Three-dimensional surgical modelling with an open-source software protocol: study of precision and reproducibility in mandibular reconstruction with the fibula free flap

Cost-effective Solution for Maxillofacial Reconstruction Surgery with Virtual Surgical Planning and 3D Printed Cutting Guides Reduces Operative Time

Background: This study aimed to explore a low-cost solution for virtual surgical planning/3D printed surgical guides in a training hospital, assessing the impact on intraoperative time and bleeding. Material and Methods: We included a total of 13 patients. 8 who underwent maxillofacial reconstruction surgery with fibula-free flap utilizing virtual surgical planning/3D printed guides (VP/SG), and 5 using conventional surgery (CS) from 2017 to 2020. The surgical time, bleeding, length of hospital stay, and comorbidities were collected and compared in two groups. We recorded the average cost for the complete surgical planning and 3D printed guides. We applied a qualitative survey to the surgeons involved in the surgical procedures. Results The mean surgical time in the VP/SG group was 8.16 ± 2.7, compared to the CS group 12.5 ± 3.8, showing a 4.34 hours difference with statistical significance (p = 0.033). Patients from the CS group had a higher bleeding volume of 921 ± 467.6 mL VS 760 ± 633.8 mL in the VP/SG group. The average cost for the complete surgical planning and 3D printed guides was 914.44 ± 46.39 USD. All the surgeons who answered the survey preferred to perform the procedure utilizing the virtual planning/3D printed guides. Conclusions Virtual planning and 3D printed surgical guides have the potential to reduce operation time in maxillofacial reconstruction.

Bone regeneration in critical-size defects of the mandible using biomechanically adapted CAD/CAM hybrid scaffolds: An in vivo study in miniature pigs

The study aimed to analyze bone regeneration in critical-size defects using hybrid scaffolds biomechanically adapted to the specific defect and adding the growth factor rhBMP-2. For this animal study, ten minipigs underwent bilateral defects in the corpus mandibulae and were subsequently treated with novel cylindrical hybrid scaffolds. These scaffolds were designed digitally to suit the biomechanical requirements of the mandibular defect, utilizing finite element analysis. The scaffolds comprised zirconium dioxide-tricalcium phosphate (ZrO2-TCP) support struts and TCP foam ceramics. One scaffold in each animal was loaded with rhBMP-2 (100 μg/cm³), while the other served as an unloaded negative control. Fluorescent dyes were administered every 2 weeks, and computed tomography (CT) scans were conducted every 4 weeks. Euthanasia was performed after 3 months, and samples were collected for examination using micro-CT and histological evaluation of both hard and soft tissue. Intravital CT examinations revealed minor changes in radiographic density from 4 to 12 weeks postoperatively. In the group treated with rhBMP-2, radiographic density shifted from 2513 ± 128 (mean ± SD) to 2606 ± 115 Hounsfield units (HU), while the group without rhBMP-2 showed a change from 2430 ± 131 to 2601 ± 67 HU. Prior to implantation, the radiological density of samples measured 1508 ± 30 mg HA/cm³, whereas post-mortem densities were 1346 ± 71 mg HA/cm³ in the rhBMP-2 group and 1282 ± 91 mg HA/cm³ in the control group (p = 0.045), as indicated by micro-CT measurements. The histological assessment demonstrated successful ossification in all specimens. The newly formed bone area proportion was significantly greater in the rhBMP-2 group (48 ± 10%) compared with the control group without rhBMP-2 (42 ± 9%, p = 0.03). The mean area proportion of remaining TCP foam was 23 ± 8% with rhBMP-2 and 24 ± 10% without rhBMP-2. Successful bone regeneration was accomplished by implanting hybrid scaffolds into critical-size mandibular defects. Loading these scaffolds with rhBMP-2 led to enhanced bone regeneration and a uniform distribution of new bone formation within the hybrid scaffolds. Further studies are required to determine the adaptability of hybrid scaffolds for larger and potentially segmental defects in the maxillofacial region.

Realizing in-house algorithm-driven free fibula flap set up within 24 hours: a pilot study evaluating accuracy with open-source tools

Objective

This study aims to critically evaluate the effectiveness and accuracy of a time safing and cost-efficient open-source algorithm for in-house planning of mandibular reconstructions using the free osteocutaneous fibula graft. The evaluation focuses on quantifying anatomical accuracy and assessing the impact on ischemia time.

Methods

A pilot study was conducted, including patients who underwent in-house planned computer-aided design and manufacturing (CAD/CAM) of free fibula flaps between 2021 and 2023. Out of all patient cases, we included all with postoperative 3D imaging in the study. The study utilized open-source software tools for the planning step, and three-dimensional (3D) printing techniques. The Hausdorff distance and Dice coefficient metrics were used to evaluate the accuracy of the planning procedure.

