3D printing in medicine: current applications and future directions

Role of Three-Dimensional Printing in Treatment Planning for Orthognathic Surgery: A Systematic Review

Three-dimensional (3D) printing refers to a wide range of additive manufacturing processes that enable the construction of structures and models. It has been rapidly adopted for a variety of surgical applications, including the printing of patient-specific anatomical models, implants and prostheses, external fixators and splints, as well as surgical instrumentation and cutting guides. In comparison to traditional methods, 3D-printed models and surgical guides offer a deeper understanding of intricate maxillofacial structures and spatial relationships. This review article examines the utilization of 3D printing in orthognathic surgery, particularly in the context of treatment planning. It discusses how 3D printing has revolutionized this sector by providing enhanced visualization, precise surgical planning, reduction in operating time, and improved patient communication. Various databases, including PubMed, Google Scholar, ScienceDirect, and Medline, were searched with relevant keywords. A total of 410 articles were retrieved, of which 71 were included in this study. This article concludes that the utilization of 3D printing in the treatment planning of orthognathic surgery offers a wide range of advantages, such as increased patient satisfaction and improved functional and aesthetic outcomes.

3D-printed external fixation guide combined with video-assisted thoracoscopic surgery for the treatment of flail chest: a technical report and case series

Background

Flail chest is a common and serious traumatic condition in thoracic surgery. The treatment of flail chest often includes open reduction and internal fixation, which is relatively traumatic, complicated, and expensive. As three-dimensional (3D) printing technology is widely used in the clinical field, the application of 3D-printed products to chest trauma will become a new treatment option. To date, the use of 3D-printed external fixation guides for flail chests has not been reported. Thus, we aimed to assess the short-term efficacy of a new technology that treated flail chests with an individualized 3D-printed external fixation guide combined with video-assisted thoracoscopic surgery (VATS).

Patients and methods

A retrospective analysis was performed on patients with flail chest treated with this new technique at our center from January 2020 to December 2022. The following parameters were included: operative time, thoracic tube extraction time, intensive care unit time, thoracic volume recovery rate, visual analog scale score 1 month postoperatively, and postoperative complication rate. All patients were followed up for at least 3 months.

Results

Five patients (mean age: 45.7 years) were enrolled; they successfully underwent surgery without chest wall deformity and quickly returned to daily life. The average number of rib fractures was 8.4; all patients had lung contusion, hemopneumothorax, and anomalous respiration. The abnormal breathing of all patients was completely corrected on postoperative day 1, and the chest wall was stable. One case experienced mild loosening of the 3D-printed guide postoperatively; however, the overall stability was not affected. The other four cases did not experience such loosening because we replaced the ordinary silk wire with a steel wire. All cases were discharged from the hospital 2 weeks postoperatively and returned to normal life 1 month after the removal of the 3D-printed guide on average. Only one case developed a superficial wound infection postoperatively, and no perioperative death occurred.

Conclusions

The 3D-printed external fixation guide combined with video-assisted thoracoscopic surgery is a novel technique in the treatment of flail chest and is safe, effective, feasible, and minimally invasive, with satisfactory clinical efficacy.

Assessment of the Extent of Intracerebral Hemorrhage Using 3D Modeling Technology

The second most common cause of stroke, accounting for 10% of hospital admissions, is intracerebral hemorrhage (ICH), and risk factors include diabetes, smoking, and hypertension. People with intracerebral bleeding experience symptoms that are related to the functions that are managed by the affected part of the brain. Having obtained 15 computed tomography (CT) scans from five patients with ICH, we decided to use three-dimensional (3D) modeling technology to estimate the bleeding volume. CT was performed on admission to hospital, and after one week and two weeks of treatment. We segmented the brain, ventricles, and hemorrhage using semi-automatic algorithms in Slicer 3D, then improved the obtained models in Blender. Moreover, the accuracy of the models was checked by comparing corresponding CT scans with 3D brain model cross-sections. The goal of the research was to examine the possibility of using 3D modeling technology to visualize intracerebral hemorrhage and assess its treatment.

