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치의과학석사 학위논문
Positional c hanges of condyle and mandibular stability after isolated
maxillary orthognathic surgery combined with mandibular autorotation in
mandibular retrognathism with high mandibular plane angle
하악평면각이 큰 하악 후퇴증 환자에서 상악 악교정수술과 하악
자가회전 후 하악과두의 위치 변화와 하악의 수술 후 안정성
2020 년 02 월
서울대학교 대학원
치의과학과 구강악안면외과학 전공
Positional c hanges of condyle and mandibular stability after isolated
maxillary orthognathic surgery combined with mandibular autorotation in
mandibular retrognathism with high mandibular plane angle
지도교수 김 성 민
이 논문을 치의과학석사 학위논문으로 제출함 2019 년 11 월
서울대학교 대학원
치의과학과 구강악안면외과학 전공 지 옹 니 (Xiong Ni)
지옹니 (Xiong Ni) 의 석사학위논문을 인준함
2020 년 01 월
위 원 장 서 병 무 (인)
부 위 원 장 김 성 민 (인)
위 원 양 훈 주 (인)
Abstract
Positional c hanges of condyle and mandibular stability after isolated maxillary orthognathic surgery combined with mandibular
autorotation in mandibular retrognathism with high mandibular plane angle
Xiong Ni
Program in Oral and Maxillofacial Surgery, Department of Dental Science, Graduate School, Seoul National University
Background and purpose
Mandibular advancement in skeletal class II malocclusion with high mandibular plane angle can cause postoperative condylar resorption. As an alternative surgical method, malocclusion is corrected by isolated maxillary orthognathic surgery combined with mandibular autorotation, and low-face esthetic improvement can be achieved by genioplasty. Postoperative positional changes in condyle and mandibular stability following this alternative surgery were investigated in short and long terms.
Materials and methods
Fifteen patients who underwent isolated maxillary orthognathic surgery
with mandibular autorotation to correct skeletal class II malocclusion with
mandibular angles of >40° were evaluated. Postoperative mandibular stability
(T0) and immediately (T1), 6 weeks (T2), 6 months (T3), 1 year (T4) and >2 years (T5) after surgery. Positional changes were analyzed with transcranial temporomandibular joint projection. Correlation between condylar displacement and parameters for surgical movement was analyzed by Spearman’s rank correlation coefficient.
Results
Although there were significant differences between postoperative values at T0 and T1, all values after T2 showed no further variation, except SNB and horizontal point B. However, the amount of decrease in SNB was only 0.5 ± 0.1°, while point B moved backward by only 1.14 ± 0.13 mm, which can be regarded as stable results. The mandibular condyle was displaced posteroinferiorly; however, it achieved a stable position at postoperative 6 weeks. Amount of vertical condylar displacement was significantly correlated with surgical change in mandibular posterior border sagittal angle, palatal plane angle, facial height ratio and point B in the horizontal dimension.
Greater mandibular rotation prompted more vertical condylar displacement.
Conclusion
Isolated maxillary orthognathic surgery with mandibular autorotation and
advancement genioplasty constitutes a stable surgical maneuver in patients
with preoperative condylar resorption/risk factors to correct skeletal class II
malocclusion with high mandibular plane angle. However, surgeons should
be aware during surgical planning that this alternative method can provoke
postoperative condylar relapse.
Keywords: isolated Le Fort I osteotomy, mandibular retrognathism, mandible autorotation, idiopathic condylar resorption, condylar positional change.
Student Number: 2018-27645
Content
I. Introduction 01
II. Materials and Methods 04
1. Patients 04
2. Cephalometric analysis 04
3. Transcranial temporomandibular joint projection analysis 05
4. Methodical errors 06
5. Statistics 07
III. Results 08
1. Surgical movement and postoperative skeletal stability 08
2. Postoperative condylar displacement 09
3. Correlations between surgical movements and postoperative 09 condylar displacement
IV. Discussion 11
V. Conclusion 15
References 16
Tables 21
Figure legends and Figures 25
Korean abstract 34
I. Introduction
Severe class II malocclusions in adult patients often require the combination of orthodontic and orthognathic treatment [1]. However, patients with preoperative idiopathic condylar resorption (ICR) or patients with risk factors such as high mandibular plane angle and anterior open bite often showed progressive relapse and condylar resorption with temporomandibular joint (TMJ) disorder and unwanted esthetic results following orthognathic surgery [2,3,9,16].
The pathophysiology of ICR, known also as idiopathic condylysis, condylar atrophy, avascular necrosis, progressive condylar resorption [4], acquired condylar hypoplasia [5], or cheerleader’s syndrome [6], is still not well understood. The main risk factors are suggested to be sex hormones and mechanical overloading on TMJ after orthodontic treatment, orthognathic surgery, trauma, internal derangement, occlusal therapy, or parafunctional habits [7].
