Computer-aided Surgical Simulation Research Articles

Advent of artificial intelligence in orthognathic surgery: Advancements and challenges

Orthognathic surgery is a procedure used to correct facial deformities and jaw bone misalignment. The use of technology, specifically virtual surgical planning (VSP), has become increasingly prevalent in preoperative planning for orthognathic surgery. High-resolution computed tomography (CT) imaging has enabled computer-aided modelling. Artificial intelligence (AI) implementation has transformed orthognathic surgery methodology. This article highlights the latest market trends and modern-day advancements in the field, including the conventional and surgery first approach for orthognathic surgery. The use of computer-aided surgical simulation (CASS) in VSP for orthognathic surgery was studied. The different software used for orthognathic surgical planning and the detailed protocol followed during the surgery, including the preoperative procedure were discussed along with utilisation of 3-dimension cone-beam computed tomography (3D CBCT) images for surgical planning. The implementation of VSP with CASS had significantly enhanced the accuracy and efficiency of orthognathic surgery for dentofacial deformity correction. The use of technology allowed improved preoperative planning, resulting in better outcomes for patients. The study of different software for orthognathic surgical planning and the protocol followed during surgery has provided valuable insight into the surgery. The continued advancement of technology in orthognathic surgery is promising for the field and for the patients.

Accuracy of Surgical Outcome Using Computer-Aided Surgical Simulation in Fronto-Orbital Advancement for Craniosynostosis: A Pilot Study.

Computer-aided surgical simulation (CASS) can be used to virtually plan ideal outcomes of craniosynostosis surgery. Our purpose was to create a workflow analyzing the accuracy of surgical outcomes relative to virtually planned fronto-orbital advancement (FOA). Patients who underwent FOA using CASS between October 1, 2017, and February 28, 2022, at our center and had postoperative computed tomography within 6 months of surgery were included. Virtual 3-dimensional (3D) models were created and coregistered using each patient's preoperative and postoperative computed tomography data. Three points on each bony segment were used to define the object in 3D space. Each planned bony segment was manipulated to match the actual postoperative outcome. The change in position of the 3D object was measured in translational (X, Y, Z) and rotational (roll, pitch, yaw) aspects to represent differences between planned and actual postoperative positions. The difference in the translational position of several bony landmarks was also recorded. Wilcoxon signed-rank tests were performed to measure significance of these differences from the ideal value of 0, which would indicate no difference between preoperative plan and postoperative outcome. Data for 63 bony segments were analyzed from 8 patients who met the inclusion criteria. Median differences between planned and actual outcomes of the segment groups ranged from -0.3 to -1.3 mm in the X plane; 1.4 to 5.6 mm in the Y plane; 0.9 to 2.7 mm in the Z plane; -1.2° to -4.5° in pitch; -0.1° to 1.0° in roll; and -2.8° to 1.0° in yaw. No significant difference from 0 was found in 21 of 24 segment region/side combinations. Translational differences of bony landmarks ranged from -2.7 to 3.6 mm. A high degree of accuracy was observed relative to the CASS plan. Virtual analysis of surgical accuracy in FOA using CASS was feasible.

Evaluation of accuracy of maxillary repositioning surgery using an observer-independent method

ObjectiveTo evaluate the accuracy of maxillary repositioning in two-jaw surgery using computer-aided surgical simulation (CASS) and computer-aided design/manufacturing (CAD/CAM) splints by using a highly accurate observer-independent method. MethodsA retrospective evaluation was conducted of 30 consecutive adults who underwent Le Fort I osteotomy by a single surgeon. Surgical planning and fabrication of occlusal splints were performed using custom-developed CASS software. Preoperative images with landmarks were superimposed on postoperative images to evaluate discrepancies between the planned and actual position of the maxilla following surgery. Translational and rotational differences were expressed as the root mean square deviation (RMSD). The number of cases that exceeded the clinically acceptable limits (2 mm for the translational difference at the centroid, 4° for the rotational difference, and 1 mm for the mediolateral difference at the dental midline) were also evaluated. ResultsPostoperative anteroposterior translation and pitch values were significantly different to and negatively correlated with the planned values, respectively. The largest translational RMSDs at the centroid and the dental midline were 1.04 mm and 1.03 mm, respectively, in the anteroposterior direction. The largest rotational RMSD was 1.86° in pitch. The percentage of discrepancies exceeding the clinically acceptable limit was 3.3% for the centroid, 3.3% for rotation, 20.0% for the midline, and 26.7% for any one criterion. ConclusionWhile maxillary repositioning using CASS and CAD/CAM splints was accurate on a population level, there remains potential for clinically significant errors to occur on an individual level, particularly in controlling the dental midline position and occlusal plane angle.

