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Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery
Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
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Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery Hoon Joo Yang a, Soon Jung Hwang a, b, * a
Orthognathic Surgery Center, Seoul National University Dental Hospital, Republic of Korea Department of Oral and Maxillofacial Surgery, School of Dentistry, Dental Research Institute, BK21 for Craniomaxillofacial Life Science, Seoul National University, Republic of Korea b
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 26 December 2017 Accepted 8 May 2018 Available online xxx
Purpose: Maxillary downgraft (MD) and mandibular setback (MS) are problematic procedures in terms of postoperative stability. While the amount of intraoperative clockwise rotation (CWR) of the proximal segment (PS) after MS combined with MD has a positive correlation with the amount of MD, mandibular relapse after MS with MD in relation to intraoperative CWR of the PS has not been reported. Moreover, the effect of mandibular relapse on maxillary stability after MS with MD remains unclear. The purpose of this study is to evaluate mandibular and maxillary stability after MS with MD in relation to intraoperative CWR of the PS and amount of MD. Materials and Methods: The study included 57 patients who underwent bimaxillary orthognathic surgery. Patients were classified into two groups according to whether MD was performed or not performed: Group I had 2 mm or more MD; and Group II had less than 2 mm MD including vertical impaction or no vertical changes. The amount of surgical movement and postoperative relapse were cephalometrically evaluated and statistically analyzed. Results: There was no significant difference in MS between Groups I and II, however, the vertical movement of the maxilla was different significantly (p < 0.001). In Group I, the intraoperative CWR and postoperative CCWR of the PS was greater than that of Group II (p ¼ 0.010; p < 0.001, respectively). Consequently, the anterior relapse of the mandible was greater in Group I than in Group II despite the same amount of MS in Groups I and II. In Group I, with direct bone contact using Le Fort I inclined osteotomy, vertical relapse at point A showed no statistical correlation with anterior relapse at point B, while the vertical and horizontal dental relapse at U1 showed significant correlations with anterior relapse at point B (r ¼ 0.403, p ¼ 0.030; r ¼ 0.581, p < 0.001, respectively). Conclusion: For more stable results, Le Fort I inclined osteotomy is recommended to obtain direct bone contact when moving the maxilla inferiorly. The PS must also be fixed while maintaining vertical bone step to prevent CWR. © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Le Fort I osteotomy Sagittal split ramus osteotomy Maxillary downgraft Mandibular setback surgery
1. Introduction Mandibular prognathism is a common dentofacial deformity in patients that frequently requires orthognathic surgery (Mah et al., 2017), and mandibular setback (MS) surgery is one of the most unstable orthognathic procedures (Proffit et al., 2007). Maxillary downgraft (MD) is an inevitable movement when there is vertical
* Corresponding author. Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University 101 Daehak-ro, Jongno-gu, 03080, Seoul, Republic of Korea. Fax: þ82 2 766 4948. E-mail address: [email protected] (S.J. Hwang).
deficiency and insufficient incisal showing, and also has a large postoperative relapse rate (Proffit et al., 2007). Several factors for skeletal relapse after MS have been reported, including preoperative orthodontic treatment to obtain a stable occlusion, amount of MS, soft tissue tension and postoperative scarring, fixation method, duration of intermaxillary fixation, condylar displacement, and positional change of the tongue (Rodriguez and Gonzalez, 1996; Chou et al., 2005; Kim et al., 2007, 2015; Proffit et al., 2007; Mucedero et al., 2008; Moure et al., 2012; Paeng et al., 2012; Lee et al., 2015). Intraoperative clockwise rotation (CWR) of the proximal segment (PS) is the main factor after MS using bilateral sagittal split ramus osteotomy (BSSRO) (Franco et al., 1989; Komori
https://doi.org/10.1016/j.jcms.2018.05.022 1010-5182/© 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
et al.,1989; Politi et al., 2004; Cho, 2007; Kim et al., 2007; Proffit et al., 2007; Yang and Hwang, 2014). In our previous study, we reported that CWR of the PS is caused by an operator avoiding the vertical bone step in the mandibular inferior border, and CWR improves bone contact between the PS and the distal segment (DS). The formation of vertical bone steps after repositioning the DS to the final occlusion was the most predictable factor for CWR of the PS, and it was significantly correlated with the amount of MD and MS (Yang and Hwang, 2014). However, there have been no reports on the occurrence of intraoperative CWR of the PS due to MD and resultant postoperative anterior relapse of the mandible. The following factors have been suggested as contributing factors to instability after MD: inadequate stabilization, inappropriate and/or lack of bone grafting, and increased masticatory bite forces (Wardrop and Wolford, 1989). Bilateral coronoidotomy, pterygomasseteric myotomy, and the use of a bite-opening appliance before surgery have been proposed as surgical methods to adapt muscles to an increased length (Ellis et al., 1989). Rigid fixation and interpositional bone grafts with hydroxyapatite or autogenous bone are effective at increasing stability (Persson et al., 1986; Ellis et al., 1989; Wardrop and Wolford, 1989; de Mol van Otterloo et al., 1996; Proffit et al., 2007). In our previous paper, we reported on Le Fort I inclined osteotomy, which can cause direct bone contact without a bone gap despite MD (Yang and Hwang, 2012). Le Fort I inclined osteotomy improves stability following MD. However, there have been no reports on the effects of mandibular anterosuperior relapse on postoperative stability of the maxilla when MS and MD coexist. The purpose of this study was to evaluate mandibular and maxillary stability after MS with MD in relation to intraoperative CWR of the PS and the amount of MD. 2. Materials and Methods 2.1. Patients
setback. The masseter muscle was not fully stripped, while the medial pterygoid muscle was fully stripped from the PS. After removing the intersegmental bone interference, the PS was manually guided to obtain an anterior-superior directed condylar position with regard to the glenoid fossa. One miniplate was used for fixation at each side. No intermaxillary fixation was used immediately following the operation, and light triangular guiding elastics were applied for 4e5 weeks after surgery. 2.3. Cephalometric analysis To measure surgical changes and to evaluate postoperative stability, lateral cephalograms of each patient were obtained in the maximum intercuspal position at a magnification ratio of 1.1:1 prior to surgery (T0), immediately postoperatively (T1), and at 1-year follow up (T2). Cephalometric analysis was carried out according to the superposition technique. Each cephalogram was traced on acetate paper. Nine cephalometric reference points (sella (S), nasion (N), point A (A), point B (B), tip of upper central incisor (U1), mesiobuccal cusp of upper first molar (U6), articulare (Ar), menton (Me), and gonion (Go)) were determined on the lateral cephalogram at T0 and were transferred to lateral cephalograms at T1 and T2 (Fig. 1). An XeY coordinate system was established (Fig. 1) in which the X axis (SN7) was constructed by rotating SeN downward by 7, and the Y axis (¼SN7v) was constructed on N perpendicular to SN7. Methodical errors for each reference point were calculated using the Dahlberg formula: S2 ¼ Sd2/2n (d, difference between remeasured values; n, number of double measurements). The maximum error of all reference points was 0.220 mm horizontal and 0.172 mm vertical (Table 1). Six angular and seven linear parameters were analyzed. The linear parameters were Av (vertical measurement, A to X axis), Ah (horizontal measurement, A to Y axis), Bv, Bh, U1v, U1h, and U6v. The angular parameters were SNA, SNB, SN-U1, occlusal plane angle
A total of 57 skeletal class III patients (male:female ¼ 31:26, mean age ¼ 22.5 years) who underwent bimaxillary orthognathic surgery (Le Fort I osteotomy with/without MD and BSSRO for MS) at Seoul National University Dental Hospital and who were followedup for 1 year were selected for this study. All patients had pre- and post-operative orthodontic treatment. This study was approved by the institutional review board (CRI10035). Patients were classified into two groups according to the amount of MD: Group I had 2 mm or more MD (n ¼ 29; male:female 17:12; mean age 22.7 years), and Group II had less than 2 mm MD including vertical impaction or no vertical changes (n ¼ 28; male:female 14:14; mean age 22.4 years). 2.2. Surgical procedure Bimaxillary surgeries were performed by one oral and maxillofacial surgeon. In patients with MD, Le Fort I inclined osteotomy was performed to increase the bony height at the piriform aperture area to obtain direct bone contact at this area after downward movement of the maxilla, as described in our previous report (Yang and Hwang, 2012), while conventional Le Fort I osteotomy was performed in patients without MD. When there was a bone gap at the piriform aperture area despite Le Fort I inclined osteotomy, autogenous bone graft was performed to fill the bone gap. This technique resulted in sufficient bone resistance against postoperative occlusal force at the piriform aperture area to provide postoperative maxillary stability. The osteotomized maxillary segment was stabilized using four miniplates at the piriform aperture and zygomatic buttress area on both sides. All patients underwent modified BSSRO according to Obwegeser-Dal Pont's method (Dal Pont, 1961) for mandibular
Fig. 1. Determination of landmarks used in cephalometric analysis and in angular and linear measurements. S, sella; N, nasion; A, point A; B, point B; Me, menton; Go, gonion; Ar, articulare; U1, tip of upper central incisor; U6, mesiobuccal cusp of upper first molar; X axis (SN7), line drawn 7 to sella-nasion line; Y axis (SN7v), line on nasion, perpendicular to x-axis; OPA, occlusal plane angle; MPA, mandibular plane angle; PSA, proximal segment angle.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7 Table 1 Methodical errors in study. Reference point
X (mm)
Y (mm)
S N A B Me Go Ar U1 U6
0 0.034 0.159 0.172 0.047 0.146 0.112 0.072 0.132
0.129 0 0.117 0.220 0.197 0.214 0.131 0.095 0.185
Differences in distance from x- and y-axes determined through double measurement of reference points as calculated using the Dahlberg formula, S2 ¼ Sd2/2n; d ¼ difference between remeasured values; n ¼ number of double measurements. S, sella; N, nasion; A, point A; B, point B; Me, menton; Go, gonion; Ar, articulare; U1, tip of the upper central incisor; U6, mesiobuccal cusp of the upper first molar.