Results

The study assessed eight patients (five males and three females, mean age 61.75 ± 3.69 years) with different diagnoses such as osteoradionecrosis and oral squamous cell carcinoma. The average ischemia time was 68.38 ± 27.95 min. For the evaluation of preoperative planning vs. the postoperative outcome, the mean Hausdorff Distance was 1.22 ± 0.40. The Dice Coefficients yielded a mean of 0.77 ± 0.07, suggesting a satisfactory concordance between the planned and postoperative states. Dice Coefficient and Hausdorff Distance revealed significant correlations with ischemia time (Spearman's rho = -0.810, p = 0.015 and Spearman's rho = 0.762, p = 0.028, respectively). Linear regression models adjusting for disease type further substantiated these findings.

Conclusions

The in-house planning algorithm not only achieved high anatomical accuracy, as reflected by the Dice Coefficients and Hausdorff Distance metrics, but this accuracy also exhibited a significant correlation with reduced ischemia time. This underlines the critical role of meticulous planning in surgical outcomes. Additionally, the algorithm's open-source nature renders it cost-efficient, easy to learn, and broadly applicable, offering promising avenues for enhancing both healthcare affordability and accessibility.

Use of Preoperative 3D Virtual Planning and 3D-Printed Patient-Specific Guides to Facilitate a Single-Stage Cranial Closing Wedge Ostectomy and Tibial Plateau Leveling Osteotomy Procedure to Address Proximal Tibial Deformity, an Excessive Tibial Plateau Angle, and Cranial Cruciate Ligament Insufficiency in a Dog

A 9-month-old mixed-breed dog was presented for bilateral proximal tibial deformity resulting in an excessive tibial plateau angle and cranial cruciate ligament insufficiency. Initial surgical management of the right pelvic limb was done by performing a cranial closing wedge ostectomy. Inadequate leveling of the plateau resulted in a postliminal meniscal tear which was addressed during a revision tibial plateau leveling osteotomy. The left pelvic limb was managed in a single-session surgery using three-dimensional (3D) virtual surgical planning and custom 3D-printed surgical guides to perform a combined cranial closing wedge ostectomy and tibial plateau leveling osteotomy. Postoperative 3D analysis of the left tibia revealed the accuracy of the surgical result within 2° of the virtual surgical plan. The dog developed a transient grade II/IV left medial patellar luxation following surgery but ultimately attained a full functional recovery and was actively engaged in competitive agility work 46 months following surgery on the left pelvic limb.

Comparison of Artificial Intelligence-Based Applications for Mandible Segmentation: From Established Platforms to In-House-Developed Software

Medical image segmentation, whether semi-automatically or manually, is labor-intensive, subjective, and needs specialized personnel. The fully automated segmentation process recently gained importance due to its better design and understanding of CNNs. Considering this, we decided to develop our in-house segmentation software and compare it to the systems of established companies, an inexperienced user, and an expert as ground truth. The companies included in the study have a cloud-based option that performs accurately in clinical routine (dice similarity coefficient of 0.912 to 0.949) with an average segmentation time ranging from 3'54″ to 85'54″. Our in-house model achieved an accuracy of 94.24% compared to the best-performing software and had the shortest mean segmentation time of 2'03″. During the study, developing in-house segmentation software gave us a glimpse into the strenuous work that companies face when offering clinically relevant solutions. All the problems encountered were discussed with the companies and solved, so both parties benefited from this experience. In doing so, we demonstrated that fully automated segmentation needs further research and collaboration between academics and the private sector to achieve full acceptance in clinical routines.

Mandibular reconstructions with free fibula flap using standardized partially adjustable cutting guides or CAD/CAM technique: a three- and two-dimensional comparison

Background

Mandibular reconstruction with the fibula free flap (FFF) is performed freehand, CAD/CAM-assisted, or by using partially adjustable resection/reconstruction aids. The two latter options represent the contemporary reconstructive solutions of the recent decade. The purpose of this study was to compare both auxiliary techniques with regard to feasibility, accuracy, and operative parameters.

Methods and materials

The first twenty consecutively operated patients requiring a mandibular reconstruction (within angle-to-angle) with the FFF using the partially adjustable resection aids between January 2017 and December 2019 at our department were included. Additionally, matching CAD/CAM FFF cases were used as control group in this cross-sectional study. Medical records and general information (sex, age, indication for surgery, extent of resection, number of segments, duration of surgery, and ischemia time) were analyzed. In addition, the pre- and postoperative Digital Imaging and Communications in Medicine data of the mandibles were converted to standard tessellation language (.stl) files. Conventional measurements - six horizontal distances (A-F) and temporo-mandibular joint (TMJ) spaces - and the root mean square error (RMSE) for three-dimensional analysis were measured and calculated.