Augmented and Virtual Reality for Preoperative Trauma Planning, Focusing on Orbital Reconstructions: A Systematic Review.

This systematic review summarizes recent literature on the use of extended reality, including augmented reality (AR), mixed reality (MR), and virtual reality (VR), in preoperative planning for orbital fractures. A systematic search was conducted in PubMed, Embase, Web of Science and Cochrane on 6 April 2023. The included studies compared extended reality with conventional planning techniques, focusing on computer-aided surgical simulation based on Computed Tomography data, patient-specific implants (PSIs), fracture reconstruction of the orbital complex, and the use of extended reality. Outcomes analyzed were technical accuracy, planning time, operative time, complications, total cost, and educational benefits. A total of 6381 articles were identified. Four articles discussed the educational use of VR, while one clinical prospective study examined AR for assisting orbital fracture management. AR was demonstrated to ameliorate the accuracy and precision of the incision and enable the better identification of deep anatomical tissues in real time. Consequently, intraoperative imaging enhancement helps to guide the orientation of the orbital reconstruction plate and better visualize the precise positioning and fixation of the PSI of the fractured orbital walls. However, the technical accuracy of 2-3 mm should be considered. VR-based educational tools provided better visualization and understanding of craniofacial trauma compared to conventional 2- or 3-dimensional images.

Validation of Andrews Analysis in the Virtual Environment

Andrews analysis is a tool to establish the aesthetic anteroposterior position of the maxilla. Andrews analysis has not been evaluated through computer-aided surgical simulation (CASS). The purpose of this study was to evaluate the accuracy of Andrews profile analysis when performed in the virtual environment. A retrospective cohort study was implemented with consecutive patients undergoing orthognathic surgery between February 2020 and February 2022 at the University of Alabama, Birmingham. Traditional Andrews analysis with lateral smiling photographs were taken during the presurgical appointment in adjusted natural head position (aNHP). The standard cone-beam CT obtained for CASS and archived on the KLS Martin (Jacksonville, Florida) database was accessed for retrospective measurement. Lateral facial photographs in aNHP were imported into the virtual environment and the three dimensional (3D) composite model was then oriented into aNHP. The software engineer, blinded to the traditional measurements, then performed the Andrews analysis in the virtual environment by placing a vertical glabella line on the 3D composite model in aNHP. The linear horizontal distance of the maxillary central incisor perpendicular to the vertical glabella line was recorded. Method of Andrews analysis measurement (traditional photographic evaluation vs CASS) MAIN OUTCOME VARIABLE: Linear Andrews analysis measurement. Additional covariates evaluated were sex, age at surgery, and dentofacial deformity diagnosis. Descriptive statistics were computed to compare photographic analysis versus CASS analysis. A P value of <.05 was considered statistically significant. The average age was 25.7years old and 54% of patients were female. For the photographic analysis, the mean incisor-goal anterior limit line distance was -0.44±7.12mm (95% CI, -1.13 to 0.37mm; P=.46). For the virtual analysis, the mean incisor-goal anterior limit line distance was 0.13±7.21 (95% CI,-0.004 to 0.30; P=.89). The Pearson correlation coefficients between the photograph and 3D analysis were very strong (0.93). The root mean square deviation between the photographic and 3D analysis cohorts was 2.7mm. Given the high correlation coefficients between all demographics, CASS can be utilized for Andrews analysis to determine ideal anteroposterior maxillary position to streamline data collection and the planning process.