(OPA), mandibular plane angle (MPA), and proximal segment angle (PSA). Mandibular ramus angle (MRA) represents PSA after postoperative bony union of the PS and DS. 2.4. Statistical analysis Data from the cephalogram measurements were processed to obtain surgical movements (T1-T0) and postoperative relapse (T2-T1). Statistical analyses were performed with PASW 21 software (IBM Inc, Chicago, IL, USA). The KolmogoroveSmirnov test was performed to determine whether data had a normal distribution. To test whether the changes in variables over time were statistically significant, a paired t test was performed. A Student t test was used to compare the surgical movement and the postoperative relapse between two groups divided according to the amount of MD. In Group I, Pearson correlation coefficients were used to determine the correlation between the amount of intraoperative CWR of the PS and other surgical movements. Correlations between skeletal relapse and other surgical movements and/or other skeletal relapses were also analyzed using Pearson correlation coefficients in Group I. 3. Results 3.1. Surgical movement of the maxillomandibular complex In Group I, the maxilla was moved inferiorly with direct bone contact at the piriform aperture area by Le Fort I inclined osteotomy
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or interpositional autogenous bone graft. Intraoperative vertical movement of the maxilla was 4.26 ± 1.49 mm at point A and 4.88 ± 1.77 mm at U1. The maxilla moved 1.58 ± 2.66 mm backward at U1. There was CWR of the maxillomandibular complex (MMC), so OPA and MPA increased by 8.6 ± 3.4 and 4.2 ± 2.8 , respectively. In consequence, maxillary incisal inclination (SN-U1) decreased from 113.4 ± 8.1 to 105.6 ± 7.3 . The DS moved backward by 10.58 ± 5.42 mm at point B. There was significant CWR of the PS by 4.9 ± 3.0 (p < 0.001) (Tables 2 and 4). Intraoperative CWR of the PS was significantly associated with vertical movement of U1, U6, and point A by surgery (r ¼ 0.375, p ¼ 0.045; r ¼ 0.372, p ¼ 0.047; r ¼ 0.377, p ¼ 0.044, respectively) (Table 5). In Group II, U1 showed no statistically significant change in vertical and anteroposterior directions during surgery. The maxilla was rotated clockwise, OPA increased by 4.4 ± 4.1 and SN-U1 decreased by 4.8 ± 4.9 , while MPA was not changed by surgery. The DS moved backward by 10.51 ± 3.36 mm at point B, and the PS rotated clockwise by 2.9 ± 2.9 (Tables 3 and 4). There were significant differences between Groups I and II in all parameters except anteroposterior movements of point A and B. In Group I, point A, point B, and U1 were repositioned downward, and MMCs of Group I showed significantly larger CWR than those of Group II. In Group I, intraoperative CWR of the PS was significantly larger than Group II (p ¼ 0.010) (Table 4). 3.2. Postoperative relapse of the maxillomandibular complex In Group I, at the 1-year follow-up, a tendency for relapse was observed in all parameters except SNA, MPA, A-Y axis, and U6-X axis. While the maxilla showed slight upward movement by 0.86 ± 0.95 mm at point A, U1 moved upward by 1.17 ± 1.11 mm and forward by 1.68 ± 1.44 mm, resulting in a significant increase in incisal inclination by 5.5 ± 4.7 (p < 0.001) (Tables 2 and 4). Although there was significant CWR of the MMC intraoperatively, significant postoperative relapse in the direction of CCWR occurred only in the maxilla; 2.5 ± 2.2 in OPA (p < 0.001). The mandible was rotated significantly counterclockwise by 2.3 ± 1.7 at the 1-year follow-up (p < 0.001), and the mandible showed significant relapse by 2.13 ± 2.04 mm anteriorly and 1.31 ± 1.30 mm superiorly at point B (p < 0.001) (Tables 2 and 4). Mandibular relapse with CCWR, or decrease in MRA, was significantly correlated with intraoperative CWR of the PS (r ¼ 0.666, p < 0.001) (Table 4). In Group II, the maxilla showed no significant vertical relapse at point A at the 1-year follow-up, while U1 moved upward by
Table 2 Cephalometric variables of Group I at each time point. Parameter
T0
Angular measurement ( )
Linear measurement (mm)
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
81.0 ± 4.0 84.9 ± 5.1 113.4 ± 8.1 15.2 ± 6.5 34.4 ± 7.3 84.1 ± 6.6 52.62 ± 4.60 2.03 ± 4.14 93.02 ± 8.36 3.92 ± 8.91 73.88 ± 5.65 3.56 ± 6.02 70.29 ± 5.68
T1
82.7 ± 3.8 79.0 ± 3.5 105.6 ± 7.3 23.8 ± 5.3 38.6 ± 6.8 89.0 ± 5.8 56.88 ± 4.62 0.09 ± 4.21 95.87 ± 7.44 6.66 ± 6.23 78.77 ± 5.62 1.98 ± 5.80 71.23 ± 5.65
T2
82.9 ± 3.6 80.3 ± 3.7 111.1 ± 8.8 21.3 ± 6.0 36.4 ± 9.4 86.7 ± 5.8 56.02 ± 4.70 0.06 ± 4.01 94.56 ± 7.29 4.53 ± 6.70 77.59 ± 5.43 3.66 ± 5.74 71.13 ± 5.74
p value T0 vs. T1
T1 vs. T2
.001 <.001 <.001 <.001 <.001 <.001 <.001 .001 <.001 <.001 <.001 .003 .001
.075 <.001 <.001 <.001 .103 <.001 <.001 .893 <.001 <.001 <.001 <.001 .538
Data are presented as mean ± SD. Statistical analyses were conducted using the paired t test. T0, prior to surgery; T1, immediately postoperatively; T2, 1 year after surgery. OPA, occlusal plane angle; MPA, mandibular plane angle; PSA, proximal segment angle. See Table 1 for other abbreviations.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Table 3 Cephalometric variables of Group II at each time point. Parameter
T0
Angular measurement ( )
Linear measurement (mm)
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
T1
80.5 ± 3.2 84.5 ± 4.1 107.5 ± 9.0 21.0 ± 5.2 39.8 ± 5.7 86.4 ± 5.5 60.13 ± 4.65 1.67 ± 4.99 110.02 ± 7.79 4.28 ± 9.16 85.74 ± 5.26 3.40 ± 7.23 78.01 ± 5.61
T2
82.2 ± 3.3 79.4 ± 3.8 102.8 ± 8.5 25.4 ± 5.9 39.4 ± 5.4 89.2 ± 5.2 59.45 ± 4.56 0.38 ± 5.32 105.68 ± 6.78 6.23 ± 8.61 85.19 ± 4.92 3.55 ± 7.57 75.35 ± 5.60
p value
82.0 ± 3.4 79.7 ± 3.8 104.8 ± 8.4 24.1 ± 6.2 39.2 ± 5.7 88.6 ± 5.4 59.17 ± 4.62 0.24 ± 5.50 104.88 ± 6.91 5.05 ± 8.76 84.76 ± 5.09 4.19 ± 7.71 75.30 ± 6.05
T0 vs. T1
T1 vs. T2
<.001 <.001 <.001 <.001 .401 <.001 .031 <.001 <.001 <.001 .114 .710 <.001
.120 .014 .002 <.001 .329 .029 .112 .374 .003 <.001 .030 .010 .839
Data are presented as mean ± SD. Statistical analyses were conducted using the paired t test. See Tables 1 and 2 for abbreviations.
