Rapid prototyped patient specific implants for reconstruction of orbital wall defects

Clinical outcomes of 3-dimensional printed custom porous polyethylene orbital implant for reconstruction

PurposeTo report the clinical outcomes with three-dimensional (3D)-printed custom orbital implants, designed using contralateral orbit mirroring techniques.MethodsCase series of 3D-printed custom orbital implants used for complex orbital reconstructions at University of Michigan Kellogg Eye Center is presented in this study. Data from 2020 to 2023 was collected.ResultsIn this case series of 8 patients, the surgical indications include diplopia, enophthalmos, hypoglobus either post-trauma or tumor removal. One patient had bilateral defects; others had unilateral defects. The mean follow-up time was 27.88 ± 9.66 months (Range: 7-38 months). Postoperative improvement was seen for enophthalmos in 7 of 8 cases, hypoglobus in 3 of 5 cases, and diplopia in 3 of 4 cases, and the average exophthalmometry asymmetry improved from 3.1 mm to 0.5 mm.Conclusions3D-printed orbital implants demonstrated effectiveness and safety in this diverse series of orbital reconstruction cases, yielding significant clinical improvements. Our findings support the use of these implants in a variety of complex orbital reconstructions.

Efficacy of absorbable vs. non-absorbable patient-specific, 3D-printed implants for the treatment of facial bone fractures: a systematic review and meta-analysis

OBJECTIVE

This systematic review and meta-analysis compares the efficacy and complication rate of absorbable versus non-absorbable 3D-printed, patient-customized, maxillofacial implants in facial trauma patients.

DATA SOURCES

A comprehensive search of four databases (PubMed, Scopus, Web of Science, and Cochrane) was conducted.

METHODS

A systematic review and single-proportion meta-analysis was conducted employing PRISMA guidelines. A comprehensive search of four databases (PubMed, Scopus, Web of Science, and Cochrane) yielded a total of 4087 results. After removing duplicates, 16 articles underwent full-text analysis, with 13 meeting the inclusion criteria. The inclusion focused on primary clinical data involving 3D-printed, patient-specific implants for facial bone fracture restorations. Exclusion criteria removed studies without full text, ongoing studies, animal studies, and studies not utilizing CAD/CAM for their implants.

RESULTS

A total of 114 patients underwent insertion of 3D-printed implants. Patients receiving non-absorbable implants had a success rate of 84% (95% CI: 74-91), with complications in 12 patients. Patients receiving absorbable implants achieved a 100% success rate (95% CI: 0-100), with zero complications.

CONCLUSION

The study suggests absorbable 3D-printed implants provide superior results with fewer complications compared to non-absorbable 3D-printed implants for the treatment of facial fractures.

CLINICAL TRIAL NUMBER

Not applicable.

Assessment of cone-beam CT technical image quality indicators and radiation dose for optimal STL model used in visual surgical planning

OBJECTIVES

The aim of this study was to identify cone-beam computed tomography (CBCT) protocols that offer an optimal balance between effective dose (ED) and 3D model for orthognathic virtual surgery planning, using CT as a reference, and to assess whether such protocols can be defined based on technical image quality metrics.

METHODS

Eleven CBCT (VISO G7, Planmeca Oy, Helsinki, Finland) scan protocols were selected out of 32 candidate protocols, based on ED and technical image quality measurements. Next, an anthropomorphic RANDO SK150 phantom was scanned using these 11 CBCT protocols and 2 CT scanners for bone quantity assessments. The resulting DICOM (Digital Imaging and Communications in Medicine) files were converted into Standard Tessellation Language (STL) models that were used for bone volume and area measurements in the predefined orbital region to assess the validity of each CBCT protocol for virtual surgical planning.

RESULTS

The highest CBCT bone volume and area of the STL models were obtained using normal dose protocol (F2) and ultra-low dose protocol (J13), which resulted in 48% and 96% of the mean STL bone volume and 48% and 95% of the bone area measured on CT scanners, respectively.

CONCLUSIONS

The normal dose CBCT protocol "F2" offered optimal bone area and volume balance for STL. The optimal CBCT protocol can be defined using contrast-to-noise ratio and modulation transfer function values that were similar to those of the reference CT scanners'. CBCT scanners with selected protocols can offer a viable alternative to CT scanners for acquiring STL models for virtual surgical planning at a lower effective dose.

Recent advances in additive manufacturing of patient-specific devices for dental and maxillofacial rehabilitation

OBJECTIVES

Customization and the production of patient-specific devices, tailoring the unique anatomy of each patient's jaw and facial structures, are the new frontiers in dentistry and maxillofacial surgery. As a technological advancement, additive manufacturing has been applied to produce customized objects based on 3D computerized models. Therefore, this paper presents advances in additive manufacturing strategies for patient-specific devices in diverse dental specialties.

METHODS

This paper overviews current 3D printing techniques to fabricate dental and maxillofacial devices. Then, the most recent literature (2018-2023) available in scientific databases reporting advances in 3D-printed patient-specific devices for dental and maxillofacial applications is critically discussed, focusing on the major outcomes, material-related details, and potential clinical advantages.

RESULTS

The recent application of 3D-printed customized devices in oral prosthodontics, implantology and maxillofacial surgery, periodontics, orthodontics, and endodontics are presented. Moreover, the potential application of 4D printing as an advanced manufacturing technology and the challenges and future perspectives for additive manufacturing in the dental and maxillofacial area are reported.

SIGNIFICANCE

Additive manufacturing techniques have been designed to benefit several areas of dentistry, and the technologies, materials, and devices continue to be optimized. Image-based and accurately printed patient-specific devices to replace, repair, and regenerate dental and maxillofacial structures hold significant potential to maximize the standard of care in dentistry.

Design of bone scaffolds with calcium phosphate and its derivatives by 3D printing: A review

Tissue engineering is a fascinating field that combines biology, engineering, and medicine to create artificial tissues and organs. It involves using living cells, biomaterials, and bioengineering techniques to develop functional tissues that can be used to replace or repair damaged or diseased organs in the human body. The process typically starts by obtaining cells from the patient or a donor. These cells are then cultured and grown in a laboratory under controlled conditions. Scaffold materials, such as biodegradable polymers or natural extracellular matrices, are used to provide support and structure for the growing cells. 3D bone scaffolds are a fascinating application within the field of tissue engineering. These scaffolds are designed to mimic the structure and properties of natural bone tissue and serve as a temporary framework for new bone growth. The main purpose of a 3D bone scaffold is to provide mechanical support to the surrounding cells and guide their growth in a specific direction. It acts as a template, encouraging the formation of new bone tissue by providing a framework for cells to attach, proliferate, and differentiate. These scaffolds are typically fabricated using biocompatible materials like ceramics, polymers, or a combination of both. The choice of material depends on factors such as strength, biodegradability, and the ability to facilitate cell adhesion and growth. Advanced techniques like 3D printing have revolutionized the fabrication process of these scaffolds. Using precise layer-by-layer deposition, it allows for the creation of complex, patient-specific geometries, mimicking the intricacies of natural bone structure. This article offers a brief overview of the latest developments in the research and development of 3D printing techniques for creating scaffolds used in bone tissue engineering.