Application of digital guide plate with drill-hole sharing technique in the mandible reconstruction

With the development of computer-assisted surgery, digital guide plate was widely used in vascularized bone flap grafts for mandibular reconstruction. The purpose of this study was to design and manufacture a digital guide plate with drill-hole sharing for mandibular reconstruction and assess for surgical accuracy. 17 patients that required mandibular reconstruction using fibula free flap or iliac crest free flap were included in the study. The computed tomography (CT) data of the patient's mandible and pelvis or fibula were acquired preoperatively. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on above date, which allowed the design of two cutting guide and a repositioning guide for mandibular reconstruction. After surgery, the accuracy of reconstruction was evaluated by superimposing the postoperative image onto the preoperative image of mandible, recording the linear and angular deviation of landmarks, measuring the differences between the planned and actual outcomes. The osteotomy and repositioning of fibula or iliac crest segments were successfully performed as planned using surgical guides. The digital guide plate with drill-hole sharing showed excellent accuracy, When the iliac crest or the fibula free flap were used for mandibular reconstruction, the largest mean differences between the preoperative and postoperative were 1.11mm and 2.8° or 1.3mm and 3.87°. The digital guide plate with drill-hole sharing designed preoperatively provides a reliable method of for the mandibular reconstruction. This can assist surgeons in accurately performing osteotomy and repositioning fibula or iliac crest segments during the mandibular reconstruction.

Clinical feasibility of deep learning-based automatic head CBCT image segmentation and landmark detection in computer-aided surgical simulation for orthognathic surgery

The purpose of this ambispective study was to investigate whether deep learning-based automatic segmentation and landmark detection, the SkullEngine, could be used for orthognathic surgical planning. Sixty-one sets of cone beam computed tomography (CBCT) images were automatically inferred for midface, mandible, upper and lower teeth, and 68 landmarks. The experimental group included automatic segmentation and landmarks, while the control group included manual ones that were previously used to plan orthognathic surgery. The qualitative analysis of segmentation showed that all of the automatic results could be used for computer-aided surgical simulation. Among these, 98.4% of midface, 70.5% of mandible, 98.4% of upper teeth, and 93.4% of lower teeth could be directly used without manual revision. The Dice similarity coefficient was 96% and the average symmetric surface distance was 0.1 mm for all four structures. With SkullEngine, it took 4 minutes to complete the automatic segmentation and an additional 10 minutes for a manual touchup. The results also showed the overall mean difference between the two groups was 2.3 mm for the midface and 2.4 mm for the mandible. In summary, the authors believe that automatic segmentation using SkullEngine is ready for daily practice. However, the accuracy of automatic landmark digitization needs to be improved.

Computer-Aided Surgical Simulation through Digital Dynamic 3D Skeletal Segments for Correcting Torsional Deformities of the Lower Limbs in Children with Cerebral Palsy

Torsional deformities of the lower limb are common in children with cerebral palsy (CP)-determining gait problems. The mechanisms underlying transverse plane gait deviations arise from a combination of dynamic and static factors. The dynamic elements may be due to spasticity, contractures and muscle imbalances, while the static ones may result from excessive femoral anteversion, which decreases the efficiency of the hip abductors by reducing the muscular lever arms. A therapeutic approach has been identified in multi-level functional surgery for the lower limb. Treating the malalignments of the lower limb with femoral or tibial derotation provides optimal results, especially when supported by adequate biomechanical planning. This planning requires an integrated static-dynamic approach of morphological and functional evaluation, based on radiological measurements, physical examination and gait analysis. Instrumented gait analysis has been confirmed as essential in the evaluation and surgical decision making process for children affected by CP with transverse plane deformities. Computational simulations based on musculoskeletal models that integrate patient-specific CT morphological data into gait analysis can be used for the implementation of a surgical simulation system in pre-operative planning to test the possible effects of the different surgical treatment options on the torsional defects of the lower limbs. Recently, a computer-aided simulation process has been implemented in the preoperative planning of complex osteotomies for limb deformities in children. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software. The aim of this study is to integrate the patient-specific CT musculoskeletal model with morphological data and gait analysis data, with the personalized calculation of kinematic and kinetic parameters, which allow us to generate an “avatar” of the patient for a more in-depth evaluation of the gait abnormalities. The computational simulation platform proposed provides a realistic movable musculoskeletal model in a virtual environment, with the possibility of planning and monitoring the effects of virtual three-dimensional surgical corrections.

