Computer-assisted three-dimensional surgical planning and simulation: 3D virtual osteotomy

Shaping the 4D frontier in maxillofacial surgery with faceMesh evolution

OBJECTIVES

This work aims to introduce a Python-based algorithm and delve into the recent paradigm shift in Maxillofacial Surgery propelled by technological advancement. The provided code exemplifies the utilization of the MediaPipe library, created by Google in C++, with an additional Python interface available as a binding.

TECHNICAL NOTE

The advent of FaceMesh coupled with artificial intelligence (AI), has brought about a transformative wave in contemporary maxillofacial surgery. This cutting-edge deep neural network, seamlessly integrated with Virtual Surgical Planning (VSP), offers surgeons precise 4D facial mapping capabilities. It accurately identifies facial landmarks, tailoring surgical interventions to individual patients, and streamlining the overall surgical procedure.

CONCLUSION

FaceMesh emerges as a revolutionary tool in modern maxillofacial surgery. This deep neural network empowers surgeons with detailed insights into facial morphology, aiding in personalized interventions and optimizing surgical outcomes. The real-time assessment of facial dynamics contributes to improved aesthetic and functional results, particularly in complex cases like facial asymmetries or reconstructions. Additionally, FaceMesh has the potential for early detection of medical conditions and disease prediction, further enhancing patient care. Ongoing refinement and validation are essential to address limitations and ensure the reliability and effectiveness of FaceMesh in clinical settings.

Emerging Trends in Virtual Surgical Planning for Orthognathic Surgery: A Global Overview of Research and Publication Patterns

PURPOSE

Anticipating trends and pursuing innovative ideas are imperative for the advancement of science. The objective of this study was to conduct a bibliometric analysis of 3-dimensional virtual simulation in orthognathic surgery, explore its implications for clinical practice, and identify future publication trends through digital tools.

METHODS

This study employed a retrospective bibliometric analysis using data obtained from the Web of Science database. The search strategy focused on articles related to orthognathic surgery and virtual simulation techniques. RStudio and bibliometrix tools were used to data mining. The independent variables retrieved from digital analysis were the emerging themes related to virtual planning in orthognathic surgery. The trends that we identified were facial esthetics, digital workflow, personalized treatments, and complex cases. The primary outcome variable was the number of publications dedicated to virtual simulation in orthognathic surgery, along with secondary outcomes such as citation rates, language of publication, country of origin, institutional affiliations, and emerging research themes. Covariates included variables related to publication characteristics, author affiliations, and geographic distribution of publications. Publication analyses over time involved descriptive statistics, regression analysis, Pearson correlation tests, and graphical representation techniques. Statistical significance was set at a 95% confidence interval (P value < .05).

RESULTS

A comprehensive analysis of 987 articles reveals the impact of included authors, with a mean h-index of 62 (SD = 18.4). The analysis further illuminates a discernible upward trend in publications on this subject, showcasing a linear pattern with a notable R2 value of 0.88 (P = .021). English remains the predominant language of publication, accounting for 97.97% of articles, while contributions hailed from a diverse spectrum of 56 countries. Interestingly, a moderate correlation emerges between publication numbers and gross domestic product per capita (r = 0.30, P = .044) and total area (r = 0.30, P = .032), whereas a more substantial correlation is evident with total population (r = 0.61, P = .034). Notably, the most cited article amassed 254 citations. Furthermore, a Pearson correlation coefficient of 0.97 underscores the correlation between citation density and the year of publication.

CONCLUSION

The bibliometric indicators provided insights for evaluating research productivity and the quality of research output. Emerging themes included facial esthetics, 3-dimensional printing, and the utilization of custom-made templates and implants. This study holds relevance for maxillofacial surgeons, academics, and researchers alike.

GA-Net: A geographical attention neural network for the segmentation of body torso tissue composition

PURPOSE

Body composition analysis (BCA) of the body torso plays a vital role in the study of physical health and pathology and provides biomarkers that facilitate the diagnosis and treatment of many diseases, such as type 2 diabetes mellitus, cardiovascular disease, obstructive sleep apnea, and osteoarthritis. In this work, we propose a body composition tissue segmentation method that can automatically delineate those key tissues, including subcutaneous adipose tissue, skeleton, skeletal muscle tissue, and visceral adipose tissue, on positron emission tomography/computed tomography scans of the body torso.

METHODS

To provide appropriate and precise semantic and spatial information that is strongly related to body composition tissues for the deep neural network, first we introduce a new concept of the body area and integrate it into our proposed segmentation network called Geographical Attention Network (GA-Net). The body areas are defined following anatomical principles such that the whole body torso region is partitioned into three non-overlapping body areas. Each body composition tissue of interest is fully contained in exactly one specific minimal body area. Secondly, the proposed GA-Net has a novel dual-decoder schema that is composed of a tissue decoder and an area decoder. The tissue decoder segments the body composition tissues, while the area decoder segments the body areas as an auxiliary task. The features of body areas and body composition tissues are fused through a soft attention mechanism to gain geographical attention relevant to the body tissues. Thirdly, we propose a body composition tissue annotation approach that takes the body area labels as the region of interest, which significantly improves the reproducibility, precision, and efficiency of delineating body composition tissues.

RESULTS

Our evaluations on 50 low-dose unenhanced CT images indicate that GA-Net outperforms other architectures statistically significantly based on the Dice metric. GA-Net also shows improvements for the 95% Hausdorff Distance metric in most comparisons. Notably, GA-Net exhibits more sensitivity to subtle boundary information and produces more reliable and robust predictions for such structures, which are the most challenging parts to manually mend in practice, with potentially significant time-savings in the post hoc correction of these subtle boundary placement errors. Due to the prior knowledge provided from body areas, GA-Net achieves competitive performance with less training data. Our extension of the dual-decoder schema to TransUNet and 3D U-Net demonstrates that the new schema significantly improves the performance of these classical neural networks as well. Heatmaps obtained from attention gate layers further illustrate the geographical guidance function of body areas for identifying body tissues.

CONCLUSIONS

(i) Prior anatomic knowledge supplied in the form of appropriately designed anatomic container objects significantly improves the segmentation of bodily tissues. (ii) Of particular note are the improvements achieved in the delineation of subtle boundary features which otherwise would take much effort for manual correction. (iii) The method can be easily extended to existing networks to improve their accuracy for this application.

Anterior cerebral falx plane in MR images to estimate the craniofacial midline

Multiple methods have been proposed for evaluating the symmetry of facial contour by utilizing the median sagittal plane of the skull as a reference and measuring the maxillofacial region. To replace the manual mark point analysis method, we used the anterior cerebral falx plane in MRI images as an indicator of the craniofacial midline. The MRI examination data of 30 individuals were analyzed with a MeVisLab workstation. Two independent examiners performed 15 anthropometric measurements (4 angular, 11 linear) and compared the MRI-based anterior cerebral falx plane with the manual mark point analysis of the craniofacial midline estimation. All measurements were repeated after 3 weeks. Statistical analyses included the repeatability and reproducibility of the 2 methods based on intra-observer and inter-observer correlation coefficients (ICCs), respectively. Precision was estimated by intergroup comparison of the coefficient of variation. The anterior falx plane derived from the MRI data resulted in an intra-observer ICC of 0.869 ± 0.065 (range 0.733-0.936) and inter-observer ICC of 0.876 ± 0.0417 (0.798-0.932) for all measurements, showing significant correlations with the ICC values obtained by the mark point method (p < 0.05). The coefficient of variation showed that the precisions of the 2 methods were statistically comparable. We conclude that, for MRI-based craniofacial midline estimation, measurements made using the anterior cerebral falx plane are as precise, repeatable, and reproducible as those using the manual mark point analysis method. It has a high potential for application in radiation-free 3-dimensional craniofacial analysis.

