Skip to main content
Maxillofacial Plastic and Reconstructive Surgery
Download PDF

Evaluation of postoperative changes in condylar positions after orthognathic surgery using balanced orthognathic surgery system

Maxillofacial Plastic and Reconstructive Surgery volume 44, Article number: 11 (2022) Cite this article

Abstract

Background

Many studies on maintaining the condyle in a normal or anatomical position during orthognathic surgery have been conducted to stabilize surgical outcomes and prevent iatrogenic temporomandibular joint complications. The aim of this study is to evaluate the changes in condylar positions after orthognathic surgery using virtual surgical planning via the balanced orthognathic surgery (BOS) system.

Methods

Postoperative changes in condylar position were retrospectively evaluated in 22 condyles of 11 patients with skeletal class III malocclusion who underwent orthognathic surgery using virtual surgical planning via the BOS system. The center point coordinates of the condylar head before and after orthognathic surgery were analyzed using voxel-based registration.

Results

Changes in the condylar position mainly occurred downward in the y-axis (−1.09 ± 0.62 mm) (P < 0.05). The change in the x-axis (0.02 ± 0.68 mm) and z-axis (0.01 ± 0.48 mm) showed no significant difference between before and after orthognathic surgery.

Conclusion

These results indicate that the changes in the condylar positions after orthognathic surgery using virtual surgical planning via the BOS system mainly occurred downward in the y-axis, with slight changes in the x- and z-axes. The change in the condylar position after orthognathic surgery using the BOS system is clinically acceptable.

Background

Orthognathic surgical planning has improved with the development of computer-aided design/computer-aided manufacturing (CAD/CAM) technology [1,2,3,4]. Virtual surgical planning and rapid prototyping (RP) technology simulate various surgical plans and predict their outcomes using three-dimensional (3D) data for the dental arch and surrounding skeletal structures [1, 5, 6]. In orthognathic surgery, the planning time for virtual surgical planning is shorter than that for conventional surgical planning [7, 8]. Three-dimensional printed splints and guiding templates are used to transform virtual surgical planning to actual results [2, 9,10,11].

After orthognathic surgery, the condylar position can be changed by several factors, such as the fixation method, surgeon’s experience, and positioning of the proximal and distal segments of the mandible [12,13,14]. Maintaining the condyle in a normal or preoperative anatomical position after orthognathic surgery is critical to achieve a stable skeletal and occlusal outcome and prevent iatrogenic temporomandibular joint complications [15,16,17]. If the condyle is distracted from the glenoid fossa during surgery, immediate relapse may occur, whereas if it is located posteriorly, condylar resorption or late relapse may occur [18, 19].

However, there is a lack of consensus on the accuracy assessment of methods for evaluating the change in the condylar position [20]. Because there is no standardized method to measure postoperative changes, it is difficult to compare data from multiple studies and assess the effectiveness of new techniques [21]. In addition, if the reference point is manually reidentified, an error of 1 mm or more can be included every four repeated measurements, so there is a limit to the repeatability of 3D measurement in orthognathic surgery [22].

A condylar positioning device (CPD) was first introduced by Leonard in 1976 [23]. CPDs, developed by clinicians, are devices that precisely position the condyle during orthognathic surgery [19, 23]. The balanced orthognathic surgery (BOS) system was first introduced in 2015 as computer-assisted simulation surgery [24]. In the BOS system, a surgical wafer that functions as a CPD is manufactured with CAD/CAM and used for orthognathic surgery. The BOS system consists of four phases: planning and simulation, modeling, surgical, and evaluation. During the planning and simulation phase, a 3D model is established by merging the dentition scan image of the stone model and the computed tomography (CT) image of the skull, and orthognathic surgery is simulated using the BOS equation. During the modeling phase, a surgical wafer is manufactured using the RP machine. In addition, a cutting guide is prepared from the 3D RP model before surgery, and the miniplates are pre-bent from the 3D RP model operated as planned. During the surgical phase, orthognathic surgery is performed using these surgical tools. Finally, in the evaluation phase, virtual surgery and postoperative CT images are merged, and the error is analyzed.

The purpose of this study was to evaluate the changes in the condylar position after orthognathic surgery using virtual surgical planning via the BOS system.