Table 4 Mean amounts of surgical movement and postoperative relapse in Groups I and II. Surgical movement
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
Postoperative relapse
Group I
Group II
p value
Group I
Group II
p value
1.7 ± 2.5 5.9 ± 3.0 7.8 ± 4.0 8.6 ± 3.4 4.2 ± 2.8 4.9 ± 3.0 4.26 ± 1.49 1.94 ± 2.73 2.85 ± 3.833 10.58 ± 5.42 4.88 ± 1.77 1.58 ± 2.66 0.94 ± 1.36
1.8 ± 1.8 5.1 ± 1.7 4.8 ± 4.9 4.4 ± 4.1 0.4 ± 2.7 2.9 ± 2.9 0.69 ± 1.60 2.05 ± 2.37 4.34 ± 3.62 10.51 ± 3.36 0.55 ± 1.77 0.15 ± 2.10 2.66 ± 2.23
.909 .216 .013 <.001 <.001 .010 <.001 .870 <.001 .957 <.001 .009 <.001
0.2 ± 0.6 1.4 ± 1.1 5.4 ± 4.7 2.5 ± 2.2 2.2 ± 7.0 2.3 ± 1.7 0.86 ± 1.95 0.03 ± 1.26 1.31 ± 1.30 2.13 ± 2.01 1.17 ± 1.11 1.68 ± 1.44 0.10 ± 0.89
0.2 ± 0.7 0.4 ± 0.7 2.0 ± 3.1 1.3 ± 1.7 0.2 ± 1.3 0.7 ± 1.6 0.28 ± 0.89 0.14 ± 0.85 0.80 ± 1.28 1.18 ± 1.37 0.43 ± 1.00 0.64 ± 1.22 0.05 ± 1.18
.018 <.001 .002 .028 .155 <.001 .019 .539 .142 .044 .011 .005 .835
Data are presented as mean ± SD. Statistical analyses were conducted using the Student t test. See Tables 1 and 2 for abbreviations.
0.43 ± 1.00 mm and forward by 0.64 ± 1.22 mm, resulting in a significant increase in incisal inclination by 2.0 ± 3.1 (p ¼ 0.002) (Tables 2 and 4). In addition, OPA decreased by 1.3 ± 1.7 postoperatively (p < 0.001). The mandible was rotated significantly counterclockwise by 0.7 ± 1.6 at the 1-year follow-up (p ¼ 0.029), and the mandible showed significant relapse by 1.18 ± 1.37 mm anteriorly and 0.80 ± 1.28 mm superiorly at point B (p < 0.001; p ¼ 0.003, respectively) (Tables 2 and 4). The postoperative CCW rotation of the mandible (PSA) was significantly larger in Group I than in Group II (p < 0.001). Consequently, it was found that the forward relapse of B point was significantly greater in Group I than in Group II (p ¼ 0.044). Similarly, the postoperative increase in SNB was significantly greater in Group I than in Group II (p < 0.001). One year after surgery, U1 showed a significant relapse superiorly and anteriorly
in both Groups I and II. Therefore, SN-U1 was increased in both Groups I and II; however, the increase in SN-U1 was significantly greater in Group I than in Group II (p ¼ 0.002). 3.3. Intervariable correlation The correlations between intraoperative CWR of the PS and other surgical movements were analyzed in Group I. Intraoperative CWR of the PS was significantly associated with surgical change in SNB (r ¼ 0.853, p < 0.001), amount of MS at point B (r ¼ 0.867, p < 0.001), and vertical movement of U1, U6, and point A by surgery (r ¼ 0.375, p ¼ 0.045; r ¼ 0.372, p ¼ 0.047; r ¼ 0.377, p ¼ 0.044, respectively) (Table 5). Mandibular relapse with CCWR was significantly correlated with intraoperative CWR of the PS (r ¼ 0.666, p < 0.001), amount of MS at point B (r ¼ 0.867,
Table 5 Correlation between clockwise rotation of the proximal segment and independent parameters. Surgical movement
Pearson correlation p value
SNA
SNB
SN-U1
OPA
MPA
Av
Ah
Bv
Bh
U1v
U1h
U6v
.041 .832
.853*** <.001
.139 .472
.160 .408
.327 .083
.377* .044
.010 .959
.204 .290
.867*** <.001
.375* .045
.101 .604
.372* .047
Statistical analyses were conducted using Pearson correlation coefficients. See Tables 1 and 2 for abbreviations. * p < .05 *** p < .001.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
.518** .004 .423* .022
.459* .012
.403* .030 .581*** <.001 .316 .094
.177 .359 .609*** <.001 .110 .572 .124 .520 .202 .292 .203 .291 .371* .047 .438* .017
.505** .005 .151 .435 .936*** <.001 .469* .010 .601*** <.001 .339 .072
.982*** <.001 .867*** <.001 .342 .070 1
.354 .059 .304 .109 .159 .409 .304 .109 .301 .113 .209 .276 .087 .653 .260 .173 .397* .033 .245 .200 .360 .055 .016 .936 .062 .749 .034 .861 .083 .668 .325 .085 .509** .005 .160 .408 .100 .607 .135 .484 .091 .638 .193 .316 .339 .072 .037 .849 .260 .174 .129 .506 .204 .289 .126 .515 correlation
correlation
correlation
correlation
correlation
correlation
.541** .002 .666*** <.001 .075 .698 .561** .002 .210 .274 .328 .083 .592*** <.001 SN-U1
U1h
U1v
Bh
Av
MRA
Statistical analyses were conducted using Pearson correlation coefficients. MRA, mandibular ramus angle. See Tables 1 and 2 for other abbreviations. * p < .05 ** p < .01 *** p < .001.
Bh U1h
.601*** <.001 .124 .520 .385* .039 .581*** <.001 .518** .004 1 .469* .010 .110 .572 .659*** <.001 .403* .030 1
U1v MPA
.616*** <.001 .489** .007 .190 .323 .651*** <.001 .420* .023 .193 .316 .350 .063 .621*** <.001 .365 .052 .209 .277 .562** .002 .666*** <.001 .411* .027 .426* .021 .505** .005 1
OPA SN-U1
.336 .074 .267 .161 .135 .486 .312 .100 .087 .652 .121 .533 .011 .954 .532** .003 .410* .027 .096 .619 .524** .004 .206 .283 .361 .054 .483** .008 correlation
Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value SNB Relapse
U1h U1v MPA OPA PSA
1
Relapse
SNB SN-U1 SNB
Bh Surgical movement
Table 6 Correlation between clockwise rotation of the proximal segment and independent parameters.
