Computer-Aided Planning in Orthognathic Surgery: A Comparative Study with the Establishment of Burstone Analysis-Derived 3D Norms

Average Three-Dimensional Skeletofacial Model as a Template for Bone Repositioning during Virtual Orthognathic Surgery

BACKGROUND

Virtual planning has revolutionized orthognathic surgery. This study presents a computer-assisted method for constructing average three-dimensional skeletofacial models that can be applied as templates for surgical planning for maxillomandibular repositioning.

METHODS

The authors used the images of 60 individuals (30 women and 30 men) who had never undergone orthognathic surgery to construct an average three-dimensional skeletofacial model for male participants and one for female participants. The authors validated the accuracy of the newly developed skeletofacial models by comparing their images with 30 surgical simulation images (ie, skulls) that had been created using three-dimensional cephalometric normative data. The comparison was conducted by superimposing surgical simulation images created using the authors' models with the previously created images to analyze their differences, particularly differences in the jawbone position.

RESULTS

For all participants, the authors compared the jaw position in the surgical simulation images created using the authors' average three-dimensional skeletofacial models with that in the images created using three-dimensional cephalometric normative data. The results revealed that the planned maxillary and mandibular positions were similar in both images and that the differences between all facial landmarks were less than 1 mm, except for one dental position. Most studies have reported less than 2 mm to be the success criterion for the distance difference between planned and outcome images; thus, the authors' data indicate high consistency between the images in terms of jawbone position.

CONCLUSION

The authors' average three-dimensional skeletofacial models provide an innovative template-assisted orthognathic surgery planning modality that can enhance the fully digital workflow for virtual orthognathic surgical planning.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, V.

Single-Splint, 2-Jaw Orthognathic Surgery for Correction of Facial Asymmetry: 3-Dimensional Planning and Surgical Execution

Three-dimensional (3D) planning of orthognathic surgery (OGS) improves the treatment of facial asymmetry and malocclusion, but no consensus exists among clinicians regarding technical details. This study verified the consistency of authors' workflow and strategies between 3D planning and surgical execution for facial asymmetry. This retrospective study recruited consecutive patients (n=54) with nonsyndromic facial asymmetry associated with malocclusion. The stepwise workflow included orthodontic treatment, 3D imaging-based evaluation, planning, and transferring the virtual of single-splint 2-jaw OGS to actual surgery in all patients. Seven landmark-based measurements were selected for postoperative assessment of facial symmetry. Fifty patients had no anesthetic/surgical-related episode and procedure-related complications. Others experienced wound infection (n=1), transient TMJ discomfort (n=1), and facial numbness (n=3). Two cases had minor residual asymmetry (cheek and chin, respectively), but did not request revisionary bone or soft tissue surgery. Comparisons between the planned and postoperative 3D images with quantitative measurement revealed acceptable outcome data. The results showed a significant increase in facial symmetry at 7 landmark-based postoperative measurements for both male and female. This 3D-assisted pathway of OGS permitted achievement of consistent satisfactory results in managing facial asymmetry, with low rate of complications and secondary management.

Automatic craniomaxillofacial landmarks detection in CT images of individuals with dentomaxillofacial deformities by a two-stage deep learning model

BACKGROUND

Accurate cephalometric analysis plays a vital role in the diagnosis and subsequent surgical planning in orthognathic and orthodontics treatment. However, manual digitization of anatomical landmarks in computed tomography (CT) is subject to limitations such as low accuracy, poor repeatability and excessive time consumption. Furthermore, the detection of landmarks has more difficulties on individuals with dentomaxillofacial deformities than normal individuals. Therefore, this study aims to develop a deep learning model to automatically detect landmarks in CT images of patients with dentomaxillofacial deformities.

METHODS

Craniomaxillofacial (CMF) CT data of 80 patients with dentomaxillofacial deformities were collected for model development. 77 anatomical landmarks digitized by experienced CMF surgeons in each CT image were set as the ground truth. 3D UX-Net, the cutting-edge medical image segmentation network, was adopted as the backbone of model architecture. Moreover, a new region division pattern for CMF structures was designed as a training strategy to optimize the utilization of computational resources and image resolution. To evaluate the performance of this model, several experiments were conducted to make comparison between the model and manual digitization approach.

RESULTS

The training set and the validation set included 58 and 22 samples respectively. The developed model can accurately detect 77 landmarks on bone, soft tissue and teeth with a mean error of 1.81 ± 0.89 mm. Removal of region division before training significantly increased the error of prediction (2.34 ± 1.01 mm). In terms of manual digitization, the inter-observer and intra-observer variations were 1.27 ± 0.70 mm and 1.01 ± 0.74 mm respectively. In all divided regions except Teeth Region (TR), our model demonstrated equivalent performance to experienced CMF surgeons in landmarks detection (p  >  0.05).

