeons have to do during the operation. Generally, a skull prosthesis is realized before the day of the intervention, based on the plan of the medical operation, on the results of computed tomography, and through image processing software. However, after the surgery is performed, a non-negligible geometrical uncertainty can be found between the part of the skull actually removed and the cut planned during the preliminary analysis, so that the realized prosthesis (or even the skull, at worse) may need to be retouched. This paper demonstrates the possibility to introduce a fully automated process in a hospital environment, to manufacture in runtime the prosthetic operculum, relying on the actual geometry of the incision of the skull detected during the intervention. By processing a 3D scan of the skull after the craniectomy, a digital model of the prosthesis can be created and then used as an input to generate the code to be run by a robotic system in charge of the workpiece machining. Focusing on this second step, i.e., the manufacturing process, the work describes the way the dimensions of the raw material block are automatically selected, and the way robot trajectories for milling operation are automatically generated. Experimental validation demonstrates the possibility to complete the prosthesis within the surgery time, thus increasing the accuracy of the produced prosthesis and consequently reducing the time needed to complete the operation.

A preliminary study of the novel antibiotic-loaded cement computer-aided design-articulating spacer for the treatment of periprosthetic knee infection

BACKGROUND

In comparison to static spacers, articulating spacers have been shown to result in a similar infection eradication rate in two-stage revision of periprosthetic knee infections. However, the optimal construct for articulating spacers has not been identified yet. The aim of this study was to present a preliminary result of treatment for periprosthetic knee infection using a novel computer-aided design (CAD)-articulating spacer.

METHODS

We retrospectively reviewed 32 consecutive cases of chronic periprosthetic knee infection occurring from January 2015 to December 2015. In these cases, we used an antibiotic-loaded, optimized CAD-articulating spacer based on the retrieved knee prosthesis. Evaluation included infection eradication rate, the Hospital of Special Surgery (HSS) knee score, range of motion (ROM), and spacer-related mechanical complications. All cases were regularly followed-up for 2 years minimum.

RESULTS

Twenty-eight of 32 patients (87.5%) had infection eradication; 18 patients (56.3%) received reimplantation successfully. The mean interval between spacer insertion and reimplantation was 8.8 months (range 4.0-12.5 months). The mean HSS knee score and ROM significantly increased during each interval (p < 0.0001 for both). The mean HSS knee scores were 31.2 (range 20-48) at initial visit, 65.4 (range 60-78.8) at 1 month after spacer insertion, and 84.2 (range 78-90) at 3 months after reimplantation (p < 0.0001). The mean ROM were 72.0° (range 15-100°), 85.6° (range 35-110°), and 102.0° (range 80-122°), respectively (p = 0.002). Two (6.3%) spacer-related mechanical complications occurred.

CONCLUSIONS

The CAD-articulating spacer in two-staged revision of periprosthetic knee infection significantly controlled infection, improved clinical outcomes, increased ROM, and decreased mechanical complications in the preliminary study. Further larger clinical studies are needed to confirm the findings presented here.

Low-cost customized cranioplasty using a 3D digital printing model: a case report

Background

Cranial defects usually occur after trauma, neurosurgical procedures like decompressive craniotomy, tumour resections, infection and congenital defects. The purpose of cranial vault repair is to protect the underlying brain tissue, to reduce any localized pain and patient anxiety, and improve cranial aesthetics. Cranioplasty is a frequent neurosurgical procedure achieved with the aid of cranial prosthesis made from materials such as: titanium, autologous bone, ceramics and polymers. Prosthesis production is often costly and requires complex intraoperative processes. Implant customized manufacturing for craniopathies allows for a precise and anatomical reconstruction in a shorter operating time compared to other conventional techniques. We present a simple, low-cost method for prosthesis manufacturing that ensures surgical success.

Case presentation

Two patients with cranial defects are presented to describe the three-dimensional (3D) printing technique for cranial reconstruction. A digital prosthesis model is designed and manufactured with the aid of a 3D computed tomography. Both the data of large sized cranial defects and the prosthesis are transferred to a 3D printer to obtain a physical model in poly-lactic acid which is then used in a laboratory to cast the final customised prosthesis in polymethyl methacrylate (PMMA).

Conclusions

A precise compliance of the prosthesis to the osseous defect was achieved. At the 6 month postoperative follow-up no complications were observed i.e. rejection, toxicity, local or systemic infection, and the aesthetic change was very significant and satisfactory. Customized 3D PMMA prosthesis offers cost advantages, a great aesthetic result, reduced operating time and good biocompatibility.

