Establishing 3D Printing at the Point of Care: Basic Principles and Tools for Success.

As the medical applications of three-dimensional (3D) printing increase, so does the number of health care organizations in which adoption or expansion of 3D printing facilities is under consideration. With recent advancements in 3D printing technology, medical practitioners have embraced this powerful tool to help them to deliver high-quality patient care, with a focus on sustainability. The use of 3D printing in the hospital or clinic at the point of care (POC) has profound potential, but its adoption is not without unanticipated challenges and considerations. The authors provide the basic principles and considerations for building the infrastructure to support 3D printing inside the hospital. This process includes building a business case; determining the requirements for facilities, space, and staff; designing a digital workflow; and considering how electronic health records may have a role in the future. The authors also discuss the supported applications and benefits of medical 3D printing and briefly highlight quality and regulatory considerations. The information presented is meant to be a practical guide to assist radiology departments in exploring the possibilities of POC 3D printing and expanding it from a niche application to a fixture of clinical care. An invited commentary by Ballard is available online. ©RSNA, 2022.

Time and Accuracy of the CEREC Omnicam Using Two Different Software Programs.

PURPOSE: The purpose of this in vitro study was to evaluate the effect of software on scan time, trueness, and precision of digital scans created using the CEREC Omnicam. MATERIAL AND METHODS: Sixty scans (20 scans/provider) of a standard reference cast were made by three different providers using the CEREC Omnicam with both CEREC Ortho 1.2.1 software (10 scans/provider) and CEREC SW 4.4.4 software (10 scans/provider). A digital full arch scan and the time to complete each scan were recorded. Trueness was calculated by overlaying the digital scans against a reference file created using the standard reference cast and a laboratory-based, white light, 3-dimensional scanner. Precision was calculated by overlaying each of digital scans against each other, using each scan as a reference. The non-parametric Mann-Whitney U-test was used to determine significant differences attributable to scanning software for each provider. RESULTS: The CEREC Ortho 1.2.1 software required a longer scan time than the CEREC SW 4.4.4 software for each provider (∼1 minute). No significant difference in trueness was observed within one provider. Two individual providers had higher precision when scanning with the CEREC Ortho 1.2.1 software than the CEREC SW 4.4.4 software. CONCLUSION: Software and scan strategy may affect the accuracy of complete-arch scans. The CEREC Ortho 1.2.1 software may demonstrate a speed-accuracy tradeoff, with generally longer scan times and possibly more precise scans.

Retentive Forces of Removable Partial Denture Clasp Assemblies Made from Polyaryletherketone and Cobalt-Chromium: A Comparative Study.

PURPOSE: To compare retentive forces of removable partial denture clasps traditionally fabricated with cobalt-chromium (CoCr) material and two computer-aided design and computer-aided manufactured (CAD/CAM) thermoplastic polymers. MATERIALS AND METHODS: Forty-eight clasp assemblies (16 CoCr, 16 polyetheretherketone (PEEK) and 16 polyetherketoneketone (PEKK) thermoplastic polymer) were fabricated for 48 mandibular tooth analogs. Individual clasps were inserted and removed on the tooth analogs utilizing a chewing simulator for 15,000 cycles to simulate 10 years of use. Retentive forces were measured utilizing a mechanical load tester at baseline and intervals of 1500 cycles. Data were analyzed with one-way Analysis of Variance, Tukey post-hoc, and paired T tests. RESULTS: Mean retentive forces between all groups were significantly different (p < 0.001). Retentive forces of CoCr clasps were significantly higher than both polymers (p < 0.001). The mean retentive forces for PEEK were not significantly different from PEKK (p = 0.23). A significant increase in retentive forces was observed for all three clasps after the first period of cycling, followed by continual decrease for the remaining cycles. At the endpoint of 15,000 cycles, no clasp assemblies showed lower retentive forces than at initial baseline. CONCLUSION: Thermoplastic polymer clasps demonstrated lower retentive forces compared to CoCr clasps. All three groups displayed a similar pattern of initial increase, followed by a gradual decrease, of retentive force. Despite this observation, the clasps maintained similar or higher retentive forces than measured at baseline. This resistance to fatigue and ability to fabricate with CAD/CAM technologies provides support for clinical use of these high-performance polymer (HPP) materials.

