Surgical Simulation Software Research Articles

Evaluation of the utility of surgical simulation software in medical postgraduate education

BackgroundThe use of medical simulation software in medical institutions is growing to address teaching challenges. The study aims to assess the effectiveness of the Touch Surgery app, a free medical simulation software, as a supplement to the teaching methodology of unified surgery for medical students. MethodsTwenty-three postgraduate students, divided into three groups based on residency training years, and five senior orthopedic surgeons took part in the study. Each participant completed three modules within the Large External Fixators module using the Touch Surgery app. The results achieved by orthopedic specialists and postgraduates in the test module were recorded separately. The orthopedic specialists' first test module scores were used as a baseline. A Likert survey assessed the usefulness and content accuracy of the app. Statistical analysis included analysis of variance and 2-tailed t-test. ResultsThe first and second scores achieved by the postgraduates in the three groups were significantly different from the baseline of the orthopedic specialists, but the mean scores of all postgraduate's groups increased with simulator usage for learning and by the third attempt they were at the same level as the orthopedic specialists. However, no significant performance differences were observed between postgraduates with different training years. Postgraduates expressed a positive opinion of the usefulness and content of Touch Surgery in the questionnaire and their intention to continue using it in their future studies. ConclusionsThis study shows that the use of Touch Surgery improves postgraduates' performance and ultimately enables them to reach the level of orthopedic specialists in simulated surgery, and received positive ratings for the software's experience and content. Touch Surgery can be a valuable complement to traditional surgical teaching methods, bridging the gap between theoretical learning from textbooks and guided rehearsals of surgical steps and skills.

Effect of using appendectomy surgical simulation software on academic achievement: Game-based learning during the COVID-19 pandemic

Effect of using appendectomy surgical simulation software on academic achievement: Game-based learning during the COVID-19 pandemic

Fully immersive virtual reality for skull-base surgery: surgical training and beyond.

A virtual reality (VR) system, where surgeons can practice procedures on virtual anatomies, is a scalable and cost-effective alternative to cadaveric training. The fully digitized virtual surgeries can also be used to assess the surgeon's skills using measurements that are otherwise hard to collect in reality. Thus, we present the Fully Immersive Virtual Reality System (FIVRS) for skull-base surgery, which combines surgical simulation software with a high-fidelity hardware setup. FIVRS allows surgeons to follow normal clinical workflows inside the VR environment. FIVRS uses advanced rendering designs and drilling algorithms for realistic bone ablation. A head-mounted display with ergonomics similar to that of surgical microscopes is used to improve immersiveness. Extensive multi-modal data are recorded for post-analysis, including eye gaze, motion, force, and video of the surgery. A user-friendly interface is also designed to ease the learning curve of using FIVRS. We present results from a user study involving surgeons with various levels of expertise. The preliminary data recorded by FIVRS differentiate between participants with different levels of expertise, promising future research on automatic skill assessment. Furthermore, informal feedback from the study participants about the system's intuitiveness and immersiveness was positive. We present FIVRS, a fully immersive VR system for skull-base surgery. FIVRS features a realistic software simulation coupled with modern hardware for improved realism. The system is completely open source and provides feature-rich data in an industry-standard format.

Platform for investigating continuum manipulator behavior in orthopedics.

