Comparison of the Accuracy of Manual and Digital Cephalometric Prediction Methods in Orthognathic Surgical Planning: A Pilot Study.
Lateral cephalometric radiographic examination and analysis are a routine and important part of orthognathic surgeries. These procedures enable physicians to predict changes in the soft tissue and skeletal structure as a result of surgery and also help the patient to be informed about the planned surgery. Conventionally, orthognathic surgery is manually planned using acetate tracing paper. Today, however, these tracings can be performed digitally using computer software.
In the literature, Cohen (1) first described the degree of mandibular retraction required in mandibular surgeries to achieve satisfactory facial esthetic results. He marked reference points on patients' preoperative lateral cephalometric radiographs and used a compass to estimate postoperative changes. In another method developed by McNeill et al. (2), preoperative plaster models were created and an articulator was used to bring the maxilla and mandible into the ideal position. Henderson (3) developed a different method in which patients' lateral cephalometric radiographs were superimposed on profile images in an attempt to predict the outcomes of osteotomy. The surgical procedure was performed virtually by applying LeFort 1 osteotomy incision lines on these superimposed images. Worms et al. (4) established a guide for use in orthognathic surgery planning, which specified the movement ratios between the soft and hard tissues. They used reference points, such as the incisor position on the jaw base and the hard tissue pogonion. Hohl et al. (5) made vertical and horizontal measurements using the nasion-pogonion line as a reference. Fish and Epker (6) developed another method of predicting postoperative changes in the skeletal and soft tissue structures following orthognathic surgery. They used the Ricketts' cephalometric analysis as well as growth estimation and objective parameters of visual treatment defined by Bench et al. to predict changes following mandibular advancement and combined maxillary and mandibular osteotomies (7). The Frankfort horizontal line and a vertical line drawn from the nasion were used as reference s to determine the optimal facial depth. In their study, the authors concluded that the repositioning of the posterior maxilla resulted in the autorotation of the mandible. In the mid-1980s, Wolford et al. (8) conducted a systematic review and developed an estimation table of hard and soft tissue changes after surgeries using different osteotomy techniques. Altug et al. (9) reported that favorable changes in the facial profile following bimaxillary orthognathic surgery were largely due to the posterior movement of the mandible and accompanying changes in the lower lip position.
Bhatia and Sowray (10) developed the first computer software for use in orthognathic surgical planning. This software could analyze reference points marked on patients' lateral cephalometric radiographs and import profile photographs to create animations of the possible postoperative changes. Moreover, programs with similar features were developed by Harradine and Burnie (11) and Walters and Walters (12). Currently, several computer programs are available to assist orthognathic surgical planning. One of these is Quick Ceph (Quick Ceph Systems, San Diego, California, USA), which was the first commercially available software developed for surgical planning. In this program, patient records are imported into the system, and surgeries can be simulated according to predefined normative values. In a similar program called Dolphin, various changes can be imposed on lateral cephalometric radiographs and profile images to facilitate a more accurate marking of reference points. In a 2009 study, Kaipatur et al. (13) showed that although surgical plans created using computer software may be clinically acceptable, they may yield misleading results, especially in the prediction of soft tissue movements involving the lower lip region. In a similar study conducted in 2007, Pektas et al (14) found that computer software provided satisfactory results in the prediction of soft tissue changes after surgery. The authors reported that digital predictions were the most accurate toward the tip of the nose and least accurate in the lower lip area. They also noted that digital predictions were more accurate in the sagittal plane than in the vertical plane.
Patients who have completed growth and development and have severe skeletal defects are managed using orthognathic surgical protocols incorporating both orthodontics and surgery. The success of these treatments is highly dependent on the pre- and postoperative orthodontic interventions used as well as presurgical planning. Changes in the skeletal and soft tissue structures after surgery can be predicted using conventional cephalometric tracings or computer software. Previous studies evaluating class III bimaxillary orthognathic surgical predictions have compared computer-generated predictions with surgical outcomes. However, no studies have compared conventional prediction using acetate tracing paper over lateral cephalometric radiographs, digital prediction using computer software, and actual postoperative results. Therefore, our objective in the present study was to determine which of these two prediction methods is more reliable by comparing them with each other and with postoperative outcomes.
Ten patients (5 females and 5 males) with skeletal class III malocclusion were included in the study. All patients underwent presurgical orthodontic decompensation in the Orthodontics Department of the Ankara University School of Dentistry, followed by bimaxillary orthognathic surgery prepared and planned by the same surgical team in the Oral and Maxillofacial Surgery Department. The mean patient age is given in Table 1.