RadioGraphics Update: Medical 3D Printing for the Radiologist.

Editor's Note.-Articles in the RadioGraphics Update section provide current knowledge to supplement or update information found in full-length articles previously published in RadioGraphics. Authors of the previously published article provide a brief synopsis that emphasizes important new information such as technological advances, revised imaging protocols, new clinical guidelines involving imaging, or updated classification schemes. Articles in this section are published solely online and are linked to the original article.

Physical Simulation Models in Oral and Maxillofacial Surgery: A New Concept in 3-Dimensional Modeling for Removal of Impacted Third Molars.

A medical-grade computed tomography scan of a mandible was obtained. A DICOM (Digital Imaging and Communications in Medicine) series was exported in 1-mm slices and digitally 3-dimensionally reconstructed to create a stereolithography file. The mandible stereolithography file was digitally manipulated to create sites for simulated placement of third molar teeth and then 3-dimensionally printed in a plastic material. Third molar tooth models were coated in red box wax, simulating a ligament space, and then submerged into the mandible site using laboratory stone. A layer of GI-Mask (Coltene/Whaldent AG, Altstätten, Switzerland) was placed over the impacted third molar site for soft tissue simulation.

CT-Based 3D Printing of the Glenoid Prior to Shoulder Arthroplasty: Bony Morphology and Model Evaluation.

To demonstrate the 3D printed appearance of glenoid morphologies relevant to shoulder replacement surgery and to evaluate the benefits of printed models of the glenoid with regard to surgical planning. A retrospective review of patients referred for shoulder CT was performed, leading to a cohort of nine patients without arthroplasty hardware and exhibiting glenoid changes relevant to shoulder arthroplasty planning. Thin slice CT images were used to create both humerus-subtracted volume renderings of the glenoid, as well as 3D surface models of the glenoid, and 11 printed models were created. Volume renderings, surface models, and printed models were reviewed by a musculoskeletal radiologist for accuracy. Four fellowship-trained orthopaedic surgeons specializing in shoulder surgery reviewed each case individually as follows: First, the source CT images were reviewed, and a score for the clarity of the bony morphologies relevant to shoulder arthroplasty surgery was given. The volume rendering was reviewed, and the clarity was again scored. Finally, the printed model was reviewed, and the clarity again scored. Each printed model was also scored for morphologic complexity, expected usefulness of the printed model, and physical properties of the model. Mann-Whitney-Wilcoxon signed rank tests of the clarity scores were calculated, and the Spearman's ρ correlation coefficient between complexity and usefulness scores was computed. Printed models demonstrated a range of glenoid bony changes including osteophytes, glenoid bone loss, retroversion, and biconcavity. Surgeons rated the glenoid morphology as more clear after review of humerus-subtracted volume rendering, compared with review of the source CT images (p = 0.00903). Clarity was also better with 3D printed models compared to CT (p = 0.00903) and better with 3D printed models compared to humerus-subtracted volume rendering (p = 0. 00879). The expected usefulness of printed models demonstrated a positive correlation with morphologic complexity, with Spearman's ρ 0.73 (p = 0.0108). 3D printing of the glenoid based on pre-operative CT provides a physical representation of patient anatomy. Printed models enabled shoulder surgeons to appreciate glenoid bony morphology more clearly compared to review of CT images or humerus-subtracted volume renderings. These models were more useful as glenoid complexity increased.

Complete-arch accuracy of intraoral scanners.