Postoperative idiopathic condylar resorption (pICR) is defined as a progressive alteration of shape and volume of the mandibular condyles following orthognathic surgery. The earliest clinical or radiological signs with occlusal disturbance or condylar resorption can occur at six months after surgery; however, pICR is often observed instead at one or two years after surgery in most patients [8–11, 13, 18–20]
and ultimately leads to long-term relapse with decreased posterior facial height, progressive mandibular retrusion, and anterior open bite [8, 10–21].
The risk factors for pICR can be stratified as either patient risk factors or surgical risk factors [14, 15]. Patient risk factors include young age, female gender, mandibular hypoplasia with high mandibular plane angle, posteriorly inclined
condylar neck, small condyle, short posterior facial height, and small posterior-to- anterior facial height ratio (FHR) [14]. In contrast, the surgical risk factors are large mandibular advancement, counterclockwise rotation of the proximal and distal mandibular segments, and surgically induced posterior condylar displacement [15].
Elsewhere, the risk factors were subclassified into preoperative factors, intraoperative factors, and postoperative factors [19]. While the preoperative factors here are similar to the aforementioned patient risk factors and the intraoperative factors are almost identical to the surgical risk factors, joint compression and/or articular damage belong uniquely to the postoperative factors category [10–13, 16–
21].
All surgical risk factors are caused by mandibular surgery with bilateral sagittal split ramus osteotomy (BSSRO) with or without maxillary surgery [9–21]. Therefore, it is logical to suppose that isolated maxillary orthognathic surgery with mandibular autorotation would be a better surgical maneuver for the correction of malocclusion among patients with risk factors for pICR if these individuals do not show mandibular asymmetry or severe mandibular retrognathism. Isolated Le Fort I osteotomy is usually indicated to reduce the anterior facial height by the correction of the anterior open bite, and concomitant mandibular autorotation holds an advantage with consequent forward chin movement [25]. Recently, a comparative study on the subject of skeletal stability one year after surgery considered between isolated Le Fort I osteotomy and conventional two-jaw surgery in patients with similar amounts of forward movement of point B indicated that the former was more stable than the latter [26].
A few studies have evaluated condylar remodeling and resorption [21] or skeletal relapse [22–24] following isolated Le Fort I osteotomy. Here, the degree of skeletal relapse was compared between wire fixation and miniplate fixation after isolated maxillary surgery or between bimaxillary surgery and isolated maxillary surgery in patients with different surgical movements at point B. However, to my knowledge, the detailed and long-term postoperative changes of skeletal parameters in relation to pICR after isolated maxillary surgery with mandibular autorotation have not been reported.
Further, while the relationship between mandibular autorotation and maxillary impaction or positional changes of the mandibular condyle after mandibular autorotation have been covered [21–26, 29], the postoperative returning movement of displaced condyles have not been widely discussed. Moreover, there is no report detailing the correlation between condylar displacement and the surgical movement inherent in mandibular autorotation for isolated maxillary surgery in patients with risk factors for pICR.
The purpose of this study was therefore to investigate postoperative condylar displacement according to mandibular autorotation and mandibular stability after isolated maxillary surgery in both short- and long-term periods among patients with risk factors for pICR.
II. Material and methods 1. Patients
The investigators designed and implemented a retrospective observational study including 15 patients with a male: female ratio of 2:13 and a mean age of 23.1 years.
Study participants were required to have skeletal class II with high mandibular plane angle and to undergo isolated Le Fort I osteotomy with/without genioplasty at Seoul National University Dental Hospital, with follow-up conducted with lateral cephalography for more than two years. This study was approved by the institutional review board of Seoul National University Dental Hospital (ERI19039). Nine patients presented preoperative condylar resorption, while six patients showed risk factors for pICR such as skeletal class II with high mandibular plane angle, young age, female gender, and posteriorly inclined condylar neck without a clear radiological sign for condylar resorption before surgery. All patients underwent pre- and postoperative orthodontic treatments. Genioplasty was conducted in 13 patients, and two patients underwent only Le Fort I osteotomy without genioplasty.
2. Cephalometric analysis
To measure surgical movements and to evaluate postoperative relapse, lateral cephalograms of each patient were obtained in the maximum intercuspal position at a magnification ratio of 1.1:1 before (T0) and immediately (T1), six weeks (T2), six months (T3), one year (T4) and more than two years (T5) after surgery.
Cephalometric analysis was carried out according to the superposition technique.
Each cephalogram was traced in acetate paper. Ten cephalometric reference points [i.e., sella (S), nasion (N), point A (A), point B (B), tip of the upper central incisor
(U1), articulare (Ar), mention (Me), gonion (Go), anterior nasal spine (ANS), and posterior nasal spine (PNS)] were noted in the lateral cephalogram at T0 and transferred to lateral cephalograms taken at T1, T2, T3, T4, and T5 (Fig. 1). An X–
Y coordinate system was established (Fig. 1), in which the X-axis (SN7) was constructed by rotating S–N downward by 7° and the Y-axis (=SN7v) was constructed on N perpendicular to SN7.