Comprehensive virtual orthognathic planning concept in surgery-first patients

The surgery-first concept is becoming increasingly popular in orthognathic surgery since it offers major advantages such as a reduction of treatment duration and an increase in patient satisfaction by eliminating phases of presurgical orthodontic decompensation. Here, we present a novel interdisciplinary pathway of a fully virtual orthodontic-surgical planning concept in a surgery-first setting using a 3D-printed cutting guide and a customised maxillary implant for the Le Fort I osteotomy as well as a CAD/CAM-based stereolithographic final splint. Patient data from cone-beam computed tomography of the skull and a full arch dental scan were processed using the OnyxCeph3TM software (Image Instruments). A mutual computer-aided surgical simulation was conducted by the orthodontist and the oral and maxillofacial surgeon to determine the three-dimensional maxillary and mandibular movements. In a separate virtual planning session, the surgeon designed a customised maxillary guide and implant for precise intraoperative transfer (Geomagic Freeform Plus software, 3DSystems). A 3D-printed CAD/CAM-based final splint was fabricated by the orthodontist and used for accurate mandibular repositioning. We established a comprehensive virtual interdisciplinary orthognathic workflow and successfully applied this concept with a high level of accuracy in a series of surgery-first patients with different types of dentofacial anomalies. This novel fully computer-based pathway offers a high potential to improve the outcomes of orthognathic surgery and reduce total treatment time in the management of the orthognathic patient.

Midsagittal Plane First: Building a Strong Facial Reference Frame for Computer-Aided Surgical Simulation

A facial reference frame is a 3-dimensional Cartesian coordinate system that includes 3 perpendicular planes: midsagittal, axial, and coronal. The order in which one defines the planes matters. The purposes of this study are to determine the following: 1) what sequence (axial-midsagittal-coronal vs midsagittal-axial-coronal) produced more appropriate reference frames and 2) whether orbital or auricular dystopia influenced the outcomes. This study is an ambispective cross-sectional study. Fifty-four subjects with facial asymmetry were included. The facial reference frames of each subject (outcome variable) were constructed using 2 methods (independent variable): axial plane first and midsagittal plane first. Two board-certified orthodontists together blindly evaluated the results using a 3-point categorical scale based on their careful inspection and expert intuition. The covariant for stratification was the existence of orbital or auricular dystopia. Finally, Wilcoxon signed rank tests were performed. The facial reference frames defined by the midsagittal plane first method was statistically significantly different from ones defined by the axial plane first method (P=.001). Using the midsagittal plane first method, the reference frames were more appropriately defined in 22 (40.7%) subjects, equivalent in 26 (48.1%) and less appropriately defined in 6 (11.1%). After stratified by orbital or auricular dystopia, the results also showed that the reference frame computed using midsagittal plane first method was statistically significantly more appropriate in both subject groups regardless of the existence of orbital or auricular dystopia (27 with orbital or auricular dystopia and 27 without, both P<.05). The midsagittal plane first sequence improves the facial reference frames compared with the traditional axial plane first approach. However, regardless of the sequence used, clinicians need to judge the correctness of the reference frame before diagnosis or surgical planning.

Correction of Condylar Displacement of the Mandible Using Early Screw Removal following Patient-Customized Orthognathic Surgery.

Objective: Orthognathic surgery (OGS) is a surgical intervention that corrects dentofacial deformities through the movement of maxillary and mandibular segments to achieve adequate masticatory function, joint health, and facial harmony. However, some patients present with occlusal discrepancies, condylar sag, and/or temporomandibular disorders after OGS. Various methods have been employed to solve these problems after surgery. This study aimed to evaluate the effectiveness of early screw removal in patients with occlusal discrepancies after OGS using three-dimensional cone-beam computed tomography (CBCT). Methods: In 44 patients with dentofacial deformities, patient-customized OGSs with customized plates were performed to correct facial deformities using customized guides with computer-aided surgical simulation. Of the 44 patients, eight patients complained of occlusal discrepancies and temporomandibular disorders after OGS. These eight patients underwent screw removal under local anesthesia around four weeks. The temporomandibular joint spaces at three time points (pre-surgical, post-surgical, and after screw removal) in the sagittal and coronal planes were compared using CBCT. Results: Eight patients showed an increase in joint space on CBCT images immediately after surgery (T1), but after early screw removal (T2), these spaces almost returned to their pre-surgical state, and the temporomandibular joint problem disappeared. Conclusions: The removal of screws located in the distal segment under local anesthesia between three and four weeks post-surgically may be a treatment option for patients with post-OGS occlusal discrepancies, condylar sag, and/or temporomandibular disorder.