Bone Regeneration Induced by Patient-Adapted Mg Alloy-Based Scaffolds for Bone Defects: Present and Future Perspectives

Treatment of bone defects resulting after tumor surgeries, accidents, or non-unions is an actual problem linked to morbidity and the necessity of a second surgery and often requires a critical healthcare cost. Although the surgical technique has changed in a modern way, the treatment outcome is still influenced by patient age, localization of the bone defect, associated comorbidities, the surgeon approach, and systemic disorders. Three-dimensional magnesium-based scaffolds are considered an important step because they can have precise bone defect geometry, high porosity grade, anatomical pore shape, and mechanical properties close to the human bone. In addition, magnesium has been proven in in vitro and in vivo studies to influence bone regeneration and new blood vessel formation positively. In this review paper, we describe the magnesium alloy's effect on bone regenerative processes, starting with a short description of magnesium's role in the bone healing process, host immune response modulation, and finishing with the primary biological mechanism of magnesium ions in angiogenesis and osteogenesis by presenting a detailed analysis based on a literature review. A strategy that must be followed when a patient-adapted scaffold dedicated to bone tissue engineering is proposed and the main fabrication technologies are combined, in some cases with artificial intelligence for Mg alloy scaffolds, are presented with examples. We emphasized the microstructure, mechanical properties, corrosion behavior, and biocompatibility of each study and made a basis for the researchers who want to start to apply the regenerative potential of magnesium-based scaffolds in clinical practice. Challenges, future directions, and special potential clinical applications such as osteosarcoma and persistent infection treatment are present at the end of our review paper.

3D Printing Applications for Craniomaxillofacial Reconstruction: A Sweeping Review

The field of craniomaxillofacial (CMF) surgery is rich in pathological diversity and broad in the ages that it treats. Moreover, the CMF skeleton is a complex confluence of sensory organs and hard and soft tissue with load-bearing demands that can change within millimeters. Computer-aided design (CAD) and additive manufacturing (AM) create extraordinary opportunities to repair the infinite array of craniomaxillofacial defects that exist because of the aforementioned circumstances. 3D printed scaffolds have the potential to serve as a comparable if not superior alternative to the "gold standard" autologous graft. In vitro and in vivo studies continue to investigate the optimal 3D printed scaffold design and composition to foster bone regeneration that is suited to the unique biological and mechanical environment of each CMF defect. Furthermore, 3D printed fixation devices serve as a patient-specific alternative to those that are available off-the-shelf with an opportunity to reduce operative time and optimize fit. Similar benefits have been found to apply to 3D printed anatomical models and surgical guides for preoperative or intraoperative use. Creation and implementation of these devices requires extensive preclinical and clinical research, novel manufacturing capabilities, and strict regulatory oversight. Researchers, manufacturers, CMF surgeons, and the United States Food and Drug Administration (FDA) are working in tandem to further the development of such technology within their respective domains, all with a mutual goal to deliver safe, effective, cost-efficient, and patient-specific CMF care. This manuscript reviews FDA regulatory status, 3D printing techniques, biomaterials, and sterilization procedures suitable for 3D printed devices of the craniomaxillofacial skeleton. It also seeks to discuss recent clinical applications, economic feasibility, and future directions of this novel technology. By reviewing the current state of 3D printing in CMF surgery, we hope to gain a better understanding of its impact and in turn identify opportunities to further the development of patient-specific surgical care.

Early experience of wafer-free Le Fort I osteotomy with patient-specific implants in cleft lip and palate patients

PURPOSE

The use of virtual surgical planning and patient-specific saw and drill guides combined with customized osteosynthesis is becoming a gold standard in orthognathic surgery. The aim of this study is to report preliminary results of the use of virtual surgical planning and the wafer-free PSI technique in cleft patients.

MATERIALS AND METHODS

Patient-specific saw and drill guides combined with milled patient-specific 3D titanium alloy implants were used in reposition and fixation in Le Fort I osteotomy of 12 cleft patients. Surgical information was retrieved from hospital records. Pre- and post-operative lateral cephalograms were analyzed.

RESULTS

In 10 of 12 cases, the implants fitted as planned to predesigned drill holes and bone contours with high precision. In one patient, the mobilization of the maxilla was too demanding for virtually planned advancement, and the implants could not be used. In another patient, PSI fitting was impaired due to an insufficient mobilization of maxilla and tension on PSI fixation with screws. After the surgery, the mean advancement of the anterior maxilla (point A) of all patients was 5.8 mm horizontally (range 2.7-10.1) and -3.1 mm vertically (range -9.2 to 3.4). Skeletal relationships of the maxilla and mandible could be corrected successfully in all patients except for the one whose PSI could not be used.

CONCLUSIONS

Virtual surgical planning combined with PSI is a possible useful clinical adjunct for the correction of maxillary hypoplasia in cleft patients. Large maxillary advancements and scarring may be cause problems for desired advancement and for the use of implants.

Ageing increases risk of lower eyelid malposition after primary orbital fracture reconstruction

Lower eyelid malposition (LEM) is a common sequela after orbital fracture reconstruction. This study aimed to analyse the development of LEM, specifically ectropion and entropion, following primary orbital fracture reconstruction, to identify predictive factors for LEM, and to assess the effect of the eyelid complication on patients' daily lives. The retrospective cohort comprised patients who had undergone orbital floor and/or medial wall fracture reconstruction for recent trauma. Demographics, fracture type and site, surgery and implant-related variables, follow-up time and number of visits, type and severity of LEM, subsequent surgical correction, and patient satisfaction, were analysed. The overall occurrence of LEM was 8%, with ectropion in 6% and entropion in 2% of patients. Older age, complex fractures, transcutaneous approaches, preoperative traumatic lower lid wounds, and implant material were associated with the development of LEM. Of all patients, 3% needed surgical correction of LEM. Six of the 13 patients (46%) who developed LEM required surgical correction. The transconjunctival approach and patient-specific implants should be preferred, especially in elderly patients and those with more complex fractures. LEM often requires subsequent surgical correction, and the treatment period is substantially prolonged, with multiple extra visits to the clinic.