The use of robotic continuum manipulators has been proposed to facilitate less-invasive orthopedic surgical procedures. While tools and strategies have been developed, critical challenges such as system control and intra-operative guidance are under-addressed. Simulation tools can help solve these challenges, but several gaps limit their utility for orthopedic surgical systems, particularly those with continuum manipulators. Herein, a simulation platform which addresses these gaps is presented as a tool to better understand and solve challenges for minimally invasive orthopedic procedures. An open-source surgical simulation software package was developed in which a continuum manipulator can interact with any volume model such as to drill bone volumes segmented from a 3D computed tomography (CT) image. Paired simulated X-ray images of the scene can also be generated. As compared to previous works, tool-anatomy interactions use a physics-based approach which leads to more stable behavior and wider procedure applicability. A new method for representing low-level volumetric drilling behavior is also introduced to capture material variability within bone as well as patient-specific properties from a CT. Similar interaction between a continuum manipulator and phantom bone was also demonstrated between a simulated manipulator and volumetric obstacle models. High-level material- and tool-driven behavior was shown to emerge directly from the improved low-level interactions, rather than by need of manual programming. This platform is a promising tool for developing and investigating control algorithms for tasks such as curved drilling. The generation of simulated X-ray images that correspond to the scene is useful for developing and validating image guidance models. The improvements to volumetric drilling offer users the ability to better tune behavior for specific tools and procedures and enable research to improve surgical simulation model fidelity. This platform will be used to develop and test control algorithms for image-guided curved drilling procedures in the femur.

A Novel Trajectory of C7 Laminar Screws Determined Using Three-Dimensional Computed Tomography and Surgical Simulation Software: Comparison with a Pre-existing Trajectory.

Examination using three-dimensional screw trajectory software and computed tomographic scans. To evaluate the feasibility of a novel trajectory for C7 laminar screws and to compare it with an old trajectory. The previously reported trajectory of C7 laminar screws has a horizontal direction without a fixed target point. Our new trajectory has a cephalad direction with a fixed target point. Computed tomographic scans of a total of 50 male and 50 female patients were utilized. The placement of C7 laminar screws was activated employing the new and old trajectories. The success rate, the causes of failure, and the maximum allowable length of each trajectory were compared. Employing the new trajectory, the success rates of the unilaminar and bilaminar screws were 93% and 83%, respectively, which were significantly better than the old trajectory (80%, p<0.0001 and 70%, p=0.0003). The most prevalent cause of failure was laminar cortical breach followed by facet joint violation. The new trajectory also offered significantly longer maximum allowable screw length in unilaminar (32.5±4.3 mm vs. 26.5±2.6 mm, p<0.001), bilaminar cephalic (29.5±3.8 mm vs. 25.9±2.6 mm, p<0.0001) and bilaminar caudal (33.1±2.6 mm vs. 25.8±3.1 mm, p<0.001) screws than the old trajectory. With the new and old trajectories, 70% vs. 6% of unilaminar, 60% vs. 2% of bilaminar caudal, and 32% vs. 4% of bilaminar cephalic screws could be protracted perfectly into the corresponding lateral mass without any laminar cortical or facet joint violation (p<0.0001). The novel trajectory possesses a substantially higher success rate, longer maximum allowable screw length, and higher chance to be extended into the lateral mass (a condition known as a lamino-lateral mass screw) than the old trajectory.

Surgical simulation education in plastic surgery: current state of the art and need for improvement

: Simulation tools continue to play an important part in surgical education, particularly allowing junior trainees an opportunity to familiarize themselves with various procedures that they either have not been exposed to or have not had enough repetition to feel confident enough to execute. It is particularly relevant when surgical training is interrupted due to unforeseen circumstances (i.e., coronavirus disease 2019, also called COVID-19) or to personal reasons (i.e., pregnancy, leave of absence). The ability to remotely work on technical skills has tremendous value and is certainly one of the reasons that we have continued to develop new surgical simulation tools, particularly in the field of plastic surgery. A review of the major surgical simulation and anatomy software tools available within the various subdivisions of plastic surgery such as craniofacial, microsurgery, aesthetic, hand/upper extremity and burn was performed. We also reviewed some of the simulation tools available in other surgical specialties and evaluated them for fit and utility in plastic and reconstructive surgery (PRS) surgical education. Our study shows that while various surgical simulators have been developed in PRS over the years, there remains a gap in terms of the ability for residents and trainees to acquire real-life skills remotely along with the capability to receive live feedback from faculty. This review shows that further tools need to be developed to optimize the acquisition and maintenance of surgical skills in a remote fashion. Taken together, it provides an overview of the evolution of surgical simulation education within plastic surgery.