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

ObjectiveThe 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 methodsThe 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%. ResultsA 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°. ConclusionAlthough 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.

An In-House Protocol for Fabrication of Patient-Specific Implants to Correct Genial Asymmetry

Facial disharmony as a result of genial malformation or malposition is a correctable condition with a mandibular osteotomy with subsequent repositioning and fixation. Surgical accuracy with osteotomy design and hardware placement in the correct position is paramount to achieve the appropriate surgical outcome and resultant facial balance. These cases highlight a unique protocol developed at Naval Medical Center San Diego to use computer-aided surgical simulation (CASS) to customize patient-specific osteotomy guides and titanium plates for corrective chin surgery. Cross sectional imaging was used to generate virtual stereolithic models of the patient’s facial skeleton. An osteotomy was then virtually performed to divide the patient’s lower jaw. A surgical guide was then designed to index the osteotomy in its precise location. Incorporated into the surgical guide were the fixation holes for a titanium implant. The titanium plate was designed in a similar fashion to align with the predetermined points of fixation and anatomically approximate the chin in its virtually planned position. The virtual files (STL) were then sent to 3D Medical Applications Center at Walter Reed National Military Medical Center for printing. The surgeries were performed in the main operating room with accurate replication of the computer assisted surgical simulation and excellent clinical outcomes to follow. Post-surgical accuracy was evaluated by comparing postoperative CT imaging with the predetermined surgical simulation. The mean difference in of the final chin position was < 1mm in the vertical and horizontal planes. These results reinforced clinical replication of the CASS with a level of accuracy less easily obtained through more traditional methods. Although the presurgical planning required time investment for virtual planning and design, intraoperative surgical time was reduced. Additionally, by managing the computer-assisted design in institution, a tremendous reduction in cost was realized. Surgical correction of facial imbalance requires the utmost intraoperative precision to optimize patient outcomes. Virtual surgical planning with guided osteotomies and patient-specific implants offers an avenue to enhance surgical predictability in the operating room. Further, guided surgery streamlines operating time and efficiency by effectively negating the need for intraoperative measurements or repositioning guides. This unique protocol nearly eliminates the significant financial burden often associated with such procedures, making it far more applicable globally.

The 5-Minute Splint (5MS): In-House 3D Printing of an Orthognathic Splint for Single-Jaw Cases

The benefits of computer-assisted surgical simulation (CASS) have been proven, including visualization of the osteotomies and interferences, increasing intra-operative efficiency, and producing reliable and accurate outcomes.1 However, the manual fabrication of orthognathic splints for single-jaw surgery using acrylic is still common today, despite being vulnerable to intrinsic inaccuracies.2 The purpose of this study was to demonstrate a novel, rapid, simple CASS protocol for in-house 3D-printing of orthognathic splints for use during single-jaw orthognathic surgery. A specific protocol, the 5 Minute Splint (5MS) protocol, was performed for consecutive patients requiring single-jaw orthognathic surgery. Using an intraoral scanner and computer-aided surgical simulation, computer-designed splints were fabricated by a rapid prototyping machine in-house. The primary outcome variable was the time associated with the design, manufacturing, and processing of the splints. The secondary outcome variable was the cost associated with the rapid prototyping of the splints. The 5 Minute Splint (5MS) protocol was utilized for 33 consecutive patients (21 female and 12 male; mean age 28.1 years) requiring single-jaw orthognathic surgery between January 2019 and February 2020. Of these patients, 10 underwent a Le Fort I osteotomy procedure and 23 a bilateral sagittal split osteotomy (BSSO) (both regardless of genioplasty). The mean time for each case was between 5 to 9 hours, including 3 minutes for scanning of models, 4.5 minutes for development of the splint, and 4-8 hours for rapid prototyping and post-processing. This time varied based on the complexity of the design and the number of splints printed simultaneously. The average cost for each splint was $0.73 Canadian dollars (CAD). The average time and cost for producing each splint using the 5MS protocol is significantly less than that seen in the literature. An average total cost of $2380.26 U.S. dollars (USD) reported in 1 study for a virtual surgical planning (VSP) session and fabrication of splints with an external company.3 The results of this study confirm that the design and rapid prototyping of orthognathic splints for single-jaw surgery can be performed in an efficient, cost-effective manner in-house using the 5MS protocol.