Five linear and seven angular and parameters were cephalometrically analyzed. The linear parameters were the vertical distance of A and B perpendicular to the X-axis (Av, Bv), the horizontal distance of A and B perpendicular to the Y-axis (Ah, Bh), and the ratio of posterior facial height (S-Go) to anterior facial height (N-Me). The angular parameters were SNA, SNB, upper incisal angle to SN (SN-U1), mandibular plane angle (MPA), mandibular posterior border sagittal angle (PSA), and palatal plane angle (PPA) (Fig. 1).
3. Transcranial temporomandibular joint projection analysis
Postoperative condylar displacement was investigated using transcranial TMJ projection before surgery (T0) and immediately (T1), six weeks (T2), six months (T3), and one year (T4) after surgery. The reference for the measurement of condylar position in this projection was the most upper and anteroposterior middle point (point P) on the condylar contour. Point P was determined as follows: the midpoint of the widest width of condyle was marked and the midpoint of the condylar width at the middle level between A and the most upper point on the condylar contour was determined. Then, the line between two midpoints was drawn and the cross-point
between the connecting line and the condylar contour was defined as point P (Fig.
2). An X–Y coordinate system was established, in which the X-axis was constructed as tangent to the roof of the glenoid fossa parallel to the horizontal upper border of the X-ray image, while the Y-axis was constructed on the top of the fossa perpendicular to the X-axis. Because of image distortion and different magnifications in transcranial TMJ projections, the positioning of point P was measured not as a linear distance but rather as a positional ratio to the X- and Y-axes to analyze the postoperative mandibular condylar displacement (Fig. 2). At this point, the glenoid fossa depth between the roof of the glenoid fossa and the lowest point of articular eminence was determined and the vertical position of point P relative to the roof of the glenoid fossa was measured. Then, the width of the condylar head was measured, where a line parallel to the X-axis and running through the midpoint of the glenoid fossa depth was drawn, while the width of the condylar head was defined as the distance between the anterior and posterior points of the condylar head contour crossed with the line. The horizontal distance of point P to the Y-axis was measured.
If point P was on the right side of the Y-axis, the value of the horizontal distance of point P was defined as positive, whereas if point P was on the left side of the Y-axis, it was defined as negative. The vertical positional ratio of point P was the ratio of the vertical position of point P to the glenoid fossa depth, while the horizontal positional ratio of point P was the ratio of the horizontal position of point P to condylar width (Fig. 2B).
4. Methodical errors
Methodical errors for each reference point were calculated using the Dahlberg formula S2= ∑ d2⁄2n, where d is the difference between remeasured values and n is the number of double measurements. The maximum error of all reference points was 0.254 mm horizontally and 0.314 mm vertically (Table 1).
5. Statistics
The data from the cephalometric analysis were reviewed to obtain the amounts of surgical movements (T1 − T0) and postoperative relapse (T5 − T1). Statistical analysis was performed using the Statistical Package for the Social Sciences version 23.0 software program (IBM Corp., Armonk, NY, USA). The data were tested for normal distribution through a Kolmogorov–Smirnov test. Quantitative data were expressed as means ± standard deviations and analyzed by one-way repeated- measures analysis of variance (RM ANOVA). Comparisons between the groups were conducted using the Bonferroni method (post-hoc test). Correlations between surgical movements and condylar displacement were analyzed using Spearman’s rank correlation coefficients. The level of significance was set at p < 0.05.
III. Results
1. Surgical movement and postoperative skeletal stability
The average surgical movements of the maxilla, autorotation of the mandible, and postoperative relapses of the mandible are shown in Table 2. The average maxillary setback was 1.43 ± 0.84 mm, and the average impaction was 3.39 ± 0.61 mm (p = 0.013) at point A. The maxilla showed a clockwise rotation with reductions of the angle SNA (1.54 ± 0.31°) and the angle SN-U1 (2.38 ± 0.24°), and an increase in the palatal plane angle (0.75 ± 1.82°). The average mandibular advancement was 2.84 ± 1.05 mm, while the average vertical movement was 2.02 ± 0.17 mm at point B. The mandible showed a counterclockwise autorotation with an increase in the angle SNB (1.07 ± 0.41°; p = 0.016) and decreased FHR (0.02 ± 0.00; p = 0.001) and a reduction in PSA (3.04 ± 0.06°; p < 0.001) and the mandibular plane angle (3.29 ± 0.02°; p <
0.001).
All cephalometric values except the SNA, SN-U1, PPA angles and Ah displayed significant differences among the six check-up times (T0 − T5) (Fig. 3). In the comparison between two check-up times, all cephalometric values at T0 had significant differences with values at all postoperative check-up times, while SNA and Ah did not show any significant difference (Fig. 3). In terms of postoperative stability, cephalometric values at each check-up time were compared with values at different postoperative check-up times, and all cephalometric values appeared statistically stable except for SNB and Bh. Instead, SNB and Bh presented significant changes between T3 and T5 (p < 0.01 for both) (Fig. 3). However, the decrease in SNB was only 0.5 ± 0.1˚ and the backward relapse at point B was just 1.14 ± 0.13
mm, constituting small differences that could be compensated for with postoperative orthodontic treatment (Fig. 4).