Evaluation of Surgical Improvement of Clinical Knowledge Ops (SICKO), an Interactive Training Platform

Over the past two decades, there have been numerous attempts at using surgical simulation software for training purposes. There has been extensive prior success at using digital laparoscopic tools and virtual and augmented reality in strengthening specific surgical techniques, but clinical decision-making simulation has been limited to multiple choice question banks. Surgical Improvement of Clinical Knowledge Ops (SICKO) is a web-based educational application that takes users through various aspects of clinical decision-making in the field of surgery.App SpecsApp name: Surgical Improvement of Clinical Knowledge Ops (SICKO)App developer: James Lau M.D., Dana Lin M.D., Julia Park M.D.App website/URL*: http://med.stanford.edu/sm/archive/sicko/game/SICKOTitle.html App price: The website is free to use and has no microtransactionsCategory: educational, surgery simulation, clinical decision makingTags: web-based app, surgical simulation, learning, healthcare, gamificationWorks offline: noBrowsers: Works on Google Chrome, Mozilla Firefox, Safari, and Microsoft EdgeFDA approval: N/A*It should be noted that although the URL leads to a website with a tab header that reads "SEPTRIS," an older iteration of the game, the interactive experience is actually SICKO, which the user can clearly see from the webpage itself.Quick Review (1 star, lowest; 5 stars, highest)Overall Rating (1-5): 4.5Content (1-5): 5Usability (1-5): 5Design (1-5): 4Ratings Disclosure: The SICKO application was reviewed by two independent medical student authors of this article, as well as a resident physician. The reviews were done anonymously through each reviewer's own input and were blinded to each other's ratings until completion of the simulation. Each reviewer completed full renditions of the game from beginning to end to experience a situation where the patient expired, as well as one where the patient was saved in order to observe the full user experience. Both authors felt that the game was remarkably useful, with the only criticism being the simple graphical design of the application. No reviewers or authors of this paper have any connection to the software content or development team of SICKO.

Tomographic similarity scan with a computed modified absolute mandibular midsagittal plane for precise and objective localization of mandibular asymmetry

The application of 3D imaging is at its cusp in craniofacial diagnosis and treatment planning. However, most applications are limited to simple subjective superimposition-based analysis. As the diagnostic accuracy dictates the precision in operability, we propose a novel method that enables objective clinical decision making for patients with mandibular asymmetry. We analyzed cone-beam computed tomography (CBCT) scans of 34 patients who underwent surgical correction for mandibular asymmetry using a high-throughput computing algorithm. Radiomic segmentation of quantitative features of surface and volume followed by exploration resulted in identification of a computed modified absolute mandibular midsagittal plane (cmAMP). Tomographic similarity scan (ToSS) curves were generated via bilateral equidistant scanning in an antero-posterior direction with cmAMP as the reference. ToSS comprised of a comprehensive similarity index (SI) score curve and a segment-wise volume curve. The SI score was computed using the Sørensen–Dice similarity coefficient ranging from 0 to 1. The volumetric analysis was represented as the non-overlapping volume (NOV) and overlapping volume (OV) for each segment, with two segmentation lines, at the mental foramen anteriorly and the intraoral vertical ramus osteotomy region posteriorly. Statistical analysis showed strong negative correlation between the NOV and SI scores for the anterior, middle, and total mandible (P < 0.001). Additionally, a significant correlation was observed between the change in the SI scores for anterior (P = 0.044) and middle segments (P < 0.001) to the total mandible when comparing the data before and after the surgery. This work demonstrated the potential of incorporating ToSS curves in surgical simulation software to improve precision in the clinical decision-making process.

Atlas-based segmentation of cochlear microstructures in cone beam CT.