Accuracy of maxillary repositioning surgery using CAD/CAM customized surgical guides and fixation plates

The advent of three-dimensional imaging and computer-aided surgical simulation (CASS) have brought about a paradigm shift in surgical planning. The aim of this study was to assess the accuracy of maxillary repositioning surgery using computer-aided design and manufacturing (CAD/CAM) customized titanium surgical guides and fixation plates. Thirty consecutive adult patients, 13 male and 17 female, with a mean age of 29.2 years and 25.5 years, respectively, requiring Le Fort I maxillary osteotomy, with or without simultaneous mandibular surgery, were evaluated retrospectively. All orthognathic surgeries were performed by one experienced surgeon. The pre-surgical and post-surgical volumetric imaging were superimposed to assess the linear and angular differences between the planned and actual positions of the maxilla following surgery. With the use of the CAD/CAM titanium surgical guides and fixation plates, all surgical movements were within 2mm and 4° of the planned movements, which is considered clinically insignificant. The overall root mean square error between the planned and actual surgical movements was 0.38mm in the transverse dimension, 0.64mm in the anteroposterior dimension, and 0.55mm in the vertical dimension. In regard to the centroid of the maxilla, the absolute angular difference of the maxillary centroid was 1.06° in pitch, 0.47° in roll, and 0.49° in yaw. Maxillary repositioning surgery can be performed with high accuracy using CAD/CAM titanium surgical guides and fixation plates.

Surgical Treatment Selection in Adult Class III Patients With Maxillary Transverse Deficiency.

The purpose of this study was to investigate the frequency of three commonly used treatments for skeletal class III malocclusion with maxillary transverse deficiency (MTD) (SCM) patients in East Asian, to find a quantitative method for precise discrepancy evaluation, and to find other potential indicators for treatment selection. A total of 239 adult SCM patients were divided into3 groups according to treatments.Dentofacial features were measured and the initial skeletal discrepancy was evaluated with computer-aided surgical simulation (CASS). Relationship between the degree of skeletal transverse discrepancy (STD) and other dentofacial features were analyzed by Spearman's rank correlation. The STD in East Asian could be quantitatively grouped as: mild (<4 mm), moderate (4-8 mm), and severe (>8 mm). Most patients (81%) could be diagnosed with mild STD, and were treated without surgical expansion. The upper first molars inclination, the required relative movement and the required maxillary movement were correlated to the degree of STD. The conventional orthodontic and orthognathic treatment without surgical expansion is the most frequent choice for East Asian SCM adults. CASS facilitated analysis is useful in an accurate MTD evaluation. Some dentofacial features were closely correlated to STD, and thus were helpful for the treatment selection.

Design and manufacture of dental-supported surgical guide for genioplasty

Background/purposeGenioplasty were used widely to correct chin deformities. The purpose of this study was to design and manufacture a dental-supported surgical guide for genioplasty surgery and assess for surgical accuracy. Materials and methodseleven patients with chin deformities were treated in this study. The computed tomography (CT) data of the patient's skull and the digital dental models of stone dental models were acquired preoperatively. For each patient, a virtual three-dimensional (3D) model of the skull was constructed and enhanced with digital dental models. A surgical simulation was then performed using computer-aided surgical simulation (CASS) technology based on clinical examination and 3D cephalometry. The surgery was simulated preoperatively which allowed the design of a cutting guide and a dental-supported repositioning guide for genioplasty, which was then 3D-printed and used during operation after disinfection. After surgery, the outcome was evaluated by superimposing the postoperative CT model onto the preoperative model, recording the linear and angular deviation of landmarks and plane, then measuring the differences between the planned and actual outcomes. ResultsThe osteotomy and repositioning were successfully performed as planned using surgical guides. No inferior alveolar nerve damage was seen in this study. The dental-supported surgical guide showed excellent accuracy, with the largest differences between the planned and the postoperative chin segment being 0.9 mm and 3.2°. ConclusionThe dental-supported surgical guide designed preoperatively provided a reliable method of transfer genioplasty planning. This can assist surgeons in accurately performing osteotomy and repositioning bone segments during a genioplasty.