2. Postoperative condylar displacement
Condylar position was horizontally and vertically significantly different on both sides among all check-up times. It was significantly changed horizontally on both sides (p < 0.05 for both) and vertically only on the right side (p < 0.01), respectively.
The mean displacement ratio from T0 and T1 was −0.15 ± 0.01 horizontally (to posterior) and 0.14 ± 0.17 vertically (to inferior) on the right side and was −0.15 ± 0.04 horizontally (to posterior) and 0.29 ± 0.42 vertically (to inferior) on the left side.
Further, the displaced condylar position at T1 was returned to a stable position at T2, which was maintained through T3 to T4 (Table 3 and Figs. 5 and 6). Additionally, the mean returning movement ratio between T1 and T2 was 0.15 ± 0.03 horizontally (to anterior) and −0.20 ± 0.16 vertically (to superior) on the right side but was 0.11
± 0.01 horizontally (to anterior) and −0.38 ± 0.45 vertically (to superior) on the left side. The returning movement between T1 and T2 was significant both horizontally and vertically on both sides (p < 0.05).
3. Correlations between surgical movements and postoperative condylar displacement
The vertical displacement of the left condyle between T0 and T1 was significantly correlated with the surgical change in mandibular posterior border sagittal angle (r =
−0.538; p < 0.05), PPA (r = −0.592; p < 0.05), FHR (r = 0.707; p < 0.01), and horizontal movement of point B (r = −0.529; p < 0.05). Additionally, vertical
displacement of the right condyle between T0 and T1 was significantly correlated with FHR (r = 0.514; p < 0.01). In general, the greater the amount of mandibular rotation observed, the larger the vertical displacement of the mandibular condyle was (Fig. 7). The vertical displacement of the condyle between T0 and T1, in particular, showed significant correlation with the surgical change of the FHR (r = −0.617; p <
0.05) (Table 4).
IV. Discussion
This study sought to investigate mandibular stability after isolated maxillary surgery in the short- and long-term periods among patients with high mandibular plane angles, which is one of the major risk factors for pICR, and the relationship between postoperative condylar displacement and the degree of surgical movement according to mandibular autorotation. The results showed that the mandible was stable until two years after surgery and greater amounts of mandibular rotation correlated with increased vertical displacement of the mandibular condyle.
After orthognathic surgery for mandibular advancement, postoperative surgical relapse is common. Kobayashi et al. suggested that advancement surgery should be conducted only when the condyles are stable, and postoperative mechanical loading on the TMJ should be avoided in high-risk patients [2]. Mobarak et al. reported that 45% of their patients showed a horizontal relapse at pogonion of more than 1 mm and 15% of patients showed a horizontal relapse at pogonion of more than 2 mm 1 to 3 years after two-jaw surgery in 20 patients with high-angle class II malocclusion [3]. In the study by Yang et al., 16 female patients with mandibular retrognathism and preoperative condylar resorption demonstrated postoperative relapse with a clockwise rotation of the mandibular plane angle of 1.08 ± 1.23° and a postoperative open bite increased by 0.69 ± 0.98 mm from six months to one year postoperatively [20]. Moreover, Hoppenreijs et al. reported that BSSRO resulted in condylar remodeling in 30% and progressive condylar resorption in 19% of their patients [21].
Those studies implied that BSSRO may be not a good treatment choice among patients showing preoperative condylar resorption or its risk factors. Isolated maxillary impaction surgery without BSSRO has been used for several decades;
12
however, there are only a few reports discussing clinical analysis findings.
Hoppenteijs et al. revealed that patients who underwent BSSRO showed significantly more radiological condylar changes relative to those who underwent only Le Fort I osteotomy [21]. Kita et al. compared one-year postoperative stability outcomes between conventional bimaxillary surgery (n = 6) and isolated maxillary impaction surgery combined with mandibular autorotation (n = 7) among patients with skeletal class II retrognathism, in whom the amount of mandibular advancement was determined to be similar between the groups. These authors additionally found, however, that the mean surgical relapse was significantly greater in patients following bimaxillary surgery than in patients following isolated maxillary surgery and suggested that isolated maxillary impaction surgery combined with mandibular autorotation may avoid late surgical relapse caused by progressive condylar resorption [26]. However, this study did not show a meaningful conclusion because the number of patients was too small, and the follow-up period was only to one year after surgery. Our study involved two years of follow-up and more patients (n = 15), even though there was no control group treated with conventional bimaxillary surgery. As compared to in previous studies with bimaxillary surgery [3, 20, 21], the outcomes in the present study appeared relatively stable, with only an increased SNB of 0.5° and a backward relapse of point B by 1.14 mm, both of which are findings that can be compensated for with postoperative orthodontic treatment. However, the deployment of this technique is limited in patients without mandibular asymmetry and the upper central incisor edge should be set to an aesthetically appropriate position on the counterclockwise rotational orbit of the mandible [26].
The exact position of the rotation center in the mandibular condyle has been differently reported over several decades. For a while, it was believed and insisted that the rotational center is located at the center of the condyle [27,28,31,34].
However, more recent studies have reported that it is variable—for example, it lies at the mastoid process [29,30], it is located below and behind the cephalometric center of the condyle [30–32] or is located within the condylar neck [30–33].