To develop an automated segmentation approach for cochlear microstructures [scala tympani (ST), scala vestibuli (SV), modiolus (Mod), mid-modiolus (Mid-Mod), and round window membrane (RW)] in clinical cone beam computed tomography (CBCT) images of the temporal bone for use in surgical simulation software and for preoperative surgical evaluation. This approach was developed using the publicly available OpenEar (OE) Library that includes temporal bone specimens with spatially registered CBCT and 3D micro-slicing images. Five of these datasets were spatially aligned to our internal OSU atlas. An atlas of cochlear microstructures was created from one of the OE datasets. An affine registration of this atlas to the remaining OE CBCT images was used for automatically segmenting the cochlear microstructures. Quantitative metrics and visual review were used for validating the automatic segmentations. The average DICE metrics were 0.77 and 0.74 for the ST and SV, respectively. The average Hausdorff distance (AVG HD) was 0.11mm and 0.12mm for both scalae. The mean distance between the centroids for the round window was 0.32mm, and the mean AVG HD was 0.09mm. The mean distance and angular rotation between the mid-modiolar axes were 0.11mm and 9.8 degrees, respectively. Visually, the segmented structures were accurate and similar to that manually traced by an expert observer. An atlas-based approach using 3D micro-slicing data and affine spatial registration in the cochlear region was successful in segmenting cochlear microstructures of temporal bone anatomy for use in simulation software and potentially for pre-surgical planning and rehearsal.

Three-dimensional surgical accuracy between virtually planned and actual surgical movements of the maxilla in two-jaw orthognathic surgery.

ObjectiveTo investigate the three-dimensional (3D) surgical accuracy between virtually planned and actual surgical movements (SM) of the maxilla in two-jaw orthognathic surgery.MethodsThe sample consisted of 15 skeletal Class III patients who underwent two-jaw orthognathic surgery performed by a single surgeon using a virtual surgical simulation (VSS) software. The 3D cone-beam computed tomography (CBCT) images were obtained before (T0) and after surgery (T1). After merging the dental cast image onto the T0 CBCT image, VSS was performed. SM were classified into midline correction (anterior and posterior), advancement, setback, anterior elongation, and impaction (total and posterior). The landmarks were the midpoint between the central incisors, the mesiobuccal cusp tip (MBCT) of both first molars, and the midpoint of the two MBCTs. The amount and direction of SM by VSS and actual surgery were measured using 3D coordinates of the landmarks. Discrepancies less than 1 mm between VSS and T1 landmarks indicated a precise outcome. The surgical achievement percentage (SAP, [amount of movement in actual surgery/amount of movement in VSS] × 100) (%) and precision percentage (PP, [number of patients with precise outcome/number of total patients] × 100) (%) were compared among SM types using Fisher’s exact and Kruskal–Wallis tests.ResultsOverall mean discrepancy between VSS and actual surgery, SAP, and PP were 0.13 mm, 89.9%, and 68.3%, respectively. There was no significant difference in the SAP and PP values among the seven SM types (all p > 0.05).ConclusionsVSS could be considered as an effective tool for increasing surgical accuracy.

Atlas-based segmentation of temporal bone surface structures.

To develop a time-efficient automated segmentation approach that could identify surface structures on the temporal bone for use in surgical simulation software and preoperative surgical training. An atlas-based segmentation approach was developed to segment the tegmen, sigmoid sulcus, exterior auditory canal, interior auditory canal, and posterior canal wall in normal temporal bone CT images. This approach was tested in images of 20 cadaver bones (10 left, 10 right). The results of the automated segmentation were compared to manual segmentation using quantitative metrics of similarity, Mahalanobis distance, average Hausdorff distance, and volume similarity. The Mahalanobis distance was less than 0.232mm for all structures. The average Hausdorff distance was less than 0.464mm for all structures except the posterior canal wall and external auditory canal for the right bones. Volume similarity was 0.80 or greater for all structures except the sigmoid sulcus that was 0.75 for both left and right bones. Visually, the segmented structures were accurate and similar to that manually traced by an expert observer. An atlas-based approach using a deformable registration of a Gaussian-smoothed temporal bone image and refinements using surface landmarks was successful in segmenting surface structures of temporal bone anatomy for use in pre-surgical planning and training.