STATEMENT OF PROBLEM: Intraoral scanners have shown varied results in complete-arch applications. PURPOSE: The purpose of this in vitro study was to evaluate the complete-arch accuracy of 4 intraoral scanners based on trueness and precision measurements compared with a known reference (trueness) and with each other (precision). MATERIAL AND METHODS: Four intraoral scanners were evaluated: CEREC Bluecam, CEREC Omnicam, TRIOS Color, and Carestream CS 3500. A complete-arch reference cast was created and printed using a 3-dimensional dental cast printer with photopolymer resin. The reference cast was digitized using a laboratory-based white light 3-dimensional scanner. The printed reference cast was scanned 10 times with each intraoral scanner. The digital standard tessellation language (STL) files from each scanner were then registered to the reference file and compared with differences in trueness and precision using a 3-dimensional modeling software. Additionally, scanning time was recorded for each scan performed. The Wilcoxon signed rank, Kruskal-Wallis, and Dunn tests were used to detect differences for trueness, precision, and scanning time (α=.05). RESULTS: Carestream CS 3500 had the lowest overall trueness and precision compared with Bluecam and TRIOS Color. The fourth scanner, Omnicam, had intermediate trueness and precision. All of the scanners tended to underestimate the size of the reference file, with exception of the Carestream CS 3500, which was more variable. Based on visual inspection of the color rendering of signed differences, the greatest amount of error tended to be in the posterior aspects of the arch, with local errors exceeding 100 µm for all scans. The single capture scanner Carestream CS 3500 had the overall longest scan times and was significantly slower than the continuous capture scanners TRIOS Color and Omnicam. CONCLUSIONS: Significant differences in both trueness and precision were found among the scanners. Scan times of the continuous capture scanners were faster than the single capture scanners.

Three-dimensional printing of MRI-visible phantoms and MR image-guided therapy simulation.

PURPOSE: To demonstrate the use of anatomic MRI-visible three-dimensional (3D)-printed phantoms and to assess process accuracy and material MR signal properties. METHODS: A cervical spine model was generated from computed tomography (CT) data and 3D-printed using an MR signal-generating material. Printed phantom accuracy and signal characteristics were assessed using 120 kVp CT and 3 Tesla (T) MR imaging. The MR relaxation rates and diffusion coefficient of the fabricated phantom were measured and 1 H spectra were acquired to provide insight into the nature of the proton signal. Finally, T2 -weighted imaging was performed during cryoablation of the model. RESULTS: The printed model produced a CT signal of 102 ± 8 Hounsfield unit, and an MR signal roughly 1/3rd that of saline in short echo time/short repetition time GRE MRI (456 ± 36 versus 1526 ± 121 arbitrary signal units). Compared with the model designed from the in vivo CT scan, the printed model differed by 0.13 ± 0.11 mm in CT, and 0.62 ± 0.28 mm in MR. The printed material had T2 ∼32 ms, T2*∼7 ms, T1 ∼193 ms, and a very small diffusion coefficient less than olive oil. MRI monitoring of the cryoablation demonstrated iceball formation similar to an in vivo procedure. CONCLUSION: Current 3D printing technology can be used to print anatomically accurate phantoms that can be imaged by both CT and MRI. Such models can be used to simulate MRI-guided interventions such as cryosurgeries. Future development of the proposed technique can potentially lead to printed models that depict different tissues and anatomical structures with different MR signal characteristics. Magn Reson Med 77:613-622, 2017. © 2016 International Society for Magnetic Resonance in Medicine.

Measuring and Establishing the Accuracy and Reproducibility of 3D Printed Medical Models.

Despite the rapid growth of three-dimensional (3D) printing applications in medicine, the accuracy and reproducibility of 3D printed medical models have not been thoroughly investigated. Although current technologies enable 3D models to be created with accuracy within the limits of clinical imaging spatial resolutions, this is not always achieved in practice. Inaccuracies are due to errors that occur during the imaging, segmentation, postprocessing, and 3D printing steps. Radiologists' understanding of the factors that influence 3D printed model accuracy and the metrics used to measure this accuracy is key in directing appropriate practices and establishing reference standards and validation procedures. The authors review the various factors in each step of the 3D model printing process that contribute to model inaccuracy, including the intrinsic limitations of each printing technology. In addition, common sources of model inaccuracy are illustrated. Metrics involving comparisons of model dimensions and morphology that have been developed to quantify differences between 3D models also are described and illustrated. These metrics can be used to define the accuracy of a model, as compared with the reference standard, and to measure the variability of models created by different observers or using different workflows. The accuracies reported for specific indications of 3D printing are summarized, and potential guidelines for quality assurance and workflow assessment are discussed. Online supplemental material is available for this article. ©RSNA, 2017.

A Craniomaxillofacial Surgical Assistance Workstation for Enhanced Single-Stage Reconstruction Using Patient-Specific Implants.