According to recent studies suggesting the rotation center lies out of the condylar center, the use of the condylar center for the center of mandibular rotation in the planning of isolated Le Fort I osteotomy can thus cause considerable error in the horizontal positioning of the maxilla in most cases [34]. In the present study, condyles were displaced posteroinferiorly; therefore, our results supported that it was located below and behind the cephalometric center of the condyle. The displaced condyle was returned to a stable position six weeks after surgery and maintained there to one year after surgery in our study, which is the first report introducing the changes of postoperative displaced condyles at different check-up times after isolated maxillary surgery combined with mandibular autorotation.
Transcranial TMJ projection has been used to evaluate condylar positioning before and after surgery, offering the advantages of a simple technique and low-dose X-ray exposure when compared with computed tomography. Rosenquist et al.
reported that transcranial TMJ projection was more accurate than lateral tomography [35], while Menezes et al. postulated that transcranial TMJ projection is an acceptable method for assessment of the condylar position and its applicability as an adjunctive method in the condylar position should not be rejected [36]. Pullinger and Hollender described the application of a linear ratio in transcranial TMJ for the
14
evaluation of condylar positioning within the intra-articular space, where the closest posterior (P) and anterior (A) distances between the roof of glenoid fossa and condylar head were measured and the linear ratio was defined as (P − A)/(P + A) × 100 [37,38]. Bonilla-Aragon et al. used this method in their research on the relationship between condyle position and disk displacement [39]. However, images in transcranial TMJ projection can appear distorted and magnified because of unstable head posture and different radiation angles during X-ray imaging. Thus, a new method with a positional ratio was designed to achieve a more accurate analysis of the horizontal and vertical positioning of mandibular condyles in the transcranial TMJ projection. In this method, the horizontal and vertical condyle positioning was defined as the ratio to the condylar width and glenoid fossa depth; therefore, the distorting influence caused by image magnification and head posture during X-ray taking can be minimized.
V. Conclusion
The present study showed that isolated maxillary surgery combined with mandibular autorotation with or without genioplasty remained relatively stable until two years after surgery. Although the mandibular condyle was displaced inferiorly and posteriorly immediately after surgery, it returned to a stable position by six weeks after surgery and remained there through six months to a year after surgery.
Condylar vertical displacement had a significant positive correlation with mandibular autorotation. However, surgeons should keep in mind during surgical planning that this alternative method can also cause a small amount of postoperative relapse.
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24. Espeland L, Dowling PA, Mobarak KA, Stenvik A. Three-year stability of open-bite correction by 1-piece maxillary osteotomy. Am J Orthod Dentofacial Orthop. 2008;134:60-6.
25. Wang YC, Ko EWC, Huang CS, Chen YR. The Inter-relationship between mandibular autorotation and maxillary le fort I impaction osteotomies. J Craniofac Surg. 2006;17:898-904.
26. Kita S, Fujita K, Aoyagi M, Shimazaki K, Tonemitsu I, Omura S, Ono T. Postoperative stability of conventional bimaxillary surgery compared with maxillary impaction surgery with mandibular autorotation for patients with skeletal class II retrognathia. Br J Oral Maxillofac Surg. 2019;pii: S0266-4356:30705-3.
27. Hohl TH. The use of an anatomical articulator in segmental orthognathic surgery. Am J Orthod. 1978;73:428-42.
28. Marko JV. Simple hinge and semiadjustable articulators in orthognathic surgery. Am J Orthod Dentofacial Orthop. 1986;90:37- 44,
29. Sperry TP, Steinberg MJ, Gans BJ. Mandibular movement during autorotation as a result of maxillary impaction surgery. Am J Orthod Dentofac Orthop. 1982;81:116-22.
30. Rekow ED, Speidel TM, Koenig RA. Location of the mandibular center of autorotation in maxillary impaction surgery.
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31. Nadjmi N, Mimmaerts MY, Abeloos JV, De Clercq CA. Prediction of Mandibular Autorotation. Oral Maxillofac Surg. 1998;56:1241-1247.
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35. Rosenquist BO, Petersson A, Rune B, Selvik G. Accuracy of the oblique lateral transcranial projection, lateral tomography, and x-ray stereometry in evaluation of mandibular condyle displacement. J Oral Maxillofac Surg. 1988;46:862-7.
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22 Tables
Table 1. Methodological errors
Reference point X-axis (mm) Y-axis (mm)
S 0.000 0.119
N 0.054 0.031
A 0.124 0.111
B 0.121 0.098
U1 0.068 0.085
Ar 0.098 0.123
Me 0.067 0.089
Go 0.158 0.231
ANS 0.099 0.314
PNS 0.254 0.178
P 0.234 0.292
Difference in distance from X- and Y-axes determined through double measurement of reference points as calculated using the Dahlberg formula, S2= ∑ d2⁄2n, where d is the difference between remeasured values and n is the number of double measurements. Lateral cephalogram: S, sella; N, nasion; A, point A; B, point B; U1, tip of the upper central incisor;
Ar, articulare; Me, mention; Go, gonion; ANS, anterior nasal spine; PNS, posterior nasal spine. Transcranial TMJ projection: P, the most upper and anteroposterior middle point of condyle.