Accuracy of Segmented Le Fort I Osteotomy with Virtual Planning in Orthognathic Surgery Using Patient-Specific Implants: A Case Series

Background: When maxillary transversal expansion is needed, two protocols of treatment can be used: a maxillary orthodontic expansion followed by a classical bimaxillary osteotomy or a bimaxillary osteotomy with maxillary segmentation. The aim of this study was to assess the accuracy of segmented Le Fort I osteotomy using computer-aided orthognathic surgery and patient-specific titanium plates in patients who underwent a bimaxillary osteotomy for occlusal trouble with maxillary transversal insufficiencies. Methods: A virtual simulation of a Le Fort I osteotomy with maxillary segmentation, a sagittal split ramus osteotomy, and genioplasty (if needed) was conducted on a preoperative three-dimensional (3D) model of each patient’s skull using ProPlan CMF 3.0 software (Materialise, Leuven, Belgium). Computer-assisted osteotomy saw-and-drill guides and patient-specific implants (PSIs, titanium plates) were produced and used during the surgery. We chose to focus on the maxillary repositioning accuracy by comparing the preoperative virtual surgical planning and the postoperative 3D outcome skulls using surface superimpositions and 13 standard dental and bone landmarks. Errors between these preoperative and postoperative landmarks were calculated and compared to discover if segmental maxillary repositioning using PSIs was accurate enough to be safely used to treat transversal insufficiencies. Results: A total of 22 consecutive patients—15 females and 7 males, with a mean age of 27.4 years—who underwent bimaxillary computer-assisted orthognathic surgery with maxillary segmentation were enrolled in the study. All patients presented with occlusion trouble, 13 with Class III malocclusions (59%) and 9 (41%) with Class II malocclusions. A quantitative analysis revealed that, overall, the mean absolute discrepancies for the x-axis (transversal dimension), y-axis (anterior−posterior dimensions), and z-axis (vertical dimension) were 0.59 mm, 0.74 mm, and 0.56 mm, respectively. The total error rate of maxillary repositioning was 0.62 mm between the postoperative cone-beam computed tomography (CBCT) and the preoperatively planned 3D skull. According to the literature, precision in maxilla repositioning is defined by an error rate (clinically relevant) at each landmark of <2 mm and a total error of <2 mm for each patient. Conclusions: A high degree of accuracy between the virtual plan and the postoperative result was observed.

Influence of head positioning during cone-beam CT imaging on the accuracy of virtual 3D models

OBJECTIVE

Cone beam computed tomography (CBCT) images are being increasingly used to acquire three-dimensional (3D) models of the skull for additive manufacturing purposes. However, the accuracy of such models remains a challenge, especially in the orbital area. The aim of this study is to assess the impact of four different CBCT imaging positions on the accuracy of the resulting 3D models in the orbital area.

METHODS

An anthropomorphic head phantom was manufactured by submerging a dry human skull in silicon to mimic the soft tissue attenuation and scattering properties of the human head. The phantom was scanned on a ProMax 3D MAX CBCT scanner using 90 and 120 kV for four different field of view positions: standard; elevated; backwards tilted; and forward tilted. All CBCT images were subsequently converted into 3D models and geometrically compared with a "gold-standard" optical scan of the dry skull.

RESULTS

Mean absolute deviations of the 3D models ranged between 0.15 ± 0.11 mm and 0.56 ± 0.28 mm. The elevated imaging position in combination with 120 kV tube voltage resulted in an improved representation of the orbital walls in the resulting 3D model without compromising the accuracy.

CONCLUSIONS

Head positioning during CBCT imaging can influence the accuracy of the resulting 3D model. The accuracy of such models may be improved by positioning the region of interest (e.g. the orbital area) in the focal plane (Figure 2a) of the CBCT X-ray beam.

The role of computer aided design/computer assisted manufacturing (CAD/CAM) and 3- dimensional printing in head and neck oncologic surgery: A review and future directions

Microvascular free flap reconstruction has remained the standard of care in reconstruction of large tissue defects following ablative head and neck oncologic surgery, especially for bony structures. Computer aided design/computer assisted manufacturing (CAD/CAM) and 3-dimensionally (3D) printed models and devices offer novel solutions for reconstruction of bony defects. Conventional free hand techniques have been enhanced using 3D printed anatomic models for reference and pre-bending of titanium reconstructive plates, which has dramatically improved intraoperative and microvascular ischemia times. Improvements led to current state of the art uses which include full virtual planning (VP), 3D printed osteotomy guides, and patient specific reconstructive plates, with advanced options incorporating dental rehabilitation and titanium bone replacements into the primary surgical plan through use of these tools. Limitations such as high costs and delays in device manufacturing may be mitigated with in house software and workflows. Future innovations still in development include printing custom prosthetics, 'bioprinting' of tissue engineered scaffolds, integration of therapeutic implants, and other possibilities as this technology continues to rapidly advance. This review summarizes the literature and serves as a summary guide to the historic, current, advanced, and future possibilities of 3D printing within head and neck oncologic surgery and bony reconstruction. This review serves as a summary guide to the historic, current, advanced, and future roles of CAD/CAM and 3D printing within the field of head and neck oncologic surgery and bony reconstruction.

Personalized Medicine Workflow in Post-Traumatic Orbital Reconstruction

Restoration of the orbit is the first and most predictable step in the surgical treatment of orbital fractures. Orbital reconstruction is keyhole surgery performed in a confined space. A technology-supported workflow called computer-assisted surgery (CAS) has become the standard for complex orbital traumatology in many hospitals. CAS technology has catalyzed the incorporation of personalized medicine in orbital reconstruction. The complete workflow consists of diagnostics, planning, surgery and evaluation. Advanced diagnostics and virtual surgical planning are techniques utilized in the preoperative phase to optimally prepare for surgery and adapt the treatment to the patient. Further personalization of the treatment is possible if reconstruction is performed with a patient-specific implant and several design options are available to tailor the implant to individual needs. Intraoperatively, visual appraisal is used to assess the obtained implant position. Surgical navigation, intraoperative imaging, and specific PSI design options are able to enhance feedback in the CAS workflow. Evaluation of the surgical result can be performed both qualitatively and quantitatively. Throughout the entire workflow, the concepts of CAS and personalized medicine are intertwined. A combination of the techniques may be applied in order to achieve the most optimal clinical outcome. The goal of this article is to provide a complete overview of the workflow for post-traumatic orbital reconstruction, with an in-depth description of the available personalization and CAS options.

Customised products for orbital wall reconstruction: a systematic review

The purpose of this systematic review was to critically analyse the recent literature and present the state of the art in customised reconstruction of orbital fractures. Three electronic databases and manual search approaches were used to identify relevant articles. Only controlled clinical studies were included. Primary outcome was defined as the status of recovery (complete/partial functional, and aesthetic disturbances). The benefit of intrasurgical navigation should be described. The secondary outcome was defined as the time of surgery, post-surgical events, and hospitalisation. Of the 552 records identified, eight met the inclusion criteria. Post-surgical results regarding recovery were superior in the customised group, and were comparable to the control group in five studies. The time of surgery was shorter in the customised groups, and liquid infusion and time of hospitalisation were reduced. Four studies documented more accurate reconstruction with the use of navigation. All the studies presented at least one bias, and considerable heterogeneity was evaluated. This review found that the use of customised meshes in combination with surgical navigation resulted in more accurate reconstruction. A significant reduction in surgical time was revealed.