Results

In total, 40 patients were enrolled (20:20). Overall operation time, ischemia time, and the interval between ischemia time start until end of operation showed no significant differences. No significant difference between the two groups were revealed in conventional measurements of distances (A-D) and TMJ spaces. The Δ differences for the distance F (between the mandibular foramina) and the right medial joint space were significantly lower in the ReconGuide group. The RMSE analysis of the two groups showed no significant difference (p=0.925), with an overall median RMSE of 3.1 mm (2.2-3.7) in the CAD/CAM and 2.9 mm (2.2-3.8) in the ReconGuide groups.

Conclusions

The reconstructive surgeon can achieve comparable postoperative results regardless of technique, which may favor the ReconGuide use in mandibular angle-to-angle reconstruction over the CAD/CAM technique because of less preoperative planning time and lower costs per case.

Additive Manufacturing of 3D Anatomical Models-Review of Processes, Materials and Applications

The methods of additive manufacturing of anatomical models are widely used in medical practice, including physician support, education and planning of treatment procedures. The aim of the review was to identify the area of additive manufacturing and the application of anatomical models, imitating both soft and hard tissue. The paper outlines the most commonly used methodologies, from medical imaging to obtaining a functional physical model. The materials used to imitate specific organs and tissues, and the related technologies used to produce, them are included. The study covers publications in English, published by the end of 2022 and included in the Scopus. The obtained results emphasise the growing popularity of the issue, especially in the areas related to the attempt to imitate soft tissues with the use of low-cost 3D printing and plastic casting techniques.

Role of 3D Printing in Post-op Rehabilitation of Palatal Bone Loss by Mucormycosis: A Survey

BACKGROUND

Three dimensions (3D) modeling, printing, and manufacturing can help in personalized and customized surgical reconstruction of complex defects in the craniofacial region with precision by manipulating tissues based on the preoperative assessment, planning the shape of metal and alloplastic materials, and reduction in the total cost and time of the surgery.

AIM

The present survey study aimed to assess the approach of treating surgeons towards the role of 3D printing in post-op rehabilitation of palatal bone loss by mucormycosis.

METHODS

One thousand eyes nose and throat (ENT) and maxillofacial surgeons were given a pre-formed structured survey questionnaire to be filled by subjects themselves for their view on the role of 3D printing for rehabilitation and reconstruction of palatal bone loss due to mucormycosis.

RESULTS

Efficacy of 3D printing to print the pneumatic sinus design and palatal contour helping to design accurate support with a lightweight prosthesis, 67.2% (n=672) subjects whereas, exact duplication of the excised tissue, 85.4% (n=854) subjects, to detect and duplicate undercuts, 58.4% (n=584) subjects, 3D printing can be helpful as the proper extension of impression 73.2% (n=732) subjects responded positively. For reconstruction of a lost palate by prosthesis 91.2% (n=912) of study participants, in making obturators using Titanium framework and Polyetheretherketone (PEEK) was given a positive response by 82.2% (n=822) subjects, to fabricate prosthesis obturator required in palatal perforation in case of mucormycosis was given a positive response by 88.1% (n=881) subjects, the role of 3D printing to overlay zygomatic implant prosthesis was responded positively by 68.9% (n=689) study subjects.

CONCLUSION

The present survey study concludes that 3D printing is a reliable and accurate method for palatal reconstruction following bone destruction by mucormycosis as reported by the majority of ENT and maxillofacial surgeons.

Point-of-Care Virtual Surgical Planning and 3D Printing in Oral and Cranio-Maxillofacial Surgery: A Narrative Review

This paper provides an overview on the use of virtual surgical planning (VSP) and point-of-care 3D printing (POC 3DP) in oral and cranio-maxillofacial (CMF) surgery based on a literature review. The authors searched PubMed, Web of Science, and Embase to find papers published between January 2015 and February 2022 in English, which describe human applications of POC 3DP in CMF surgery, resulting in 63 articles being included. The main review findings were as follows: most used clinical applications were anatomical models and cutting guides; production took place in-house or as "in-house-outsourced" workflows; the surgeon alone was involved in POC 3DP in 36 papers; the use of free versus paid planning software was balanced (50.72% vs. 49.27%); average planning time was 4.44 h; overall operating time decreased and outcomes were favorable, though evidence-based studies were limited; and finally, the heterogenous cost reports made a comprehensive financial analysis difficult. Overall, the development of in-house 3D printed devices supports CMF surgery, and encouraging results indicate that the technology has matured considerably.