23
Table 2. Surgical movement and postoperative relapse.
Data are presented as means ± standard deviations. Statistical analyses were conducted by one-way RM ANOVA. T0, before surgery; T1, immediately postoperatively; T2, six weeks after surgery; T3, six months after surgery; T4, one year after surgery; T5, two years afsurgery MPA, mandibular plane angle; PSA, mandibular posterior border sagittal angle; PPA, palatal plane angle; FHR, facial height ratio. *p < 0.05, **p < 0.01, ***p < 0.001 with Bonferroni method (post-hoc test) of one-way RM ANOVA. Linearmeasurement Angularmeasurement
Bh Bv Ah Av FHR PPA MPA PSA SN-U1 SNB SNA
-2.84 ± 1.05* -2.02 ± 0.17** 1.43 ± 0.84 -3.39 ± 0.61* 0.02 ± 0.00** 0.75 ± 1.82 -3.29 ± 0.02*** -3.04 ± 0.06*** -2.38 ± 0.24 1.07 ± 0.41 -1.54 ± 0.31 T1-T0
0.51 ± 0.20 0.01 ± 0.36 -0.13 ± 0.05 0.13 ± 0.23 -0.01 ± 0.00 -0.03 ± 0.14 0.86 ± 0.52 0.85 ± 0.43 0.58 ± 0.25 -0.20 ± 0.18* -0.03 ± 0.03 T2-T1
-0.40 ± 0.49 -0.50 ± 0.13 0.25 ± 0.08 -0.39 ± 0.10 0.00 ± 0.00 -0.26 ± 0.25 -0.20 ± 0.04 -0.24 ± 0.03 0.27 ± 0.16 0.17 ± 0.29 -0.03 ± 0.04 T3-T2
0.51 ± 0.35 0.06 ± 0.02 0.01 ± 0.14 0.15 ± 0.06 0.01 ± 0.00 -0.03 ± 0.22 0.24 ± 0.04 -0.03 ± 0.18 -0.37 ± 0.25 -0.21 ± 0.09 -0.18 ± 0.01 T4-T3
0.64 ± 0.18 0.22 ± 0.31 0.20 ± 0.00 0.40 ± 0.10 0.00 ± 0.00 0.04 ± 0.10 -0.05 ± 0.08 0.27 ± 0.12 -0.51 ± 0.21 -0.32 ± 0.06 -0.16 ± 0.14 T5-T4
1.15 ± 0.53* 0.28 ± 0.29 0.31 ± 0.14 0.55 ± 0.04 0.01 ± 0.00 0.05 ± 0.32 0.74 ± 0.04 0.24 ± 0.30 -0.88 ± 0.04 -0.53 ± 0.15** -0.44 ± 0.13 T5-T3
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Table 3. Transcranial projection variables at each time point
Data are presented as means ± standard deviations. Statistical analyses were conducted
using the one-way RM ANOVA.
T0, before surgery; T1, immediately postoperatively; T2, six weeks after surgery; T3, six months after surgery; T4, one year after surgery.
T0 T1 T2 T3 T4 p value
Rt
AP 0.01 ± 0.23
-0.16 ± 0.22
-0.01 ± 0.19
-0.03 ± 0.14
-0.07 ±
0.21 0.001 Vertical 0.62 ±
0.29
0.76 ± 0.46
0.56 ± 0.30
0.52 ± 0.30
0.74 ±
0.28 0.003
Lt
AP -0.05 ± 0.28
-0.20 ± 0.24
-0.09 ± 0.23
-0.08 ± 0.21
-0.05 ±
0.22 < 0.001 Vertical 0.67 ±
0.35
0.96 ± 0.77
0.58 ± 0.32
0.56 ± 0.27
0.53 ±
0.30 0.034
Table 4. Correlation between surgical movement and condylar displacement
CD, condylar displacement Statistical analyses were conducted using Spearman ,s rank correlation coefficient *p < 0.05, **p<0.01 CD
Both Lt Rt
Vertical AP Vertical AP Vertical AP
p Rho p Rho p Rho p Rho p Rho p Rho
0.899 0.036 0.718 -0.102 0.301 -0.286 0.647 -0.129 0.685 0.114 0.914 -0.030 SNA
0.112 0.427 0.164 0.379 0.095 0.447 0.283 0.297 0.305 0.284 0.324 0.273 SNB
0.364 -0.252 0.815 0.066 0.038 -0.538* 0.611 0.143 0.975 -0.009 0.593 0.150 PSA
0.454 -0.209 0.602 0.147 0.054 -0.506 0.704 0.107 0.919 0.029 0.354 0.257 MPA
0.607 -0.145 0.528 -0.177 0.020 -0.592* 0.511 -0.184 0.884 0.041 0.584 -0.154 PPA
0.001 0.757** 0.940 -0.021 0.003 0.707** 0.553 -0.175 0.050 0.514* 0.685 -0.114 FHR
0.889 -0.039 0.791 0.075 0.062 -0.493 0.860 -0.050 0.657 0.125 0.550 0.168 Av
0.791 -0.075 0.558 0.164 0.475 0.200 0.516 0.182 0.594 -0.150 0.899 0.036 Ah
0.723 -0.100 0.156 0.386 0.111 -0.429 0.334 0.268 0.791 0.075 0.187 0.361 Bv
0.147 -0.393 0.147 -0.393 0.043 -0.529* 0.289 -0.293 0.405 -0.232 0.362 -0.254 Bh
26
Figure legends and Figures
Figure 1. Determination of landmarks used in cephalometric analysis and in angular and linear measurements. S, sella; N, nasion; A, point A; B, point B; U1, tip of the upper central incisor; Ar, articulare; Me, mention; Go, gonion; ANS, anterior nasal spine; PNS, posterior nasal spine; X axis (SN7), line drawn 7° to sella-nasion line;
Y axis (SN7v), line on nasion, perpendicular to X-axis; MPA, mandibular plane angle; PSA, mandibular posterior border sagittal angle ; PPA, palatal plane angle.