Guide for starting or optimizing a 3D printing clinical service

Three-dimensional (3D) printing has applications in many fields and has gained substantial traction in medicine as a modality to transform two-dimensional scans into three-dimensional renderings. Patient-specific 3D printed models have direct patient care uses in surgical and procedural specialties, allowing for increased precision and accuracy in developing treatment plans and guiding surgeries. Medical applications include surgical planning, surgical guides, patient and trainee education, and implant fabrication. 3D printing workflow for a laboratory or clinical service that produces anatomic models and guides includes optimizing imaging acquisition and post-processing, segmenting the imaging, and printing the model. Quality assurance considerations include supervising medical imaging expert radiologists' guidance and self-implementing in-house quality control programs. The purpose of this review is to provide a workflow and guide for starting or optimizing laboratories and clinical services that 3D-print anatomic models or guides for clinical use.

Bacterial Biofilm Formation on Nano-Copper Added PLA Suited for 3D Printed Face Masks

The COVID-19 Pandemic leads to an increased worldwide demand for personal protection equipment in the medical field, such as face masks. New approaches to satisfy this demand have been developed, and one example is the use of 3D printing face masks. The reusable 3D printed mask may also have a positive effect on the environment due to decreased littering. However, the microbial load on the 3D printed objects is often disregarded. Here we analyze the biofilm formation of Pseudomonas aeruginosa, Staphylococcus aureus, and Escherichia coli on suspected antimicrobial Plactive™ PLA 3D printing filaments and non-antimicrobial Giantarm™ PLA. To characterize the biofilm-forming potential scanning electron microscopy (SEM), Confocal scanning electron microscopy (CLSM) and colony-forming unit assays (CFU) were performed. Attached cells could be observed on all tested 3D printing materials. Gram-negative strains P. aeruginosa and E. coli reveal a strong uniform growth independent of the tested 3D filament (for P. aeruginosa even with stressed induced growth reaction by Plactive™). Only Gram-positive S. aureus shows strong growth reduction on Plactive™. These results suggest that the postulated antimicrobial Plactive™ PLA does not affect Gram-negative bacteria species. These results indicate that reusable masks, while better for our environment, may pose another health risk.

3D-Printed Coronary Plaques to Simulate High Calcification in the Coronary Arteries for Investigation of Blooming Artifacts

The diagnostic value of coronary computed tomography angiography (CCTA) is significantly affected by high calcification in the coronary arteries owing to blooming artifacts limiting its accuracy in assessing the calcified plaques. This study aimed to simulate highly calcified plaques in 3D-printed coronary models. A combination of silicone + 32.8% calcium carbonate was found to produce 800 HU, representing extensive calcification. Six patient-specific coronary artery models were printed using the photosensitive polyurethane resin and a total of 22 calcified plaques with diameters ranging from 1 to 4 mm were inserted into different segments of these 3D-printed coronary models. The coronary models were scanned on a 192-slice CT scanner with 70 kV, pitch of 1.4, and slice thickness of 1 mm. Plaque attenuation was measured between 1100 and 1400 HU. Both maximum-intensity projection (MIP) and volume rendering (VR) images (wide and narrow window widths) were generated for measuring the diameters of these calcified plaques. An overestimation of plaque diameters was noticed on both MIP and VR images, with measurements on the MIP images close to those of the actual plaque sizes (<10% deviation), and a large measurement discrepancy observed on the VR images (up to 50% overestimation). This study proves the feasibility of simulating extensive calcification in coronary arteries using a 3D printing technique to develop calcified plaques and generate 3D-printed coronary models.

Examination in the Time of COVID-19-MCh Plastic Surgery Examination: How Did We Do It?

Background Many aspects of life have been changed, after the starting of the pandemic. Modifications and improvisation in our day-to-day activities is now a new norm. During the pandemic period, continuation academic activities and conductance of examination is difficult but essential. We are sharing our experience of conductance of MCh examination during the pandemic and preparations made. This article also discussed the future of surgical assessment examination, use of technology in surgical assessment changing times.

Methods Procedural flow of the examination, Logistics and arrangements were planned and checked. Reliability and validity of questions were maintained by providing a similar set of questions and stepwise objective assessment. Assessment and feedback by the examinees and examiners on the pattern and conductance of examination were assessed by a Likert scale.