BACKGROUND: Craniomaxillofacial reconstruction with patient-specific, customized craniofacial implants (CCIs) is ideal for skeletal defects involving areas of aesthetic concern-the non-weight-bearing facial skeleton, temporal skull, and/or frontal-forehead region. Results to date are superior to a variety of "off-the-shelf" materials, but require a protocol computed tomography scan and preexisting defect for computer-assisted design/computer-assisted manufacturing of the CCI. The authors developed a craniomaxillofacial surgical assistance workstation to address these challenges and intraoperatively guide CCI modification for an unknown defect size/shape. METHODS: First, the surgeon designed an oversized CCI based on his/her surgical plan. Intraoperatively, the surgeon resected the bone and digitized the resection using a navigation pointer. Next, a projector displayed the limits of the craniofacial bone defect onto the prefabricated, oversized CCI for the size modification process; the surgeon followed the projected trace to modify the implant. A cadaveric study compared the standard technique (n = 1) to the experimental technique (n = 5) using surgical time and implant fit. RESULTS: The technology reduced the time and effort needed to resize the oversized CCI by an order of magnitude as compared with the standard manual resizing process. Implant fit was consistently better for the computer-assisted case compared with the control by at least 30%, requiring only 5.17 minutes in the computer-assisted cases compared with 35 minutes for the control. CONCLUSION: This approach demonstrated improvement in surgical time and accuracy of CCI-based craniomaxillofacial reconstruction compared with previously reported methods. The craniomaxillofacial surgical assistance workstation will provide craniofacial surgeons a computer-assisted technology for effective and efficient single-stage reconstruction when exact craniofacial bone defect sizes are unknown.

Medical 3D Printing for the Radiologist.

While use of advanced visualization in radiology is instrumental in diagnosis and communication with referring clinicians, there is an unmet need to render Digital Imaging and Communications in Medicine (DICOM) images as three-dimensional (3D) printed models capable of providing both tactile feedback and tangible depth information about anatomic and pathologic states. Three-dimensional printed models, already entrenched in the nonmedical sciences, are rapidly being embraced in medicine as well as in the lay community. Incorporating 3D printing from images generated and interpreted by radiologists presents particular challenges, including training, materials and equipment, and guidelines. The overall costs of a 3D printing laboratory must be balanced by the clinical benefits. It is expected that the number of 3D-printed models generated from DICOM images for planning interventions and fabricating implants will grow exponentially. Radiologists should at a minimum be familiar with 3D printing as it relates to their field, including types of 3D printing technologies and materials used to create 3D-printed anatomic models, published applications of models to date, and clinical benefits in radiology. Online supplemental material is available for this article.

Digital capture, design, and manufacturing of a facial prosthesis: Clinical report on a pediatric patient.

A digitally captured, designed, and fabricated facial prosthesis is presented as an alternative to customary maxillofacial prosthodontics fabrication techniques, where a facial moulage and patient cooperation may be difficult.

Digital capture, design, and manufacturing of an extraoral device for a clarinet player with Bell's palsy.

An extraoral device was fabricated to assist a clarinet player with Bell's palsy. The device was fabricated by using stereophotogrammetry, digital design, and additive manufacturing technologies.

Restoration of the donor face after facial allotransplantation: digital manufacturing techniques.

INTRODUCTION: Current protocols for facial transplantation include the mandatory fabrication of an alloplastic "mask" to restore the congruency of the donor site in the setting of "open casket" burial. However, there is currently a paucity of literature describing the current state-of-the-art and available options. METHODS: During this study, we identified that most of donor masks are fabricated using conventional methods of impression, molds, silicone, and/or acrylic application by an experienced anaplastologist or maxillofacial prosthetics technician. However, with the recent introduction of several enhanced computer-assisted technologies, our facial transplant team hypothesized that there were areas for improvement with respect to cost and preparation time. RESULTS: The use of digital imaging for virtual surgical manipulation, computer-assisted planning, and prefabricated surgical cutting guides-in the setting of facial transplantation-provided us a novel opportunity for digital design and fabrication of a donor mask. The results shown here demonstrate an acceptable appearance for "open-casket" burial while maintaining donor identity after facial organ recovery. CONCLUSIONS: Several newer techniques for fabrication of facial transplant donor masks exist currently and are described within the article. These encompass digital impression, digital design, and additive manufacturing technology.

Preliminary development of a workstation for craniomaxillofacial surgical procedures: introducing a computer-assisted planning and execution system.