Materials and methods

Sample patients

The Institutional Review Board of Gangneung-Wonju National University approved this retrospective study of patients, who were requested to produce a surgical guide with the BOS system for orthognathic surgery (GWNUIRB-R2021-64). The Institute of BOS provided retrospective anonymous data for 22 condyles of 11 patients (four men and seven women; mean age, 21.1 years; age range, 18–29 years) with skeletal class III malocclusion; the patients underwent orthognathic surgery using the BOS system. Four patients underwent only mandibular surgery, and seven underwent bimaxillary surgery. The average mandibular setback was 8.97 mm.

Virtual surgical planning and surgical procedure

Virtual surgery was planned using the BOS system (Fig. 1). The cutting guide was manually produced in the RP model, and the wafer was manufactured using CAD/CAM. Bilateral sagittal split ramus osteotomy with or without LeFort I osteotomy was performed using the conventional method, and metal plates pre-bent from the RP model were used for fixation.

Fig. 1
figure 1

Preparation process for orthognathic surgery using BOS system

Full size image

Evaluation of surgical accuracy in BOS system

The nasion was set to the coordinate points (0, 0, 0), and the orientation was set to the Frankfurt horizontal (FH) plane. The x-, y-, and z-axes were used to set the coordinates (Fig. 2). The x-axis was a straight line parallel to the line passing through both orbitales on the FH plane. The y-axis was a straight line passing through the nasion and perpendicular to the FH plane. The z-axis was an anteroposterior line, with a straight line passing through the nasion parallel to the FH plane and perpendicular to the x-axis. The coordinates of the center points of the condyle heads on both sides were obtained. The center point of the condylar head was defined as the middle part between the lateral and medial poles. The center point coordinates of the condylar head before and after orthognathic surgery were compared. Postoperative CT was performed on postoperative days 0–3. The data for patients that underwent orthognathic surgery using the BOS system were analyzed after superimposing using voxel-based registration (Invivo5; Anatomage Inc., CA, USA). The quaternion was obtained by superimposing the CT data before and after surgery and converted to Euler’s angle, which was then calculated using the direction cosine matrix method to obtain the amount of change at each point. By substituting the coordinate values resulting from the designating points in the preoperative CT, the coordinate values in the postoperative CT were obtained.

Fig. 2
figure 2

Three-dimensional coordinate system. The Frankfort horizontal plane is the reference plane, and the nasion is the center of all axes. The medial-lateral movement was evaluated by the x-axis. The vertical movement was evaluated by the y-axis. The anterior-posterior movement was evaluated by the z-axis

Full size image

Statistical analysis

Statistical analysis was performed on the amount of changes in the coordinate values of each of the x-axis, y-axis, and z-axis before and after surgery in 22 condyles. After testing for normality using Kolmogorov-Smirnov test and Shapiro-Wilk test, statistical analysis was performed using the paired t-test, and the significance level was set at 0.05.

Results

Table 1 lists the changes in coordinate values of each patient's preoperative and postoperative condylar heads. The changes in the condylar position were mainly observed downward on the y-axis (−1.09 ± 0.62 mm) (P < 0.05). The changes in the x-axis (0.02 ± 0.68 mm) and z-axis (0.01 ± 0.48 mm) showed no significant difference between before and after orthognathic surgery (Table 2).

Table 1 Changes in coordinate values of each patient’s preoperative and postoperative condylar heads
Full size table
Table 2 Surgical changes in condylar position after surgery, using BOS system or intended manual condylar positioning
Full size table

Discussion

The aim of this study was to evaluate the changes in condylar positions after orthognathic surgery using virtual surgical planning via the BOS system. In this study, there was no statistically significant difference in the change in condyle after surgery in the x- and z-axes. In contrast, a statistically significant difference was observed only in the y-axis. The change in the condylar position on the y-axis after surgery occurred mainly downward, and the change was approximately 1 mm. These results are similar to those of Park et al. [25], who used the same analysis software (Table 2). Both studies used a voxel-based registration method to assess the accuracy of 3D virtually planned orthognathic surgery. Park et al. [25] determined the position of the condyle using the intended manual positioning during orthognathic surgery. A significant downward movement of the condyle was observed immediately after orthognathic surgery, but a gradual return to the preoperative condylar position was observed up to 6 months after surgery [25]. There was no statistically significant difference between the preoperative and 6-month postoperative condylar positions (a difference of less than 1 mm) [25]. Therefore, Park et al. [25] concluded that the intended manual condylar positioning might minimize changes in the condylar position. Comparatively, the changes in condylar positions after orthognathic surgery via the BOS system showed less change in the condylar position than when using the intended manual condylar positioning. Therefore, changes in the condylar positions after orthognathic surgery via the BOS system are also clinically acceptable.