Virtual planning and 3D-printed guides for mandibular reconstruction: Factors impacting accuracy

Objectives

Examine accuracy and factors impacting accuracy for mandibular reconstruction with virtual surgical planning, 3D printed osteotomy guides and preoperatively bent mandibular reconstruction plate (VSP/3Dprinted-guide/plate).

Method

Retrospective review of osseous-free-flap mandibular reconstructions with VSP/3Dprinted-guide/plate between January 2015 and July 2020 at a single academic medical center.Patient demographics, disease, and treatment variables were extracted. Accuracy was assessed by 3D-model-overlay with cephalometric and donor-bone segment length measurements. Multivariate analyses were performed to determine factors impacting cephalometric accuracy.

Results

60 cases met criteria: 41 (68%) cancer, 14 (23%) osteoradionecrosis (ORN), 5 (8%) secondary mandibular reconstruction. Thirteen cases (22%) were Brown class III or IV. Thirty-nine cases (65%) had ≥2 flap bone segments. Average donor-bone length was 82 mm (SD: 28). 3D-model-overlay accuracy demonstrated minimal deviation between planned and actual reconstruction: intercondylar distance = 2.10 mm (SD: 2.2); intergonial distance = 2.23 mm (SD: 1.9); anterior-posterior distance (APD) = 1.76 mm (SD: 1.5); gonial angle (GA) = 3.11 degrees (SD: 2.4). Mean change in donor-bone segment length inferiorly was 2.67 mm (SD: 2.6) and superiorly 3.27 mm (SD: 3.2). Higher number of donor-bone segments was associated with decreased accuracy in GA (p = .023) and longer donor-bone length was associated with decreased accuracy in APD (p = .031).

Conclusion

To our knowledge this is the largest series assessing surgical accuracy of VSP/3Dprinted-guide/plate for osseous-free-flap mandibular reconstruction. We demonstrate highly accurate results, with increased number of donor-bone segments and donor-bone length associated with decreased accuracy. Our findings further support VSP/3Dprinted-guide/plate as a reliable and accurate tool for mandibular reconstruction.

Level of Evidence

Level 4.

Low-Cost and Simple Frontal Sinus Surgical Cutting Guide Modeling for Anterior Cranioplasty in Facial Feminization Surgery: How To Do It

BACKGROUND

This study demonstrates a novel and simple design to create a low cost frontal sinus surgical cutting guide, using patient's frontal sinus cavities as references, to perform an anterior cranioplasty in facial feminization surgery. A clinical series demonstrates its clinical use and safety.

MATERIAL AND METHODS

Authors used a 4 open-source software protocol for the virtual surgical modeling (VSP). Retrospectively, pre- and post-operative complications were reviewed, and a FACE-Q questionnaires were used to evaluate patient's postoperative "Satisfaction with forehead and eyebrows." Recordings of the VSP and surgical technic are presented.

RESULTS

Sixteen patients were operated between November 2018 and November 2020 using in-house surgical guides. All were performed by authors in 5 to 10 minutes using Blender open-source Software. No complications were reported and authors always found an optimal retention of the surgical guide on the convex bony surface of the forehead and frontonasal area. FACE-Q questionnaire reported a very high satisfaction for all patients (mean score: 22/24).

DISCUSSION

This simplify organic design can be performed efficiently by any surgeon even without previous training in home staging VSP. Patient satisfaction was very high, along with an absence of postoperative complications.

Deviation Analyses of Computer-Assisted, Template-Guided Mandibular Reconstruction With Combined Osteotomy and Reconstruction Pre-Shaped Plate Position Technology: A Comparative Study

Background

Computer-assisted and template-guided mandibular reconstruction provides higher accuracy and less variation than conventional freehand surgeries. The combined osteotomy and reconstruction pre-shaped plate position (CORPPP) technique is a reliable choice for mandibular reconstruction. This study aimed to evaluate the accuracy of CORPPP-guided fibular flap mandibular reconstruction and analyze the possible causes of the deviations.

Patients and Methods

From June 2015 to December 2016, 28 patients underwent fibular flap mandibular reconstruction. Virtual planning and personalized CORPPP-guided templates were applied in 15 patients while 13 patients received conventional freehand surgeries. Deviations during mandibulectomy and fibular osteotomy, and overall and triaxial deviation of the corresponding mandibular anatomical landmarks were measured by superimposing the pre- and postoperative virtual models.