Gender Facial Affirmation Surgery; Techniques for Feminizing the Chin

The shape and size of the chin are very important in feminizing the lower third of the face, and osseous genioplasty is commonly used in FFS. Different variations of the osseous genioplasty can be used to feminize the chin. The 1-piece genioplasty reduces the size and rounds the chin. 2-piece genioplasty reduces or increases the projection of the chin, but retains the same shape. 3-piece genioplasty also reduces or increases the projection, but has the additional benefit of narrowing the chin. This narrowing helps to create the "V" shaped lower face that is often desired by patients seeking facial feminization. Protection of the mental nerve and resuspension of the mentalis muscle is essential to prevent permanent lower lip numbness and ptosis respectively.

Accuracy of mandibular repositioning surgery using new technology: Computer-aided design and manufacturing customized surgical cutting guides and fixation plates

INTRODUCTION

Recent 3-dimensional technology advancements have resulted in new techniques to improve the accuracy of intraoperative transfer. This study aimed to validate the accuracy of computer-aided design and manufacturing (CAD-CAM) customized surgical cutting guides and fixation plates on mandibular repositioning surgery performed in isolation or combined with simultaneous maxillary repositioning surgery.

METHODS

Sixty patients who underwent mandibular advancement surgery by the same surgeon were retrospectively evaluated by 3-dimensional surface-based superimposition. A 3-point coordinate system (x, y, z) was used to identify the linear and angular discrepancies between the planned movements and actual outcomes. Wilcoxon rank sum test was used to compare the outcomes between the mandible-only and the bimaxillary surgery groups with significance at P <0.05. Pearson correlation coefficient compared planned mandible advancement to the outcome from advancement planned. The centroid, which represents the mandible as a single unit, was computed from 3 landmarks, and the discrepancies were evaluated by the root mean square error (RMSE) for clinical significance set at 2 mm for linear discrepancies and 4° for angular discrepancies.

RESULTS

There was no statistically significant difference between the planned and actual position of the mandible in either group when considering absolute values of the differences. When considering raw directional data, a statistically significant difference was identified in the y-axis suggesting a tendency for under-advancement of the mandible in the bimaxillary group. The largest translational RMSE for the centroid was 0.77 mm in the sagittal dimension for the bimaxillary surgery group. The largest rotational RMSE for the centroid was 1.25° in the transverse dimension for the bimaxillary surgery group. Our results show that the precision and clinical feasibility of CAD-CAM customized surgical cutting guides and fixation plates on mandibular repositioning surgery is well within clinically acceptable parameters.

CONCLUSION

Mandibular repositioning surgery can be performed predictably and accurately with the aid of CAD-CAM customized surgical cutting guides and fixation plates with or without maxillary surgery.

The Feasibility of Computer Simulations and 3-Dimensional-Printed Resection Guides for Skin Cancer Resection

The surgical resection margin in skin cancer is traditionally determined by the lesion's surface boundary without 3-dimensional information. Computed tomography (CT) can offer additional information, such as tumor invasion and the exact cancer extent. This study aimed to demonstrate the clinical application of and to evaluate the safety and accuracy of resection guides for skin cancer treatment. This prospective randomized comparison of skin cancer resection with (guide group; n=34) or without (control group; n=28) resection guide use was conducted between February 2020 and November 2021. Patients with squamous cell carcinoma or basal cell carcinoma were included. In the guide group, based on CT images, the surgical margin was defined, and a 3-dimensional-printed resection guide was fabricated. The intraoperative frozen biopsy results and distance from tumor boundary to resection margin were measured. The margin involvement rates were 8.8% and 17.9% in the guide and control groups, respectively. The margin involvement rate was nonsignificantly higher in the control group as compared with the guide group ( P =0.393). The margin distances of squamous cell carcinoma were 2.3±0.8 and 3.4±1.6 mm ( P =0.01) and those of basal cell carcinoma were 2.8±1.0 and 4.7±3.2 mm in the guide and control groups, respectively ( P =0.015). Margin distance was significantly lower in the guide group than the control group. The resection guide demonstrated similar safety to traditional surgical excision but enabled the minimal removal of normal tissue by precisely estimating the tumor border on CT scans.

The Feasibility of Robot-Assisted Chin Osteotomy on Skull Models: Comparison with Surgical Guides Technique

Surgical robotic technology is characterized by its high accuracy, good stability, and repeatability. The accuracy of mandibular osteotomy is important in tumor resection, function reconstruction, and abnormality correction. This study is designed to compare the operative accuracy between robot-assisted osteotomy and surgical guide technique in the skull model trials which simulated the genioplasty. In an experimental group, robot-assisted chin osteotomy was automatically performed in 12 models of 12 patients according to the preoperative virtual surgical planning (VSP). In a control group, with the assistance of a surgical guide, a surgeon performed the chin osteotomy in another 12 models of the same patients. All the mandibular osteotomies were successfully completed, and then the distance error and direction error of the osteotomy plane were measured and analyzed. The overall distance errors of the osteotomy plane were 1.57 ± 0.26 mm in the experimental group and 1.55 ± 0.23 mm in the control group, and the direction errors were 7.99 ± 1.10° in the experimental group and 8.61 ± 1.05° in the control group. The Bland-Altman analysis results revealed that the distance error of 91.7% (11/12) and the direction error of 100% (12/12) of the osteotomy plane were within the 95% limits of agreement, suggesting the consistency of differences in the osteotomy planes between the two groups. Robot-assisted chin osteotomy is a feasible auxiliary technology and achieves the accuracy level of surgical guide-assisted manual operation.

The untold history of planning in orthognathic surgery: a narrative review from the beginning to virtual surgical simulation

We aimed to produce a narrative review of planning orthognathic surgery, chronologically. Also, to present flaws of methods and the future of orthognathic surgery planning. The search was carried out mainly in PubMed, SCOPUS, Embase, and Cochrane databases. Also was complemented by manual search in reference lists from identified studies and in grey literature. The first orthognathic surgery was reported in 1849, and it took more than a century for the development of the traditional orthognathic 2D planning. Besides the advances, surgeons observed failures and lacks on 2D method in representing with reliability the facial and maxillary tridimensional structure (3D). With technological developments in 90s and 2000s, methodological improvements were granted, and the 3D protocol was created. The CASS and Charlotte protocols were the earliest 3D planning protocols conceived. Since then, some steps were simplified, and new technologies are being developed and added to create a more reliable and precise way of planning orthognathic surgery.