Biocompatible Materials for Orbital Wall Reconstruction-An Overview

The reconstruction of an orbit after complex craniofacial fractures can be extremely demanding. For satisfactory functional and aesthetic results, it is necessary to restore the orbital walls and the craniofacial skeleton using various types of materials. The reconstruction materials can be divided into autografts (bone or cartilage tissue) or allografts (metals, ceramics, or plastic materials, and combinations of these materials). Over time, different types of materials have been used, considering characteristics such as their stability, biocompatibility, cost, safety, and intraoperative flexibility. Although the ideal material for orbital reconstruction could not be unanimously identified, much progress has been achieved in recent years. In this article, we summarise the advantages and disadvantages of each category of reconstruction materials. We also provide an update on improvements in material properties through various modern processing techniques. Good results in reconstructive surgery of the orbit require both material and technological innovations.

3D Printing in Eye Care

Three-dimensional printing enables precise modeling of anatomical structures and has been employed in a broad range of applications across medicine. Its earliest use in eye care included orbital models for training and surgical planning, which have subsequently enabled the design of custom-fit prostheses in oculoplastic surgery. It has evolved to include the production of surgical instruments, diagnostic tools, spectacles, and devices for delivery of drug and radiation therapy. During the COVID-19 pandemic, increased demand for personal protective equipment and supply chain shortages inspired many institutions to 3D-print their own eye protection. Cataract surgery, the most common procedure performed worldwide, may someday make use of custom-printed intraocular lenses. Perhaps its most alluring potential resides in the possibility of printing tissues at a cellular level to address unmet needs in the world of corneal and retinal diseases. Early models toward this end have shown promise for engineering tissues which, while not quite ready for transplantation, can serve as a useful model for in vitro disease and therapeutic research. As more institutions incorporate in-house or outsourced 3D printing for research models and clinical care, ethical and regulatory concerns will become a greater consideration. This report highlights the uses of 3D printing in eye care by subspecialty and clinical modality, with an aim to provide a useful entry point for anyone seeking to engage with the technology in their area of interest.

Accuracy of free-hand positioned patient specific implants (PSI) in primary reconstruction after inferior and/or medial orbital wall fractures

BACKGROUND

To assess the accuracy with which CAD/CAM-fabricated patient-specific titanium implants (PSI) are positioned for inferior and/or medial orbital wall reconstruction without the use of intraoperative navigation.

METHODS

Patients who underwent a primary reconstruction of the orbital walls with PSI due to fractures were enrolled in this retrospective cohort analysis. The primary outcome variables were the mean surface distances (MSD) between virtually planned and postoperative PSI position and single linear deviations in the x-, y- and z-axis at corresponding reference points. Secondary outcome variables included demographic data, classification of orbital wall defects and clinical outcomes.

RESULTS

A total of 33 PSI (orbital floor n = 22; medial wall, n = 11) were examined in 27 patients. MSD was on a comparable level for the orbital floor and medial wall (median 0.39 mm, range 0.22-1.53 mm vs. median 0.42 mm, range 0.21-0.98 mm; p = 0.56). Single linear deviations were lower for reconstructions of the orbital floor compared to the medial wall (median 0.45 vs. 0.79 mm; p < 0.05). There was no association between the occurrence of diplopia and the accuracy level (p = 0.418).

CONCLUSIONS

Free-hand positioning of PSI reaches a clinically appropriate level of accuracy, limiting the necessity of navigational systems to selected cases.

The accuracy of clinical 3D printing in reconstructive surgery: literature review and in vivo validation study

A growing number of studies demonstrate the benefits of 3D printing in improving surgical efficiency and subsequently clinical outcomes. However, the number of studies evaluating the accuracy of 3D printing techniques remains scarce. All publications appraising the accuracy of 3D printing between 1950 and 2018 were reviewed using well-established databases, including PubMed, Medline, Web of Science and Embase. An in vivo validation study of our 3D printing technique was undertaken using unprocessed chicken radius bones (Gallus gallus domesticus). Calculating its maximum length, we compared the measurements from computed tomography (CT) scans (CT group), image segmentation (SEG group) and 3D-printed (3DP) models (3DP group). Twenty-eight comparison studies in 19 papers have been identified. Published mean error of CT-based 3D printing techniques were 0.46 mm (1.06%) in stereolithography, 1.05 mm (1.78%) in binder jet technology, 0.72 mm (0.82%) in PolyJet technique, 0.20 mm (0.95%) in fused filament fabrication (FFF) and 0.72 mm (1.25%) in selective laser sintering (SLS). In the current in vivo validation study, mean errors were 0.34 mm (0.86%) in CT group, 1.02 mm (2.51%) in SEG group and 1.16 mm (2.84%) in 3DP group. Our Peninsula 3D printing technique using a FFF 3D printer thus produced accuracy similar to the published studies (1.16 mm, 2.84%). There was a statistically significant difference (P<10-4) between the CT group and the latter SEG and 3DP groups indicating that most of the error is introduced during image segmentation stage.

Accuracy of Patient-Specific Meshes as a Reconstruction of Orbital Floor Blow-Out Fractures

ABSTRACT

Computer-aided design and manufacturing (CAD-CAM)-based techniques are developing fast in facial reconstruction and osteosynthesis. Patient-specific implant (PSI) production is already sufficiently fast for everyday use and can be utilized even for primary trauma surgery such as orbital floor reconstruction after blowout fracture. Purpose of our study is to retrospectively analyze the 3-dimensional (3D) success of PSI reconstructions of orbital floor fractures in our unit. The authors analyzed retrospectively a 1-year cohort (n = 8) of orbital floor blow-out fractures that have been reconstructed using virtual surgical plan and CAD-CAM PSI. Postoperative computed topographies of patients were compared to their original virtual surgical plans. The 3D outcome and fitting of the PSI was good in all patients. Mean error for 3D position of the PSI was 1.3 to 1.8 mm (range 0.4 to 4.8 mm) and postoperative orbital volume was successfully restored in all of the patients. Use of CAD-CAM PSI for reconstruction of orbital floor blow out fracture is reliable method and thus recommended.

Implant malposition and revision surgery in primary orbital fracture reconstructions

The aim of the study was to assess factors leading to revision surgery and implant position of primary orbital fracture reconstructions. A retrospective cohort included patients who underwent orbital floor and/or medial wall fracture reconstruction for recent trauma. Demographics, fracture type, surgery and implant-related variables, and postoperative implant position were analyzed. The overall revision surgery rate was 6.5% (15 of 232 surgeries). The rate was highest in combined midfacial fractures with rim involvement (14.0%), lower in zygomatico-orbital fractures (8.7%), and lowest in isolated blowout fractures (3.8%). Fracture type, orbital rim fixation and implant malposition predicted revision. The best positioning was achieved with patient-specific milled titanium implants (mtPSI) and resorbable materials, whereas the poorest with preformed three-dimensional titanium plates. Combined midfacial fractures with rim involvement in particular have a high risk for orbital revision surgery. Within the limitations of the present study, mtPSIs should be preferred in the reconstruction of primary orbital fractures if possible.