Patients Meeting the Following Criteria were Included in the Study
- Completed growth and development and skeletal class III malocclusion (ANB<0);
- Absence of any craniofacial syndrome;
- Skeletal class III malocclusion corrected through maxillary advancement (LeFort 1 osteotomy) and mandibular set-back (sagittal split osteotomy);
- Orthognathic surgery planned and performed by the same team;
- Absence of any additional treatment.
Patients Meeting Any of the Following Criteria were Excluded from the Study
- Incomplete growth and development, currently developing;
- Open or deep skeletal bites and severe hyperdivergent growth pattern;
- Any condition involving the craniofacial region;
- Inadequate or inaccessible radiographic records.
The study was conducted using pre- and postoperative lateral cephalometric radiographs, which were analyzed using the Steiner and McNamara normative values. All orthodontic radiographic records were collected using the same x-ray machine (Sirona Orthophos XG5, Sirona Dental Company, Long Island City, NY, USA). Postoperative lateral cephalometric radiographs were obtained 6 months after the surgery. Conventional surgical predictions (manual tracings on acetate paper) and computer-generated predictions (Dolphin Imaging 11.8, Dolphin Imaging & Management Solutions, Chatsworth, CA, USA) based on the same preoperative lateral cephalometric radiographs and the same surgical manipulations were compared with the actual postoperative values. The conventional method comprised manual tracing of the preoperative lateral cephalometric radiographs on acetate paper with a light box. Once the anatomical structures were traced, desired surgical movements were performed on the maxilla and mandible by cutting and repositioning the skeletal segments. The soft tissue structures were manipulated depending on the hard tissue changes, as described in literature (13).
Cephalometric Points and Measurements
Reference points and planes used in lateral cephalometric radiographs (Figure 3).
Craniofacial Cephalometric Measurements
* SELLA-NASION PLANE (SN): The plane between the sella and nasion points
* FRANKFURT HORIZONTAL PLANE (FH): The plane passing through the porion and orbita points
Reference Points Used in Lateral Cephalometric Radiographs
The cephalometric landmarks used in our study are shown in Figure 1 and are as follows:
* S: Sella
* N: Nasion
* ANS: Anterior nasal spine
* PNS: Posterior nasal spine
* Point A: Subsipinale
* U1i: Incisal edge of maxillary first incisor
* U6t: Tip of the mesiobuccal cusp of the maxillary first molar
* B Point: Supramentale
* Pg: Pogonion
* Gn: Gnathion
* Me: Menton
* Go: Gonion
* Co: Condylion
* Po: Porion
* Or: Orbita
* SNA: The angle between the SN and nasion-point A planes
* Nperp-A: Perpendicular distance between point A and nasion
* Co-A: Distance between condylion and point A
* U1i-FH: Distance between the Frankfurt Horizontal Plane and incisal edge of the maxillary first incisor
* U6t-FH: Distance between the FH plane and the tip of the mesiobuccal cusp of the maxillary first molar
* SNB: The angle between the SN and nasion-point B planes
* Nperp-Pg: Perpendicular distance between pogonion and nasion
* Co-Gn: Distance between condylion and gnathion
* ANB: The angle between the nasion-point A and nasion-point B planes.
* GoGnSN: The angle between the gonion-gnathion and SN planes.
* N-Me: The distance between the nasion and menton.
Paired t-test was used to analyze the mean pre- and postoperative values of the treatment group and to evaluate changes that occurred as a result of surgery. Variation between manual predictions and actual postoperative values as well as that between digital predictions and actual postoperative values was assessed using the intraclass correlation coefficient (ICC) (reproducibility) and square root of the mean square (root mean square).
The patient's cephalometric values before and after the orthognathic surgery and the differences between these measurements are presented in Table 2.
Following bimaxillary orthognathic surgery, significant increases were observed in the maxillary parameters SNA (4.17[degrees], p<0.001), Nperp-A (4.35 mm, p<0.001), and Co-A (4.99 mm, p<0.05). Significant decreases were noted in the mandibular parameters SNB (2.32[degrees], p<0.001) and Nperp-Pg (3.37 mm, p<0.05).
Of the maxillomandibular measurements, there was a significant increase of 6.56[degrees] in ANB (p<0.001).
Dental measurements showed a statistically significant increase of 9.80 mm in overjet and significant decrease of 3.65 mm in U1i-FH (p<0.001).
When conventional surgical predictions were compared with actual postoperative values using ICC and root mean square, overbite measurement was the most unpredictable parameter (0.5000). Following overbite, manual predictions of Co-A, overjet, ANB, and U6t-HF were less accurate (0.6278, 0.6920, 0.7879, and 0.7893, respectively; Table 3).
Comparison of digital predictions with actual postoperative values revealed that overjet was the most unpredictable parameter (0.3944). Moreover, digital predictions of ANB and overbite were less accurate (0.6450 and 0.7500, respectively).
Comparisons of manual and digital orthognathic surgical predictions with actual postoperative results are presented in Tables 3 and 4, respectively.