Generally, three methods can be applied to assess the accuracy of 3D virtually planned orthognathic surgery: landmark-based, surface-based, and voxel-based registration, depending on the manner in which CT images are superimposed [20, 26,27,28,29]. The landmark-based registration method involves manually setting stable anatomic landmarks and superimposing them through point matching, similar to the conventional method of superimposing two-dimensional cephalometric radiographs [26]. It generates human errors, depending on the landmark setting and interobserver variations [27, 28]. The surface-based registration method involves manually setting stable anatomic regions and superimposing them by matching the corresponding closest point on the same 3D reference surface based on the interactive closest-point algorithm [26]. The voxel-based registration method is a relatively recent method used for aligning two CT images based on the grayscale differences of voxels [29]. Voxels, each with a unique grayscale value that depends on the opacity of the scanned structure, are units of volume with isotropic x, y, and z dimensions [29]. This method calculates the rotation and translation required to align two CT images based on mathematical algorithms [26]. It automatically superimposes two CT scans based on volumetric similarities and significantly reduces the possibility of human error by eliminating the need to set cephalometric landmarks multiple times [20, 28]. Although all three methods are reliable for detecting changes in landmark positions when superimposed, the surface-based and voxel-based registration methods are more accurate than the landmark-based registration method [20, 26].

A limitation of this study is that only changes in the position of the condyles immediately after orthognathic surgery were observed. The position of the condyle changes over a long period and immediately after orthognathic surgery [25]. Therefore, further studies on the long-term changes in the condylar position after orthognathic surgery using the BOS system are needed.

Conclusion

The results of this study indicate that the changes in the condylar positions after orthognathic surgery using virtual surgical planning via the BOS system were mainly observed downward on the y-axis, with slight changes in the x- and z-axes. The change in the condylar position after orthognathic surgery using the BOS system is clinically acceptable.

Availability of data and materials

All data were shown in this manuscript.

Abbreviations

BOS:

Balanced orthognathic surgery

CAD/CAM:

Computer-aided design/computer-aided manufacturing

RP:

Rapid prototyping

3D:

Three-dimensional

CPD:

Condylar positioning device

CT:

Computed tomography

FH:

Frankfurt horizontal

DICOM:

Digital Imaging and Communications in Medicine

STO:

Surgical treatment objective

References

  1. Zhang N, Liu S, Hu Z, Hu J, Zhu S, Li Y (2016) Accuracy of virtual surgical planning in two-jaw orthognathic surgery: comparison of planned and actual results. Oral Surg Oral Med Oral Pathol Oral Radiol 122(2):143–151

    Article  Google Scholar 

  2. De Riu G, Virdis PI, Meloni SM, Lumbau A, Vaira LA (2018) Accuracy of computer-assisted orthognathic surgery. J Craniomaxillofac Surg 46(2):293–298

    Article  Google Scholar 

  3. Zavattero E, Romano M, Gerbino G, Rossi DS, Gianni AB, Ramieri G et al (2019) Evaluation of the accuracy of virtual planning in orthognathic surgery: a morphometric study. J Craniofac Surg 30(4):1214–1220

    Article  Google Scholar 

  4. Tran NH, Tantidhnazet S, Raocharernporn S, Kiattavornchareon S, Pairuchvej V, Wongsirichat N (2018) Accuracy of three-dimensional planning in surgery-first orthognathic aurgery: planning versus outcome. J Clin Med Res 10(5):429–436

    Article  Google Scholar 

  5. Uribe F, Janakiraman N, Shafer D, Nanda R (2013) Three-dimensional cone-beam computed tomography-based virtual treatment planning and fabrication of a surgical splint for asymmetric patients: surgery first approach. Am J Orthod Dentofacial Orthop 144(5):748–758