Collaborative Control Method and Experimental Research on Robot-Assisted Craniomaxillofacial Osteotomy Based on the Force Feedback and Optical Navigation

Surgical robot has advantages in high accuracy and stability. But during the robot-assisted bone surgery, the lack of force information from surgical area and incapability of intervention from surgeons become the obstacle. The aim of the study is to introduce a collaborative control method based on the force feedback and optical navigation, which may optimally combine the excellent performance of surgical robot with clinical experiences of surgeons.

Computer Aided Orthognathic Surgery: A General Method for Designing and Manufacturing Personalized Cutting/Repositioning Templates

Orthognathic surgery allows broad-spectrum deformity correction involving both aesthetic and functional aspects on the TMJ (temporo-mandibular joint) and on the facial skull district. The combination of Reverse Engineering (RE), Virtual Surgery Planning (VSP), Computer Aided Design (CAD), Additive Manufacturing (AM), and 3D visualization allows surgeons to plan, virtually, manipulations and the translation of the human parts in the operating room. This work’s aim was to define a methodology, in the form of a workflow, for surgery planning and for designing and manufacturing templates for orthognathic surgery. Along the workflow, the error chain was checked and the maximum error in virtual planning was evaluated. The three-dimensional reconstruction of the mandibular shape and bone fragment movements after segmentation allow complete planning of the surgery and, following the proposed method, the introduction of both the innovative evaluation of the transversal intercondylar distance variation after mandibular arch advancement/set and the possibility of use of standard plates to plan and realize a customized surgery. The procedure was adopted in one clinical case on a patient affected by a class III malocclusion with an associated open bite and right deviation of the mandible with expected good results. Compared with the methods from most recent literature, the presented method introduces two elements of novelty and improves surgery results by optimizing costs and operating time. A new era of collaboration among surgeons and engineer has begun and is now bringing several benefits in personalized surgery.

The validity of using profile predictions for class III patients planned for bimaxillary orthognathic surgery

This study assessed whether preoperative class III patients could recreate their facial difference based on a profile photograph. Twenty class III pre-surgery bimaxillary orthognathic patients used CASSOS (SoftEnable Technology Ltd.) to manipulate a distorted soft tissue image of them until they felt it resembled their current soft tissue profile. Patients were able to move their upper lip and lower chin backward and forwards, as well as the lower chin up and down. Differences in the mean absolute distance between the patient-perceived position of the upper lip (Labrale superious) and chin (Pogonion) and the actual position of their upper lip and chin were measured on two occasions. Intra-patient reproducibility was found to be excellent (ICC 0.93 to 0.98). All differences were statistically significantly greater than 3mm, and would be clinically significant. Patients were better at re-creating their AP chin position rather than their AP upper lip and vertical chin positions. Approximately half of patients undergoing surgical correction of their class III skeletal pattern were unable to correctly identify their pre-surgical facial profile. Given the lack of awareness of their profile, this questions the validity of using profile planning for informed consent.

Trade-Off between Task Accuracy, Task Completion Time and Naturalness for Direct Object Manipulation in Virtual Reality

Virtual reality devices are used for several application domains, such as medicine, entertainment, marketing and training. A handheld controller is the common interaction method for direct object manipulation in virtual reality environments. Using hands would be a straightforward way to directly manipulate objects in the virtual environment if hand-tracking technology were reliable enough. In recent comparison studies, hand-based systems compared unfavorably against the handheld controllers in task completion times and accuracy. In our controlled study, we compare these two interaction techniques with a new hybrid interaction technique which combines the controller tracking with hand gestures for a rigid object manipulation task. The results demonstrate that the hybrid interaction technique is the most preferred because it is intuitive, easy to use, fast, reliable and it provides haptic feedback resembling the real-world object grab. This suggests that there is a trade-off between naturalness, task accuracy and task completion time when using these direct manipulation interaction techniques, and participants prefer to use interaction techniques that provide a balance between these three factors.

Communication tools and patient satisfaction: A scoping review

Objective

This scoping review aimed to present an overview of the literature on communication tools in esthetic dentistry. A variety of communication tools have been proposed to include patients in the shared decision‐making (SDM) workflow. Only little is known about implementing communication tools in dentistry and their impact on patient communication and patient satisfaction. A systematic literature search was performed in Medline, Embase, Cochrane, and World of Science to identify if communication tools have an impact on patient satisfaction.

Material and Methods

The search included studies from January 1, 2000 to March 3, 2020 published in English, focusing on patient communication tools and patient satisfaction in esthetic dentistry.

Results

Out of 6678 records, 53 full‐texts were examined. Ten studies were included. Data of the included studies were extracted systematically and subsequently analyzed. All studies found that patient communication utilizing specific communication tools positively impacted either patient satisfaction, patient‐dentist relationship, information retention, treatment acceptance, quality of care or treatment outcome.

Conclusions

Additional communication tools besides conventional verbal communication are able to enhance patient satisfaction, improve quality of care and establish a better patient‐dentist relationship. It seems essential to further develop standardized communication tools for SDM in dental medicine, which will allow the comparison of research on this topic.

Clinical significance

This scoping review shows the importance of patient involvement in the decision‐making process for improved patient satisfaction with esthetic dental treatments. With an increased implementation of communication tools, patient satisfaction and SDM may further improve in the future.

Complications on maxilar impaction: A systematic review and meta-analysis

OBJECTIVES

Maxillary impactions are seen as an orthognathic surgical movement that increases the number of complications. The aim of this paper is to research literature on this topic, with special attention to avoiding of complications.

METHODS

A systematic review was carried out according to the PRISMA guidelines. The PROSPERO registration has been performed. A risk of bias assessment was carried out with RevMan and graphics were created. A total of 20 articles were included in this systematic review.

RESULTS

Some interesting and conclusive facts about maxillary impactions. Relapses are not common due to the higher bone contact. Bleeding is a common complication due to the location of palatal artery. Aesthetic and functional complications can arise, especially in the nasal region. Bimaxillary orthognathic surgeries has a higher incidence of complications.

CONCLUSIONS

Today it is not possible to confirm that maxillary impactions alone are responsible for a higher incidence of complications due to the complexity of the three-dimensional movements. Some surgical steps could be safer and cause fewer complications.

Accurate transfer of bimaxillary orthognathic surgical plans using computer-aided intraoperative navigation

Objective

To examine the accuracy of computer-aided intraoperative navigation (Ci-Navi) in bimaxillary orthognathic surgery by comparing preoperative planning and postoperative outcome.

Methods

The study comprised 45 patients with congenital dentomaxillofacial deformities who were scheduled to undergo bimaxillary orthognathic surgery. Virtual bimaxillary orthognathic surgery was simulated using Mimics software. Intraoperatively, a Le Fort I osteotomy of the maxilla was performed using osteotomy guide plates. After the Le Fort I osteotomy and bilateral sagittal split ramus osteotomy of the mandible, the mobilized maxilla and the distal mandibular segment were fixed using an occlusal splint, forming the maxillomandibular complex (MMC). Realtime Ci-Navi was used to lead the MMC in the designated direction. Osteoplasty of the inferior border of the mandible was performed using Ci-Navi when facial symmetry and skeletal harmony were of concern. Linear and angular distinctions between preoperative planning and postoperative outcomes were calculated.

Results

The mean linear difference was 0.79 mm (maxilla: 0.62 mm, mandible: 0.88 mm) and the overall mean angular difference was 1.20°. The observed difference in the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was < 1 mm in 40 cases.