Results

The deviation of the resection line and resection angle was 1.23 ± 0.98 mm and 4.11° ± 2.60°. The actual length of fibula segments was longer than the designed length in 7 cases (mean: 0.35 ± 0.32 mm) and shorter in 22 cases (mean: 1.53 ± 1.19 mm). In patients without ramus reconstruction, deviations of the ipsilateral condylar head point (Co.), gonion point (Go.), and coracoid process point (Cor.) were 6.71 ± 3.42 mm, 5.38 ± 1.71 mm, and 11.05 ± 3.24 mm in the freehand group and 1.73 ± 1.13 mm, 1.86 ± 0.96 mm, and 2.54 ± 0.50 mm in the CORPPP group, respectively, with significant statistical differences (p < 0.05). In patients with ramus reconstruction, deviations of ipsilateral Co. and Go. were 9.79 ± 4.74 mm vs. 3.57 ± 1.62 mm (p < 0.05), and 15.17 ± 6.53 mm vs. 4.36 ± 1.68 mm (p < 0.05) in the freehand group and CORPPP group, respectively.

Conclusion

Mandibular reconstructions employing virtual planning and personalized CORPPP-guided templates show significantly higher predictability, convenience, and accuracy of mandibular reconstruction compared with conventional freehand surgeries. However, more clinical cases were required for further dimensional deviation analysis. The application and exploration of clinical practice would also continuously improve the design of templates.

In-House, Open-Source 3D-Software-Based, CAD/CAM-Planned Mandibular Reconstructions in 20 Consecutive Free Fibula Flap Cases: An Explorative Cross-Sectional Study With Three-Dimensional Performance Analysis

Background

Mandibular reconstruction is conventionally performed freehand, CAD/CAM-assisted, or by using partially adjustable resection aids. CAD/CAM-assisted reconstructions are usually done in cooperation with osteosynthesis manufacturers, which entails additional costs and longer lead time. The purpose of this study is to analyze an in-house, open-source software-based solution for virtual planning.

Methods and Materials

All consecutive cases between January 2019 and April 2021 that underwent in-house, software-based (Blender) mandibular reconstruction with a free fibula flap (FFF) were included in this cross-sectional study. The pre- and postoperative Digital Imaging and Com munications in Medicine (DICOM) data were converted to standard tessellation language (STL) files. In addition to documenting general information (sex, age, indication for surgery, extent of resection, number of segments, duration of surgery, and ischemia time), conventional measurements and three-dimensional analysis methods (root mean square error [RMSE], mean surface distance [MSD], and Hausdorff distance [HD]) were used.

Results

Twenty consecutive cases were enrolled. Three-dimensional analysis of preoperative and virtually planned neomandibula models was associated with a median RMSE of 1.4 (0.4–7.2), MSD of 0.3 (-0.1–2.9), and HD of 0.7 (0.1–3.1). Three-dimensional comparison of preoperative and postoperative models showed a median RMSE of 2.2 (1.5–11.1), MSD of 0.5 (-0.6–6.1), and HD of 1.5 (1.1–6.5) and the differences were significantly different for RMSE (p < 0.001) and HD (p < 0.001). The difference was not significantly different for MSD (p = 0.554). Three-dimensional analysis of virtual and postoperative models had a median RMSE of 2.3 (1.3–10.7), MSD of -0.1 (-1.0–5.6), and HD of 1.7 (0.1–5.9).

Conclusions

Open-source software-based in-house planning is a feasible, inexpensive, and fast method that enables accurate reconstructions. Additionally, it is excellent for teaching purposes.

Use of Dental Impression Silicone to Fabricate Simple Surgical Guides in Mandibular Reconstruction

BACKGROUND

Several recent reports have described the development and use of three-dimensional (3D) printed surgical osteotomy guides. However, these methods: are usually costly. Here, we introduce a novel method of manufacturing surgical guides built from inexpensive, easy-to-use, and sterilizable dental impression silicone.

METHODS

Mandibular and fibular models were prepared using a 3D printer for 10 patients undergoing free fibula flap transfer after mandibular resection. During preoperative simulation surgery, Protesil labor, a dental silicone, was molded to the same size as the fibular models to act as surgical guides.

RESULTS

The authors compared pre- and post-operative bone angles and bone lengths for all cases using simulation surgery models and postoperative 3D computed tomography. Mean bone angle difference was 2.6° and mean bone length difference was 1.7 mm. Cost of the dental silicone was approximately US$5/patient.

CONCLUSIONS

In our series this method allowed the surgeon to perform an accurate osteotomy, inexpensively and time-efficiently.