RADIOGRAPHIC ASSESSMENT OF MANDIBULAR SYMMETRY FOLLOWING RECONSTRUCTION OF SEGMENTAL MANDIBULAR DEFECTS

Restoration of symmetric facial contours after resection of mandibular tumors is one of the requisites of a successful reconstructive surgery. For unilateral mandibular defects and using the “mirroring” feature available in many surgical simulation software, it is possible to restore the undistorted mandibular contours and bend the reconstruction plate prior to surgery. The aim of this study: is to assess whether pre-bent mandibular reconstruction plates using computer-assisted techniques for post tumor-ablation defects are good enough at restoring mandibular symmetry radiographically. Patients and Methods: eight patients with segmental mandibular post-tumor resection defects, to whom a computer assisted planning and pre-bending of the reconstruction plates were performed; were included in this study. For each patient, on the 3D reformatted image, a midsagittal plane was constructed and the perpendicular distances were measured from the midsagittal plane to the titanium reconstruction plate and to the contralateral intact side on the axial cuts. The mean differences calculated and statistically analyzed. Results: The mean of the differences between the intact and reconstructed sides of the mandible showed normal data distribution. Overall mean among all patients was 0.7225 mm ± 0.24467. One-sample t test against a hypothetical mean difference of 0 mm revealed an extremely statistically significant difference between the intact and reconstructed sides with a p-value < 0.0001. Conclusion: Computer-assisted precontoured mandibular reconstruction plates can be considered to offer a very good degree of symmetry during mandibular reconstruction procedures.

Atlas-Based Segmentation of Temporal Bone Anatomy.

To develop a time-efficient automated segmentation approach that could identify critical structures in the temporal bone for visual enhancement and use in surgical simulation software. An atlas-based segmentation approach was developed to segment the cochlea, ossicles, semicircular canals (SCCs), and facial nerve in normal temporal bone CT images. This approach was tested in images of 26 cadaver bones (13 left, 13 right). The results of the automated segmentation were compared to manual segmentation visually and using DICE metric, average Hausdorff distance, and volume similarity. The DICE metrics were greater than 0.8 for the cochlea, malleus, incus, and the SCCs combined. It was slightly lower for the facial nerve. The average Hausdorff distance was less than one voxel for all structures, and the volume similarity was 0.86 or greater for all structures except the stapes. The atlas-based approach with rigid body registration of the otic capsule was successful in segmenting critical structures of temporal bone anatomy for use in surgical simulation software.

Risk factor analysis of bone resorption following secondary alveolar bone grafting using three-dimensional computed tomography

The purpose of this study is to analyze the risk factors for bone resorption following secondary bone grafting in the alveolar cleft, using three-dimensional (3D) computed tomography (CT) based on surgical simulation software (SimPlant OMS, Materialise Dental, Leuven, Belgium). We reviewed the secondary alveolar bone grafts performed by a single surgeon between January 2005 and January 2014. A total of 40 patients with unilateral alveolar cleft were included in this study. The grafted alveolar bone was measured using surgical simulation software. In order to validate the measurement, each data set was measured by three different analysts and the inter- and intraobserver variabilities were calculated. A total of eight risk factors for grafted bone survival, including patient age, sex, body mass index (BMI), palatal fistula, amount of grafted bone, dental appliance, canine or incisor eruption, and preoperative upper respiratory tract infection, were evaluated using the linear mixed model and Mann-Whitney test. The average alveolar defect size was 4.98cc and the average graft survival was 67.5%. The inter- and intraobserver variabilities of simulation software were 0.758 and 0.915, respectively. Among the risk factors, only dental appliance (p=0.02) and canine eruption (p=0.041) were significantly correlated with graft survival. Other risk factors, including the amount of grafted bone, did not show a significant relationship with graft survival. Measurement of an alveolar bone defect using a simulation program based on 3D CT is reliable and reproducible. Secondary bone grafting survival was significantly correlated with canine eruption and dental appliance in the alveolar cleft.