Results We found, 73% agreed examination patterns were able to test the knowledge fairly. While 80 % believed the pattern was the same for all the candidates. All the stakeholders agreed the examination conducted in a Safe and stress-free atmosphere and use of technology helpful. Fifty- three % agreed the case scenarios correctly simulate the clinical presentations. Lastly, 66 % felt the examination process is adequate for summative assessment.

Conclusions It is vital to reflect regarding the need for a uniform module to handle changing scenarios keeping the integrity and quality of the examination. Interactive screen, mannequin, and 3D model will be useful in the examination. In future, standardized examination modules for the surgical trainees will be required to perform a comprehensive assessment.

Bacterial Biofilm Growth on 3D-Printed Materials

Recent advances in 3D printing have led to a rise in the use of 3D printed materials in prosthetics and external medical devices. These devices, while inexpensive, have not been adequately studied for their ability to resist biofouling and biofilm buildup. Bacterial biofilms are a major cause of biofouling in the medical field and, therefore, hospital-acquired, and medical device infections. These surface-attached bacteria are highly recalcitrant to conventional antimicrobial agents and result in chronic infections. During the COVID-19 pandemic, the U.S. Food and Drug Administration and medical officials have considered 3D printed medical devices as alternatives to conventional devices, due to manufacturing shortages. This abundant use of 3D printed devices in the medical fields warrants studies to assess the ability of different microorganisms to attach and colonize to such surfaces. In this study, we describe methods to determine bacterial biofouling and biofilm formation on 3D printed materials. We explored the biofilm-forming ability of multiple opportunistic pathogens commonly found on the human body including Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus to colonize eight commonly used polylactic acid (PLA) polymers. Biofilm quantification, surface topography, digital optical microscopy, and 3D projections were employed to better understand the bacterial attachment to 3D printed surfaces. We found that biofilm formation depends on surface structure, hydrophobicity, and that there was a wide range of antimicrobial properties among the tested polymers. We compared our tested materials with commercially available antimicrobial PLA polymers.

Quantitative Assessment of 3D Printed Model Accuracy in Delineating Congenital Heart Disease

Background: Three-dimensional (3D) printing is promising in medical applications, especially presurgical planning and the simulation of congenital heart disease (CHD). Thus, it is clinically important to generate highly accurate 3D-printed models in replicating cardiac anatomy and defects. The present study aimed to investigate the accuracy of the 3D-printed CHD model by comparing them with computed tomography (CT) images and standard tessellation language (STL) files. Methods: Three models were printed, comprising different CHD pathologies, including the tetralogy of Fallot (ToF), ventricular septal defect (VSD) and double-outlet right-ventricle (DORV). The ten anatomical locations were measured in each comparison. Pearson’s correlation coefficient, Bland–Altman analysis and intra-class correlation coefficient (ICC) determined the model accuracy. Results: All measurements with three printed models showed a strong correlation (r = 0.99) and excellent reliability (ICC = 0.97) when compared to original CT images, CT images of the 3D-printed models, STL files and 3D-printed CHD models. Conclusion: This study demonstrated the high accuracy of 3D-printed heart models with excellent correlation and reliability when compared to multiple source data. Further investigation into 3D printing in CHD should focus on the clinical value and the benefits to patients.

[Application of 3D visualization and 3D printing in individualized precision surgery for Bismuth-Corlette type Ⅲ and Ⅳ hilar cholangiocarcinoma]

OBJECTIVE

To explore the application of 3D visualization and 3D printing in individualized precision surgical treatment of Bismuth-Corlette type Ⅲ and Ⅳ hilar cholangiocarcinoma.

METHODS

We retrospectively analyzed the data of 10 patients with hilar cholangiocarcinoma undergoing surgeries under the guidance of 3D visualization and 3D printing in the Department of Hepatobiliary Surgery, Zhujiang Hospital from May 2016 to March 2019. Thin-section CT data of the patients were collected for 3D reconstruction and 3D printing, and the 3D printed models were used for observing the 3D relationship of tumor with the intrahepatic bile duct, hepatic artery, portal vein and hepatic vein system and for performing preoperative simulated surgery and surgical planning. The 3D printed models were subsequently used for real-time intraoperative navigation to guide surgeries in the operating room.