Some amount of skeletal or dental relapse after orthognathic surgery is inevitable (Komori et al., 1989). In particular, MS and MD are regarded as the most problematic movements, with a high relapse tendency (Proffit et al., 2007). If the vertical growth of the maxilla is insufficient, the maxilla is moved downward to create a normal exposure of the maxillary incisors during orthognathic surgery. The vertical deficiency of the maxilla determines the amount of MD. Direct bone contact in MD is important to achieving stable postoperative results (Fig. 2C) (Yang and Hwang, 2012). If the size of the bone defect exceeded 3 mm, interpositional bone graft was needed because bone recovery would be inadequate (Ueki et al., 2011). Lack of long-term stability may be due to insufficient bone contact at the osteotomy site, which prevents primary bone healing (Jünger et al., 2003). The Le Fort I inclined osteotomy is a modified technique designed to obtain direct bone contact after MD (Yang and Hwang, 2012). The lateral wall of the nasal cavity is osteotomized in the superiorposterior direction by changing the inclination of the reciprocating saw. The bony height at the piriform aperture area can be increased with this technique. Direct bone contact can be most effectively obtained by clockwise maxillary rotation accomplished with anterior downward movement and simultaneous posterior impaction (Yang and Hwang, 2012). When the Le Fort I inclined osteotomy was performed for MD in our previous study, the amount of vertical relapse at point A was 0.96 ± 0.70 mm (34.4%) of the 2 to 4 mm MD and 0.68 ± 1.04 mm (12.5%) of the 4 mm or more MD (Yang and Hwang, 2012). The results seem to be more stable than those obtained for MD using conventional Le Fort I osteotomy, which showed a greater than 40% tendency for vertical relapse, with 2 to 4 mm maxillary downward movement and less than 20% tendency with 4 mm or more MD (Proffit et al., 2007). If total setback of the maxilla is performed concurrently with MD, direct bone contact may be impractical in Le Fort I inclined osteotomy (Yang and Hwang, 2012). If direct bone contact is not achieved, it may be helpful to perform interpositional bone graft with hydroxyapatite and autogenous bone graft and fixation using a rigid plate (Perez et al., 1997). Perez et al. reported an average 28.2% vertical relapse in patients undergoing Le Fort I MD of an average 4.6 mm (Perez et al., 1997). We performed autogenous bone graft in patients without direct bone contact after MD. The amount of MS is determined by final occlusion. In addition, the anterior and posterior position of the chin is appropriately controlled by moving the posterior maxilla vertically. Many studies have identified several contributing factors for skeletal relapse after mandibular setback surgery, indicating that the causes of skeletal
MRA
4. Discussion
.339 .072 .202 .292 .153 .428 .316 .094 .423* .022 .459* .012 1
p < 0.001), and amount of MD at U1 (r ¼ 0.397, p ¼ 0.033). Postoperative CCWR of the mandible also has a significant association with mandibular forward (r ¼ 0.505, p ¼ 0.005) and upward (r ¼ 0.489, p ¼ 0.007) relapse (Table 6). In maxillary vertical relapse, skeletal relapse at point A showed a significant correlation with surgical increase in MPA (r ¼ 0.509, p ¼ 0.005), while it showed no statistical correlation with other relapse variables. Conversely, vertical dental relapse at U1 showed a significant correlation only with postoperative increase in SNB (r ¼ 0.469, p ¼ 0.010), anterior relapse at point B (r ¼ 0.403, p ¼ 0.030), and decrease in MPA (r ¼ 0.420, p ¼ 0.023). Similarly, the horizontal dental relapse at U1 showed a significant correlation with postoperative increase in SNB (r ¼ 0.601, p ¼ 0.001) and anterior relapse at point B (r ¼ 0.581, p < 0.001). The greater the amount of MS and the larger intraoperative CWR of the PS was, the greater U1 protruded labially postoperatively (r ¼ 0.438, p ¼ 0.017; r ¼ 0.592, p < 0.001, respectively) (Table 6).
5
.936*** <.001 .609*** <.001 .036 .852 1
H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Fig. 2. Schematic drawing of pushing and rebounding action in MD with MS. (A) Before surgery. (B) Surgical movement of MD with MS. MD and MS together causes vertical bone step (yellow asterisk). Intraoperative CWR of the PS due to adjustment of the inferior borders of the PS and the DS. (C) Immediately after surgery. Le Fort I inclined osteotomy leads to a direct bone contact after MD due to the beveled bone surface at the piriform aperture area (black circle). (D) Postoperative relapse. CCWR of the mandible and skeletal (vertical) and dental (vertical and horizontal) relapse of the maxilla are observed. (E) One year after surgery.
relapse are multifactorial (Mucedero et al., 2008; Jakobsone et al., 2011; Yang and Hwang, 2014). Among the various factors contributing to skeletal relapse, intraoperative CWR of the PS is considered a primary relapse factor in BSSRO for mandibular prognathism (Franco et al., 1989; Komori et al., 1989; Politi et al., 2004; Cho, 2007; Proffit et al., 2007; Yang and Hwang, 2014). Intraoperative CWR of the PS (2.9e5.4 ) and subsequent postoperative CCWR (0.9e3.5 ) of the mandible have been reported in previous studies (Mobarak et al., 2000; Politi et al., 2004; Jakobsone et al., 2011). When the PS is rotated clockwise, the masseter and temporal muscles attached to the PS are stretched. Rebound of the mandibular ramus to its original position is often accompanied by anterosuperior relapse of the mandible, especially when rigid fixation is performed (Franco et al., 1989; Yang and Hwang, 2014; Santos et al., 2017). In this study, strong relationships were revealed among CWR of the PS during surgery, postoperative CCWR
of the mandible, and mandibular forward and upward relapse during the postsurgical phase. CWR of the PS is influenced by several parameters, particularly vertical bone steps, which are height differences between the inferior border of the DS and PS when the DS is positioned in the final occlusal state (Yang and Hwang, 2014). The amount of vertical bone step is positively correlated with the amount of MS and MD (Yang and Hwang, 2014). Therefore, the relapse tendencies of the MMC after MD with MS have to be closely linked each other. The anterior relapse after MS was different according to the amount of MD. In this study, Group I with great MD, the intraoperative CWR and postoperative CCWR of the PS was greater than that of the Group II with small or no MD, while there was no significant difference of the amount of MS between Groups I and II. Consequently, the anterior relapse of the mandible was greater in Group I than in Group II despite the same amount of MS in Groups I and II.