Modified method of recording and reproducing natural head position with a multicamera system and a laser level

As computer-assisted surgical design becomes increasingly popular in maxillofacial surgery, recording patients' natural head position (NHP) and reproducing it in the virtual environment are vital for preoperative design and postoperative evaluation. Our objective was to test the repeatability and accuracy of recording NHP using a multicamera system and a laser level. A laser level was used to project a horizontal reference line on a physical model, and a 3-dimensional image was obtained using a multicamera system. In surgical simulation software, the recorded NHP was reproduced in the virtual head position by registering the coordinate axes with the horizontal reference on both the frontal and lateral views. The repeatability and accuracy of the method were assessed using a gyroscopic procedure as the gold standard. The interclass correlation coefficients for pitch and roll were 0.982 (0.966, 0.991) and 0.995 (0.992, 0.998), respectively, indicating a high degree of repeatability. Regarding accuracy, the lack of agreement in orientation between the new method and the gold standard was within the ranges for pitch (-0.69°, 1.71°) and for roll (-0.92°, 1.20°); these have no clinical significance. This method of recording and reproducing NHP with a multicamera system and a laser level is repeatable, accurate, and clinically feasible.

Is Premorbid Glenoid Anatomy Altered in Patients with Glenohumeral Osteoarthritis?

Restoration of native, premorbid glenoid anatomy may be a goal in component placement during total shoulder arthroplasty. However, if patients with unilateral glenohumeral osteoarthritis are predisposed to the development of arthritis owing to abnormal native glenoid anatomy, this recommendation may be inappropriate. The purpose of this study was to determine if patients with glenohumeral osteoarthritis have abnormal premorbid glenoid version or inclination, thereby predisposing them to subsequent glenoid disorders. We specifically tested whether: (1) premorbid glenoid version or inclination in the pathologic shoulder of patients with unilateral osteoarthritis, as determined by the glenoid vault model, is different from glenoid version or inclination in the contralateral nonpathologic shoulder of these patients; (2) there are differences between glenoid version or inclination in normal cadaver shoulders and the nonpathologic side of patients with unilateral osteoarthritis; and (3) there are differences between glenoid version or inclination in normal cadaver shoulders and the premorbid glenoid version and inclination in the pathologic shoulder of patients with unilateral osteoarthritis, as determined by the glenoid vault model. Bilateral CT scans were obtained in 27 patients with unilateral glenohumeral osteoarthritis. Thirty normal cadaver control shoulders also underwent CT scans. Premorbid glenoid version and inclination in the pathologic shoulder, as measured by the glenoid vault model, were compared with the contralateral nonpathologic shoulder and the normal cadaver control shoulders. Glenoid version and inclination of the normal shoulders were compared with the nonpathologic side from patients with unilateral osteoarthritis. Measurements were made by two different methods using three-dimensional surgical simulation software: (1) a direct measurement technique and (2) measurements derived from placement of a glenoid vault model. Mean differences in these parameters were compared between shoulder groups using paired and unpaired Student's t-tests. Premorbid glenoid version and inclination in the pathologic shoulder as measured by the vault model averaged -7° (SD, 5) and 10° (SD, 6), respectively, compared with -7° (SD, 5) and 12° (SD, 6) as directly measured on the nonpathologic side, and -7° (SD, 4) and 12° (SD, 5) as directly measured in the normal cadaver control shoulders. There were no differences in glenoid version or inclination between the normal shoulders and the nonpathologic side of patients with unilateral osteoarthritis or between these shoulders and the premorbid version and inclination of the arthritic shoulder as measured by the vault model. Patients with glenohumeral osteoarthritis do not appear to have abnormal premorbid glenoid retroversion or inclination. The glenoid vault model can be used to determine premorbid glenoid version and inclination. The glenoid vault model may be a clinically useful tool to estimate patient-specific premorbid glenoid anatomy, which may help in preoperative or intraoperative surgical planning for total shoulder arthroplasty.