INTRODUCTION: Facial transplantation represents one of the most complicated scenarios in craniofacial surgery because of skeletal, aesthetic, and dental discrepancies between donor and recipient. However, standard off-the-shelf vendor computer-assisted surgery systems may not provide custom features to mitigate the increased complexity of this particular procedure. We propose to develop a computer-assisted surgery solution customized for preoperative planning, intraoperative navigation including cutting guides, and dynamic, instantaneous feedback of cephalometric measurements/angles as needed for facial transplantation and other related craniomaxillofacial procedures. METHODS: We developed the Computer-Assisted Planning and Execution (CAPE) workstation to assist with planning and execution of facial transplantation. Preoperative maxillofacial computed tomography (CT) scans were obtained on 4 size-mismatched miniature swine encompassing 2 live face-jaw-teeth transplants. The system was tested in a laboratory setting using plastic models of mismatched swine, after which the system was used in 2 live swine transplants. Postoperative CT imaging was obtained and compared with the preoperative plan and intraoperative measures from the CAPE workstation for both transplants. RESULTS: Plastic model tests familiarized the team with the CAPE workstation and identified several defects in the workflow. Live swine surgeries demonstrated utility of the CAPE system in the operating room, showing submillimeter registration error of 0.6 ± 0.24 mm and promising qualitative comparisons between intraoperative data and postoperative CT imaging. CONCLUSIONS: The initial development of the CAPE workstation demonstrated that integration of computer planning and intraoperative navigation for facial transplantation are possible with submillimeter accuracy. This approach can potentially improve preoperative planning, allowing ideal donor-recipient matching despite significant size mismatch, and accurate surgical execution for numerous types of craniofacial and orthognathic surgical procedures.

Development of Ventral Hernia Repair Curriculum Using the AWSSOM-a Synthetic Abdominal Wall Surgical Skills Operational Model.

INTRODUCTION: Ventral hernia repair cost the U.S. healthcare system nearly 3 billion dollars annually. Surgical repair is a critical competency for residents yet hernia recurrence rates following mesh-based repair range from 0.8% to 24%. Improving surgical techniques using cadavers is often cost-prohibited for many education programs and limited research exists using simulation models with a corresponding hernia repair curriculum in the graduate medical education setting. This pilot project aimed to develop a low cost, easily reproducible novel abdominal wall reconstruction model and pilot-test the ventral hernia repair curriculum to inform further refinement prior to formal evaluation. MATERIAL AND METHODS: This descriptive study pilot-tested the newly refined Abdominal Wall Surgical Skills Operative Model (AWSSOM) simulator for ventral hernia repair with mesh and its corresponding 2-h training curriculum for use at all levels of general surgery graduate medical education. The AWSSOM is a 3D printed synthetic anatomically realistic abdominal wall model consisting of silicone cured layers of skin, fat, rectus abdominis and a posterior rectus sheath fascia, and silicone tubules to simulate lateral neurovascular bundles. The curriculum incorporated didactic content reflecting surgical practice guidelines, hands-on practice, and faculty guidance promoting interactive critical thinking development during task performance. A pre-/post-assessment included a 10-item knowledge test, a 19-item psychomotor assessment, and 4-items confidence survey to examine changes in performance, knowledge, and confidence in competently completing the ventral hernia repair technique. Descriptive statistics were used to report the limited results of six military surgical resident participants and inform further model and curriculum refinement prior to formal evaluation. RESULTS: The five-layer AWSSOM model was manufactured in 65 h at a material cost of $87 per model frame, is reusable model, and secure base. Six surgical residents were recruited; only four completed both pre- and post-tests due to resident schedule conflicts. The average increase in knowledge was 25%, although variable changes in confidence were observed over the four program year participants. A larger sample size and a control group are needed to demonstrate curriculum effectiveness at improving knowledge, performance, and confidence in ventral hernia repair with mesh and better delineate if high scores translate to better operative skills. A key improvement requested by residents was a more secure model base for dissection and performance of the hernia repair. CONCLUSIONS: The novel abdominal wall surgical skills operative model fills an important proof of concept gap in simulation training. It is low cost with the potential to improve cognitive and psychomotor skills, as well as confidence to competently complete ventral hernia repair with mesh in the graduate medical education setting. Prior to formal effectiveness testing, our lessons learned should be addressed in both the model and curriculum. Future studies must include an adequately powered statistical evaluation with a larger sample across all levels of training.