Figure 2. Determination of the referenced point P (the most upper and anteroposterior middle point of the condyle) (A) and X and Y axis, and the reference lines for condylar head positioning in transcranial TMJ projection (B).
A: Determination of point P: the midpoint of the widest width of condyle was marked, and the midpoint of condylar width at the middle level between A and the most upper point on the condylar contour was determined. The line between the two midpoints was drawn, and the cross point between the connecting line and the condylar contour was defined as point P.
B: X-axis, tangent to the roof of the glenoid fossa parallel to the horizontal border of the X-ray image; Y axis, line on the point P of the fossa, perpendicular to the X axis;
a, glenoid fossa depth between the roof of the glenoid fossa and the lowest point of articular eminence; b, the vertical position of point P to the roof of glenoid fossa; c, the width of the condylar head. A line parallel to the X axis and through the midpoint of the glenoid fossa depth (a) is drawn, and the width of the condylar head is the distance between the anterior and posterior crossing points of the condylar head contour crossed with the line; d, the horizontal position of point P to the Y-axis, If the point P is on the right side of the Y-axis, the value of D is positive, while, if the point P is on the left side of the y-axis, the value of D is negative.
B/A, the vertical positional ratio of point P; D/C, the horizontal positional ratio of point P.
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Figure 3. Comparison of cephalometric values among the six check-up times.
T0, before surgery; T1, immediately postoperatively; T2, six weeks after surgery;
T3, six months after surgery; T4, one year after surgery; T5, two years after surgery.
*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 with Bonferroni method (post- hoc test) of one-way RM ANOVA.
A,G. SNA and Ah did not show any significant difference; B.
SNB presented significant differences between T0 and T1, T0 and T3, T0 and T4; T3 and T5;
C, E. PSA and FHR presented significant differences between T0 and almost
all postoperative check-up times except T5; D, F ,H. MPA, Av and Bv
presented significant differences between T0 and all postoperative check-up
times; I. Bh presented significant differences between T0 and T1, T0 and T2,
T0 and T3, T0 and T4; T3 and T5.
30
Figure. 4 Superimposed traced preoperative and immediate postoperative lateral cephalograms (A) and at the six weeks and two years postoperative stages (B).
Diagrams showed stable skeletal results.
32
Figure 5. Condylar displacement ratio in transcranial TMJ projection at each check- up time.
T0, before surgery; T1, immediately postoperatively; T2, six weeks after surgery;
T3, six months after surgery; T4, one year after surgery.
RT, right side; LT, left side; AP, anteroposterior.
*p < 0.05, **p < 0.01, ***p < 0.001, ****p < 0.0001 with Bonferroni method (post- hoc test) of one-way repeated measured analysis of variance (RM ANOVA).
On the right side, condylar position presented significant anteroposterior changes between T0 and T1, T1 and T2, T1 and T3(A), and significant vertical changes between T0 and T4, T1 and T4(B).
On the left side, condylar position presented significant anteroposterior changes between T0 and T1, T1 and T2, T1 and T3, T1 and T4(C), and no significant vertical changes(D).
Figure 6. Representative case of postoperative changes in condylar positioning.
There was obvious condylar displacement to posteroinferior immediate after surgery (A). However, the displaced condyle appeared settled at a stable position six weeks after surgery (A), a position that was maintained through six months to one year after surgery (B).
34
Figure 7. Representative cases of the correlation between surgical movement
and condylar displacement. A case without mandibular autorotation (A) and
a case with great mandibular autorotation (B). The condylar vertical
displacement was positively correlated with the amount of mandibular
autorotation.