    Article  Google Scholar 

  6. Narita M, Takaki T, Shibahara T, Iwamoto M, Yakushiji T, Kamio T (2020) Utilization of desktop 3D printer-fabricated “cost-effective” 3D models in orthognathic surgery. Maxillofac Plast Reconstr Surg 42(1):24

    Article  Google Scholar 

  7. Steinhuber T, Brunold S, Gartner C, Offermanns V, Ulmer H, Ploder O (2018) Is virtual surgical planning in orthognathic surgery faster than conventional planning? A time and workflow analysis of an office-based workflow for single- and double-jaw surgery. J Oral Maxillofac Surg 76(2):397–407

    Article  Google Scholar 

  8. Park S-Y, Hwang D-S, Song J-M, Kim U-K (2021) Comparison of time and cost between conventional surgical planning and virtual surgical planning in orthognathic surgery in Korea. Maxillofac Plastic Reconstruct Surg 43(1):1–7

    Article  Google Scholar 

  9. Adolphs N, Liu W, Keeve E, Hoffmeister B (2014) RapidSplint: virtual splint generation for orthognathic surgery - results of a pilot series. Comput Aided Surg 19(1-3):20–28

    Article  Google Scholar 

  10. Keyhan SO, Azari A, Yousefi P, Cheshmi B, Fallahi HR, Valipour MA (2020) Computer-assisted horizontal translational osseous genioplasty: a simple method to correct chin deviation. Maxillofac Plast Reconstr Surg 42(1):36

    Article  Google Scholar 

  11. Sugahara K, Koyachi M, Odaka K, Matsunaga S, Katakura A (2020) A safe, stable, and convenient three-dimensional device for high Le Fort I osteotomy. Maxillofac Plast Reconstr Surg 42(1):32

    Article  Google Scholar 

  12. Berkoz O, Karaali S, Kozanoglu E, Akalin BE, Ceri A, Baris S et al (2020) The relationship between fixation method and early central condylar sagging after bilateral sagittal split ramus osteotomy in orthognathic surgery. J Craniomaxillofac Surg 48(10):928–932

    Article  Google Scholar 

  13. Lee W, Park JU (2002) Three-dimensional evaluation of positional change of the condyle after mandibular setback by means of bilateral sagittal split ramus osteotomy. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 94(3):305–309

    Article  Google Scholar 

  14. Wolford LM, Reiche-Fischel O, Mehra P (2003) Changes in temporomandibular joint dysfunction after orthognathic surgery. J Oral Maxillofac Surg 61(6):655–660 discussion 661

    Article  Google Scholar 

  15. Costa F, Robiony M, Toro C, Sembronio S, Polini F, Politi M (2008) Condylar positioning devices for orthognathic surgery: a literature review. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 106(2):179–190

    Article  Google Scholar 

  16. Epker BN, Wylie GA (1986) Control of the condylar-proximal mandibular segments after sagittal split osteotomies to advance the mandible. Oral Surg Oral Med Oral Pathol 62(6):613–617

    Article  Google Scholar 

  17. Rotskoff KS, Herbosa EG, Villa P (1991) Maintenance of condyle-proximal segment position in orthognathic surgery. J Oral Maxillofac Surg 49(1):2–7 discussion 7-8

    Article  Google Scholar 

  18. Oh SM, Lee CY, Kim JW, Jang CS, Kim JY, Yang BE (2013) Condylar repositioning in bilateral sagittal split ramus osteotomy with centric relation bite. J Craniofac Surg 24(5):1535–1538

    Article  Google Scholar 

  19. Ellis E 3rd (1994) Condylar positioning devices for orthognathic surgery: are they necessary? J Oral Maxillofac Surg 52(6):536–552 discussion 552-534

    Article  Google Scholar 

  20. Gaber RM, Shaheen E, Falter B, Araya S, Politis C, Swennen GRJ et al (2017) A systematic review to uncover a universal protocol for accuracy assessment of 3-dimensional virtually planned orthognathic surgery. J Oral Maxillofac Surg 75(11):2430–2440

    Article  Google Scholar 

  21. Stokbro K, Aagaard E, Torkov P, Bell RB, Thygesen T (2014) Virtual planning in orthognathic surgery. Int J Oral Maxillofac Surg 43(8):957–965