Fig. 3. Lateral cephalograms taken at T0, T1 and T2 of a representative case. Tracings are superimposed between T0 and T1, T1 and T2.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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In Group I, the maxilla was repositioned inferiorly by 4.26 ± 1.49 mm at point A intraoperatively, and the amount of MS was 10.58 ± 5.42 mm at point B. The PSA of the mandible increased by 4.9 ± 3.0 as the maxilla moved downward and the DS moved backward (Fig. 2B). The mandible was rotated significantly counterclockwise by 2.3 ± 1.7 at the 1-year follow-up with anterior and superior relapse at point B. The maxilla showed vertical relapse by 0.86 ± 0.95 mm at point A. Because of the Le Fort I inclined osteotomy and direct bone contact with or without interpositional bone graft, the maxilla showed more stable skeletal progression. There was no significant change in horizontal direction, and there was a significant difference in vertical direction at the point A. However, vertical relapse of less than 1 mm suggests that the relapse may have resulted from bony remodeling during bone healing (Fig. 2) (Yang and Hwang, 2012). However, even if skeletal relapse was prevented, dental relapse was inevitable. As the mandible undergoes forward relapse, it collides with the maxillary incisors, which promotes significant relapse of U1 vertically and horizontally. The vertical relapse of U1 was 1.17 ± 1.11 mm upward, and the horizontal relapse was 1.68 ± 1.44 mm forward. This may cause difficulty during postoperative orthodontic treatment and aesthetic deterioration due to labial protrusion of the maxillary incisor (Figs. 2E and 3). 5. Conclusion Le Fort I inclined osteotomy is recommended to obtain direct bone contact when moving the maxilla inferiorly for more stable results. When MS and MD coexist, the PS should be fixed while maintaining vertical bone step to prevent CWR of the PS. CWR of the PS during surgery can lead to mandibular forward and upward relapse during the postsurgical phase, which can increase the labial inclination of the maxillary incisors. Because this study involves a small number of cases, further investigation with a larger number of patients may provide more information on predictable postoperative stability. Conflicts of interest The authors have no financial interests to declare in relation to the content of this article. Acknowledgements This study was supported by a grant (HI13C1491) from the Korea Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea. References Cho HJ: Long-term stability of surgical mandibular setback. Angle Orthod 77: 851e856, 2007 Chou JI, Fong HJ, Kuang SH, Gi LY, Hwang FY, Lai YC, et al: A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients. J Oral Maxillofac Surg 63: 355e361, 2005 Dal Pont G: Retromolar osteotomy for the correction of prognathism. J Oral Surg Anesth Hosp Dent Serv 19: 42e47, 1961
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de Mol van Otterloo JJ, Tuinzing DB, Kostense P: Inferior positioning of the maxilla by a Le Fort I osteotomy: a review of 25 patients with vertical maxillary deficiency. J Craniomaxillofac Surg 24: 69e77, 1996 Ellis 3rd E, Carlson DS, Frydenlund S: Stability of midface augmentation: an experimental study of musculoskeletal interaction and fixation methods. J Oral Maxillofac Surg 47: 1062e1068, 1989 discussion 1068-1069 Franco JE, Van Sickels JE, Thrash WJ: Factors contributing to relapse in rigidly fixed mandibular setbacks. J Oral Maxillofac Surg 47: 451e456, 1989 Jakobsone G, Stenvik A, Sandvik L, Espeland L: Three-year follow-up of bimaxillary surgery to correct skeletal class III malocclusion: stability and risk factors for relapse. Am J Orthod Dentofacial Orthop 139: 80e89, 2011 Jünger TH, Krenkel C, Howaldt HP: Le Fort I sliding osteotomyea procedure for stable inferior repositioning of the maxilla. J Craniomaxillofac Surg 31: 92e96, 2003 Kim CH, Lee JH, Cho JY, Lee JH, Kim KW: Skeletal stability after simultaneous mandibular angle resection and sagittal split ramus osteotomy for correction of mandible prognathism. J Oral Maxillofac Surg 65: 192e197, 2007 Kim MI, Kim JH, Jung S, Park HJ, Oh HK, Ryu SY, et al: Condylar positioning changes following unilateral sagittal split ramus osteotomy in patients with mandibular prognathism. Maxillofac Plast Reconstr Surg 37: 36, 2015 Komori E, Aigase K, Sugisaki M, Tanabe H: Cause of early skeletal relapse after mandibular setback. Am J Orthod Dentofacial Orthop 95: 29e36, 1989 Lee YC, Sohn HB, Kim SK, Bae OY, Lee JH: 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: 21, 2015 Mah DH, Kim SG, Oh JS, You JS, Jung SY, Kim WG, et al: Comparative study of postoperative stability between conventional orthognathic surgery and a surgery-first orthognathic approach after bilateral sagittal split ramus osteotomy for skeletal class III correction. J Korean Assoc Oral Maxillofac Surg 43: 23e28, 2017 Mobarak KA, Krogstad O, Espeland L, Lyberg T: Long-term stability of mandibular setback surgery: a follow-up of 80 bilateral sagittal split osteotomy patients. Int J Adult Orthodon Orthognath Surg 15: 83e95, 2000 Moure C, Qassemyar Q, Dunaud O, Neiva C, Testelin S, Devauchelle B: Skeletal stability and morbidity with self-reinforced P (L/DL) LA resorbable osteosynthesis in bimaxillary orthognathic surgery. J Craniomaxillofac Surg 40: 55e60, 2012 Mucedero M, Coviello A, Baccetti T, Franchi L, Cozza P: Stability factors after doublejaw surgery in class III malocclusion. A systematic review. Angle Orthod 78: 1141e1152, 2008 Paeng JY, Hong J, Kim CS, Kim MJ: Comparative study of skeletal stability between bicortical resorbable and titanium screw fixation after sagittal split ramus osteotomy for mandibular prognathism. J Craniomaxillofac Surg 40: 660e664, 2012 Perez MM, Sameshima GT, Sinclair PM: The long-term stability of LeFort I maxillary downgrafts with rigid fixation to correct vertical maxillary deficiency. Am J Orthod Dentofacial Orthop 112: 104e108, 1997 Persson G, Hellem S, Nord PG: Bone-plates for stabilizing Le Fort I osteotomies. J Maxillofac Surg 14: 69e73, 1986 Politi M, Costa F, Cian R, Polini F, Robiony M: Stability of skeletal class III malocclusion after combined maxillary and mandibular procedures: rigid internal fixation versus wire osteosynthesis of the mandible. J Oral Maxillofac Surg 62: 169e181, 2004 Proffit WR, Turvey TA, Phillips C: The hierarchy of stability and predictability in orthognathic surgery with rigid fixation: an update and extension. Head Face Med 3: 21, 2007 Rodriguez RR, Gonzalez M: Skeletal stability after mandibular setback surgery. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 81: 31e33, 1996 Santos ZTBV, Goulart DR, Sigua-Rodriguez EA, Pozzer L, Olate S, AlbergariaBarbosa JR: Mechanical evaluation of the use of conventional and locking miniplate/screw systems used in sagittal split ramus osteotomy. J Korean Assoc Oral Maxillofac Surg 43: 77e82, 2017 Ueki K, Miyazaki M, Okabe K, Mukozawa A, Marukawa K, Moroi A, et al: Assessment of bone healing after Le Fort I osteotomy with 3-dimensional computed tomography. J Craniomaxillofac Surg 39: 237e243, 2011 Wardrop RW, Wolford LM: Maxillary stability following downgraft and/or advancement procedures with stabilization using rigid fixation and porous block hydroxyapatite implants. J Oral Maxillofac Surg 47: 336e342, 1989 Yang HJ, Hwang SJ: Postoperative stability following maxillary downward movement with Le Fort I inclined osteotomy at the lateral nasal cavity wall. J Craniomaxillofac Surg 40: 793e798, 2012 Yang HJ, Hwang SJ: Contributing factors to intraoperative clockwise rotation of the proximal segment as a relapse factor after mandibular setback with sagittal split ramus osteotomy. J Craniomaxillofac Surg 42: E57eE63, 2014
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery Hoon Joo Yang a, Soon Jung Hwang a, b, * a
Orthognathic Surgery Center, Seoul National University Dental Hospital, Republic of Korea Department of Oral and Maxillofacial Surgery, School of Dentistry, Dental Research Institute, BK21 for Craniomaxillofacial Life Science, Seoul National University, Republic of Korea b
a r t i c l e i n f o
a b s t r a c t
Article history: Paper received 26 December 2017 Accepted 8 May 2018 Available online xxx
Purpose: Maxillary downgraft (MD) and mandibular setback (MS) are problematic procedures in terms of postoperative stability. While the amount of intraoperative clockwise rotation (CWR) of the proximal segment (PS) after MS combined with MD has a positive correlation with the amount of MD, mandibular relapse after MS with MD in relation to intraoperative CWR of the PS has not been reported. Moreover, the effect of mandibular relapse on maxillary stability after MS with MD remains unclear. The purpose of this study is to evaluate mandibular and maxillary stability after MS with MD in relation to intraoperative CWR of the PS and amount of MD. Materials and Methods: The study included 57 patients who underwent bimaxillary orthognathic surgery. Patients were classified into two groups according to whether MD was performed or not performed: Group I had 2 mm or more MD; and Group II had less than 2 mm MD including vertical impaction or no vertical changes. The amount of surgical movement and postoperative relapse were cephalometrically evaluated and statistically analyzed. Results: There was no significant difference in MS between Groups I and II, however, the vertical movement of the maxilla was different significantly (p < 0.001). In Group I, the intraoperative CWR and postoperative CCWR of the PS was greater than that of Group II (p ¼ 0.010; p < 0.001, respectively). Consequently, the anterior relapse of the mandible was greater in Group I than in Group II despite the same amount of MS in Groups I and II. In Group I, with direct bone contact using Le Fort I inclined osteotomy, vertical relapse at point A showed no statistical correlation with anterior relapse at point B, while the vertical and horizontal dental relapse at U1 showed significant correlations with anterior relapse at point B (r ¼ 0.403, p ¼ 0.030; r ¼ 0.581, p < 0.001, respectively). Conclusion: For more stable results, Le Fort I inclined osteotomy is recommended to obtain direct bone contact when moving the maxilla inferiorly. The PS must also be fixed while maintaining vertical bone step to prevent CWR. © 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Keywords: Le Fort I osteotomy Sagittal split ramus osteotomy Maxillary downgraft Mandibular setback surgery
1. Introduction Mandibular prognathism is a common dentofacial deformity in patients that frequently requires orthognathic surgery (Mah et al., 2017), and mandibular setback (MS) surgery is one of the most unstable orthognathic procedures (Proffit et al., 2007). Maxillary downgraft (MD) is an inevitable movement when there is vertical
* Corresponding author. Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University 101 Daehak-ro, Jongno-gu, 03080, Seoul, Republic of Korea. Fax: þ82 2 766 4948. E-mail address: [email protected] (S.J. Hwang).