Comparison in clinical performance of surgical guides for mandibular surgery and temporomandibular joint implants fabricated by additive manufacturing techniques

Additive manufacturing (AM) offers great design freedom that enables objects with desired unique and complex geometry and topology to be readily and cost-effectively fabricated. The overall benefits of AM are well known, such as increased material and resource efficiency, enhanced design and production flexibility, the ability to create porous structures and on-demand manufacturing. When AM is applied to medical devices, these benefits are naturally assumed. However, hard clinical evidence collected from clinical trials and studies seems to be lacking and, as a result, systematic assessment is yet difficult. In the present work, we have reviewed 23 studies on the clinical use of AM patient-specific surgical guides (PSGs) for the mandible surgeries (n = 17) and temporomandibular joint (TMJ) patient-specific implants (PSIs) (n = 6) with respect to expected clinical outcomes. It is concluded that the data published on these AM medical devices are often lacking in comprehensive evaluation of clinical outcomes. A complete set of clinical data, including those on time management, costs, clinical outcomes, range of motion, accuracy of the placement with respect to the pre-operative planning, and extra complications, as well as manufacturing data are needed to demonstrate the real benefits gained from applying AM to these medical devices and to satisfy regulatory requirements.

Clinical outcome of patients with orbital fractures treated with patient specific CAD/CAM ceramic implants - A retrospective study

The aim of this study was to determine whether patients benefit from a secondary reconstruction since it carries the risks of no improvement or worsening of their current situation. Patients treated with individual computer-aided-design/computer-aided-manufacturing (CAD/CAM) ceramic implants were reviewed. To ascertain changes throughout the secondary reconstruction, the study investigators reviewed ophthalmological examinations, took volumetric measurements of the orbits and asked the patients for evaluation of their situation before and after the reconstruction. Points addressed were double vision, visual acuity, field of vision, limitations in daily life and aesthetic considerations. A total of 14 patients were reviewed and 11 answered the questionnaire. Ophthalmological examinations showed that the physical integrity of the eye was maintained. Volumetric measurements preopeatively (33.94 ± 3.24 cm³) and postoperatively (30.67 ± 2.07 cm³) showed that a statistically significant overcorrection of orbital volume leads to good functional and aesthetic outcomes. Patients' subjective opinions were that they greatly benefitted, especially concerning limitations in daily life, which improved by 4.4 ± 2.8 points out of 10 possible points, and aesthetics, with an improvement of 5.9 ± 1.78 points. Based on these findings, we conclude that secondary reconstructions contribute to improvement of the patients' quality of life and therefore should be considered as an option to improve patients' condition.

Patient-Specific Three-Dimensional Printing Guide for Single-Stage Skull Bone Tumor Surgery: Novel Software Workflow with Manufacturing of Prefabricated Jigs for Bone Resection and Reconstruction

OBJECTIVE

To describe a novel system workflow to design and manufacture patient-specific three-dimensional (3D) printing jigs for single-stage skull bone tumor excision and reconstruction and to present surgical outcomes of 14 patients.

METHODS

A specific computer-aided design/computer-aided manufacturing software and hardware system was set up, including a virtual surgical planning subsystem and a 3D printing-associated manufacturing subsystem. Computed tomography data of the patient's skull were used for 3D rendering of the skull and tumor. The output of patient-specific designing included a 3D printing guide for tumor resection and a 3D printing model of the bone defect after tumor excision. A polymethyl methacrylate implant was fabricated preoperatively and used for repair.

RESULTS

The specific 3D printing guide was used to design intraoperative jigs and implants for 14 patients (age range, 1-72 years) with skull bone tumors. In all cases, the cutting jig allowed precise excision of tumor and bone, and implants were exact fits for the defects created. All operative results were successful, without intraoperative or postoperative complications. Postoperative computed tomography scans were obtained for analysis. Postoperative 3D measurement of the skull symmetry index (cranial vault asymmetry index) showed significant improvement of head contour after surgery.

CONCLUSIONS

The computer-aided design/computer-aided manufacturing system described allows definitive preoperative planning and fabrication for treatment of skull bone tumors. Apparent benefits of the method include more accurate determination of surgical margins and better oncological outcomes.

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.

Three-dimensional (3D) synthetic printing for the manufacture of non-biodegradable models, tools and implants used in surgery: a review of current methods

The advent of three-dimensional (3D) printing in the 1980s ushered in a new era of manufacturing. Original 3D printers were large, expensive and difficult to operate, but recent advances in 3D printer technologies have drastically increased the accessibility of these machines such that individual surgical departments can now afford their own 3D printers. As adoption of 3D printing technology has increased within the medical industry so too has the number of 3D printable materials. Selection of the appropriate printer and material for a given application can be a daunting task for any clinician. This review seeks to describe the benefits and drawbacks of different 3D printing technologies and the materials used therein. Commercially available printers using fused deposition modelling or fused filament fabrication technology and relatively inexpensive thermoplastic materials have enabled rapid manufacture of anatomic models and intraoperative tools as well as implant prototyping. Titanium alloys remain the gold-standard material for various implants used in the fixation of craniofacial or extremity fractures, but polymers and ceramics are showing increasing promise for these types of applications. An understanding of these materials and their compatibility with various 3D printers is essential for application of this technology in a healthcare setting.

Challenges on optimization of 3D-printed bone scaffolds

Advances in biomaterials and the need for patient-specific bone scaffolds require modern manufacturing approaches in addition to a design strategy. Hybrid materials such as those with functionally graded properties are highly needed in tissue replacement and repair. However, their constituents, proportions, sizes, configurations and their connection to each other are a challenge to manufacturing. On the other hand, various bone defect sizes and sites require a cost-effective readily adaptive manufacturing technique to provide components (scaffolds) matching with the anatomical shape of the bone defect. Additive manufacturing or three-dimensional (3D) printing is capable of fabricating functional physical components with or without porosity by depositing the materials layer-by-layer using 3D computer models. Therefore, it facilitates the production of advanced bone scaffolds with the feasibility of making changes to the model. This review paper first discusses the development of a computer-aided-design (CAD) approach for the manufacture of bone scaffolds, from the anatomical data acquisition to the final model. It also provides information on the optimization of scaffold's internal architecture, advanced materials, and process parameters to achieve the best biomimetic performance. Furthermore, the review paper describes the advantages and limitations of 3D printing technologies applied to the production of bone tissue scaffolds.