Dental 3D-Printing: Transferring Art from the Laboratories to the Clinics

The rise of three-dimensional (3D) printing technology has changed the face of dentistry over the past decade. 3D printing is a versatile technique that allows the fabrication of fully automated, tailor-made treatment plans, thereby delivering personalized dental devices and aids to the patients. It is highly efficient, reproducible, and provides fast and accurate results in an affordable manner. With persistent efforts among dentists for refining their practice, dental clinics are now acclimatizing from conventional treatment methods to a fully digital workflow to treat their patients. Apart from its clinical success, 3D printing techniques are now employed in developing haptic simulators, precise models for dental education, including patient awareness. In this narrative review, we discuss the evolution and current trends in 3D printing applications among various areas of dentistry. We aim to focus on the process of the digital workflow used in the clinical diagnosis of different dental conditions and how they are transferred from laboratories to clinics. A brief outlook on the most recent manufacturing methods of 3D printed objects and their current and future implications are also discussed.

Computer-Aided Surgical Simulation in Severe Atrophic Mandibular Fractures: A New Method for Guided Reduction and Temporary Stabilization Before Fixation

In severe atrophic mandibular fractures, the absence of stable occlusion, as well as poor bone volume at the fracture site, constitutes a lack of references during surgery to achieve accurate fracture reduction. Unsuccessful reduction and stabilization can lead to several complications, such as fracture misalignments, malunion, and facial asymmetry. An alternative to avoid the aforementioned issues is fracture reduction based on virtual surgical planning (VSP) technology. However, there is little information regarding VSP protocols for the management of mandible fractures. Herein, a new technique with low cost is reported in which VSP and computer-aided manufacturing of a positioning guide were applied in a 72-year-old female patient with bilateral fractures in her atrophic mandible in the body region. The positioning guide was used during fracture reduction on the inferior surface of the mandible as per the virtual reduction. A 3-dimensional mandible model was also printed, facilitating the prebent 2.4-mm reconstructive plate. The surgical procedure was performed with no complications, resulting in the accurate fit of both the bent plate and the guide. A postoperative computed tomography scan showed good condylar position, fracture reduction, and hardware adaptation. A follow-up approximately 2 years later showed that she was successfully rehabilitated with the dental prosthesis. Therefore, VSP is a valuable tool for attaining a predictable result in the treatment of severe atrophic mandibular fracture, with a reduced operative duration, acceptable precision of fracture reduction, and low cost.

Design and Fabrication of Implants for Mandibular and Craniofacial Defects Using Different Medical-Additive Manufacturing Technologies: A Review

Mandibular and craniofacial bone defects can be caused by trauma, inflammatory disease, and benign or malignant tumors. Patients with bone defects suffer from problems with aesthetics, speech, and mastication, resulting in the need for implants. Conventional methods do not always provide satisfactory results. Most of the techniques proposed by researchers in the field of biomedical engineering use reverse engineering, computer-aided design (CAD), and additive manufacturing (AM), whose implementation can improve the outcomes of reconstructive surgeries. Several literature reviews on this particular topic have been conducted. However, they provide mostly overviews of AM technologies for general biomedical devices. This paper summarizes the use of existing medical AM techniques for the design and fabrication of mandibular and craniofacial implants, and then discusses their advantages and disadvantages in terms of accuracy, costs, energy consumption, and production rate. The aim of this study is to present a comparative review of the most commonly used AM technologies to aid researchers in selecting the best possible AM technologies for medical use. Studies included in this review contain CAD designs of mandibular or cranial implants, as well as their fabrication using AM technologies. Special attention is paid to PolyJet technology, because of its high accuracy, and economical efficiency.

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.

Recent advance in patient-specific 3D printing templates in mandibular reconstruction

Patient-specific 3D printing template is used in mandibular defect reconstruction with multiple deficiencies. During the operation, the template can accurately transfer the preoperative design, assisting surgeons to complete the surgery with high efficiency and accuracy. The template design has been continuously improved to obtain good application for miscellaneous classification and description. This review attempted to preliminarily analyse and summarise recent advancements in personalized 3D printing templates in mandibular reconstruction from the aspects of functional classification, existing problems, improved strategies and post-surgery evaluation by reviewing studies and through our combined clinical work and experience on hundreds of reconstruction surgeries.

Three-Dimensional Printing of the Nasal Cavities for Clinical Experiments

3D printing has produced many beneficial applications for surgery. The technique´s applicability in replicating nasal cavity anatomy for clinical use has not been studied. Our aim was to determine whether 3D printing could realistically replicate the nasal cavities and the airflow passing through them from a clinical point of view. We included Cone Beam Computed Tomography (CBCT) scans of five patients with symptoms of chronic nasal congestion. These CBCT scans were used to print plastic 3D prints of the nasal cavities, which were also CBCT scanned and the measurements were compared. The results in vivo were higher than the results in vitro in maxillary sinus volumes with a ratio of 1.05 ± 0.01 (mean ± SD) and in the nasal cavities with a ratio of 1.20 ± 0.1 (mean ± SD). Linear measurements in vitro were very close to those in vivo. Rhinomanometric results showed some differences, but rhinomanometric graphs in vitro were close to the graphs in vivo. 3D printing proved to be a suitable and fast method for replicating nasal cavity structures and for the experimental testing of nasal function. It can be used as a complementary examination tool for rhinomanometry.