deficiency and insufficient incisal showing, and also has a large postoperative relapse rate (Proffit et al., 2007). Several factors for skeletal relapse after MS have been reported, including preoperative orthodontic treatment to obtain a stable occlusion, amount of MS, soft tissue tension and postoperative scarring, fixation method, duration of intermaxillary fixation, condylar displacement, and positional change of the tongue (Rodriguez and Gonzalez, 1996; Chou et al., 2005; Kim et al., 2007, 2015; Proffit et al., 2007; Mucedero et al., 2008; Moure et al., 2012; Paeng et al., 2012; Lee et al., 2015). Intraoperative clockwise rotation (CWR) of the proximal segment (PS) is the main factor after MS using bilateral sagittal split ramus osteotomy (BSSRO) (Franco et al., 1989; Komori
https://doi.org/10.1016/j.jcms.2018.05.022 1010-5182/© 2018 European Association for Cranio-Maxillo-Facial Surgery. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
et al.,1989; Politi et al., 2004; Cho, 2007; Kim et al., 2007; Proffit et al., 2007; Yang and Hwang, 2014). In our previous study, we reported that CWR of the PS is caused by an operator avoiding the vertical bone step in the mandibular inferior border, and CWR improves bone contact between the PS and the distal segment (DS). The formation of vertical bone steps after repositioning the DS to the final occlusion was the most predictable factor for CWR of the PS, and it was significantly correlated with the amount of MD and MS (Yang and Hwang, 2014). However, there have been no reports on the occurrence of intraoperative CWR of the PS due to MD and resultant postoperative anterior relapse of the mandible. The following factors have been suggested as contributing factors to instability after MD: inadequate stabilization, inappropriate and/or lack of bone grafting, and increased masticatory bite forces (Wardrop and Wolford, 1989). Bilateral coronoidotomy, pterygomasseteric myotomy, and the use of a bite-opening appliance before surgery have been proposed as surgical methods to adapt muscles to an increased length (Ellis et al., 1989). Rigid fixation and interpositional bone grafts with hydroxyapatite or autogenous bone are effective at increasing stability (Persson et al., 1986; Ellis et al., 1989; Wardrop and Wolford, 1989; de Mol van Otterloo et al., 1996; Proffit et al., 2007). In our previous paper, we reported on Le Fort I inclined osteotomy, which can cause direct bone contact without a bone gap despite MD (Yang and Hwang, 2012). Le Fort I inclined osteotomy improves stability following MD. However, there have been no reports on the effects of mandibular anterosuperior relapse on postoperative stability of the maxilla when MS and MD coexist. The purpose of this study was to evaluate mandibular and maxillary stability after MS with MD in relation to intraoperative CWR of the PS and the amount of MD. 2. Materials and Methods 2.1. Patients
setback. The masseter muscle was not fully stripped, while the medial pterygoid muscle was fully stripped from the PS. After removing the intersegmental bone interference, the PS was manually guided to obtain an anterior-superior directed condylar position with regard to the glenoid fossa. One miniplate was used for fixation at each side. No intermaxillary fixation was used immediately following the operation, and light triangular guiding elastics were applied for 4e5 weeks after surgery. 2.3. Cephalometric analysis To measure surgical changes and to evaluate postoperative stability, lateral cephalograms of each patient were obtained in the maximum intercuspal position at a magnification ratio of 1.1:1 prior to surgery (T0), immediately postoperatively (T1), and at 1-year follow up (T2). Cephalometric analysis was carried out according to the superposition technique. Each cephalogram was traced on acetate paper. Nine cephalometric reference points (sella (S), nasion (N), point A (A), point B (B), tip of upper central incisor (U1), mesiobuccal cusp of upper first molar (U6), articulare (Ar), menton (Me), and gonion (Go)) were determined on the lateral cephalogram at T0 and were transferred to lateral cephalograms at T1 and T2 (Fig. 1). An XeY coordinate system was established (Fig. 1) in which the X axis (SN7) was constructed by rotating SeN downward by 7, and the Y axis (¼SN7v) was constructed on N perpendicular to SN7. Methodical errors for each reference point were calculated using the Dahlberg formula: S2 ¼ Sd2/2n (d, difference between remeasured values; n, number of double measurements). The maximum error of all reference points was 0.220 mm horizontal and 0.172 mm vertical (Table 1). Six angular and seven linear parameters were analyzed. The linear parameters were Av (vertical measurement, A to X axis), Ah (horizontal measurement, A to Y axis), Bv, Bh, U1v, U1h, and U6v. The angular parameters were SNA, SNB, SN-U1, occlusal plane angle
A total of 57 skeletal class III patients (male:female ¼ 31:26, mean age ¼ 22.5 years) who underwent bimaxillary orthognathic surgery (Le Fort I osteotomy with/without MD and BSSRO for MS) at Seoul National University Dental Hospital and who were followedup for 1 year were selected for this study. All patients had pre- and post-operative orthodontic treatment. This study was approved by the institutional review board (CRI10035). Patients were classified into two groups according to the amount of MD: Group I had 2 mm or more MD (n ¼ 29; male:female 17:12; mean age 22.7 years), and Group II had less than 2 mm MD including vertical impaction or no vertical changes (n ¼ 28; male:female 14:14; mean age 22.4 years). 2.2. Surgical procedure Bimaxillary surgeries were performed by one oral and maxillofacial surgeon. In patients with MD, Le Fort I inclined osteotomy was performed to increase the bony height at the piriform aperture area to obtain direct bone contact at this area after downward movement of the maxilla, as described in our previous report (Yang and Hwang, 2012), while conventional Le Fort I osteotomy was performed in patients without MD. When there was a bone gap at the piriform aperture area despite Le Fort I inclined osteotomy, autogenous bone graft was performed to fill the bone gap. This technique resulted in sufficient bone resistance against postoperative occlusal force at the piriform aperture area to provide postoperative maxillary stability. The osteotomized maxillary segment was stabilized using four miniplates at the piriform aperture and zygomatic buttress area on both sides. All patients underwent modified BSSRO according to Obwegeser-Dal Pont's method (Dal Pont, 1961) for mandibular
Fig. 1. Determination of landmarks used in cephalometric analysis and in angular and linear measurements. S, sella; N, nasion; A, point A; B, point B; Me, menton; Go, gonion; Ar, articulare; U1, tip of upper central incisor; U6, mesiobuccal cusp of upper first molar; X axis (SN7), line drawn 7 to sella-nasion line; Y axis (SN7v), line on nasion, perpendicular to x-axis; OPA, occlusal plane angle; MPA, mandibular plane angle; PSA, proximal segment angle.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7 Table 1 Methodical errors in study. Reference point
X (mm)
Y (mm)
S N A B Me Go Ar U1 U6
0 0.034 0.159 0.172 0.047 0.146 0.112 0.072 0.132
0.129 0 0.117 0.220 0.197 0.214 0.131 0.095 0.185
Differences in distance from x- and y-axes determined through double measurement of reference points as calculated using the Dahlberg formula, S2 ¼ Sd2/2n; d ¼ difference between remeasured values; n ¼ number of double measurements. S, sella; N, nasion; A, point A; B, point B; Me, menton; Go, gonion; Ar, articulare; U1, tip of the upper central incisor; U6, mesiobuccal cusp of the upper first molar.