[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.

3D-printing techniques in a medical setting: a systematic literature review

BACKGROUND

Three-dimensional (3D) printing has numerous applications and has gained much interest in the medical world. The constantly improving quality of 3D-printing applications has contributed to their increased use on patients. This paper summarizes the literature on surgical 3D-printing applications used on patients, with a focus on reported clinical and economic outcomes.

METHODS

Three major literature databases were screened for case series (more than three cases described in the same study) and trials of surgical applications of 3D printing in humans.

RESULTS

227 surgical papers were analyzed and summarized using an evidence table. The papers described the use of 3D printing for surgical guides, anatomical models, and custom implants. 3D printing is used in multiple surgical domains, such as orthopedics, maxillofacial surgery, cranial surgery, and spinal surgery. In general, the advantages of 3D-printed parts are said to include reduced surgical time, improved medical outcome, and decreased radiation exposure. The costs of printing and additional scans generally increase the overall cost of the procedure.

CONCLUSION

3D printing is well integrated in surgical practice and research. Applications vary from anatomical models mainly intended for surgical planning to surgical guides and implants. Our research suggests that there are several advantages to 3D-printed applications, but that further research is needed to determine whether the increased intervention costs can be balanced with the observable advantages of this new technology. There is a need for a formal cost-effectiveness analysis.

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.

Combining regenerative medicine strategies to provide durable reconstructive options: auricular cartilage tissue engineering

Recent advances in regenerative medicine place us in a unique position to improve the quality of engineered tissue. We use auricular cartilage as an exemplar to illustrate how the use of tissue-specific adult stem cells, assembly through additive manufacturing and improved understanding of postnatal tissue maturation will allow us to more accurately replicate native tissue anisotropy. This review highlights the limitations of autologous auricular reconstruction, including donor site morbidity, technical considerations and long-term complications. Current tissue-engineered auricular constructs implanted into immune-competent animal models have been observed to undergo inflammation, fibrosis, foreign body reaction, calcification and degradation. Combining biomimetic regenerative medicine strategies will allow us to improve tissue-engineered auricular cartilage with respect to biochemical composition and functionality, as well as microstructural organization and overall shape. Creating functional and durable tissue has the potential to shift the paradigm in reconstructive surgery by obviating the need for donor sites.

3D modeling, custom implants and its future perspectives in craniofacial surgery

Custom implants for the reconstruction of craniofacial defects have gained importance due to better performance over their generic counterparts. This is due to the precise adaptation to the region of implantation, reduced surgical times and better cosmesis. Application of 3D modeling in craniofacial surgery is changing the way surgeons are planning surgeries and graphic designers are designing custom implants. Advances in manufacturing processes and ushering of additive manufacturing for direct production of implants has eliminated the constraints of shape, size and internal structure and mechanical properties making it possible for the fabrication of implants that conform to the physical and mechanical requirements of the region of implantation. This article will review recent trends in 3D modeling and custom implants in craniofacial reconstruction.

Cranioplasty with polymethylmethacrylate prostheses fabricated by hand using original bone flaps: Technical note and surgical outcomes

Background:

Decompressive craniectomies (DC) mandate future cranioplasties, accounting for the large array of biomaterials for this purpose. Polymethylmethacrylate (PMMA) is a very reliable thermoplastic that can be prefabricated or even molded intraoperatively to create an adequate prosthesis. Preformed PMMA implants made by hand have been superseded by newer 3-D printed implants, but this is accompanied by higher costs and timing issues, apart from having limited availability in developing and third-world countries.

Methods:

A total of 26 patients were operated over a span of 11 years. A total of 26 custom hand-made PMMA prostheses were fabricated using original bone flaps with the aid of a prosthodontist, in a process that took approximately 70 minutes for each implant. The result was an exact duplication of the patient's bone flap.

Results:

Of the 26 patients who underwent cranioplasty, the majority of patients were males, with a mean age of 39.2 years and traumatic brain injury as main indication for DC. After a mean interval of 2.4 months, all 26 patients underwent a cranioplasty and prosthesis placement. Only two patients (7.6%) suffered from direct cranioplasty-related complications after a median follow-up of 10.4 months. Median Glasgow Outcome Scale scores improved significantly from 3 to 4 after cranioplasty (P = 0.008).

Conclusion:

Prefabrication of custom PMMA prostheses by hand when original bone flaps are available is an excellent alternative to newer 3-D printing techniques, because it is relatively cheaper, less time consuming, and offers excellent results in terms of anatomical reconstruction and improvement of neurological function in long-term follow-ups.