Precise Coronoidectomy and Zygomatic Arch Reduction for Unilateral Hyperplasia of the Coronoid Process (Jacob's Disease) via Computer-aided Design and Manufacture.

Jacob disease is the new formation of a pseudo-joint between both of enlarged coronoid process and even zygomatic arch. A 23-year-old female patient with facial asymmetry and limited mouth opening was reported. Computed tomography images showed the classic symptom of Jacob disease with a mushroom-shaped tumor mass from the coronoid process a pseudoarthrosis joint with zygomatic arch. Coronoidectomy and zygomatic arch reduction were planned to operate based on computer-aided design/computer-aided manufacturing. During the actual operation, the excision of coronoid process and reconstruction of zygomatic arch were all navigated by 3-dimensional-printed surgical templates as designed through an intraoral approach. As a result, the enlarged coronoid process was smoothly removed without sequela and mouth opening along with facial symmetry were successfully improved. The authors suggested that computer-aided design/computer-aided manufacturing should be considered as an auxiliary technique to shorten operation time and enhance surgical accuracy.

Prediction of orthognathic surgery plan from 3D cephalometric analysis via deep learning.

BACKGROUND: Preoperative planning of orthognathic surgery is indispensable for achieving ideal surgical outcome regarding the occlusion and jaws' position. However, orthognathic surgery planning is sophisticated and highly experience-dependent, which requires comprehensive consideration of facial morphology and occlusal function. This study aimed to investigate a robust and automatic method based on deep learning to predict reposition vectors of jawbones in orthognathic surgery plan. METHODS: A regression neural network named VSP transformer was developed based on Transformer architecture. Firstly, 3D cephalometric analysis was employed to quantify skeletal-facial morphology as input features. Next, input features were weighted using pretrained results to minimize bias resulted from multicollinearity. Through encoder-decoder blocks, ten landmark-based reposition vectors of jawbones were predicted. Permutation importance (PI) method was used to calculate contributions of each feature to final prediction to reveal interpretability of the proposed model. RESULTS: VSP transformer model was developed with 383 samples and clinically tested with 49 prospectively collected samples. Our proposed model outperformed other four classic regression models in prediction accuracy. Mean absolute errors (MAE) of prediction were 1.41 mm in validation set and 1.34 mm in clinical test set. The interpretability results of the model were highly consistent with clinical knowledge and experience. CONCLUSIONS: The developed model can predict reposition vectors of orthognathic surgery plan with high accuracy and good clinically practical-effectiveness. Moreover, the model was proved reliable because of its good interpretability.

Mandibular stability and condylar changes following orthognathic surgery in mandibular hypoplasia patients associated with preoperative condylar resorption.

OBJECTIVES: To evaluate postoperative mandibular stability and condylar changes in patients with mandibular hypoplasia and preoperative condylar resorption (CR) undergoing orthognathic surgery. MATERIALS AND METHODS: Fifty-four patients were included in this retrospective study. Computed tomography (CT) scans were acquired preoperatively (T0), 2-7 days immediate postoperatively (T1), and at least 1 year postoperatively (T2). Three-dimensional (3D) cephalometric analysis and measurements of condylar angle, volume, and position (joint spaces) were performed. A 2-mm mandibular relapse was deemed clinically acceptable. We also analyzed the correlations between relapse and postoperative CR and susceptible factors using a multivariate logistic regression model. RESULTS: The results showed one year after the surgery, the average mandibular relapse was 1.0 mm (p < 0.05), and the average reduction of condylar volume was 152.4 mm3 (12.7%). Condyle-fossa relationships were improved immediately after the surgery, with a tendency of returning to their original state in the follow-up (p < 0.05). Anteroposterior advancement at point B (B-CP advancement) at T1 and superior joint space (SJS) at T0 were significantly correlated with mandibular relapse, and postoperative CR was mainly associated with vertical increasement at point B (B-AP increasement) at T1. The optimal cut-off values were as follows: 1.6 mm for SJS, 4.2 mm for B-CP advancement, and 1.8 mm for B-AP increasement. Concomitant advancement Genioplasty showed no significant correlation with relapse and postoperative CR. CONCLUSIONS: While patients with mandibular hypoplasia and preoperative CR were vulnerable to further condylar resorption after mandibular advancement, the treatment outcomes were generally clinically acceptable. Postoperative relapse was associated with a larger than 4.2 mm of mandibular advancement measured at B-CP and a larger than 1.6 mm of superior joint space measured at SJS, and postoperative CR was associated with a larger than 1.8 mm of mandibular vertical increasement measured at B-AP. CLINICAL RELEVANCE: The findings of this study suggested that the mandibular advancement might be limited to 5 mm for patients with preoperative CR. A concomitant advancement genioplasty might also be considered to achieve a better facial profile in these patients.