Conclusions

This study demonstrates the role of Ci-Navi in the accurate positioning of bone segments during bimaxillary orthognathic surgery. Ci-Navi was found to be a reliable method for the accurate transfer of the surgical plan during an operation.

Randomized Controlled Clinical Trial to Assess the Utility of Computer-Aided Intraoperative Navigation in Bimaxillary Orthognathic Surgery

ABSTRACT

Accurate application of the preoperative surgical plan in actual surgical settings is of paramount importance in orthognathic surgery. This randomized controlled clinical trial aimed to evaluate the accuracy of computer-aided intraoperative navigation (Ci-Navi) compared with that of conventional navigation methods in bimaxillary orthognathic surgery. Fifty-two patients were randomly divided into 2 groups. Group A (n = 26) patients underwent surgery assisted with Ci-Navi and group B (n = 26) patients underwent surgery assisted with conventional intraoperative navigation methods. During the operation, after LeFort I osteotomy, the mobile maxilla was repositioned to the designated position either using assistance from real-time Ci-Navi (group A) or using an intermediate splint (group B). Intra- and intergroup linear and angular differences between preoperative planning and postoperative outcomes were calculated. In group A, the overall mean linear difference was 0.79 mm (0.62 mm for the maxilla and 0.88 mm for the mandible) and the overall mean angular difference was 1.20°. In 23 cases, the difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm. In group B, the overall mean linear difference was 1.98 mm (1.76 mm for the maxilla and 2.02 mm for the mandible) and the overall mean angular difference was 2.08°. The difference from the upper incisor point to the Frankfort horizontal plane, midfacial sagittal plane, and coronal plane was less than 1 mm in 15 cases. This study demonstrates the utility of Ci-Navi is superior to the conventional methods in aiding the accurate repositioning of bony segments in bimaxillary orthognathic surgery.

A Complete Digital Workflow for Planning, Simulation, and Evaluation in Orthognathic Surgery

The purpose of this study was to develop a complete digital workflow for planning, simulation, and evaluation for orthognathic surgery based on 3D digital natural head position reproduction, a cloud-based collaboration platform, and 3D landmark-based evaluation. We included 24 patients who underwent bimaxillary orthognathic surgery. Surgeons and engineers could share the massive image data immediately and conveniently and collaborate closely in surgical planning and simulation using a cloud-based platform. The digital surgical splint could be optimized for a specific patient before or after the physical fabrication of 3D printing splints through close collaboration. The surgical accuracy was evaluated comprehensively via the translational (linear) and rotational (angular) discrepancies between identical 3D landmarks on the simulation and postoperative computed tomography (CT) models. The means of the absolute linear discrepancy at eight tooth landmarks were 0.61 ± 0.55, 0.86 ± 0.68, and 1.00 ± 0.79 mm in left–right, advance–setback, and impaction–elongation directions, respectively, and 1.67 mm in the root mean square direction. The linear discrepancy in the left–right direction was significantly different from the other two directions as shown by analysis of variance (ANOVA, p < 0.05). The means of the absolute angular discrepancies were 1.43 ± 1.06°, 0.50 ± 0.31°, and 0.58 ± 0.41° in the pitch, roll, and yaw orientations, respectively. The angular discrepancy in the pitch orientation was significantly different from the other two orientations (ANOVA, p < 0.05). The complete digital workflow that we developed for orthognathic patients provides efficient and streamlined procedures for orthognathic surgery and shows high surgical accuracy with efficient image data sharing and close collaboration.

Orthognathic Surgery: A Bibliometric Analysis of the Top 100 Cited Articles

PURPOSE

An increasing number of articles on orthognathic surgery are published every year. This paper aims to provide a list of the top 100 cited articles on orthognathic surgery to help any professional level with interest in this topic and to map the trends of orthognathic surgery publications over time.

METHODS

A bibliographic search (retrospective study) following STROBE guidelines was performed on Google Scholar (GS) and Dimensions with the term "orthognathic surgery" in the title, abstract, and keywords. The number of citations, citations per year, authors, and publication year were evaluated. A ranking was created in GS citations order with the top 100 cited articles and variables discussed individually. A graphical illustration of keywords was created using VOSviewer. These steps are fundamental in creating this list and relating it to all published articles on the topic.

RESULTS

A helpful list of the top 100 articles was developed to help professionals in entirely different manners. Virtual planning and complications in orthognathic surgery were the most cited topics, with a 95% confidence interval (P < .05). Some curiosities are discussed, such as increasing interest in surgery first and the relation between airway/obstructive sleep apnea and orthognathic surgery.

CONCLUSIONS

Bibliometric and altmetric analysis for free using Google Scholar and Dimensions is laborious but possible. Bibliometrics is a powerful tool to become actualized at any health professional level, from students to academics; and could save considerable effort and time for parties interested in the topic. Appropriate keywords are a crucial step to wider article dissemination.

Error Analysis of Robot-Assisted Orthognathic Surgery

OBJECTIVE

Orthognathic surgery is an effective method to correct the dentomaxillofacial deformities. The aim of the study is to introduce the robot-assisted orthognathic surgery and demonstrate the accuracy and feasibility of robot-assisted osteotomy in transferring the preoperative virtual surgical planning (VSP) into the intraoperative phase.

METHODS

The CMF robot system, a craniomaxillofacial surgical robot system was developed, consisted of a robotic arm with 6 degrees of freedom, a self-developed end-effector, and an optical localizer. The individualized end-effector was installed with reciprocating saw so that it could perform osteotomy. The study included control and experimental groups. In control group, under the guidance of navigation system, surgeon performed the osteotomies on 3 skull models. In experimental group, according to the preoperative VSP, the robot completed the osteotomies on 3 skull models automatically with assistance of navigation. Statistical analysis was carried out to evaluate the accuracy and feasibility of robot-assisted orthognathic surgery and compare the errors between robot-assisted automatic osteotomy and navigation-assisted manual osteotomy.

RESULTS

All the osteotomies were successfully completed. The overall osteotomy error was 1.07 ± 0.19 mm in the control group, and 1.12 ± 0.20 mm in the experimental group. No significant difference in osteotomy errors was found in the robot-assisted osteotomy groups (P = 0.353). There was consistence of errors between robot-assisted automatic osteotomy and navigation-assisted manual osteotomy.

CONCLUSION

In robot-assisted orthognathic surgery, the robot can complete an osteotomy according to the preoperative VSP and transfer a preoperative VSP into the actual surgical operation with good accuracy and feasibility.

A comparative study of the accuracy between two computer-aided surgical simulation methods in virtual surgical planning

OBJECTIVE

The aim of this retrospective and observational study was to compare the accuracy of two different virtual surgical planning (VSP) protocols, namely, the CASS method and the modified CASS method.

MATERIALS AND METHODS

The patients underwent bimaxillary orthognathic surgery, planned using either the CASS method or the modified CASS method. Linear and angular discrepancies between the VSP outcome and postoperative outcome for both groups were compared for maxilla, mandible, and chin segments. Aside from the comparison between both groups, additional criteria were used to determine the accuracy of the protocol based on a linear and angular difference between planned and actual outcomes of less than 2 mm and 4°, respectively. The intergroup comparisons were performed by one-way ANOVA, with the level of significance set at 5%.