Automatic detection of symmetry plane for computer-aided surgical simulation in craniomaxillofacial surgery.

Symmetry plane calculation is used in fracture reduction or reconstruction in the midface. Estimating a reliable symmetry plane without advanced anatomic knowledge is the most critical challenge. In this work, we developed a new automated method to find the mid-plane in CT images of an intact skull and a skull with a unilateral midface fracture. By use of a 3D point-cloud of a skull, we demonstrate that the proposed algorithm could find a mid-plane that meets clinical criteria. There is no need for advanced anatomical knowledge through the use of this algorithm. The algorithm used principal component analysis to find the initial plane. Then the rotation matrix, derived from an iterative closest point (ICP) registration method, is used to update the normal vector of the plane and find the optimum symmetry plane. A mathematical index, Hausdorff distance (HD), is used to evaluate the similarity of one mid-plane side in comparison to the contralateral side. HD decreased by 66% in the intact skull and 65% in a fractured skull and converged in just six iterations. High convergence speed, low computational load, and high accuracy suggest the use of the algorithm in the planning procedure. This easy-to-use algorithm with its advantages, as mentioned above, could be used as an operator in craniomaxillofacial software.

Computer-Aided Surgical Simulation for Correcting Complex Limb Deformities in Children

This work aims to present an in-house low-cost computer-aided simulation (CASS) process that was recently implemented in the preoperative planning of complex osteotomies for limb deformities in children. Five patients admitted to the Unit of Paediatric Orthopaedics and Traumatology from April 2018 to December 2019, for correcting congenital or post-traumatic limb deformities were included in the study. Three-dimensional (3D) digital models were generated from Computed Tomography (CT) scans, using free open-source software, and the surgery was planned and simulated starting from the 3D digital model. 3D printed sterilizable models were fabricated using a low-cost 3D printer, and animations of the operation were generated with the aim to accurately explain the operation to parents. All procedures were successfully planned using our CASS method and the 3D printed models were used during the operation, improving the understanding of the severely abnormal bony anatomy. The surgery was precisely reproduced according to CASS and the deformities were successfully corrected in four cases, while in one case, the intraoperative intentional undersizing of the bone osteotomy produced an incomplete correction of a congenital forearm deformity. Our study describes the application of a safe, effective, user-friendly, and low-cost CASS process in paediatric orthopaedics (PO) surgery. We are convinced that our study will stimulate the widespread adoption of this technological innovation in routine clinical practice for the treatment of rare congenital and post-traumatic limb deformities during childhood.

A Modified Method Using Double Computed Tomography Scan Procedure to Maintain Mandibular Width in Mandibular Reconstruction.

The purpose of this study was to evaluate the use of a modified template system and double computed tomography scan procedure to maintain mandibular width in cases of mandibular reconstruction. Ten patients who underwent mandibular reconstruction with a fibular flap were enrolled. The surgeries were planned with a computer-aided surgical simulation (CASS) planning method. Following double computed tomography scan procedure, the template system was designed in a computer and was fabricated using a three-dimensional printing technique. The cutting guides were designed with the holes of the conventional reconstruction plate on the remnant mandibular segments. After surgery, the outcome evaluation was compared by first superimposing the post-operative computed tomography model onto the planned model and then measuring the differences between the planned and actual outcomes. All surgeries were completed successfully using the template system. With the use of the templates, the largest linear root-mean-square deviation (RMSD) between the planned and post-operative remnant segments was 1.01 mm, and the largest angular RMSD was 4.05°. The authors conclude that this template system and double computed tomography scan procedure provides a reliable method to maintain mandibular width in mandibular reconstruction using a fibular flap.