CONCLUSIONS

The developed model demonstrated excellent performance in detecting craniomaxillofacial landmarks when considering manual digitization work of expertise as benchmark. It is also verified that the region division pattern designed in this study remarkably improved the detection accuracy.

[Research progress of digital occlusion setup in orthognathic surgery]

Objective

To review the research progress of digital occlusion setup in orthognathic surgery.

Methods

The literature related to digital occlusion setup in orthognathic surgery in recent years was consulted, and the imaging basis, methods, clinical applications as well as existing problems were reviewed.

Results

Digital occlusion setup in orthognathic surgery includes manual, semi-automatics, and fully automatic methods. The manual method mainly relies on visual cues for operation, which is difficult to ensure the best occlusion set up, though relatively flexible. The semi-automatic method utilizes the computer software for partial occlusion set up and adjustment, but the occlusion result is still largely depended by manual operation. The fully automatic method completely depends on the operation of computer software, and targeted algorithms for different occlusion reconstruction situations are needed.

Conclusion

The preliminary research results have confirmed the accuracy and reliability of digital occlusion setup in orthognathic surgery, but there are still some limitations. Further research is needed in terms of postoperative outcomes, doctor and patient acceptance, planning time and cost-effectiveness.

Refining Orthognathic Surgery Results by Synchronous Cheek Fat Compartment Augmentation with Fat Grafting in Adult Females with Class III Skeletal Profiles

SUMMARY

Patients with maxillomandibular disharmony may present with a flat to concave midface. The effects of orthognathic surgery concomitant with midface fat grafting on facial appearance and midface volumetric and positional change have not formally been assessed to date. The authors' approach for synchronous orthognathic surgery and fat grafting is described and evaluated. Adult female patients (n = 20) who underwent synchronous two-jaw orthognathic surgery and cheek-specific fat grafting (1.9 ± 0.6 cm3 per side) for correction of skeletal class III deformity and anteromedial cheek deficiency were prospectively included. Preoperative and postoperative photographs were appraised by 42 blinded raters using facial appearance scales for beauty, attractiveness, and pleasantness parameters. The three-dimensional midface soft-tissue volume change and postoperative cheek mass position were computed. Facial imaging data from gender-, ethnic-, and facial pattern-matched adult patients (n = 20) who underwent isolated two-jaw orthognathic surgery (n = 20) were included for comparison. The three-dimensional facial norms database-derived cheek mass position information (2.19 ± 1.31mm) was also adopted for analysis. Patients treated with the synchronous procedure had significantly (p < 0.001) increased facial appearance-related perception change for beauty (2.9 ± 1.6), attractiveness (2.8 ± 1.8), and pleasantness (3.0 ± 1.5) parameters, three-dimensional midface volume change (1.8 ± 0.5 cm3), and postoperative cheek mass position (2.16 ± 0.47 mm) in comparison with those treated with the isolated procedure (2.0 ± 1.5, 1.9 ± 1.6, 2.3 ± 1.6, 0.6 ± 0.2 cm3, and 1.84 ± 0.43 mm, respectively). Healthy female individuals had similar and larger cheek mass position than patients treated with synchronous (p > 0.05) and isolated (p < 0.001) procedures, respectively. Synchronous orthognathic surgery and check-specific fat grafting resulted in superior enhancement of facial appearance and midface volume and position compared with isolated orthognathic surgery.

CLINICAL QUESTION/LEVEL OF EVIDENCE

Therapeutic, III.

Cheek soft tissue prediction in cleft orthognathic surgery: A 3D computer-assisted investigation with comparative analysis

BACKGROUND

The Le Fort I maxillary advancement and rotational movement have been adopted to treat patients with cleft-related skeletal Class III pattern and anteromedial cheek soft tissue deficiency, but cleft-specific cheek soft tissue prediction data are insufficient. This 3D imaging-based study addressed the issue.

METHODS

3D craniofacial soft tissue and bone models were created from 32 consecutive patients who received computer-aided two-jaw orthognathic surgery for the correction of cleft-related Class III deformity and cheek soft tissue deficiency. Using superimposed 3D models, the cheek volumetric change, the cheek sagittal movement, and the 3D cheek mass position were calculated. 3D data from orthognathic surgery-treated patients with no cleft (noncleft cohort) and individuals with no facial deformity (3D norm value) were retrieved for comparative analysis.