RESULTS

A total of 21 patients, of both genders, were assigned into group I (n = 11), planned with the CASS method, and group II (n = 10), planned with the modified CASS method. Both the CASS and modified CASS methods presented similar accuracy with regard to linear differences for the maxilla, mandible, and chin segments, except for ΔX for the mandibular segment, where the modified CASS method showed slightly better accuracy. However, there was a statistically significant difference with regard to angular differences in the chin segment, with the CASS method shown to be the more accurate. Aside from Δpitch for the chin segment, no linear or angular differences exceeded 2 mm or 4°.

CONCLUSION

Although statistically significant differences were found with regard to angular measurements in the chin segment, the accuracy of the modified CASS method for virtual planning can be considered as clinically equivalent, with a performance comparable to that of the CASS method.

Accuracy of splint vs splintless technique for virtually planned orthognathic surgery: A voxel-based three-dimensional analysis

PURPOSE

This study compared two transferring methods for virtually planned orthognathic surgery - the CAD/CAM intermediate splint and the customized surgical guide with fixation plates.

METHODS

This was a prospective clinical study in which participants were consecutively recruited and underwent bimaxillary orthognathic surgery. They were divided into two groups based on the transferring method used. The pre- and postoperative CBCTs were aligned using voxel-based landmark-free registration, and the discrepancies for selected points were compared with the planned displacement of the virtually planned surgery. The maxilla and mandible were analyzed separately, and translation and rotation movements were considered.

RESULTS

A total of 16 patients, divided into two groups of eight patients each, were included in this study. The splintless group was significantly more accurate for the translation movement along the x-axes for points A (p = 0.008; mean absolute error 0.527 ± 0.387 for the splint group and 0.137 ± 0.067 for the splintless group) and Ans (p = 0.045; mean absolute error 0.535 ± 0.446 for the splint group and 0.156 ± 0.002 for the splintless group). For the mandible there was a significant difference in accuracy along the x-axes for points B (p = 0.049; mean absolute errors 1.728 ± 1.181 and 0.697 ± 0.519 for the splint and splintless groups, respectively), LL3 (p = 0.049; mean absolute error 1.629 ± 0.912 and 0.851 ± 0.797 for the splint and splintless groups, respectively), LR3 (p = 0.049; mean absolute error 1.711 ± 0.906 and 0.844 ± 0.780 for the splint and splintless groups, respectively), with the splintless group being more accurate. For the rotation the splintless group was significantly more accurate along the y-axes (p = 0.04; mean absolute error 1.62 ± 0.78 and 0.49 ± 0.31 for the splint and splintless groups, respectively) and z-axes (p = 0.04; mean absolute error 0.63 ± 0.45 and 0.17 ± 0.05 for the splint and splintless groups, respectively) for the maxilla, while no significant difference was found for the mandible.

CONCLUSIONS

Overall, the customized fixation plate system is more accurate than the intermediate CAD/CAM splint for transferring the virtual plan into the operation room.

Accuracy of three-dimensional virtual simulation of the soft tissues of the face in OrtogOnBlender for correction of class II dentofacial deformities: an uncontrolled experimental case-series study

Purpose

To assess whether virtual simulations of the projection of the soft tissues of the face after class II bimaxillary orthognathic surgery, generated from 3D reconstruction of preoperative computed tomography (CT) scans, differed significantly from the actual soft tissue profile obtained in the late postoperative period (beyond 6 months). Secondarily, to validate the accuracy of a free, open-source software suite for virtual soft tissue planning in orthognathic surgery.

Methods

Helical CT scans were obtained pre- and postoperatively from 16 patients with Angle class II malocclusion who underwent bimaxillary orthognathic surgery. A comparative study between soft tissue meshes constructed for surgical simulation (M1) and the actual meshes obtained from postoperative scans (M2) was then performed. To establish the accuracy of 3D facial soft tissue simulation in a free and open-source software suite (OrtogOnBlender-OOB), 17 predetermined anatomic landmarks were measured in M1 and M2 scans after alignment of cranial structures.

Results

The mean error between preoperative simulations and actual postoperative findings was < 2 mm for all anthropometric landmarks. The overall average error for the facial soft tissues was 1.07 mm.

Conclusion

Comparison between preoperative simulation (M1) and actual postoperative findings (M2) showed clinically relevant ability of the method to reproduce actual surgical movement reliably (< 2-mm error). OOB is capable of accurate soft tissue planning for orthognathic surgery, but mesh deformation methods still require improvement.

Trial registration

RBR-88jff9. Retrospectively registered at Brazilian Registry of Clinical trials-ReBec (http://www.ensaiosclinicos.gov.br) May 06, 2020.

Simplified orthognathic surgical treatment using non-surgical asymmetric maxillary expansion: A case report

BACKGROUND

Transverse problems can be exacerbated by highly compensated occlusion in patients with skeletal asymmetry, which makes pre-surgical decompensation harder to achieve.

OBJECTIVE

This case report describes a case of combined orthognathic surgery with facial asymmetry. We used pre-orthodontic surgical simulation to visualize the goal for presurgical orthodontics, planning for a one-jaw surgical treatment option.

METHODS

The planned asymmetric expansion was performed using a maxillary skeletal expander (MSE II) with surgical corticopuncture over only the left side before MSE activation. Surgery was performed to achieve mandibular left outward yaw rotation to correct the patient's facial asymmetry after the planned amount of expansion was reached.

RESULTS

The results showed substantial improvement of facial aesthetics as well as skeletal symmetry. Cooperation and communication between surgeon and orthodontist ensured that the final results were satisfactory.

Titanium Alloy Cutting Guides in Craniomaxillofacial Surgery-A Minimally Invasive Alternative to Synthetic Polymer Guides

PURPOSE

Historically, synthetic polymers, such as polyamide, have been the predominate material used for patient-specific cutting guides in 3-dimensionally guided craniomaxillofacial surgery. The physical properties of polyamide result in guides that are bulky and difficult to place within the confines of the facial soft tissue envelope, requiring larger incisions with resultant morbidity. Despite their utility, we found the need for wider exposure simply for guide placement was unacceptable. The purpose of the present study was to evaluate our experience with the newly marketed titanium alloy cutting guides.

MATERIALS AND METHODS

We conducted a retrospective cohort study of patients who had undergone either segmental mandibulectomy or maxillectomy using patient-specific titanium alloy cutting guides from May to December 2019. The primary outcome variable was the need for an extended-access cervical incision or a transfacial incision for either maxillectomy or segmental mandibulectomy in patients with benign disorders. The secondary outcome variables included the need for a transfacial incision in patients with malignant pathology requiring either maxillectomy or composite oromandibular resection and the final histopathologic bone margin status.

RESULTS

Of the 21 included patients, 11 had undergone maxillectomy (1 of 2) or segmental mandibulectomy (9 of 9) for benign disorders, with 91% (10 of 11) having undergone titanium alloy guide placement and resection entirely transorally without the need for an extended cervical or a transfacial incision. For 10 of the 11 patients undergoing immediate reconstruction with vascularized bone flaps, transcervical access was limited to small 1.5- to 2.5-cm incisions for target vessel access and microvascular anastomosis. None of the 10 patients with a malignant disorder requiring either maxillectomy or composite oromandibular resection required a transfacial incision. The bone margins, as determined by histopathologic analysis, were negative for 100% of the patients.

