Computer-assisted teaching of bilateral sagittal split osteotomy: Learning curve for condylar positioning

A proximal segment positioning method to enhance condylar stability after bilateral sagittal split ramus osteotomy in skeletal class II patients: A randomized controlled study

This study compared condylar stability using two proximal segment positioning methods during bilateral sagittal split ramus osteotom in patients with skeletal Class II malocclusion. 12 patients in the experimental group underwent positioning guided by preoperative mandibular movement trajectory data, a guiding device, and prebent titanium plates, while 13 patients in the control group had manual positioning. Postoperative imaging was performed at 2 weeks (T1), 3 months (T2), and 6 months (T3) to assess condylar and mandibular positions. At T1, both groups showed increased joint space, but the increase in anterior joint space (AJS) was significantly smaller in the experimental group (0.39 ± 0.70 mm) than in the control group (1.10 ± 0.97 mm, P < 0.05). Between T1 and T2, both groups experienced joint space reduction and upward-inward condylar movement, with a less pronounced reduction in AJS in the experimental group (0.28 ± 1.01 mm) compared to the control group (0.98 ± 0.89 mm, P < 0.05). By T3, condylar positions had stabilized, with mandibular relapse significantly lower in the experimental group (12.71 ± 6.43 %) than in the control group (27.09 ± 8.9 %, P < 0.05). These findings suggest that trajectory-guided proximal segment positioning improves postoperative condylar and mandibular stability.

3-Dimensional accuracy of navigation-guided bimaxillary orthognathic surgery: A systematic review and meta-analysis

The transfer of a virtual orthognathic surgical plan to the patient still relies on the use of occlusal splints, which have limitations for vertical positioning of the maxilla. The use of real-time navigation has been proposed to enhance surgical accuracy. This systematic review (PROSPERO CRD42024497588) aimed to investigate if surgical navigation can improve the three-dimensional accuracy of orthognathic surgery. The inclusion criteria were orthognathic surgery, use of intra-operative navigation and quantitative assessment of surgical accuracy. The exclusion criteria were non-bimaxillary orthognathic surgeries, non-clinical studies, studies without post-operative 3D analysis and publications not in the English language. A search of PubMed, Embase and Cochrane Library generated 940 records, of which 12 were found relevant. Risk of bias was assessed done using the Joanna Briggs Institute Critical Appraisal Checklist Tool. Among the included studies, there were nine of observational character and three randomized control studies (RCTs). All studies demonstrated promising outcomes with reported good surgical accuracy within a 2 mm difference between the planned and post-surgical result. Meta-analysis of two RCTs was carried out and results were in favor of surgical navigation with a total odds ratio of 4.44 [2.11, 9.37] and an overall effect outcome of Z = 3.92 (p < 0.0001). Navigation was up to 0.60 mm more accurate than occlusal wafers only (p < 0.001). However, there were variations in the application of surgical navigation and methods of analysis, leading to a heterogenous data set. Future studies should focus on standardized protocols and analysis methods to further validate the use of surgical navigation in orthognathic surgery. Despite some limitations, surgical navigation shows potential as a valuable tool in improving the accuracy of orthognathic surgery.

Evaluation of mandibular condyle position in Class III patients after bimaxillary orthognathic surgery: A cone-beam computed tomography study

Objective

This retrospective study evaluated the mandibular condyle position before and after bimaxillary orthognathic surgery performed with the mandibular condyle positioned manually in patients with mandibular prognathism using cone-beam computed tomography.

Methods

Overall, 88 mandibular condyles from 44 adult patients (20 female and 24 male) diagnosed with mandibular prognathism due to skeletal Class III malocclusion who underwent bilateral sagittal split ramus osteotomy (BSSRO) and Le Fort I performed using the manual condyle positioning method were included. Cone-beam computed tomography images obtained 1-2 weeks before (T0) and approximately 6 months after (T1) surgery were analyzed in three planes using 3D Slicer software. Statistical significance was set at P < 0.05 level.

Results

Significant inward rotation of the left mandibular condyle and significant outward rotation of the right mandibular condyle were observed in the axial and coronal planes (P < 0.05). The positions of the right and left condyles in the sagittal plane and the distance between the most medial points of the condyles in the coronal plane did not differ significantly (P > 0.05).

Conclusions

While the change in the sagittal plane can be maintained as before surgery with manual positioning during the BSSRO procedure, significant inward and outward rotation was observed in the axial and coronal planes, respectively, even in the absence of concomitant temporomandibular joint disorder before or after the operation. Further long-term studies are needed to correlate these findings with possible clinical consequences.

Comparison of Patient-Specific Condylar Positioning Devices and Manual Methods in Orthognathic Surgery: A Prospective Randomized Trial

BACKGROUND

This study investigated whether patient-specific condylar positioning devices (CPDs) are beneficial compared to the conventional manual positioning of the condyles.