Virtual reality surgical simulator software development tools

Virtual reality (VR) surgical simulations are among the most difficult software applications to develop mainly because of the type of user interactions that they must support. Surgery typically includes precise cutting of often intricate structures. Modelling these structures and accurately simulating their response to user interaction requires many software components to effectively work in unison. Some of these components are readily available but are tailored to more common applications such as computer games or open-world simulations such as flight-simulators. This article explores the software libraries that are currently available to developers of VR surgical simulation software. Like computer games and other VR simulations, VR surgical simulations require real-time lighting and rendering systems and physics-based interactions. However, in addition they require haptic interaction with cut-able and deformable soft-tissue, a key requirement that is not supported by the majority of the available tools. In this article, we introduce currently available software development tools and the specific benefits and limitations that can be encountered when using them to develop VR surgical simulations. We also provide a detailed review of collision detection libraries that are central to achieving reliable haptic rendering.

Use of the surface-based registration function of computer-aided design/computer-aided manufacturing software in medical simulation software for three-dimensional simulation of orthognathic surgery

Three-dimensional (3D) computed tomography image models are helpful in reproducing the maxillofacial area; however, they do not necessarily provide an accurate representation of dental occlusion and the state of the teeth. Recent efforts have focused on improvement of dental imaging by replacement of computed tomography with other detailed digital images. Unfortunately, despite the advantages of medical simulation software in dentofacial analysis, diagnosis, and surgical simulation, it lacks adequate registration tools. Following up on our previous report on orthognathic simulation surgery using computer-aided design/computer-aided manufacturing (CAD/CAM) software, we recently used the registration functions of a CAD/CAM platform in conjunction with surgical simulation software. Therefore, we would like to introduce a new technique, which involves use of the registration functions of CAD/CAM software followed by transfer of the images into medical simulation software. This technique may be applicable when using various registration function tools from different software platforms.

Rapid prototyping in craniofacial surgery: Using a positioning guide after zygomatic osteotomy – A case report

Introduction The management of post-traumatic deformity in the midface region poses challenges for the maxillofacial surgeon. Ensuring symmetry after zygomatic osteotomy can be difficult and precise positioning of the osteotomised bony fragments requires careful treatment planning. It may be necessary to use a coronal flap to allow the surgeon to compare the contralateral zygomatic bone to allow symmetrical reduction. The authors present a new technique for the positioning of osteotomised zygomatic bones using a combination of computer assisted surgical simulation and rapid prototyping. Method A patient presented to our unit with a post-traumatic zygomatic deformity. Using surgical simulation software the displaced zygomatic bone was osteotomised and placed in the idéal position on a three-dimensional computed tomography scan (3D CT). The position was determined by reference to the contralateral zygoma. In addition the repositioning of the soft tissues was simulated. A surgical guide which allowed intraoperative positioning of the osteotomised zygoma was manufactured by a rapid prototyping process. Use of the guide allowed a minimally invasive approach to the affected zygoma. The post-operative results were compared to the predicted outcome. Results The post-operative appearance was satisfactory and corresponded well with the predicted result. There was a significant reduction in operative time compared to the previous management of similar cases.

Analysis of bone volume using computer simulation system for secondary bone graft in alveolar cleft

The purpose of this study was to measure the bone volume necessary for secondary bone grafting in the alveolar cleft using surgical simulation software based on three-dimensional computed tomography (CT) scan data, to compare this measurement with the actual volume of the bone graft, and to evaluate consistency. The subjects were 13 patients with cleft lip and palate who underwent CT using a cone-beam CT unit (CB-CT) 1 month before surgery, followed by bone grafting with particulate cancellous bone and marrow (PCBM) to close the cleft. The bone volume necessary for grafting was measured based on the CB-CT scan data. Correlation analysis, a test of the population mean between two samples, and Wilcoxon's signed rank test were conducted between these measurements and the actual bone volume (PCBM volume) used for grafting. SPSS was used for statistical analysis, and the level of significance was set below the 5% level. The results showed a significant correlation, with no significant differences between the two in all tests. These results suggest that measuring and preoperatively calculating the bone volume necessary for bone grafting with surgical simulation software using CB-CT scan data is beneficial.