(OPA), mandibular plane angle (MPA), and proximal segment angle (PSA). Mandibular ramus angle (MRA) represents PSA after postoperative bony union of the PS and DS. 2.4. Statistical analysis Data from the cephalogram measurements were processed to obtain surgical movements (T1-T0) and postoperative relapse (T2-T1). Statistical analyses were performed with PASW 21 software (IBM Inc, Chicago, IL, USA). The KolmogoroveSmirnov test was performed to determine whether data had a normal distribution. To test whether the changes in variables over time were statistically significant, a paired t test was performed. A Student t test was used to compare the surgical movement and the postoperative relapse between two groups divided according to the amount of MD. In Group I, Pearson correlation coefficients were used to determine the correlation between the amount of intraoperative CWR of the PS and other surgical movements. Correlations between skeletal relapse and other surgical movements and/or other skeletal relapses were also analyzed using Pearson correlation coefficients in Group I. 3. Results 3.1. Surgical movement of the maxillomandibular complex In Group I, the maxilla was moved inferiorly with direct bone contact at the piriform aperture area by Le Fort I inclined osteotomy
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or interpositional autogenous bone graft. Intraoperative vertical movement of the maxilla was 4.26 ± 1.49 mm at point A and 4.88 ± 1.77 mm at U1. The maxilla moved 1.58 ± 2.66 mm backward at U1. There was CWR of the maxillomandibular complex (MMC), so OPA and MPA increased by 8.6 ± 3.4 and 4.2 ± 2.8 , respectively. In consequence, maxillary incisal inclination (SN-U1) decreased from 113.4 ± 8.1 to 105.6 ± 7.3 . The DS moved backward by 10.58 ± 5.42 mm at point B. There was significant CWR of the PS by 4.9 ± 3.0 (p < 0.001) (Tables 2 and 4). Intraoperative CWR of the PS was significantly associated with vertical movement of U1, U6, and point A by surgery (r ¼ 0.375, p ¼ 0.045; r ¼ 0.372, p ¼ 0.047; r ¼ 0.377, p ¼ 0.044, respectively) (Table 5). In Group II, U1 showed no statistically significant change in vertical and anteroposterior directions during surgery. The maxilla was rotated clockwise, OPA increased by 4.4 ± 4.1 and SN-U1 decreased by 4.8 ± 4.9 , while MPA was not changed by surgery. The DS moved backward by 10.51 ± 3.36 mm at point B, and the PS rotated clockwise by 2.9 ± 2.9 (Tables 3 and 4). There were significant differences between Groups I and II in all parameters except anteroposterior movements of point A and B. In Group I, point A, point B, and U1 were repositioned downward, and MMCs of Group I showed significantly larger CWR than those of Group II. In Group I, intraoperative CWR of the PS was significantly larger than Group II (p ¼ 0.010) (Table 4). 3.2. Postoperative relapse of the maxillomandibular complex In Group I, at the 1-year follow-up, a tendency for relapse was observed in all parameters except SNA, MPA, A-Y axis, and U6-X axis. While the maxilla showed slight upward movement by 0.86 ± 0.95 mm at point A, U1 moved upward by 1.17 ± 1.11 mm and forward by 1.68 ± 1.44 mm, resulting in a significant increase in incisal inclination by 5.5 ± 4.7 (p < 0.001) (Tables 2 and 4). Although there was significant CWR of the MMC intraoperatively, significant postoperative relapse in the direction of CCWR occurred only in the maxilla; 2.5 ± 2.2 in OPA (p < 0.001). The mandible was rotated significantly counterclockwise by 2.3 ± 1.7 at the 1-year follow-up (p < 0.001), and the mandible showed significant relapse by 2.13 ± 2.04 mm anteriorly and 1.31 ± 1.30 mm superiorly at point B (p < 0.001) (Tables 2 and 4). Mandibular relapse with CCWR, or decrease in MRA, was significantly correlated with intraoperative CWR of the PS (r ¼ 0.666, p < 0.001) (Table 4). In Group II, the maxilla showed no significant vertical relapse at point A at the 1-year follow-up, while U1 moved upward by
Table 2 Cephalometric variables of Group I at each time point. Parameter
T0
Angular measurement ( )
Linear measurement (mm)
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
81.0 ± 4.0 84.9 ± 5.1 113.4 ± 8.1 15.2 ± 6.5 34.4 ± 7.3 84.1 ± 6.6 52.62 ± 4.60 2.03 ± 4.14 93.02 ± 8.36 3.92 ± 8.91 73.88 ± 5.65 3.56 ± 6.02 70.29 ± 5.68
T1
82.7 ± 3.8 79.0 ± 3.5 105.6 ± 7.3 23.8 ± 5.3 38.6 ± 6.8 89.0 ± 5.8 56.88 ± 4.62 0.09 ± 4.21 95.87 ± 7.44 6.66 ± 6.23 78.77 ± 5.62 1.98 ± 5.80 71.23 ± 5.65
T2
82.9 ± 3.6 80.3 ± 3.7 111.1 ± 8.8 21.3 ± 6.0 36.4 ± 9.4 86.7 ± 5.8 56.02 ± 4.70 0.06 ± 4.01 94.56 ± 7.29 4.53 ± 6.70 77.59 ± 5.43 3.66 ± 5.74 71.13 ± 5.74
p value T0 vs. T1
T1 vs. T2
.001 <.001 <.001 <.001 <.001 <.001 <.001 .001 <.001 <.001 <.001 .003 .001
.075 <.001 <.001 <.001 .103 <.001 <.001 .893 <.001 <.001 <.001 <.001 .538
Data are presented as mean ± SD. Statistical analyses were conducted using the paired t test. T0, prior to surgery; T1, immediately postoperatively; T2, 1 year after surgery. OPA, occlusal plane angle; MPA, mandibular plane angle; PSA, proximal segment angle. See Table 1 for other abbreviations.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Table 3 Cephalometric variables of Group II at each time point. Parameter
T0
Angular measurement ( )
Linear measurement (mm)
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
T1
80.5 ± 3.2 84.5 ± 4.1 107.5 ± 9.0 21.0 ± 5.2 39.8 ± 5.7 86.4 ± 5.5 60.13 ± 4.65 1.67 ± 4.99 110.02 ± 7.79 4.28 ± 9.16 85.74 ± 5.26 3.40 ± 7.23 78.01 ± 5.61
T2
82.2 ± 3.3 79.4 ± 3.8 102.8 ± 8.5 25.4 ± 5.9 39.4 ± 5.4 89.2 ± 5.2 59.45 ± 4.56 0.38 ± 5.32 105.68 ± 6.78 6.23 ± 8.61 85.19 ± 4.92 3.55 ± 7.57 75.35 ± 5.60
p value
82.0 ± 3.4 79.7 ± 3.8 104.8 ± 8.4 24.1 ± 6.2 39.2 ± 5.7 88.6 ± 5.4 59.17 ± 4.62 0.24 ± 5.50 104.88 ± 6.91 5.05 ± 8.76 84.76 ± 5.09 4.19 ± 7.71 75.30 ± 6.05
T0 vs. T1
T1 vs. T2
<.001 <.001 <.001 <.001 .401 <.001 .031 <.001 <.001 <.001 .114 .710 <.001
.120 .014 .002 <.001 .329 .029 .112 .374 .003 <.001 .030 .010 .839
Data are presented as mean ± SD. Statistical analyses were conducted using the paired t test. See Tables 1 and 2 for abbreviations.