RESULTS

3D visualization models were successfully reconstructed for all the 10 patients and printed into 3D models. The 3D visualization types in Bismuth-Corlette classification included type Ⅲa (4 cases), type Ⅲb (4 cases), and type Ⅳ (2 cases); 4 patients showed portal vein variation, 3 had hepatic artery variation, and 2 had both portal vein and hepatic artery variations. Two patients were found to have trifurcation type of portal vein variation, one had "I-shaped" variation, and one showed the absence of the right anterior branch of the portal vein; 3 patients had hepatic artery variations with the left hepatic artery originating from the left gastric artery (1 case) and the right hepatic artery originating from the superior mesenteric artery (2 cases). Four patients with type Ⅲb underwent left hepatectomy; 4 with type Ⅲa received right hepatectomy; 1 patient with of type Ⅳ received peripheral hepatic resection and another underwent left hepatectomy. The results of preoperative 3D reconstruction, 3D printed model and preoperative planning were consistent with the intraoperative findings. The operative time was 452±75.12 min with a mean intraoperative blood loss of 356±62.35 mL and a mean hospital stay of 15 ± 4.61 days in these cases. One patient had bile leakage and 3 patients had pleural effusion postoperatively, and they were discharged after drainage and medications. No liver failure or death occurred in these cases perioperatively.

CONCLUSIONS

3D visualization and 3D printing can facilitate accurate preoperative assessment, surgical planning and surgical procedure optimization for Bismuth-Corlette type Ⅲ and Ⅳ hilar cholangiocarcinoma to improve surgical safety and reduce surgical risks especially in cases of intrahepatic vascular variations.

A novel method for fabricating nasoalveolar molding appliances for infants with cleft lip and palate using 3-dimensional workflow and clear aligners

INTRODUCTION

Nasoalveolar molding (NAM) was introduced over 20 years ago as adjunctive therapy for the correction of cleft lip and palate. In the current study, we propose a new approach using a digital workflow and 3-dimensional printing to fabricate clear aligner NAM devices.

METHODS

A polyvinyl siloxane (PVS) impression of an infant with a unilateral complete cleft lip and palate (UCLP) is acquired and poured, and the stone model is scanned with an intraoral scanner. The stereolithography file is digitized, and the alveolar segments are digitally segmented and moved to the desired final position. The total distance moved is divided into a sequence of 1-1.5 mm increments, creating a series of digital models. The models are 3-dimensionally printed along with button templates to allow free form positioning of the button on each model. A Vacuform machine (Taglus, Mumbai, India) was used to fabricate a 0.040-in aligner for each stage.

RESULTS

We present 1 case that was treated successfully with this approach. Appointments for the NAM adjustments were primarily to monitor progress and counseling with less time spent adjusting the appliance. The appointment length was reduced by over 30 minutes. Benefits of the aligner are improved fit, more precise increments of activation, reduced chairside time, and potentially minimized number of visits.

CONCLUSIONS

NAM custom aligners may provide similar benefits to the traditional approach while reducing the burden of care by reducing the number of visits and appointment duration. Further studies with a sample and longitudinal observations are needed to investigate the benefits of the proposed digital approach.

Identifying a commercially-available 3D printing process that minimizes model distortion after annealing and autoclaving and the effect of steam sterilization on mechanical strength

BACKGROUND

Fused deposition modeling 3D printing is used in medicine for diverse purposes such as creating patient-specific anatomical models and surgical instruments. For use in the sterile surgical field, it is necessary to understand the mechanical behavior of these prints across 3D printing materials and after autoclaving. It has been previously understood that steam sterilization weakens polylactic acid, however, annealing heat treatment of polylactic acid increases its crystallinity and mechanical strength. We aim to identify an optimal and commercially available 3D printing process that minimizes distortion after annealing and autoclaving and to quantify mechanical strength after these interventions.

METHODS

Thirty millimeters cubes with four different infill geometries were 3D printed and subjected to hot water-bath annealing then immediate autoclaving. Seven commercially available 3D printing materials were tested to understand their mechanical behavior after intervention. The dimensions in the X, Y, and Z axes were measured before and after annealing, and again after subsequent autoclaving. Standard and strength-optimized Army-Navy retractor designs were printed using the 3D printing material and infill geometry that deformed the least. These retractors were subjected to annealing and autoclaving interventions and tested for differences in mechanical strength.