CONCLUSIONS

Patient-specific titanium alloy cutting guides represent a viable alternative to traditional synthetic polymer guides. Their superior properties permit easier intraoral placement, decreasing the need for cutaneous incisions and excessive periosteal stripping.

Stability of Orthognathic Surgery in the Treatment of Condylar Osteochondroma Combined With Jaw Deformity by CT Measurements

PURPOSE

We evaluated the stability of orthognathic surgery in the treatment of unilateral condylar osteochondroma combined with jaw deformity.

PATIENTS AND METHODS

Patients with unilateral condylar osteochondroma and jaw deviation deformity who had undergone surgery at the Ninth People's Hospital of Shanghai Jiaotong University School of Medicine from July 2014 to March 2017 were enrolled. The operation included a low condylectomy and both Le Fort I osteotomy and bilateral mandibular sagittal split osteotomies. ProPlan CMF, version 1.4, software (Materialise, Leuven, Belgium) was used to reconstruct and measure the preoperative, immediately postoperative, and follow-up (>6 months) maxillofacial computed tomography images. The position of the jaw and contralateral condyle and remodeling of the affected side were compared during follow-up.

RESULTS

Eight patients were included in the present study. The canting of the maxilla was significantly decreased postoperatively, and the contralateral condyle had rotated inward. The position of the maxillary and contralateral condyles was stable during follow-up, and the posterior aspect of the affected condyle demonstrated significant resorption.

CONCLUSIONS

The results of single-stage surgery combined with orthognathic surgery and condylar osteochondroma resection were stable, and the affected condyle stump had adaptively reconstructed.

The Accuracy of Maxillary Position Using a Computer-Aided Design/Computer-Aided Manufacturing Intermediate Splint Derived Via Surgical Simulation in Bimaxillary Orthognathic Surgery

PURPOSE

The purpose of this study was to assess the clinical interventions and the accuracy of maxillary reposition using a computer-aided design/computer-aided manufacturing (CAD/CAM) splint derived via surgical simulation.

MATERIALS AND METHODS

The retrospective study comprised 24 patients who underwent bimaxillary surgery. The patients were assigned to 1 of 2 groups by a way of maxillary repositioning. One group received conventional intermediate wafers and the other CAD/CAM wafers during Le Fort I osteotomy. We recorded operation time, blood loss, the operative accuracy. Accuracy was analyzed by 3-dimensional computed tomography images before and immediately after the operation. The evaluation points were the right maxillary first incisor (U1), the right maxillary second molar (M2-right), and the left maxillary second molar (M2-left).

RESULTS

The 2 groups did not differ significantly in operation time and blood losses. The vertical axis of U1 data differed significantly between the 2 groups (P = 0.008). None of the horizontal, vertical, or anteroposterior axis of M2-right data differed significantly, and anteroposterior axis of M2-left data differed significantly (P = 0.0296). The CAD/CAM group 3-dimensional distance errors were less than those of the conventional group for all points.

CONCLUSION

Placement of CAD/CAM splint allowed highly accurate repositioning; the accuracy exceeded that afforded by conventional model surgery using a facebow and articulator.

Clinical Application of a Patient-Specific, Three-Dimensional Printing Guide Based on Computer Simulation for Rhinoplasty

BACKGROUND

A practical application of three-dimensional printing technology has been considered a difficult area in rhinoplasty. However, the patient-specific three-dimensionally printed rhinoplasty guide based on the simulation program the authors developed could be a solution for minimizing the gap between simulation and actual surgical results. The aims of this study were to determine how a three-dimensional rhinoplasty guide based on three-dimensional simulation would link the patient to the surgeon to investigate its effectiveness.

METHODS

Fifty patients who underwent rhinoplasty between January of 2017 and February of 2018 were included in this study. The patients were consulted about the desired shape of their nose based on preoperative three-dimensional photography. The confirmed three-dimensional simulation was sent to a manufacturing company for three-dimensionally printed rhinoplasty guides. In the guide group, rhinoplasty was performed based on the three-dimensionally printed rhinoplasty guide, and in the control group, procedures were performed based on the surgeon's intuition.

RESULTS

The intraclass correlation coefficient test for comparing the simulated and postoperative measurements showed higher correlation in the three-dimensional printing guide group: higher correlation 11.3 percent in nasal tip projection, 21.6 percent in dorsum height, and 9.8 percent in nasolabial angle. The postoperative result of the nasal dorsum had a statistically significant difference between the two groups (p < 0.05).

CONCLUSIONS

This study demonstrated the usefulness of the three-dimensionally-printed rhinoplasty guide, which delivers the preoperative simulated image in the actual clinical practice of rhinoplasty. This approach could cause a paradigm shift in simulation-based rhinoplasty.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Three-dimensional computed tomography evaluation of craniofacial characteristics according to lateral deviation of chin

Background

The relationship between the lateral deviation of chin and the upper and middle facial third asymmetry is still controversial. The purpose of this study is to evaluate the correlation of upper and middle facial third asymmetry with lateral deviation of chin using 3-dimensional computed tomography. The study was conducted on patients who underwent orthognathic surgery from January 2016 to August 2017. A total of 40 patients were included in this retrospective study. A spiral scanner was used to obtain the 3-dimensional computed tomography scans. The landmarks were assigned on the reconstructed 3-dimensional images, and their locations were verified on the axial, midsagittal, and coronal slices. The Pearson correlation analysis was performed to evaluate the correlation between chin deviation and difference between the measurements of distances in paired craniofacial structures. Statistical analysis was performed at a significance level of 5%.

Results

In mandible, the degree of chin deviation was correlated with the mandibular length and mandibular body length. Mandibular length and mandibular body length are shorter on the deviated-chin side compared to that on the non-deviated side (mandibular length, r = −0.897, p value < 0.001; mandibular body length, r = −0.318, p value = 0.045). In the upper and middle facial thirds, the degree of chin deviation was correlated with the vertical asymmetry of the glenoid fossa and zygonion. Glenoid fossa and zygonion are superior on the deviated-chin side than on the non-deviated side (glenoid fossa, r = 0.317, p value = 0.046; zygonion, r = 0.357, p value = 0.024).

Conclusion

Lateral deviation of chin is correlated with upper and middle facial third asymmetry as well as lower facial third asymmetry. As a result, treatment planning in patients with chin deviation should involve a careful evaluation of the asymmetry of the upper and middle facial thirds to ensure complete patient satisfaction.