- 국문 초록 -
하악평면각이 큰 하악 후퇴증 환자에서 상악 악교정수술과 하악
자가회전 후 하악과두의 위치 변화와 하악의 수술 후 안정성
Xiong Ni
서울대학교 대학원 치의과학과 구강악안면외과학전공 ( 지도교수 김 성 민 )
연구 목적
큰 하악평면각을 동반하는 골격성 2 급 부정교합 환자에서 하악 전방이동을 위한 악교정수술 후에 하악과두 흡수가 심화되어 후하방으로의 하악 회귀현상이 자주 발생한다. 본 연구의 목적은 이러한 환자에서수술후 회귀을 최소화 하기 위하여 하악 전진이동을 위한 골절단술을 시행하지 않고, 하악의 자가회전과 상악 악교정수술만 시행하여 교합을 개선하고 이부성형술을 통해 하안모를 심미적으로 개선시키는 치료 방법에서 하악의 수술후 안정성과 하악의 자가회전에 따른 하악과두 위치변화에 대해서 분석하고자 한다.
재료 및 방법
하악평면각이 큰 골격성 II 급 부정교합 환자에서 하악은 하악지시상분할골절단술을 시행하지 않고 자가회전만 하고 상악
36
악교정수술을 시행받은 환자 (n=15)를 대상으로 하여 수술전(T0), 수술직후(T1), 수술 6 주(T2), 6 개월(T3), 1 년(T4)과 2 년(T5) 후의 측모 두부방사선 분석을 통해 수술 이동량과 수술후 하악의 안정성을 평가하였고, 턱관절 경두개촬영술 영상자료에서 하악과두 위치 변화를 평가하고 통계적으로 분석하였다. 하악과두의 변위와 다양한 수술이동 변수와의 상관관계도 통계 분석하였다.
결과
T0 와 수술 이후 T1 에서부터 T5 까지의 측모두부방사선 변수값들은 여러 개가 유의한 차이를 있으나, 수술후 6 주인 T2 이후로는 측모두부방사선 변수값들의 유의한 차이가 없었으며, SNB 와 B point 의 수평적 위치만 T3 와 T5 간에 유의한 변화를 있었다. 하지만 SNB 는 평균 0.5° 감소하였고, B point 도 1.14mm 후방 회귀한 것으로 작은 양의 변화만 있어, 비교적 안정된 결과를 보였다. 수술직후 변위된 과두위치는 수술후 6 주에 안정된 위치로 자리 잡아서 수술후 6 주에서 1 년까지는 유의한 변화없이 유지되었다. 수술직후 하악과두의 수평적 변화는 수술에 의한 하악평면각과 근심골편 후방경사도의 변화, 그리고 B point 수평적 변화와 양의 상관관계를 보여, 하악의 반시계방향의 자가 회전 양이 많을수록 하악과두의 수직적 변위가 증가하는 관계를 보였다.
결론
하악전진 이동을 최소화하기 위하여 하악의 자가회전과 상악만의 악교정수술 방법은 수술후 회귀량 적은 안정된 결과를 보였고, 수술직후 하악과두의 변위는 하악의 반시계방향의 자가 회전 양이 많을수록 하악과두의 수직적 변위가 증가하는 관계를 보였다. 하지만 수술 후, 하악과두 흡수의 위험성을 가진 환자에서는 상악만 수술을 하는 기법을 사용하더라도 적은 양이지만 회귀현상이 생길 수 있음을 인지하여야 한다.
주요어 : 단독 르포트 I형 골절단술, 하악 후퇴증, 하악 자가회전, 하악과두흡수, 하악과두 변위
학 번 : 2018-27645
38
I am fortunate to further my study in the Seoul national university school of dentistry.
And there are many influential people who I need to appreciate.
To my parents, Xiong Xiaoming and Sun Meiwen who support me all the time.
Thanks for respecting my choice and sacrificing most for me all the time. Without you, I wouldn’t be where I am today. Thank you and I love you both.
To my original mentor Prof. Soon-Jung Hwang, who have taught me a lot about the orthognathic surgery and how to be a good dentist and surgeon. I really thanks to your patient to me, that give me more courage to ask the questions and give my opinions. Because of you , I always feel warm in Korea.
To my mentor Prof. Soung-Min Kim, who have taken care of me in my last semester for master’s degree. I really learnt a lot from your classes and respect your attitude to study and research. That means a lot to me and let me know how to be a highly competent dentist.
To Prof. Hoon-Joo Yang, who helps me a lot in my study and life. Your serious attitude to the operation and optimistic open and bright disposition really have a deep influence on me. Thanks for giving me the suggestions and comforting me everytime when I feel confused.
To Ji-Hye Oh, who takes care of me like a sister. Because of you , my laboratory life become interesting and warm. Thank you for taking care of me all the time like a family.
To Dr. Nguyen Thi Hoang Truc, who is my friend in the Seoul national university school of dentistry. You came here earlier than me and thanks for your friendship and patient to ask my question all the time.
To Dr. Buyanbileg Sodnom-Ish, who is my friend in the Seoul national university school of dentistry. Thanks for your friendship and I will miss the time taking breakfast with you.
To Mi-young Eo, who is really kind to me. Thanks for your kind and helping me everytime when I ask for help.
To Emily Cho, who always prepare delicious food to laboratory members. Thanks for your kind and always preparing and sharing delicious food to me.
Xiong Ni