RESULTS

For both the annealing and subsequent autoclaving intervention, the material and infill geometry that deformed the least, respectively, was Essentium PLA Gray and "grid". Standard retractors without intervention failed at 95 N +/- 2.4 N. Annealed retractors failed at 127.3 N +/- 10 N. Autoclave only retractors failed at 15.7 N +/- 1.4 N. Annealed then autoclaved retractors failed at 19.8 N +/- 3.1 N. Strength-optimized retractors, after the annealing then autoclaving intervention, failed at 164.8 N +/- 12.5 N.

CONCLUSION

For 30 mm cubes, the 3D printing material and infill geometry that deformed the least, respectively, was Essentium PLA and "grid". Hot water-bath annealing results in increased 3D printed model strength, however autoclaving 3D prints markedly diminishes strength. Strength-optimized 3D printed PLA Army-Navy retractors overcome the strength limitation due to autoclaving.

3D printed PLA Army-Navy retractors when used as linear retractors yield clinically acceptable tolerances

BACKGROUND

Modern low-cost 3D printing technologies offer the promise of access to surgical tools in resource scarce areas, however optimal designs for manufacturing have not yet been established. We explore how the optimization of 3D printing parameters when manufacturing polylactic acid filament based Army-Navy retractors vastly increases the strength of retractors, and investigate sources of variability in retractor strength, material cost, printing time, and parameter limitations.

METHODS

Standard retractors were printed from various polylactic acid filament spools intra-manufacturer and inter-manufacturer to measure variability in retractor strength. Printing parameters were systematically varied to determine optimum printing parameters. These parameters include retractor width, thickness, infill percentage, infill geometry, perimeter number, and a reinforced joint design. Estimated retractor mass from computer models allows us to estimate material cost.

RESULTS

We found statistically significant differences in retractor strength between spools of the same manufacturer and between manufacturers. We determined the true strength optimized retractor to have 30% infill, 3 perimeters, 0.25 in. thickness, 0.75 in. width, and has "Triangle" infill geometry and reinforced joints, failing at more than 15X the threshold for clinically excessive retraction and costs $1.25 USD.

CONCLUSIONS

The optimization of 3D printed Army-Navy retractors greatly improve the efficacy of this instrument and expedite the adoption of 3D printing technology in many diverse fields in medicine not necessarily limited to resource poor settings.

A Systematic Review of the Clinical Value and Applications of Three-Dimensional Printing in Renal Surgery

The purpose of this systematic review is to collate and analyse the current literature which examines clinical applications of 3D printing for renal disease, alongside cost and time duration factors associated with the printing process. A comprehensive search of the literature was performed across five different databases to identify studies that qualitatively and quantitatively assessed the value of 3D-printed kidney models for renal disease. Twenty-seven studies met the selection criteria for inclusion in the review. Twenty-five were original studies, and two were case reports. Of the 22 studies reporting a qualitative evaluation, the analysis of findings demonstrated the value of the 3D-printed models in areas of clinician and patient education, and pre-surgical simulation for complex cases of renal disease. Of five studies performing a quantitative analysis, the analysis of results displayed a high level of spatial and anatomical accuracy amongst models, with benefits including reducing estimated blood loss and risk of intra-operative complications. Fourteen studies evaluated manufacturing costs and time duration, with costs ranging from USD 1 to 1000 per model, and time duration ranging from 15 min to 9 days. This review shows that the use of customised 3D-printed models is valuable in the education of junior surgeons as well as the enhancement of operative skills for senior surgeons due to a superior visualisation of anatomical networks and pathologic morphology compared to volumetric imaging alone. Furthermore, 3D-printed kidney models may facilitate interdisciplinary communication and decision-making regarding the management of patients undergoing operative treatment for renal disease. It cannot be suggested that a more expensive material constitutes a higher level of user-satisfaction and model accuracy. However, higher costs in the manufacturing of the 3D-printed models reported, on average, a slightly shorter time duration for the 3D-printing process and total manufacturing time.