Severe skeletal defects are managed using orthognathic surgical protocols incorporating both orthodontics and surgery. Pre- and postoperative orthodontic interventions and surgical planning based on preoperative lateral cephalometric radiographs are important factors for the success of these treatments. Changes in the skeletal and soft tissue structures after surgery can be predicted using conventional cephalometric tracings or computer software. Several previous studies evaluating class III bimaxillary orthognathic surgical predictions have compared computer-generated predictions with surgical outcomes (15-17). However, no studies have compared conventional prediction using acetate tracing paper over lateral cephalometric radiographs, digital prediction using computer software, and actual postoperative results. Therefore, we aimed to compare these two commonly used prediction methods (manual and digital) with each other and with postoperative values.
Ten patients (5 females and 5 females) with similar skeletal class III malocclusion characteristics and who had completed growth and development were included. Ensuring that all orthodontic treatments and orthognathic surgical preparations, planning, and procedures are performed by the same team is important for the reliability of the study.
In the present study, the same researcher made conventional surgical predictions based on preoperative lateral cephalometric radiographs (manual tracings on acetate paper), obtained computer-generated predictions (Dolphin Imaging 11.8, Dolphin Imaging & Management Solutions, Chatsworth, CA, USA), and measured actual postoperative values.
In both manual and digital predictions, the mean impaction, advancement, and set-back were 2.4, 4.9, and 4.45 mm. Predicted impaction and advancement values were similar to actual postoperative values (N-Me: -2.90 mm and Nperp-A: 4.35 mm), while actual set-back values were different (Nperp-Pg: -3.37 mm).
Manual predictions of Co-A, Co-Gn, and U6t-FH were less accurate compared with digital predictions. This may be attributed to the ability to adjust the contrast values of cephalometric images in computer software, thus allowing a clear visualization of points, which may be difficult to distinguish otherwise.
Overjet and overbite predictions showed poor agreement with postoperative values in both methods. Postoperative radiographs of the study subjects were obtained after a period of intermaxillary fixation. Therefore, strong elastics used in the anterior region during this phase may have affected the measurements. Moreover, unpredictable dental movement may occur because of the low anchorage value of the incisors.
Being a pilot study, there are certain limitations in this research. First, the sample size is small (5 females and 5 males), but a more detailed study with 30 subjects is ongoing. Second, this study did not include the assessment and comparison of soft tissue changes after orthognathic surgery. Soft tissue parameters were intentionally excluded while designing the pilot study as the complete healing of soft tissues following orthognathic surgeries requires a long time. As mentioned before, a more detailed study is ongoing to specifically address these limitations. Nevertheless, this pilot study provides valuable initial data regarding the accuracy of manual and digital cephalometric prediction methods.
Cephalometric points and their associated parameters (Co and U6) with low reproducibility reduce the reliability of prediction.
Cephalometric points that are difficult to distinguish using the manual method can be visualized through digital images by adjusting contrast settings.
Dental predictions were inaccurate in both methods due to the effects of intermaxillary elastics.
Both methods yielded similar predictions for skeletal parameters. Skeletal predictions were more accurate than dental predictions.
The effect of applying strong elastics for postoperative intermaxillary fixation should be considered in manual or digital predictions.
Mechanisms that enhance anchorage, such as skeletal anchorage units, can be used to reduce unwanted dental movement caused by strong elastics.
Ethics Committee Approval: Ethics committee approval was received for this study from the Ethical Committee of Ankara University School of Dentistry (24.04.2017).
Informed Consent: Written informed consent was obtained from the volunteers who participated in this study.
Peer-review: Externally peer-reviewed.
Author Contributions: Concept - C.A., A.T.A.; Design - C.A., A.T.A.; Supervision - A.T.A., T.U.T.M; Data Collection and/or Processing - E.M.A., E.B.; Analysis and/or Interpretation - A.T.A., T.U.T.M.; Writing Manuscript - C.A., A.T.A.
Conflict of Interest: The authors have no conflict of interest to declare.
Financial Disclosure: The authors declared that this study has received no financial support.
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Can Arslan (1), Ayse Tuba Altug (1), Tulin Ufuk Toygar Memikoglu (1), Elif Merve Arslan (1), Ensar Baspinar (2)
(1) Department of Orthodontics, Ankara University School of Dentistry, Ankara, Turkey
(2) Department of Biotechnology, Ankara University School of Agriculture, Ankara, Turkey
Cite this article as: Arslan C, Altug AT, Toygar Memikoglu TU, Arslan EM, Baspinar E. Comparison of the Accuracy of Manual and Digital Cephalometric Prediction Methods in Orthognathic Surgical Planning: A Pilot Study. Turk J Orthod 2018; 31(4): 133-8.