METHODS

In this prospective, randomized trial, patients undergoing orthognathic surgery with a bilateral sagittal split osteotomy of the mandible were included. The ascending ramus was positioned with computer-aided designed and computer-aided manufactured (CAD/CAM) patient-specific devices in the CPD group and manually in the control group. Postoperatively, cone-beam computed tomography (CBCT) was performed to align the virtually planned position with the postoperative result.

RESULTS

Thirty patients were enrolled in the study, with 14 randomized to the CPD group and 16 to the control group. In the CPD group, the ascending ramus differed in the postoperative CBCT scan from the virtually planned position by 0.8 mm in the left/right, 0.8 mm in the front/back, and 1.3 mm in the cranial/caudal direction. The corresponding control-group values were 1.1 mm, 1.3 mm, and 1.6 mm. CPD and controls differed significantly for the left/right movement of the rami (p = 0.04) but not for the other directions or rotations (p > 0.05).

CONCLUSIONS

The results demonstrate that both methods are accurate, and postoperative results matched the virtually planned position precisely. It can be assumed that the described CPDs are beneficial when a condylar position different from the preoperative is desired.

Intraoperative condylar positioning techniques on mandible in orthognathic surgery

PURPOSE

The surgical condylar displacement often resulted in relapse and serious symptoms of temporomandibular joint disorders (TMD) after orthognathic surgery. To minimize the displacement, numerous techniques have been proposed. To verify their accuracy in positioning and effectiveness in preventing postoperative TMD and relapse, we reviewed the literature related to intraoperative condylar positioning techniques on the mandible in this study.

METHODS

The literature on condylar positioning techniques was reviewed with 2 charts, including the non-computer-assisted and the computer-assisted positioning methods. The pre- and postoperative alterations of condyles, the postoperative temporomandibular joint (TMJ) function, and surgical relapse were analyzed regarding the techniques. The clinical usage and characteristics were reviewed as well.

RESULTS

A total of 22 articles, including 907 patients, have been reported since 2001. Nearly all methods reach a considerable positioning accuracy within the range of 1-2 mm and 1-2° from the preoperative position. We ranked the accuracy of the methods from high to low: CAD/CAM CPDs>CAD/CAM titanium plate positioning>manual positioning>computer-assisted navigation systems>imaging positioning systems. Most skeletal class II and class III patients achieved great occlusion and had no TMJ dysfunction or relapse after condylar positioning.

CONCLUSION

Both the non-computer-assisted and computer-assisted condylar positioning techniques reach considerable accuracy in locating the preoperative condyle position and preventing TMJ dysfunction and surgical relapse. Different levels of surgeons and cases can benefit from multiple suggested positioning methods. Further research with large samples and long-term follow-up is worth looking forward to upgrading the current methods, improving the clinical utility, and developing new positioning techniques.

A new method for individual condylar osteotomy and repositioning guides used in patients with severe deformity secondary to condylar osteochondroma

Background

Mandibular condylar osteochondroma (OC) could lead to facial morphologic and functional disturbances, such as facial asymmetry, malocclusion, and temporomandibular joint dysfunction. However, after condylar OC resection, the inaccurate reposition of the neocondyle still needs to be solved. The purpose of this study was to explore the feasibility of the condylar osteotomy and repositioning guide to reposition the neocondyle in the treatment of patients with severe deformity secondary to condylar OC.

Results

Three patients with severe deformity secondary to OC of the mandibular condyle were enrolled in this study. With the aid of condylar osteotomy and repositioning guide, condylar OC resection and repositioning were carried out, and the accuracy and stability of these guides were evaluated. All patients healed uneventfully, and no facial nerve injury and condylar ankylosis occurred. Compared with the computerized tomography scans in centric relation before surgery and 3 days after surgery, the results showed that the facial symmetry was greatly improved in all the patients. Also, after the superimposition of the condylar segments before surgery and 3 days after surgery, the postoperative reconstructed condyles had a high degree of similarity to the reconstruction of the virtual surgical planning. Observed from the sagittal and coronal directions, the measurements of condylar positions were very close to those of virtual surgical planning. Moreover, it also showed stable results after a 1-year follow-up.

Conclusions

For patients with severe deformity secondary to condylar OC, condylar osteotomy, and repositioning guide was expected to provide a new option for the improvement of facial symmetry and occlusal relationship.

Current Orthognathic Practice in India: Do We Need to Change?

The last decade or so has seen paradigm shifts in the various aspects of orthognathic surgery. A lot of these changes are to do with digitalization of the orthodontic-surgical workflow, optimization of surgery-first protocols, virtual surgical planning-based 3D printing solutions and changing patient-health-care dynamics. The aim of this article is to provide evidence-based recommendations that are both practical and economically viable for the current orthognathic practice in India.