Should You Buy a Three-Dimensional Printer? A Study of an Orbital Fracture

The use of three-dimensional (3D) printing has been growing significantly in medicine for the past 10 years, especially in maxillofacial surgery. A lot a different softwares and printers are available on the market, and it can be difficult to choose which one fits best one's needs. In the authors' institution, the authors regularly print orbits to prepare the reconstruction. The authors then compared the 3D printing of an orbital fracture between a professional and nonprofessional software and between a bottom of the range and a more elaborated printer. The results show that there is a wide variation between the quality of the printing, as well as the time used for the preparation. Costs between free or professional software must also be considered. In conclusion, an analysis of needs and what is available on the market must be studied before investing in 3D printing.

Accuracy of computer-assisted surgery in mandibular reconstruction: A systematic review

Computer-assisted surgery (CAS) for mandibular reconstruction was developed to improve conventional treatment methods. In the past years, many different software programs have entered the market, offering numerous approaches for preoperative planning and postoperative evaluation of the CAS process of mandibular reconstruction. In this systematic review, we reviewed planning and evaluation methods in studies that quantitatively assessed accuracy of mandibular reconstruction performed with CAS. We included 42 studies describing 413 mandibular reconstructions planned and evaluated using CAS. The commonest software was Proplan/Surgicase CMF (55%). In most cases, the postoperative virtual 3-dimensional model was compared to the preoperative 3-dimensional model, revised to the virtual plan (64%). The commonest landmark for accuracy measurements was the condyle (54%). Accuracy deviations ranged between 0 mm and 12.5 mm and between 0.9° and 17.5°. Because of a lack of uniformity in planning (e.g., image acquisition, mandibular resection size) and evaluation methodologies, the ability to compare postoperative outcomes was limited; meta-analysis was not performed. A practical and simple guideline for standardizing planning and evaluation methods needs to be considered to allow valid comparisons of postoperative results and facilitate meta-analysis in the future.

A 3-Dimensional-Printed Short-Segment Template Prototype for Mandibular Fracture Repair

IMPORTANCE

After reduction of complex mandibular fractures, contouring of the fracture plates to fixate the reduced mandibular segments can be time-consuming.

OBJECTIVE

To explore the potential application of a 3-dimensional (3-D)-printed short-segment mandibular template in the management of complex mandibular fractures.

DESIGN, SETTING, AND PARTICIPANTS

A feasibility study was performed at a tertiary academic center using maxillofacial computed tomography data of 3 patients with comminuted mandibular fractures who required preoperative planning with a perfected complete mandible model.

INTERVENTIONS

Thresholding, segmentation, and realignment of the fractured mandible were performed based on computed tomography data. Each reduced mandible design was divided to create 3-D templates for 6 fracture sites: right and left angle, body, and symphyseal/parasymphyseal. Sessions were conducted with junior otolaryngology and plastic surgery residents, during which mandibular fracture plates were contoured in a "preoperative" setting against the 3-D-printed short-segment templates, and an "intraoperative" setting against the previously manufactured, complete mandible model. The previously manufactured, complete model served as a surrogate for the intraoperative mandible with the fracture site reduced.

MAIN OUTCOMES AND MEASURES

The time for 3-D template printing, the "preoperative" (measure of the time consumed preoperatively), and "intraoperative" (measure of the time saved intraoperatively) times were recorded. Comparisons were made for cost estimates between a complete model and the 3-D-printed short-segment template. The operating room charge equivalent of the intraoperative time was also calculated.

RESULTS

Of the 3 patients whose data were used, 1 was a teenager and 2 were young adults. The total time for 3-D modeling and printing per short-segment template was less than 3 hours. The median (range) intraoperative time saved by precontouring the fracture plates was 7 (1-14), 5 (1-30), and 7 (2-15) minutes, and the operating room charge equivalents were $350.35 ($50.05-$700.70), $250 ($50.05-$1501.50), and $350.35 ($100.10-$750.75) for the angle, body, and symphyseal/parasymphyseal segments, respectively. The total cost for a single 3-D-printed template was less than $20, while that for a perfected complete model was approximately $2200.

CONCLUSIONS AND RELEVANCE

We demonstrate that patient- and site-specific 3-D-printed short-segment templates can be created within the timeframe required for mandibular fracture repair. These novel 3-D-printed templates also demonstrate cost efficiency in the preoperative planning for complex mandibular fracture management compared with perfected models and facilitate plate contouring in a similar fashion. Estimation of reduced operative room cost and time with the application of these short-segment templates warrants studies in actual patient care.