Cumulative Inaccuracies in Implementation of Additive Manufacturing Through Medical Imaging, 3D Thresholding, and 3D Modeling: A Case Study for an End-Use Implant

In craniomaxillofacial surgical procedures, an emerging practice adopts the preoperative virtual planning that uses medical imaging (computed tomography), 3D thresholding (segmentation), 3D modeling (digital design), and additive manufacturing (3D printing) for the procurement of an end-use implant. The objective of this case study was to evaluate the cumulative spatial inaccuracies arising from each step of the process chain when various computed tomography protocols and thresholding values were independently changed. A custom-made quality assurance instrument (Phantom) was used to evaluate the medical imaging error. A sus domesticus (domestic pig) head was analyzed to determine the 3D thresholding error. The 3D modeling error was estimated from the computer-aided design software. Finally, the end-use implant was used to evaluate the additive manufacturing error. The results were verified using accurate measurement instruments and techniques. A worst-case cumulative error of 1.7 mm (3.0%) was estimated for one boundary condition and 2.3 mm (4.1%) for two boundary conditions considering the maximum length (56.9 mm) of the end-use implant. Uncertainty from the clinical imaging to the end-use implant was 0.8 mm (1.4%). This study helps practitioners establish and corroborate surgical practices that are within the bounds of an appropriate accuracy for clinical treatment and restoration.

Characterization of a composite polylactic acid-hydroxyapatite 3D-printing filament for bone-regeneration

Autologous cancellous-bone grafts are the current gold standard for therapeutic interventions in which bone-regeneration is desired. The main limitations of these implants are the need for a secondary surgical site, creating a wound on the patient, the limited availability of harvest-safe bone, and the lack of structural integrity of the grafts. Synthetic, resorbable, bone-regeneration materials could pose a viable treatment alternative, that could be implemented through 3D-printing. We present here the development of a polylactic acid-hydroxyapatite (PLA-HAp) composite that can be processed through a commercial-grade 3D-printer. We have shown that this material could be a viable option for the development of therapeutic implants for bone regeneration. Biocompatibility in vitro was demonstrated through cell viability studies using the osteoblastic MG63 cell-line, and we have also provided evidence that the presence of HAp in the polymer matrix enhances cell attachment and osteogenicity of the material. We have also provided guidelines for the optimal PLA-HAp ratio for this application, as well as further characterisation of the mechanical and thermal properties of the composite. This study encompasses the base for further research on the possibilities and safety of 3D-printable, polymer-based, resorbable composites for bone regeneration.

Orbital floor repair using patient specific osteoinductive implant made by stereolithography

The orbital floor (OF) is an anatomical location in the craniomaxillofacial (CMF) region known to be highly variable in shape and size. When fractured, implants commonly consisting of titanium meshes are customized by plying and crude hand-shaping. Nevertheless, more precise customized synthetic grafts are needed to meticulously reconstruct the patients' OF anatomy with better fidelity. As alternative to titanium mesh implants dedicated to OF repair, we propose a flexible patient-specific implant (PSI) made by stereolithography (SLA), offering a high degree of control over its geometry and architecture. The PSI is made of biodegradable poly(trimethylene carbonate) (PTMC) loaded with 40 wt % of hydroxyapatite (called Osteo-PTMC). In this work, we developed a complete work-flow for the additive manufacturing of PSIs to be used to repair the fractured OF, which is clinically relevant for individualized medicine. This work-flow consists of (i) the surgical planning, (ii) the design of virtual PSIs and (iii) their fabrication by SLA, (iv) the monitoring and (v) the biological evaluation in a preclinical large-animal model. We have found that once implanted, titanium meshes resulted in fibrous tissue encapsulation, whereas Osteo-PMTC resulted in rapid neovascularization and bone morphogenesis, both ectopically and in the OF region, and without the need of additional biotherapeutics such as bone morphogenic proteins. Our study supports the hypothesis that the composite osteoinductive Osteo-PTMC brings advantages compared to standard titanium mesh, by stimulating bone neoformation in the OF defects. PSIs made of Osteo-PTMC represent a significant advancement for patients whereby the anatomical characteristics of the OF defect restrict the utilization of traditional hand-shaped titanium mesh.

Restoration of the inferomedial orbital strut using a standardized three-dimensional printing implant

The inferomedial orbital strut (IOS) is the thin bony junction of the orbital medial wall and floor. Its fracture is common and leads to serious complications, including enophthalmos, globe dystopia and diplopia. However, anatomical restoration of the IOS is challenging owing to reduced structural support; sound anatomical background and accurate implants are therefore essential. The aim of the present study was to incorporate data from cadaveric orbit anatomy into three-dimensional (3D) printing technology and to reconstruct the complex orbital fracture elaborately. After averaging the data from computed tomography (CT) images of 100 adult cadavers, the dimensions of the IOS were extracted, and a tangent sphere was created using a computer-aided design program. The curves were compared with the CT data of 10 adult patients from the simulation test. Based on these data, a standardized 3D implant, 1.15 mm thick, was designed using polycaprolactone. The implant was placed in five patients with complex orbital fractures. The radius of the sphere in contact with the orbit, measuring 33.54 mm, was confirmed to be appropriate. A comparison between the normal side volume (V0) and the postoperative volume (V_post ) showed that they were statistically similar. Furthermore, a comparison between V0 and the preoperative volume (V_pre ), and V_post compared with V_pre also showed a statistically significant difference (P < 0.05). On follow-up, the preoperative ocular symptoms were resolved. The orbital data obtained from 100 cadavers provided standardized orbital anatomy, and 3D printed implants were created. The implants were anatomically accurate with regard to the orbital cavity and adequately covered the simulation model. The implant also showed satisfactory results when applied clinically in actual patients.

Segmentation of dental cone-beam CT scans affected by metal artifacts using a mixed-scale dense convolutional neural network

PURPOSE

In order to attain anatomical models, surgical guides and implants for computer-assisted surgery, accurate segmentation of bony structures in cone-beam computed tomography (CBCT) scans is required. However, this image segmentation step is often impeded by metal artifacts. Therefore, this study aimed to develop a mixed-scale dense convolutional neural network (MS-D network) for bone segmentation in CBCT scans affected by metal artifacts.

METHOD

Training data were acquired from 20 dental CBCT scans affected by metal artifacts. An experienced medical engineer segmented the bony structures in all CBCT scans using global thresholding and manually removed all remaining noise and metal artifacts. The resulting gold standard segmentations were used to train an MS-D network comprising 100 convolutional layers using far fewer trainable parameters than alternative convolutional neural network (CNN) architectures. The bone segmentation performance of the MS-D network was evaluated using a leave-2-out scheme and compared with a clinical snake evolution algorithm and two state-of-the-art CNN architectures (U-Net and ResNet). All segmented CBCT scans were subsequently converted into standard tessellation language (STL) models and geometrically compared with the gold standard.

RESULTS

CBCT scans segmented using the MS-D network, U-Net, ResNet and the snake evolution algorithm demonstrated mean Dice similarity coefficients of 0.87 ± 0.06, 0.87 ± 0.07, 0.86 ± 0.05, and 0.78 ± 0.07, respectively. The STL models acquired using the MS-D network, U-Net, ResNet and the snake evolution algorithm demonstrated mean absolute deviations of 0.44 mm ± 0.13 mm, 0.43 mm ± 0.16 mm, 0.40 mm ± 0.12 mm and 0.57 mm ± 0.22 mm, respectively. In contrast to the MS-D network, the ResNet introduced wave-like artifacts in the STL models, whereas the U-Net incorrectly labeled background voxels as bone around the vertebrae in 4 of the 9 CBCT scans containing vertebrae.