Fixation Methods for Mandibular Advancement and Their Effects on Temporomandibular Joint: A Finite Element Analysis Study

Objectives

Bilateral sagittal split osteotomy (BSSO) is a common surgical procedure to correct dentofacial deformities that involve the mandible. Usually bicortical bone fixation screw or miniplates with monocortical bone fixation screw were used to gain stability after BSSO. On the other hand, the use of resorbable screw materials had been reported. In this study, our aim is to determine first stress distribution values at the temporomandibular joint (TMJ) and second displacement amounts of each mandibular bone segment.

Methods

A three-dimensional virtual mesh model of the mandible was constructed. Then, BSSO with 9 mm advancement was simulated using the finite element model (FEM). Fixation between each mandibular segment was also virtually performed using seven different combinations of fixation materials, as follows: miniplate only (M), miniplate and a titanium bicortical bone fixation screw (H), miniplate and a resorbable bicortical bone fixation screw (HR), 3 L-shaped titanium bicortical bone fixation screws (L), 3 L-shaped resorbable bicortical bone fixation screws (LR), 3 inverted L-shaped titanium bicortical bone fixation screws (IL), and 3 inverted L-shaped resorbable bicortical bone fixation screws (ILR).

Results

At 9 mm advancement, the biggest stress values at the anterior area TMJ was seen at M fixation and LR fixation at posterior TMJ. The minimum stress values on anterior TMJ were seen at L fixation and M fixation at posterior TMJ. Minimum displacement was seen in IL method. It was followed by L, H, HR, M, ILR, and LR, respectively.

Conclusion

According to our results, bicortical screw fixation was associated with more stress on the condyle. In terms of total stress value, especially LR and ILR lead to higher amounts.

Changes of temporomandibular joint position after surgery first orthognathic treatment concept

Orthognathic surgery treatment (OGS) after orthodontic treatment of dentofacial deformities is a widely performed procedure, often accompanied by a bilateral sagittal split osteotomy (BSSO). Positioning of the condyle during this procedure is a crucial step for achieving optimal functional and anatomical results. Intraoperatively poorly positioned condyles can have a negative effect on the postoperative result and the patient’s well-being. Changes of the condylar position during OGS Procedures and its effects on the temporomandibular joint in orthognathic surgical interventions (OGS) are subject of scientific discussions. However, up to date, no study has investigated the role of condyle position in the surgery first treatment concept. The aim of this study was to investigate the influence of OGS on the three-dimensional position of the condyle in the joint in a surgery first treatment concept without positioning device and to record the change in position quantitatively and qualitatively. Analysis of our data indicated that OGS in surgery first treatment concept has no significant effect on the position of the condyle and the anatomy of the temporomandibular joint.

Real-time augmented model guidance for mandibular proximal segment repositioning in orthognathic surgery, using electromagnetic tracking

It is essential to reposition the mandibular proximal segment (MPS) as close to its original position as possible during orthognathic surgery. Conventional methods cannot pinpoint the exact position of the condyle in the fossa in real time during repositioning. In this study, based on an improved registration method and a separable electromagnetic tracking tool, we developed a real-time, augmented, model-guided method for MPS surgery to reposition the condyle into its original position more accurately. After virtual surgery planning, using a complex maxillomandibular model, the final position of the virtual MPS model was simulated via 3D rotations. The displacements resulting from the MPS simulation were applied to the MPS landmarks to indicate their final postoperative positions. We designed a new registration body with 24 fiducial points for registration, and determined the optimal point group on the registration body through a phantom study. The registration between the patient's CT image and physical spaces was performed preoperatively using the optimal points. We also developed a separable frame for installing the electromagnetic tracking tool on the patient's MPS. During MPS surgery, the electromagnetic tracking tool was repeatedly attached to, and separated from, the MPS using the separable frame. The MPS movement resulting from the surgeon's manipulation was tracked by the electromagnetic tracking system. The augmented condyle model and its landmarks were visualized continuously in real time with respect to the simulated model and landmarks. Our method also provides augmented 3D coronal and sagittal views of the fossa and condyle, to allow the surgeon to examine the 3D condyle-fossa positional relationship more accurately. The root mean square differences between the simulated and intraoperative MPS models, and between the simulated and postoperative CT models, were 1.71 ± 0.63 mm and 1.89 ± 0.22 mm respectively at three condylar landmarks. Thus, the surgeons could perform MPS repositioning conveniently and accurately based on real-time augmented model guidance on the 3D condyle positional relationship with respect to the glenoid fossa, using augmented and simulated models and landmarks.