LEVEL OF EVIDENCE

NA.

Designing CAD/CAM Surgical Guides for Maxillary Reconstruction Using an In-house Approach

Computer-aided design/computer-assisted manufacturing (CAD/CAM) is now being evaluated as a preparative technique for maxillofacial surgery. Because this technique is expensive and available in only limited areas of the world, we developed a novel CAD/CAM surgical guide using an in-house approach. By using the CAD software, the maxillary resection area and cutting planes and the fibular cutting planes and angles are determined. Once the resection area is decided, the necessary faces are extracted using a Boolean modifier. These superficial faces are united to fit the surface of the bones and thickened to stabilize the solids. Not only the cutting guides for the fibula and maxilla but also the location arrangement of the transferred bone segments is defined by thickening the superficial faces. The CAD design is recorded as .stl files and three-dimensionally (3-D) printed as actual surgical guides. To check the accuracy of the guides, model surgery using 3-D-printed facial and fibular models is performed. These methods may be used to assist surgeons where commercial guides are not available.

All-in-one surgical guide: A new method for cranial vault resection and reconstruction

INTRODUCTION

Great precision is required for craniofacial surgery, and computer-aided design (CAD) methods may be used to plan surgery before it is performed. In this study, three-dimensional (3D)-printed cutting guides are used to match computer models with surgical procedures. We describe a novel method of computer-aided surgery for autologous cranioplasty that includes a new strategy for generating and using cutting guides. These guides may be used not only for osteotomies, but also for many other steps in the surgical procedure.

MATERIALS AND METHODS

Preoperatively, anatomical data were imported into a CAD package and used for virtual surgical planning (VSP). Cutting guides were designed after considering how to integrate all the surgical steps. Models of the microplates and micro-screws were also made. Surgical guides were exported and printed, and preoperative simulations using a replica of the patient's skull established the sequence of steps. The accuracy of the procedure was evaluated postoperatively using computed tomography (CT) scans.

RESULTS

In every patient examined, the all-in-one surgical-guide system was able to automate the many steps in the procedure and dramatically decreased the duration of surgery. The experimental guide enhanced every phase of surgery, including excising the lesion, and harvesting, positioning, and fixing the graft. In each step, precision was enhanced and the outcome corresponded with the VSP.

CONCLUSIONS

The few previous reports on cutting guides used in cranioplasty generally describe the use of separate guides for dismantling and reconstruction. The ability to perform more surgical sequences using a single tool can improve surgical accuracy. Clearly there is no single perfect surgical guide; however, effective surgical-design strategies should be used to build the best approach to each procedure.

Using an In-House Approach to Computer-Assisted Design and Computer-Aided Manufacturing Reconstruction of the Maxilla

PURPOSE

Computer-assisted design (CAD) and computer-aided manufacturing (CAM) techniques are in widespread use for maxillofacial reconstruction. However, CAD/CAM surgical guides are commercially available only in limited areas. To use this technology in areas where these commercial guides are not available, the authors developed a CAD/CAM technique in which all processes are performed by the surgeon (in-house approach). The authors describe their experience and the characteristics of their in-house CAD/CAM reconstruction of the maxilla.

PATIENTS AND METHODS

This was a retrospective study of maxillary reconstruction with a free osteocutaneous flap. Free CAD software was used for virtual surgery and to design the cutting guides (maxilla and fibula), which were printed by a 3-dimensional printer. After the model surgery and pre-bending of the titanium plates, the actual reconstructions were performed. The authors compared the clinical information, preoperative plan, and postoperative reconstruction data. The reconstruction was judged as accurate if more than 80% of the reconstructed points were within a deviation of 2 mm.

RESULTS

Although on-site adjustment was necessary in particular cases, all 4 reconstructions were judged as accurate. In total, 3 days were needed before the surgery for planning, printing, and pre-bending of plates. The average ischemic time was 134 minutes (flap suturing and bone fixation, 70 minutes; vascular anastomoses, 64 minutes). The mean deviation after reconstruction was 0.44 mm (standard deviation, 0.97). The deviations were 67.8% for 1 mm, 93.8% for 2 mm, and 98.6% for 3 mm. The disadvantages of the regular use of CAD/CAM reconstruction are the intraoperative changes in defect size and local tissue scarring.

CONCLUSION

Good accuracy was obtained for CAD/CAM-guided reconstructions based on an in-house approach. The theoretical advantage of computer simulation contributes to the accuracy. An in-house approach could be an option for maxillary reconstruction.