RESULTS

Surgical maxillary advancement (p < 0.001) but not maxillary clockwise rotation (p > 0.05) had a significant impact on the cheek soft tissue change, with prediction models showing that maxillary advancement elucidated 77 and 79% of this change on the cleft and noncleft sides, respectively. Cleft cohort (0.46±0.12) had a significantly (p < 0.001) smaller cheek soft-to-hard tissue ratio than that of the noncleft cohort (0.73±0.13). Cleft maxillary advancements >4 mm resulted in a 3D cheek mass position (2.1±1.1 mm) similar (p > 0.05) to the 3D norm value (2.2±1.2 mm), but different (p = 0.037) from the noncleft cohort (2.38±0.7 mm).

CONCLUSION

This study showed that maxillary advancement but not the maxillary rotation affects the cheek soft tissue change, and the predictive values and comparative data could assist the orthodontist-surgeon interaction during preoperative planning and patient counseling.

Three-Dimensional Computer-Assisted Orthognathic Surgery: Traditional Hybrid Versus Full Digital Planning Models

PURPOSE

Three-dimensional (3D) computer-aided planning has truly revolutionized orthognathic surgery (OGS) treatment, but no study has compared the traditional hybrid and full 3D digital planning models. This study compared these virtual planning models in the treatment of asymmetric maxillomandibular disharmony.

METHODS

Young adult patients with an asymmetric skeletal class III deformity who underwent 3D computer-aided 2-jaw OGS using hybrid (alginate dental impression, 2D cephalometric tracings, manual-guided stone model surgery, occlusion setup, and splint fabrication; n = 30) or full digital (laser-scanned dentition, 3D cephalometric tracings, virtual-based occlusion setup and surgery, and computer-generated surgical splint; n = 30) planning models were consecutively recruited. Preoperative and postoperative 3D cephalometric analyses (dental relation, skeletal assessments based on sagittal and frontal views, and soft tissue evaluations) were adopted for intragroup and intergroup comparisons. Postoperative patient-perceived satisfaction with facial appearance was also recorded.

RESULTS

Both hybrid and full digital planning groups had significant (all P < 0.05) improvements after surgery with respect to facial convexity, incisor overjet, and frontal symmetry parameters. The full 3D digital planning-based OGS treatment had similar (all P > 0.05) 3D cephalometric-derived outcomes (preoperative, postoperative, and treatment-induced change data) and patient-perceived outcomes compared with the traditional hybrid 3D planning method.

CONCLUSIONS

For the decision-making process in selecting the planning model, multidisciplinary teams could consider additional parameters such as patient comfort, storage needs, convenience for data reuse, overall planning time, availability, and costs.

Effect of Le Fort I Maxillary Advancement and Clockwise Rotation on the Anteromedial Cheek Soft Tissue Change in Patients with Skeletal Class III Pattern and Midface Deficiency: A 3D Imaging-Based Prediction Study

Patients with a skeletal Class III deformity may present with a concave contour of the anteromedial cheek region. Le Fort I maxillary advancement and rotational movements correct the problem but information on the impact on the anteromedial cheek soft tissue change has been insufficient to date. This three-dimensional (3D) imaging-assisted study assessed the effect of surgical maxillary advancement and clockwise rotational movements on the anteromedial cheek soft tissue change. Two-week preoperative and 6-month postoperative cone-beam computed tomography scans were obtained from 48 consecutive patients who received 3D-guided two-jaw orthognathic surgery for the correction of Class III malocclusion associated with a midface deficiency and concave facial profile. Postoperative 3D facial bone and soft tissue models were superimposed on the corresponding preoperative models. The region of interest at the anteromedial cheek area was defined. The 3D cheek volumetric change (mm3; postoperative minus preoperative models) and the preoperative surface area (mm2) were computed to estimate the average sagittal movement (mm). The 3D cheek mass position from orthognathic surgery-treated patients was compared with published 3D normative data. Surgical maxillary advancement (all p < 0.001) and maxillary rotation (all p < 0.006) had a significant effect on the 3D anteromedial cheek soft tissue change. In total, 78.9%, 78.8%, and 78.8% of the variation in the cheek soft tissue sagittal movement was explained by the variation in the maxillary advancement and rotation movements for the right, left, and total cheek regions, respectively. The multiple linear regression models defined ratio values (relationship) between the 3D cheek soft tissue sagittal movement and maxillary bone advancement and rotational movements of 0.627 and 0.070, respectively. Maxillary advancements of 3-4 mm and >4 mm resulted in a 3D cheek mass position (1.91 ± 0.53 mm and 2.36 ± 0.72 mm, respectively) similar (all p > 0.05) to the 3D norm value (2.15 ± 1.2 mm). This study showed that both Le Fort I maxillary advancement and rotational movements affect the anteromedial cheek soft tissue change, with the maxillary advancement movement presenting a larger effect on the cheek soft tissue movement than the maxillary rotational movement. These findings can be applied in future multidisciplinary-based decision-making processes for planning and executing orthognathic surgery.