Study for Cephalometrics of Facial Bone by Computerized Tomography Images

Authors tried to investigate the maxillomandibular morphology of Korean nationality with computerized tomography images and establish a series of cephalometric values which should be considered in orthognathic plastic surgery in Korea.The computerized tomography images of 200 patients were retrospectively reviewed with the computer workstation in Sanggye Paik Hospital, Inje University College of Medicine from 2016 to 2017.The mean distance between nasion to point A (NA) line and the maxillary central incisor was 5.07 cm. The mean distance from nasion to point B (NB) line to the mandibular central incisor was 7.11 cm. The mean angle between NA line and the long axis of the maxillary central incisor was 20.58 degree. The mean angle between NB line and the long axis of the mandibular central incisor was 26.47 degree. The mean angle between SN (sella to nasion) line and NA line was 83.18 degree. The mean angle between SN line and NB line was 78.83 degree. The mean angle between NA line and NB line was 4.35 degree. There were no any statistically significant differences between age groups. But there were statistically significant difference in the mean of angle between NB line and the long axis of the mandibular central incisor (P = 0.025, between sex groups) and in the mean of angle between NA line and the long axis of the maxillary central incisor between sex groups in the 51 to 60 age group (P = 0.045).The maxillomandibular profile of Korean adults was established which can be applied for orthognathic surgery of Korean patients.

Three-Dimensional Outcome Assessments of Cleft Lip and Palate Patients Undergoing Maxillary Advancement

BACKGROUND

The aim of this retrospective case series study was to compare three-dimensional postsurgical outcomes of patients with cleft lip and palate following maxillary advancement.

METHODS

Fifty consecutive cleft lip and palate patients who underwent whole-pieced Le Fort I advancements were assigned to the major (advancement ≥ 5 mm) or minor (advancement < 5 mm) groups. Three-dimensional surgical simulation was used for presurgical evaluation and planning. Virtual triangles of the presurgical, simulated, and 6-month postoperative stages were used for comparison. Translational and angular changes of each endpoint (A-point, MxR, and MxL) on the virtual triangles and reference planes were recorded and analyzed. Relationships between possible related variables and outcome discrepancies from simulations among all subgroups were also investigated.

RESULTS

Analysis of covariance and the least significant difference test revealed that the outcome discrepancy measurements were affected by different combinations of independent variables. The reliability test showed high consistency of the authors' method for three-dimensional measurements.

CONCLUSIONS

The actual surgical outcomes of cleft lip and palate patients differed from the virtual simulations. The outcome discrepancies are impacted by multiple factors. The outcome discrepancies of all rotational surgical corrections (roll, yaw, and pitch) were positively correlated to the degree of planned surgical movement. Meanwhile, bilateral cleft lip and palate patients are more likely to incur outcome discrepancies in yaw correction with major maxillary advancement. However, a maxillary advancement cutoff value of 5 mm would not necessarily lead to significant translational outcome discrepancies among cleft lip and palate patients.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, IV.

Current status and applications of additive manufacturing in dentistry: A literature-based review

Objective

To study the current status and applications of additive manufacturing (AM) in dentistry along with various technologies, benefits and future scope.

Methods

A significant number of relevant research papers on the additive manufacturing application in dentistry are identified through Scopus and studied using bibliometric analysis that shows an increasing trend of research in this field. This paper briefly describes various types of AM technologies with their accuracy, pros and cons along with different dental materials. Paper also discusses various benefits of AM in dentistry and steps used to create 3D printed dental model using this technology. Further, ten major AM applications in dentistry are identified along with primary references and objectives.

Results

Additive manufacturing is an innovative technique moving towards the customised production of dental implants and other dental tools using computer-aided design (CAD) data. This technology is used to manufacture elaborate dental crowns, bridges, orthodontic braces and can also various other models, devices and instruments with lesser time and cost. With the help of this disruptive innovation, dental implants are fabricated accurately as per patient data captured by the dental 3D scanner. The application of this technology is also being explored for the precise manufacturing of removal prosthetics, aligners, surgical templates for implants and produce models that for the planning of treatment and preoperative positioning of the jaws.

Computer-assisted osteotomy guides and pre-bent titanium plates improve the planning for correction of facial asymmetry

This study investigated the surgical outcomes and accuracy of computer-assisted osteotomy guides and pre-bent titanium plates in the treatment of patients with facial asymmetry. Thirteen patients with facial asymmetry undergoing bimaxillary orthognathic surgery were included. Virtual simulation of Le Fort I osteotomy, sagittal split ramus osteotomy, and genioplasty, if needed, was conducted on the preoperative three-dimensional model. Computer-assisted osteotomy guides and pre-bent titanium plates were produced and used in the actual operation. The postoperative outcome was assessed for facial symmetry and surgical accuracy. All patients were followed up for at least 18 months and their level of satisfaction was investigated. Use of the computer-assisted osteotomy guides and pre-bent titanium plates was successful in all patients. Maxillary canting, mandibular ramus inclination, and mandibular length were corrected on both sides postoperatively. Superimposition of the surgical simulation and postoperative images demonstrated favourable accuracy. Quantitative analysis revealed a mean linear difference of <0.60mm in the maxilla and 1.57mm in the mandible. All patients were satisfied with the surgical outcome; there were no complications or cases of relapse during follow-up. The application of computer-assisted osteotomy guides and pre-bent titanium plates achieved favourable outcomes and accuracy, improving planning for the correction of facial asymmetry.

An integrated haptic-enabled virtual reality system for orthognathic surgery planning

Conventional Orthognathic surgery (OGS) planning involves cephalometric analyses and dental casts to be mounted on an articulator. Dental segments are subsequently identified, cut and repositioned to allow the fabrication of intraoral wafers that guide the positioning of the osteotomy bone segments. This conventional planning introduces many inaccuracies that affect the post-surgery outcomes. Although computer technologies have advanced computational tools for OGS planning, they have failed in providing a practical solution. Many focuses only on some specific stages of the planning process, and their ability to transfer preoperative planning data to the operating room is limited. This paper proposes a new integrated haptic-enabled virtual reality (VR) system for OGS planning. The system incorporates CAD tools and haptics to facilitate a complete planning process and is able to automatically generate preoperative plans. A clinical pre-diagnosis is also provided automatically by the system based on the patient's digital data. A functional evaluation based on a real patient case study demonstrates that the proposed virtual OGS planning method is feasible and more effective than the traditional approach at increasing the intuitiveness and reducing errors and planning times.

Does two-dimensional vs. three-dimensional surgical simulation produce better surgical outcomes among patients with class III facial asymmetry?

The aim of this study was to compare the outcomes of traditional two-dimensional planning (2DP) and three-dimensional surgical simulation (3DS) in the surgical correction of skeletal class III with facial asymmetry. This retrospective cohort study included 37 consecutive adult Taiwanese patients. Preoperative and postoperative three-dimensional cephalometric measurements were obtained from cone beam computed tomography scans. The outcome variables were the differences in preoperative and postoperative linear and angular measurements and the differences between the two groups after surgery. When the surgical result was compared between the 2DP and 3DS groups, significant differences were found for four cephalometric variables: the distance from gonion on the non-deviated side to the midsagittal plane (MSP), mid-gonion to the MSP, upper first molar on the non-deviated side to the Frankfort horizontal plane, and the yaw angle. In the 3DS group, mandibular symmetry was achieved because the centre between the bilateral gonions was improved, and because there was no significant difference in the horizontal gonion (Go to the MSP) between the deviated and non-deviated sides after surgery. 3DS provides all the necessary information for planned surgical movements for the correction of facial asymmetry; it should be considered during surgical planning to improve surgical outcomes, particularly the achievement of bilateral mandibular contour symmetry.