Computer-Aided Autogenous Coronoid Process Graft Combined With Median and Unilateral Sagittal Split Osteotomy for Late Reconstruction of Condylar Fracture and Occlusion after Trauma.

PURPOSE: This study proposes a high-precision surgical technique that combines both computer-aided design/computer-aided manufacturing (CAD/CAM) and the screw-track transfer technique for condylar and occlusal reconstruction. MATERIALS AND METHODS: A 43-year-old male patient with facial asymmetry, limited mouth opening, and malocclusion underwent condylar and occlusal reconstruction surgery. An autogenous cor-onoid process graft was performed by combining CAD/CAM and the screw-track transfer technique. RESULTS: The surgical plan was transformed successfully from preoperative virtual surgical planning to actual surgery; this was confirmed by merging the postoperative computed tomography images with the preoperative three-dimensional surgical design. The patient recovered well and had better occlusion and facial symmetry, as well as an increased degree of mouth opening post-surgery. No complications were observed. CONCLUSIONS: CAD/CAM combined with the screw-track transfer technique is a precise and feasible method that can be applied to autogenous coronoid process grafts. This approach can be used to reconstruct the condylar process and achieve a good occlusal relationship.

A virtual surgical prototype system based on gesture recognition for virtual surgical training in maxillofacial surgery.

BACKGROUND: Virtual reality (VR) technology is an ideal alternative of operation training and surgical teaching. However, virtual surgery is usually carried out using the mouse or data gloves, which affects the authenticity of virtual operation. A virtual surgery system with gesture recognition and real-time image feedback was explored to realize more authentic immersion. METHOD: Gesture recognition technology proposed with an efficient and real-time algorithm and high fidelity was explored. The recognition of hand contour, palm and fingertip was firstly realized by hand data extraction. Then, an Support Vector Machine classifier was utilized to classify and recognize common gestures after extraction of feature recognition. The algorithm of collision detection adopted Axis Aligned Bounding Box binary tree to build hand and scalpel collision models. What's more, nominal radius theorem (NRT) and separating axis theorem (SAT) were applied for speeding up collision detection. Based on the maxillofacial virtual surgical system we proposed before, the feasibility of integration of the above technologies in this prototype system was evaluated. RESULTS: Ten kinds of signal static gestures were designed to test gesture recognition algorithms. The accuracy of gestures recognition is more than 80%, some of which were over 90%. The generation speed of collision detection model met the software requirements with the method of NRT and SAT. The response time of gesture] recognition was less than 40 ms, namely the speed of hand gesture recognition system was greater than 25 Hz. On the condition of integration of hand gesture recognition, typical virtual surgical procedures including grabbing a scalpel, puncture site selection, virtual puncture operation and incision were carried out with realization of real-time image feedback. CONCLUSION: Based on the previous maxillofacial virtual surgical system that consisted of VR, triangular mesh collision detection and maxillofacial biomechanical model construction, the integration of hand gesture recognition was a feasible method to improve the interactivity and immersion of virtual surgical operation training.

Development of a maxillofacial virtual surgical system based on biomechanical parameters of facial soft tissue.

PURPOSE: Lack of biomechanical force model of soft tissue hinders the development of virtual surgical simulation in maxillofacial surgery. In this study, a physical model of facial soft tissue based on real biomechanical parameters was constructed, and a haptics-enabled virtual surgical system was developed to simulate incision-making process on facial soft tissue and to help maxillofacial surgery training. METHODS: CT data of a 25-year-old female patient were imported into Mimics software to reconstruct 3D models of maxillofacial soft and skeletal tissues. 3dMD stereo-photo of the patient was fused on facial surface to include texture information. Insertion and cutting parameters of facial soft tissue measured on fresh cadavers were integrated, and a maxillofacial biomechanical force model was established. Rapid deformation and force feedback were realized through localized deformation algorithm and axis aligned bounding box (AABB)-based collision detection. The virtual model was validated quantitatively and qualitatively. RESULTS: A patient-specific physical model composed of skeletal and facial soft tissue was constructed and embedded in the virtual surgical system. Insertion and cutting in different regions of facial soft tissue were simulated using omega 6, and real-time feedback force was recorded. The feedback force was consistent with acquired force data of experiments conducted on tissue specimen. Real-time graphic and haptic feedback were realized. The mean score of the system performance was 3.71 given by surgeons in evaluation questionnaires. CONCLUSION: The maxillofacial physical model enabled operators to simulate insertion and cutting on facial soft tissue with realization of realistic deformation and haptic feedback. The combination of localized deformation algorithm and AABB-based collision detection improved computational efficiency. The proposed virtual surgical system demonstrated excellent performance in simulation and training of incision-making process.