Address for Correspondence: Can Arslan, Department of Orthodontics, Ankara University School of Dentistry, Ankara, Turkey
Received: 11 December 2017
Accepted: 2 July 2018
Table 1. Preoperative mean age of patients with skeletal Class III malocclusion, presented as mean with standard error (SE), minimum (min), and maximum (max) values N Chronological Age (years) Mean SE Min Max 10 21.97 2.01 18.58 25.00 Table 2. Preoperative (pre-op) to postoperative (post-op) changes in skeletal class III anomalies treated by bimaxillary orthognathic surgery were evaluated using paired t-test (SE: Standard error, Sig.: Level of significance (*) p<0.05, (**) p<0.01, (***) p<0.001) Measurements Pre-op Post-op Mean [+ or -]SE Mean [+ or -] SE Maxillary Measurements 1. SNA ([degrees]) 79.05 0.99 83.22 0.85 2. Nperp-A (mm) -0.18 0.99 4.17 1.0 3. Co-A (mm) 80.60 1.1 85.59 1.4 Mandibular Measurements 4. SNB ([degrees]) 83.24 1.2 80.92 1.2 5. Nperp-Pg (mm) 6.39 2.0 3.02 1.7 6. Co-Gn (mm) 119.70 1.3 117.43 2.3 Maxillomandibular Measurements 7. ANB ([degrees]) -4.23 0.96 2.33 0.70 8. SN/GoGn ([degrees]) 36.27 2.1 34.68 1.9 9. N-Me (mm) 126.40 2.8 123.50 2.9 Dental Measurements 10. Overjet (mm) -7.40 0.85 2.40 0.21 11. Overbite (mm) 1.60 0.16 1.50 0.15 12. U1i-FH (mm) 55.45 1.5 51.80 2.0 13. U6t-FH (mm) 50.30 1.1 49.15 1.6 Measurements Difference Sig. Mean [+ or -] SE Maxillary Measurements 1. SNA ([degrees]) 4.17 0.85 (***) 2. Nperp-A (mm) 4.35 0.76 (***) 3. Co-A (mm) 4.99 1.73 (*) Mandibular Measurements 4. SNB ([degrees]) -2.32 0.46 (***) 5. Nperp-Pg (mm) -3.37 1.06 (*) 6. Co-Gn (mm) -2.27 1.68 Maxillomandibular Measurements 7. ANB ([degrees]) 6.56 0.99 (***) 8. SN/GoGn ([degrees]) -1.59 1.08 9. N-Me (mm) -2.90 0.67 Dental Measurements 10. Overjet (mm) 9.80 0.80 (***) 11. Overbite (mm) -0.10 0.22 12. U1i-FH (mm) -3.65 0.80 (***) 13. U6t-FH (mm) -1.15 1.10 Table 3. Comparison of conventional surgical predictions based on lateral cephalometric radiographs with actual postoperative results using intraclass correlation coefficient (ICC) and root mean square Parameter Standard Deviation ICC SNA ([degrees]) 0.714 0.9613 Nperp-A (mm) 1.017 0.9492 Co-A (mm) 4.508 0.6278 SNB ([degrees]) 1.409 0.9209 Nperp-Pg (mm) 2.439 0.8968 Co-Gn (mm) 4.094 0.8460 ANB ([degrees]) 1.388 0.7879 SN/GoGn ([degrees]) 2.205 0.9212 N-Me (mm) 1.466 0.9829 Overjet (mm) 0.716 0.6920 Overbite (mm) 0.612 0.5000 U1i-FH (mm) 1.984 0.9306 U6t-FH (mm) 2.695 0.7893 Table 4. Comparison of digital surgical predictions based on lateral cephalometric radiographs with actual postoperative results using intraclass correlation coefficient (ICC) and root mean square Parameter Standard Deviation ICC SNA ([degrees]) 1.581 0.8626 Nperp-A (mm) 1.308 0.9121 Co-A (mm) 1.525 0.9312 SNB ([degrees]) 1.392 0.9187 Nperp-Pg (mm) 2.282 0.9136 Co-Gn (mm) 2.795 0.9194 ANB ([degrees]) 1.598 0.6450 SN/GoGn ([degrees]) 2.368 0.9088 N-Me (mm) 2.127 0.9676 Overjet (mm) 0.680 0.3944 Overbite (mm) 0.316 0.7500 U1i-FH (mm) 2.550 0.9178 U6t-FH (mm) 2.188 0.8957
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|Title Annotation:||ORIGINAL ARTICLE|
|Author:||Arslan, Can; Altug, Ayse Tuba; Memikoglu, Tulin Ufuk Toygar; Arslan, Elif Merve; Baspinar, Ensar|
|Publication:||Turkish Journal of Orthodontics|
|Date:||Dec 1, 2018|
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