    Article  Google Scholar 

  22. Stokbro K, Thygesen T (2018) A 3dimensional approach for analysis in orthognathic surgery-using free software for voxel-based alignment and semiautomatic measurement. J Oral Maxillofac Surg 76(6):1316–1326

    Article  Google Scholar 

  23. Leonard M (1976) Preventing rotation of the proximal fragment in the sagittal ramus split operation. J Oral Surg 34(10):942

    PubMed  Google Scholar 

  24. Lee YC, Sohn HB, Kim SK, Bae OY, Lee JH (2015) A novel method for the management of proximal segment using computer assisted simulation surgery: correct condyle head positioning and better proximal segment placement. Maxillofac Plast Reconstr Surg 37(1):21

    Article  Google Scholar 

  25. Park JC, Kim UK, Hwang DS (2018) Three-dimensional analysis of perioperative condylar displacement after mandibular setback surgery with intended manual condylar positioning. J Craniofac Surg 29(8):e767–e773

    Article  Google Scholar 

  26. Ghoneima A, Cho H, Farouk K, Kula K (2017) Accuracy and reliability of landmark-based, surface-based and voxel-based 3D cone-beam computed tomography superimposition methods. Orthod Craniofac Res 20(4):227–236

    Article  Google Scholar 

  27. Xi T, van Luijn R, Baan F, Schreurs R, de Koning M, Berge S et al (2020) Landmark-based versus voxel-based 3-dimensional quantitative analysis of bimaxillary osteotomies: a comparative study. J Oral Maxillofac Surg 78(3):468 e461–468 e410

    Article  Google Scholar 

  28. Shaheen E, Shujaat S, Saeed T, Jacobs R, Politis C (2019) Three-dimensional planning accuracy and follow-up protocol in orthognathic surgery: a validation study. Int J Oral Maxillofac Surg 48(1):71–76

    Article  Google Scholar 

  29. Almukhtar A, Ju X, Khambay B, McDonald J, Ayoub A (2014) Comparison of the accuracy of voxel based registration and surface based registration for 3D assessment of surgical change following orthognathic surgery. PLoS One 9(4):e93402

    Article  Google Scholar 

Download references

Acknowledgements

Not applicable.

Funding

No funding was needed.

Author information

Authors and Affiliations

  1. Bestian Oral & Maxillofacial Surgery Clinic, 429, Dogok-ro, Gangnam-gu, Seoul, 06208, Republic of Korea

    Yong-Chan Lee

  2. Department of Orthodontics, Eton Dental Clinics, 98, Bangsong-gil, Chuncheon, Gangwondo, 24364, Republic of Korea

    Hong-Bum Sohn

  3. Department of Oral and Maxillofacial Surgery, College of Dentistry, Gangneung-Wonju National University, 7, Jukheon-gil, Gangneung, Gangwondo, 28644, Republic of Korea

    Young-Wook Park & Ji-Hyeon Oh

Authors
  1. Yong-Chan Lee
    View author publications

    You can also search for this author in PubMed Google Scholar

  2. Hong-Bum Sohn
    View author publications

    You can also search for this author in PubMed Google Scholar

  3. Young-Wook Park
    View author publications

    You can also search for this author in PubMed Google Scholar

  4. Ji-Hyeon Oh
    View author publications

    You can also search for this author in PubMed Google Scholar

Contributions

YCL designed the study. YCL and HBS performed the data collection and analysis. YWP performed the critical review. JHO wrote the manuscript and developed the statistical method. All the authors read and approved the final version of the manuscript.

Corresponding author

Correspondence to Ji-Hyeon Oh.

Ethics declarations

Ethics approval and consent to participate

This study was approved by the Institutional Review Board of Gangneung-Wonju National University (GWNUIRB-R2021-64).

Consent for publication

Not applicable.

Competing interests

The authors declare that they have no competing interests.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Lee, YC., Sohn, HB., Park, YW. et al. Evaluation of postoperative changes in condylar positions after orthognathic surgery using balanced orthognathic surgery system. Maxillofac Plast Reconstr Surg 44, 11 (2022). https://doi.org/10.1186/s40902-022-00341-x

Download citation

  • Received:

  • Accepted:

  • Published:

  • DOI: https://doi.org/10.1186/s40902-022-00341-x

Keywords