CONCLUSION

The MS-D network was able to accurately segment bony structures in CBCT scans affected by metal artifacts.

Applications of three-dimensional printing in orbital diseases and disorders

PURPOSE OF REVIEW

To comprehensively review the applications of advanced three-dimensional printing technology in the management of orbital abnormalities.

RECENT FINDINGS

Three-dimensional printing has added value in the preoperative planning and manufacturing of patient-specific implants and surgical guides in the reconstruction of orbital trauma, congenital defects and tumor resection. In view of the costs and time, it is reserved as strategy for large and complex craniofacial cases, in particular those including the bony contour. There is anecdotal evidence of a benefit of three-dimensional printing in the manufacturing of prostheses for the exenterated and anophthalmic socket, and in the fabrication of patient-specific boluses, applicators and shielding devices for orbital radiation therapy. In addition, three-dimensional printed healthy and diseased orbits as phantom tangible models may augment the teaching and learning process of orbital surgery.

SUMMARY

Three-dimensional printing allows precision treatment tailored to the unique orbital anatomy of the patient. Advancement in technology and further research are required to support its wider use in orbital clinical practice.

Computer-Aided Design and Computer-Aided Manufacturing Cutting Guides in Eminoplasty for the Treatment of Temporomandibular Joint Dislocation

OBJECTIVE

Temporomandibular joint (TMJ) dislocation means the condyle moves out of the normal position. There are several treatments for TMJ dislocation, including conservative treatment, injection treatment, minimally invasive treatment, and open surgical treatment. In this study, we tried to review the literature related to the augmentation of the articular eminence and proposed a modified eminoplasty technique of TMJ dislocation by computer-aided design and computer-aided manufacturing (CAD/CAM) cutting guides.

METHODS

The literature on eminoplasty for TMJ was reviewed with 3 charts. Besides, 2 (67 and 69 years old) patients with chronic recurrent dislocation were treated by the CAD/CAM-guided surgical technique in our study, and postoperative measures were recorded to verify the safety and effectiveness regarding this technique.

RESULTS

A total of 28 studies (including 268 patients) of the augmentation of the articular eminence have been reported since 1967, including the 2 present patients. According to the analysis of the recurrence and complications in the review, we found the modified technique had an obvious advantage. The technique with cutting guides was also found having higher accuracy.

CONCLUSION

The modified technique was a reliable method when treating the TMJ dislocation, and the combination of CAD/CAM cutting guides was useful for more accuracy, even reduced the operation difficulty.

Intensity of artefacts in cone beam CT examinations caused by titanium and glass fibre-reinforced composite implants

OBJECTIVES:

The aim was to compare titanium and glass fibre-reinforced composite (FRC) orbital floor implants using cone beam CT (CBCT). FRC implants are nonmetallic and these implants have not been analysed in CBCT images before. The purpose of this study is to compare the artefact formation of the titanium and the FRC orbital floor implants in CBCT images.

METHODS:

One commercially pure titanium and one S-glass FRC with bioactive glass particles implant were imaged with CBCT using the same imaging values (80 kV, 1 mA, FOV 60 × 60 mm). CBCT images were analysed in axial slices from three areas to determine the magnitude of the artefacts in the vicinity of the implants. Quantified results based on the gray values of images were analysed using analysis-of-variance.

RESULTS:

Compared to the reference the gray values of the titanium implant are more negative in every region of interest in all slices (p < 0.05) whereas the gray values of the FRC implant differ statistically significantly in less than half of the examined areas.

CONCLUSIONS:

The titanium implant caused artefacts in all of the analysed CBCT slices. Compared to the reference the gray values of the FRC implant changed only slightly and this feature enables to use wider imaging options postoperatively.

Three-dimensional printing of a patient-specific engineered nasal cartilage for augmentative rhinoplasty

Autologous cartilages or synthetic nasal implants have been utilized in augmentative rhinoplasty to reconstruct the nasal shape for therapeutic and cosmetic purposes. Autologous cartilage is considered to be an ideal graft, but has drawbacks, such as limited cartilage source, requirements of additional surgery for obtaining autologous cartilage, and donor site morbidity. In contrast, synthetic nasal implants are abundantly available but have low biocompatibility than the autologous cartilages. Moreover, the currently used nasal cartilage grafts involve additional reshaping processes, by meticulous manual carving during surgery to fit the diverse nose shape of each patient. The final shapes of the manually tailored implants are highly dependent on the surgeons' proficiency and often result in patient dissatisfaction and even undesired separation of the implant. This study describes a new process of rhinoplasty, which integrates three-dimensional printing and tissue engineering approaches. We established a serial procedure based on computer-aided design to generate a three-dimensional model of customized nasal implant, and the model was fabricated through three-dimensional printing. An engineered nasal cartilage implant was generated by injecting cartilage-derived hydrogel containing human adipose-derived stem cells into the implant containing the octahedral interior architecture. We observed remarkable expression levels of chondrogenic markers from the human adipose-derived stem cells grown in the engineered nasal cartilage with the cartilage-derived hydrogel. In addition, the engineered nasal cartilage, which was implanted into mouse subcutaneous region, exhibited maintenance of the exquisite shape and structure, and striking formation of the cartilaginous tissues for 12 weeks. We expect that the developed process, which combines computer-aided design, three-dimensional printing, and tissue-derived hydrogel, would be beneficial in generating implants of other types of tissue.

Implantation of Customized, Preshaped Implant for Orbital Fractures with the Aid of Three-dimensional Printing

Orbital floor fractures alone or in conjunction with other facial skeletal fractures are the most commonly encountered midfacial fractures. The technological advances in 3-dimensional (3D) printing allow the physical prototyping of 3D models, so creates an accurate representation of the patient's specific anatomy. A 56-year-old Caucasian man with severe hypoglobus and enophthalmos with an extensive blowout fracture was scheduled for reconstruction. First, 3D physical models were created based on the computed tomography scan datasets from patient. Then, this model was used as templates for preoperative trimming the implant. Surgical reconstruction with the aid of pre-shaped, customized prosthesis based on 3D anatomical model resulted in significant esthetic and clinical improvement. It is possible to build anatomical models on the basis of computed tomography scan datasets. It is relatively inexpensive and can be used in the repair of complex orbital floor fractures.