Clinical situations for which 3D printing is considered an appropriate representation or extension of data contained in a medical imaging examination: pediatric congenital heart disease conditions.

BACKGROUND: The use of medical 3D printing (focusing on anatomical modeling) has continued to grow since the Radiological Society of North America's (RSNA) 3D Printing Special Interest Group (3DPSIG) released its initial guideline and appropriateness rating document in 2018. The 3DPSIG formed a focused writing group to provide updated appropriateness ratings for 3D printing anatomical models across a variety of congenital heart disease. Evidence-based- (where available) and expert-consensus-driven appropriateness ratings are provided for twenty-eight congenital heart lesion categories. METHODS: A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with pediatric congenital heart disease indications. Each study was vetted by the authors and strength of evidence was assessed according to published appropriateness ratings. RESULTS: Evidence-based recommendations for when 3D printing is appropriate are provided for pediatric congenital heart lesions. Recommendations are provided in accordance with strength of evidence of publications corresponding to each cardiac clinical scenario combined with expert opinion from members of the 3DPSIG. CONCLUSIONS: This consensus appropriateness ratings document, created by the members of the RSNA 3DPSIG, provides a reference for clinical standards of 3D printing for pediatric congenital heart disease clinical scenarios.

Overcoming cross-gender differences and challenges in Le Fort-based, craniomaxillofacial transplantation with enhanced computer-assisted technology.

BACKGROUND: Sex-specific anthropometrics, skin texture/adnexae mismatch, and social apprehension have prevented cross-gender facial transplantation from evolving. However, the scarce donor pool and extreme waitlist times are currently suboptimal. Our objective was to (1) perform and assess cadaveric facial transplantation for each sex-mismatched scenario using virtual planning with cutting guide fabrication and (2) review the advantages/disadvantages of cross-gender facial transplantation. METHODS: Cross-gender facial transplantation feasibility was evaluated through 2 mock, double-jaw, Le Fort-based cadaveric allotransplants, including female donor-to-male recipient and male donor-to-female recipient. Hybrid facial-skeletal relationships were investigated using cephalometric measurements, including sellion-nasion-A point and sellion-nasion-B point angles, and lower-anterior-facial-height to total-anterior-facial-height ratio. Donor and recipient cutting guides were designed with virtual planning based on our team's experience in swine dissections and used to optimize the results. RESULTS: Skeletal proportions and facial-aesthetic harmony of the transplants (n = 2) were found to be equivalent to all reported experimental/clinical sex-matched cases by using custom guides and Mimics technology. Cephalometric measurements relative to Eastman Normal Values are shown. CONCLUSIONS: On the basis of our results, we believe that cross-gender facial transplantation can offer equivalent, anatomical skeletal outcomes to those of sex-matched pairs using preoperative planning and custom guides for execution. Lack of literature discussion of cross-gender facial transplantation highlights the general stigmata encompassing the subject. We hypothesize that concerns over sex-specific anthropometrics, skin texture/adnexae disparity, and increased immunological resistance have prevented full acceptance thus far. Advantages include an increased donor pool with expedited reconstruction, as well as size-matched donors.

Cranioplasty in the deployed environment: experience for host-country nationals.