Autonomous bone reposition around anatomical landmark for robot-assisted orthognathic surgery

The purpose of this study was to develop a new method for enabling a robot to assist a surgeon in repositioning a bone segment to accurately transfer a preoperative virtual plan into the intraoperative phase in orthognathic surgery. We developed a robot system consisting of an arm with six degrees of freedom, a robot motion-controller, and a PC. An end-effector at the end of the robot arm transferred the movements of the robot arm to the patient's jawbone. The registration between the robot and CT image spaces was performed completely preoperatively, and the intraoperative registration could be finished using only position changes of the tracking tools at the robot end-effector and the patient's splint. The phantom's maxillomandibular complex (MMC) connected to the robot's end-effector was repositioned autonomously by the robot movements around an anatomical landmark of interest based on the tool center point (TCP) principle. The robot repositioned the MMC around the TCP of the incisor of the maxilla and the pogonion of the mandible following plans for real orthognathic patients. The accuracy of the robot's repositioning increased when an anatomical landmark for the TCP was close to the registration fiducials. In spite of this influence, we could increase the repositioning accuracy at the landmark by using the landmark itself as the TCP. With its ability to incorporate virtual planning using a CT image and autonomously execute the plan around an anatomical landmark of interest, the robot could help surgeons reposition bones more accurately and dexterously.

One visualization simulation operation system for distal femoral fracture

A computer-aided 3-dimensional (3D) visualization operation simulation system based on computer-aided design (CAD) Unigraphics NX and Mimics software was established to provide orthopedic surgeons with an actual and reliable system in treating of distal femoral fracture.According to the preoperative CT data, 3D reconstruction of the distal femoral fracture could be achieved by the Mimics software. Then, the CAD Unigraphics NX software was used to measure the model function of all the related surgical instruments, including less invasive stabilization system (LISS) and retrograde intramedullary nail fixation.The function of CAD Unigraphics NX and Mimics software was successful in assisting in the treatment of distal femoral fracture with LISS and retrograde intramedullary nail fixation. The operation procedure was actual, visualized, and lifelike. Moreover, the operation effect could be estimated before surgery.The virtual surgery system may improve the reliability and safety of the operative care of distal femoral fracture.

Accuracy of virtual surgical planning of orthognathic surgery with aid of CAD/CAM fabricated surgical splint-A novel 3D analyzing algorithm

The benefit of computer-assisted planning in orthognathic surgery has been extensively documented over the last decade. This study aims to evaluate the accuracy of a virtual orthognathic surgical plan by a novel three dimensional (3D) analysis method. Ten patients who required orthognathic surgery were included in this study. A virtual surgical plan was achieved by the combination of a 3D skull model acquired from computed tomography (CT) and surface scanning of the upper and lower dental arch respectively and final occlusal position. Osteotomies and movement of maxilla and mandible were simulated by Dolphin Imaging 11.8 Premium^® (Dolphin Imaging and Management Solutions, Chatsworth, CA). The surgical plan was transferred to surgical splints fabricated by means of Computer Aided Design/Computer Aided Manufacturing (CAD/CAM). Differences of three dimensional measurements between the virtual surgical plan and postoperative results were evaluated. The results from all parameters showed that the virtual surgical plans were successfully transferred by the assistance of CAD/CAM fabricated surgical splint. Wilcoxon's signed rank test showed that no statistically significant deviation between surgical plan and post-operational result could be detected. However, deviation of angle U1 axis-HP and distance of A-CP could not fulfill the clinical success criteria. Virtual surgical planning and CAD/CAM fabricated surgical splint are proven to facilitate treatment planning and offer an accurate surgical result in orthognathic surgery.

Design, development and clinical validation of computer-aided surgical simulation system for streamlined orthognathic surgical planning

PURPOSE

There are many proven problems associated with traditional surgical planning methods for orthognathic surgery. To address these problems, we developed a computer-aided surgical simulation (CASS) system, the AnatomicAligner, to plan orthognathic surgery following our streamlined clinical protocol.

METHODS

The system includes six modules: image segmentation and three-dimensional (3D) reconstruction, registration and reorientation of models to neutral head posture, 3D cephalometric analysis, virtual osteotomy, surgical simulation, and surgical splint generation. The accuracy of the system was validated in a stepwise fashion: first to evaluate the accuracy of AnatomicAligner using 30 sets of patient data, then to evaluate the fitting of splints generated by AnatomicAligner using 10 sets of patient data. The industrial gold standard system, Mimics, was used as the reference.

RESULT

When comparing the results of segmentation, virtual osteotomy and transformation achieved with AnatomicAligner to the ones achieved with Mimics, the absolute deviation between the two systems was clinically insignificant. The average surface deviation between the two models after 3D model reconstruction in AnatomicAligner and Mimics was 0.3 mm with a standard deviation (SD) of 0.03 mm. All the average surface deviations between the two models after virtual osteotomy and transformations were smaller than 0.01 mm with a SD of 0.01 mm. In addition, the fitting of splints generated by AnatomicAligner was at least as good as the ones generated by Mimics.

CONCLUSION

We successfully developed a CASS system, the AnatomicAligner, for planning orthognathic surgery following the streamlined planning protocol. The system has been proven accurate. AnatomicAligner will soon be available freely to the boarder clinical and research communities.

Three-dimensional surgical simulation improves the planning for correction of facial prognathism and asymmetry: A qualitative and quantitative study

Traditional planning method for orthognathic surgery has limitations of cephalometric analysis, especially for patients with asymmetry. The aim of this study was to assess surgical plan modification after 3-demensional (3D) simulation. The procedures were to perform traditional surgical planning, construction of 3D model for the initial surgical plan (P1), 3D model of altered surgical plan after simulation (P2), comparison between P1 and P2 models, surgical execution, and postoperative validation using superimposition and root-mean-square difference (RMSD) between postoperative 3D image and P2 simulation model. Surgical plan was modified after 3D simulation in 93% of the cases. Absolute linear changes of landmarks in mediolateral direction (x-axis) were significant and between 1.11 to 1.62 mm. The pitch, yaw, and roll rotation as well as ramus inclination correction also showed significant changes after the 3D planning. Yaw rotation of the maxillomandibular complex (1.88 ± 0.32°) and change of ramus inclination (3.37 ± 3.21°) were most frequently performed for correction of the facial asymmetry. Errors between the postsurgical image and 3D simulation were acceptable, with RMSD 0.63 ± 0.25 mm for the maxilla and 0.85 ± 0.41 mm for the mandible. The information from this study could be used to augment the clinical planning and surgical execution when a conventional approach is applied.

Algorithm for planning a double-jaw orthognathic surgery using a computer-aided surgical simulation (CASS) protocol. Part 1: planning sequence

The success of craniomaxillofacial (CMF) surgery depends not only on the surgical techniques, but also on an accurate surgical plan. The adoption of computer-aided surgical simulation (CASS) has created a paradigm shift in surgical planning. However, planning an orthognathic operation using CASS differs fundamentally from planning using traditional methods. With this in mind, the Surgical Planning Laboratory of Houston Methodist Research Institute has developed a CASS protocol designed specifically for orthognathic surgery. The purpose of this article is to present an algorithm using virtual tools for planning a double-jaw orthognathic operation. This paper will serve as an operation manual for surgeons wanting to incorporate CASS into their clinical practice.