Reducing relapse and accelerating osteogenesis in rapid maxillary expansion using an injectable mesoporous bioactive glass/fibrin glue composite hydrogel.

Rapid maxillary expansion (RME), as a common treatment for craniomaxillofacial deformity, faces the challenge of high relapse rates and unsatisfactory therapeutic effects. In this study, a standardized Sprague-Dawley (SD) rat RME model was first established with a modified expander as well as retainer design and optimized anterior maxillary expanding force of 100 g which exerted the most synchronized mobility of mid-palatal suture and incisors. Via the standardized model, the high relapse rate was proven to be attributed to insufficient osteogenesis in expanded suture, requiring long-term retainer wearing in clinical situations. To reduce the relapse rate, mesoporous bioactive glass/fibrin glue (MBG/FG) composite hydrogels were developed for an in situ minimal invasive injection that enhance osteogenesis in the expanded palate. The component of 1 wt% MBG was adopted for enhanced mechanical strength, matched degradation rate and ion dissolution, excellent in vitro biocompatibility and osteoinductivity. Effects of 1%MBG/FG composite hydrogel on osteogenesis in expanded mid-palatal sutures with/without retention were evaluated in the standardized model. The results demonstrated that injection of 1%MBG/FG composite hydrogel significantly promoted bone formation within the expanded mid-palatal suture, inhibited osteoclastogenesis and benefited the balance of bone remodeling towards osteogenesis. Combination of retainer and injectable biomaterial was demonstrated as a promising treatment to reduce relapse rate and enhance osteogenesis after RME. The model establishment and the composite hydrogel development in this article might provide new insight to other craniomaxillofacial deformity treatment and design of bone-repairing biomaterials with higher regenerative efficiency.

Optimized BMSC-derived osteoinductive exosomes immobilized in hierarchical scaffold via lyophilization for bone repair through Bmpr2/Acvr2b competitive receptor-activated Smad pathway.

Mesenchymal stem cell-derived exosomes (MSC-exos), with its inherent capacity to modulate cellular behavior, are emerging as a novel cell-free therapy for bone regeneration. Herein, focusing on practical applying problems, the osteoinductivity of MSC-exos produced by different stem cell sources (rBMSCs/rASCs) and culture conditions (osteoinductive/common) were systematically compared to screen out an optimized osteogenic exosome (BMSC-OI-exo). Via bioinformatic analyses by miRNA microarray and in vitro pathway verification by gene silencing and miRNA transfection, we first revealed that the osteoinductivity of BMSC-OI-exo was attributed to multi-component exosomal miRNAs (let-7a-5p, let-7c-5p, miR-328a-5p and miR-31a-5p). These miRNAs targeted Acvr2b/Acvr1 and regulated the competitive balance of Bmpr2/Acvr2b toward Bmpr-elicited Smad1/5/9 phosphorylation. On these bases, lyophilized delivery of BMSC-OI-exo on hierarchical mesoporous bioactive glass (MBG) scaffold was developed to realize bioactivity maintenance and sustained release by entrapment in the surface microporosity of the scaffold. In a rat cranial defect model, the loading of BMSC-OI-exo efficiently enhanced the bone forming capacity of the scaffold and induced rapid initiation of bone regeneration. This paper could provide empirical bases of MSC-exo-based therapy for bone regeneration and theoretical bases of MSC-exo-induced osteogenesis mechanism. The BMSC-OI-exo-loaded MBG scaffold developed here represented a promising bone repairing strategy for future clinical application.

Stimulating Factors and Origins of Precursor Cells in Traumatic Heterotopic Ossification Around the Temporomandibular Joint in Mice.

The contributing factors and the origins of precursor cells in traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ), which causes obvious restriction of mouth opening and maxillofacial malformation, remain unclear. In this study, our findings demonstrated that injured chondrocytes in the condylar cartilage, but not osteoblasts in the injured subchondral bone, played definite roles in the development of THO-TMJ in mice. Injured condylar chondrocytes without articular disc reserves might secrete growth factors, such as IGF1 and TGFß2, that stimulate precursor cells, such as endothelial cells and muscle-derived cells, to differentiate into chondrocytes or osteoblasts and induce THO-TMJ. Preserved articular discs can alleviate the pressure on the injured cartilage and inhibit the development of THO-TMJ by inhibiting the secretion of these growth factors from injured chondrocytes. However, the exact molecular relationships among trauma, the injured condylar cartilage, growth factors such as TGFß2, and pressure need to be explored in detail in the future.