OBJECTIVE: Decompressive craniectomy (DC) is the definitive neurosurgical treatment for managing refractory malignant cerebral edema and intracranial hypertension due to combat-related severe traumatic brain injury (TBI). To date, the long-term outcomes and sequelae of this procedure on host-country national (HCN) populations during Operation Iraqi Freedom (Iraq, 2003-2011), Operation Enduring Freedom (Afghanistan, 2001-2014), and Operation Freedom's Sentinel (Afghanistan, 2015-2021) have not been described, specifically the process and results of delayed custom synthetic cranioplasty. The Joint Trauma System's Clinical Practice Guidelines (JTS-CPG) for severe head injury counsels surgeons to discard the cranial osseous explant when treating coalition service members. Ongoing political and healthcare system instabilities often preclude opportunities for delayed cranioplasty by host-country assets. Various surgical options (such as hinge craniectomy) are inadequate in the setting of complicated cranial comminution from blast or missile injuries, severe cerebral edema, grossly contaminated wounds, complex polytrauma, and tissue devitalization. Delayed cranioplasty with a custom synthetic implant is a viable but logistically challenging alternative. In this retrospective review, the authors present the first patient series describing delayed custom synthetic cranioplasty in an HCN population performed during active military conflict. METHODS: Patients were identified through the Joint Trauma System/Theater Medical Data Store, and subgroup analyses were performed to include mechanisms of injury, surgical complications, and clinical outcomes. RESULTS: Twenty-five patients underwent DC between 2012 and 2020 to treat penetrating, blast, and high-energy closed head injuries per JTS-CPG criteria. The average time from injury to surgery was 1.4 days, although 6 patients received delayed care (3-6 days) due to protracted evacuation from local hospitals. Delayed care correlated with an increased rate of intracranial abscess and empyema. The average time to cranioplasty was 134 days due to a lack of robust mechanisms for patient follow-up, tracking, and access to NATO hospitals. HCN patients who recovered from DC demonstrated overall benefit from custom synthetic cranioplasty, although formal statistical analysis was impeded by a lack of long-term follow-up. CONCLUSIONS: This review demonstrates that cranioplasty with a custom synthetic implant is a safe and feasible treatment for vulnerable HCN patients who survive their index DC surgery. This unique paradigm of care highlights the capabilities of deployed neurosurgical healthcare teams working in partnership with the prosthetics laboratory at Walter Reed National Military Medical Center.

Additive Manufacturing for Fabrication of Point-of-Care Therapies in Austere Environments.

INTRODUCTION: Known as the "golden hour," survival of most critically injured patients is highly dependent on providing the required treatment within the first hour of injury. Recent technological advances in additive manufacturing (also known as three-dimensional [3D] printing) allow for austere deployment and point-of-care rapid fabrication of a variety of medical supplies, including human tissues and bioactive bandages, in prolonged field care scenarios. In this pilot project, our aim was to investigate the ability to 3D print a range of potential biomedical supplies and solutions in an austere field environment. MATERIALS AND METHODS: We specifically designed and fabricated novel surgical tools, bioactive bandages, objects (screw and anatomic models), and human meniscal tissue in an austere African desert environment. A total of seven packages were sent using a commercial carrier directly to the end destination. A multi-tool ruggedized 3D printer was used as the manufacturing platform for all objects fabricated downrange. Human mesenchymal stem cells were shipped for 3D bioprinting of human menisci and bioactive bandages. Design and fabrication for all 3D-printed products utilized computer-aided design (CAD) tools. RESULTS: Initial shipment from a single U.S. site to the sub-Saharan Africa location was relatively prompt, taking an average of 4.7 days to deliver three test packages. However, the actual delivery of the seven packages from Orlando, FL, to the same sub-Saharan Africa site took an average of 16 days (range 7-23 days). The ruggedized printer successfully fabricated relevant medical supplies using biocompatible filament, bioink hydrogels, and stem cell-loaded bioinks. This prototype did not, however, have the capacity to provide a sterile environment. A multi-material complete bandage was 3D printed using polyamide polyolefin and cellulose, live cells, neomycin salve, and adhesive. The bandage, wound covering backing, and adhesive backing print took under 2 min to 3D print. Surgical instrument CAD files were based on commercially available medical-grade stainless-steel instruments. The screw CAD file was downloaded from the NIH 3D Print Exchange website. The prints of the two surgical tools and screw using thermoplastic material were successful. Menisci, relatively complex forms of the cartilage, were 3D bioprinted with a gel that held their form well after printing and were then solidified slightly using a cross-linking solution. After 2 min of solidification, it was possible to remove and handle the menisci. CONCLUSION: The current and future challenges of prolonged field care need to be addressed with new techniques, training, and technology. Ruggedized, deployable 3D printers allow for the direct fabrication of medical tools, supplies, and biological solutions for austere use. Delivery of packages can vary, and attention to routes and location is key, especially for transit of time-sensitive perishable supplies such as live cells. The significance of this study provides the real possibility to 3D print "just-in-time" medical solutions tailored to the need of an individual service member in any environment. This is a potentially exciting opportunity to bring critical products to the war front.