Craniomaxillofacial patient-specific CAD/CAM implants based on cone-beam tomography data - A feasibility study

Customized implants have simplified surgical procedures and have improved patient outcome in craniomaxillofacial surgery. Traditionally, patient-specific data is gathered by conventional computed tomography (CT). However, cone-beam CT (CBCT) can generate a 3D reconstruction of the area of interest with a lower dose of radiation at reduced cost. In this study, we investigated the feasibility of using CBCT data to design and generate customized implants for patients requiring craniomaxillofacial reconstruction. We used CBCT to generate 62 implants for 51 consecutive patients admitted to our department between January 2015 and December 2017. The indications for reconstruction and types of reconstruction were very variable. In all cases, the implants were well fitted and no implant-related complications were detected. Pre-surgical planning was faster and more efficient as we did not have to consult a radiologist. Although CBCT data is more difficult to process than conventional CT data for the implant provider, the clinical advantages are pronounced and we now use CBCT as standard in our department. In conclusion, we have shown that using CBCT to design and manufacture customized implants for reconstruction of the craniomaxillofacial area is feasible and recommend this approach to other departments.

Application of quality by design for 3D printed bone prostheses and scaffolds

3D printing is an emergent manufacturing technology recently being applied in the medical field for the development of custom bone prostheses and scaffolds. However, successful industry transformation to this new design and manufacturing approach requires technology integration, concurrent multi-disciplinary collaboration, and a robust quality management framework. This latter change enabler is the focus of this study. While a number of comprehensive quality frameworks have been developed in recent decades to ensure that the manufacturing of medical devices produces reliable products, they are centred on the traditional context of standardised manufacturing techniques. The advent of 3D printing technologies and the prospects for mass customisation provides significant market opportunities, but also presents a serious challenge to regulatory bodies tasked with managing and assuring product quality and safety. Before 3D printing bone prostheses and scaffolds can gain traction, industry stakeholders, such as regulators, clients, medical practitioners, insurers, lawyers, and manufacturers, would all require a high degree of confidence that customised manufacturing can achieve the same quality outcomes as standardised manufacturing. A Quality by Design (QbD) approach to custom 3D printed prostheses can help to ensure that products are designed and manufactured correctly from the beginning without errors. This paper reports on the adaptation of the QbD approach for the development process of 3D printed custom bone prosthesis and scaffolds. This was achieved through the identification of the Critical Quality Attributes of such products, and an extensive review of different design and fabrication methods for 3D printed bone prostheses. Research outcomes include the development of a comprehensive design and fabrication process flow diagram, and categorised risks associated with the design and fabrication processes of such products. An extensive systematic literature review and post-hoc evaluation survey with experts was completed to evaluate the likely effectiveness of the herein suggested QbD framework.

Influences of geometrical and mechanical properties of bone tissues in mandible behaviour - experimental and numerical predictions

The properties and geometry of bone in the mandible play a key role in mandible behaviour during a person's lifetime, and attention needs to be paid to the influence of bone properties. We analysed the effect of bone geometry, size and bone properties in mandible behaviour, experimenting on cadaveric mandibles and FE models. The study was developed using the geometry of a cadaveric mandible without teeth. Three models of cadaveric condyles were experimentally tested with instrumented with four rosettes, and a condyle reaction of 300 N. Four finite element models were considered to validate the experiments and analyse mandible behaviour. One numeric model was simulated with 10 muscles in a quasi-static condition. The experimental results present different condyle stiffness's, of 448, 215 and 254 N/mm. The values presented in the rosettes are influenced by bone geometry and bone thickness; maximum value was -600 με in rosette #4, and the maximum strain difference between mandibles was 111%. The numerical results show that bone density decreases and strain distribution increases in the thinner mandible regions. Nevertheless, the global behaviour of the structure remains similar, but presents different strain magnitudes. The study shows the need to take into account bone characteristics and their evolutions in order to improve implant design and fixation throughout the patient life. The change in bone stiffness promotes a change in maximum strain distribution with same global behaviour.

3D printing: clinical applications in orthopaedics and traumatology

Advances in image processing have led to the clinical use of 3D printing technology, giving the surgeon a realistic physical model of the anatomy upon which he or she will operate.

Relying on CT images, the surgeon creates a virtual 3D model of the target anatomy from a series of bi-dimensional images, translating the information contained in CT images into a more usable format.

3D printed models can play a central role in surgical planning and in the training of novice surgeons, as well as reducing the rate of re-operation.

Cite this article: Auricchio F, Marconi S. 3D printing: clinical applications in orthopaedics and traumatology. EFORT Open Rev 2016;1:121–127. DOI: 10.1302/2058-5241.1.000012.

The use of patient-specific implants in orthognathic surgery: A series of 30 mandible sagittal split osteotomy patients

PURPOSE

Virtual surgery combined with patient-specific saw and drill guides and osteosynthesis materials are rapidly spreading from reconstructive surgery to orthognathic surgery. Most commercial partners are already providing computer-aided design and computer-aided manufacture (CAD/CAM) wafers and patient-specific saw guides. Clear benefits have been demonstrated for custom-made drill guides combined with individually designed three-dimensional (3D) printed patient-specific implants (PSI) as a reposition and fixation system in Le Fort I osteotomy.

MATERIALS AND METHODS

We treated 30 patients who underwent bilateral sagittal split osteotomy (BSSO) due to class II dento-skeletal deformities with the additional use of drill guides combined with PSI as a fixation and positioning system.

RESULTS

The PSIs fitted bilaterally with total precision in 11 of the 30 patients. In 17 patients, the PSIs were used with some modifications. In 2 of 30 patients, the PSIs could not be used as a fixation due to misfit.

CONCLUSION

Due to unpredictable fitting, the use of PSIs with drill guides alone in BSSO without wafers cannot be recommended. Further studies are needed to evaluate the interfering parts, which seem to be related to condylar positioning and bony interferences at the osteotomy sites.

Evolution of design considerations in complex craniofacial reconstruction using patient-specific implants

Previously published evidence has established major clinical benefits from using computer-aided design, computer-aided manufacturing, and additive manufacturing to produce patient-specific devices. These include cutting guides, drilling guides, positioning guides, and implants. However, custom devices produced using these methods are still not in routine use, particularly by the UK National Health Service. Oft-cited reasons for this slow uptake include the following: a higher up-front cost than conventionally fabricated devices, material-choice uncertainty, and a lack of long-term follow-up due to their relatively recent introduction. This article identifies a further gap in current knowledge – that of design rules, or key specification considerations for complex computer-aided design/computer-aided manufacturing/additive manufacturing devices. This research begins to address the gap by combining a detailed review of the literature with first-hand experience of interdisciplinary collaboration on five craniofacial patient case studies. In each patient case, bony lesions in the orbito-temporal region were segmented, excised, and reconstructed in the virtual environment. Three cases translated these digital plans into theatre via polymer surgical guides. Four cases utilised additive manufacturing to fabricate titanium implants. One implant was machined from polyether ether ketone. From the literature, articles with relevant abstracts were analysed to extract design considerations. In all, 19 frequently recurring design considerations were extracted from previous publications. Nine new design considerations were extracted from the case studies – on the basis of subjective clinical evaluation. These were synthesised to produce a design considerations framework to assist clinicians with prescribing and design engineers with modelling. Promising avenues for further research are proposed.