Table 4 Mean amounts of surgical movement and postoperative relapse in Groups I and II. Surgical movement
SNA SNB SN-U1 OPA MPA PSA Av Ah Bv Bh U1v U1h U6v
Postoperative relapse
Group I
Group II
p value
Group I
Group II
p value
1.7 ± 2.5 5.9 ± 3.0 7.8 ± 4.0 8.6 ± 3.4 4.2 ± 2.8 4.9 ± 3.0 4.26 ± 1.49 1.94 ± 2.73 2.85 ± 3.833 10.58 ± 5.42 4.88 ± 1.77 1.58 ± 2.66 0.94 ± 1.36
1.8 ± 1.8 5.1 ± 1.7 4.8 ± 4.9 4.4 ± 4.1 0.4 ± 2.7 2.9 ± 2.9 0.69 ± 1.60 2.05 ± 2.37 4.34 ± 3.62 10.51 ± 3.36 0.55 ± 1.77 0.15 ± 2.10 2.66 ± 2.23
.909 .216 .013 <.001 <.001 .010 <.001 .870 <.001 .957 <.001 .009 <.001
0.2 ± 0.6 1.4 ± 1.1 5.4 ± 4.7 2.5 ± 2.2 2.2 ± 7.0 2.3 ± 1.7 0.86 ± 1.95 0.03 ± 1.26 1.31 ± 1.30 2.13 ± 2.01 1.17 ± 1.11 1.68 ± 1.44 0.10 ± 0.89
0.2 ± 0.7 0.4 ± 0.7 2.0 ± 3.1 1.3 ± 1.7 0.2 ± 1.3 0.7 ± 1.6 0.28 ± 0.89 0.14 ± 0.85 0.80 ± 1.28 1.18 ± 1.37 0.43 ± 1.00 0.64 ± 1.22 0.05 ± 1.18
.018 <.001 .002 .028 .155 <.001 .019 .539 .142 .044 .011 .005 .835
Data are presented as mean ± SD. Statistical analyses were conducted using the Student t test. See Tables 1 and 2 for abbreviations.
0.43 ± 1.00 mm and forward by 0.64 ± 1.22 mm, resulting in a significant increase in incisal inclination by 2.0 ± 3.1 (p ¼ 0.002) (Tables 2 and 4). In addition, OPA decreased by 1.3 ± 1.7 postoperatively (p < 0.001). The mandible was rotated significantly counterclockwise by 0.7 ± 1.6 at the 1-year follow-up (p ¼ 0.029), and the mandible showed significant relapse by 1.18 ± 1.37 mm anteriorly and 0.80 ± 1.28 mm superiorly at point B (p < 0.001; p ¼ 0.003, respectively) (Tables 2 and 4). The postoperative CCW rotation of the mandible (PSA) was significantly larger in Group I than in Group II (p < 0.001). Consequently, it was found that the forward relapse of B point was significantly greater in Group I than in Group II (p ¼ 0.044). Similarly, the postoperative increase in SNB was significantly greater in Group I than in Group II (p < 0.001). One year after surgery, U1 showed a significant relapse superiorly and anteriorly
in both Groups I and II. Therefore, SN-U1 was increased in both Groups I and II; however, the increase in SN-U1 was significantly greater in Group I than in Group II (p ¼ 0.002). 3.3. Intervariable correlation The correlations between intraoperative CWR of the PS and other surgical movements were analyzed in Group I. Intraoperative CWR of the PS was significantly associated with surgical change in SNB (r ¼ 0.853, p < 0.001), amount of MS at point B (r ¼ 0.867, p < 0.001), and vertical movement of U1, U6, and point A by surgery (r ¼ 0.375, p ¼ 0.045; r ¼ 0.372, p ¼ 0.047; r ¼ 0.377, p ¼ 0.044, respectively) (Table 5). Mandibular relapse with CCWR was significantly correlated with intraoperative CWR of the PS (r ¼ 0.666, p < 0.001), amount of MS at point B (r ¼ 0.867,
Table 5 Correlation between clockwise rotation of the proximal segment and independent parameters. Surgical movement
Pearson correlation p value
SNA
SNB
SN-U1
OPA
MPA
Av
Ah
Bv
Bh
U1v
U1h
U6v
.041 .832
.853*** <.001
.139 .472
.160 .408
.327 .083
.377* .044
.010 .959
.204 .290
.867*** <.001
.375* .045
.101 .604
.372* .047
Statistical analyses were conducted using Pearson correlation coefficients. See Tables 1 and 2 for abbreviations. * p < .05 *** p < .001.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
.518** .004 .423* .022
.459* .012
.403* .030 .581*** <.001 .316 .094
.177 .359 .609*** <.001 .110 .572 .124 .520 .202 .292 .203 .291 .371* .047 .438* .017
.505** .005 .151 .435 .936*** <.001 .469* .010 .601*** <.001 .339 .072
.982*** <.001 .867*** <.001 .342 .070 1
.354 .059 .304 .109 .159 .409 .304 .109 .301 .113 .209 .276 .087 .653 .260 .173 .397* .033 .245 .200 .360 .055 .016 .936 .062 .749 .034 .861 .083 .668 .325 .085 .509** .005 .160 .408 .100 .607 .135 .484 .091 .638 .193 .316 .339 .072 .037 .849 .260 .174 .129 .506 .204 .289 .126 .515 correlation
correlation
correlation
correlation
correlation
correlation
.541** .002 .666*** <.001 .075 .698 .561** .002 .210 .274 .328 .083 .592*** <.001 SN-U1
U1h
U1v
Bh
Av
MRA
Statistical analyses were conducted using Pearson correlation coefficients. MRA, mandibular ramus angle. See Tables 1 and 2 for other abbreviations. * p < .05 ** p < .01 *** p < .001.
Bh U1h
.601*** <.001 .124 .520 .385* .039 .581*** <.001 .518** .004 1 .469* .010 .110 .572 .659*** <.001 .403* .030 1
U1v MPA
.616*** <.001 .489** .007 .190 .323 .651*** <.001 .420* .023 .193 .316 .350 .063 .621*** <.001 .365 .052 .209 .277 .562** .002 .666*** <.001 .411* .027 .426* .021 .505** .005 1
OPA SN-U1
.336 .074 .267 .161 .135 .486 .312 .100 .087 .652 .121 .533 .011 .954 .532** .003 .410* .027 .096 .619 .524** .004 .206 .283 .361 .054 .483** .008 correlation
Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value Pearson p value SNB Relapse
U1h U1v MPA OPA PSA
1
Relapse
SNB SN-U1 SNB
Bh Surgical movement
Table 6 Correlation between clockwise rotation of the proximal segment and independent parameters.
Some amount of skeletal or dental relapse after orthognathic surgery is inevitable (Komori et al., 1989). In particular, MS and MD are regarded as the most problematic movements, with a high relapse tendency (Proffit et al., 2007). If the vertical growth of the maxilla is insufficient, the maxilla is moved downward to create a normal exposure of the maxillary incisors during orthognathic surgery. The vertical deficiency of the maxilla determines the amount of MD. Direct bone contact in MD is important to achieving stable postoperative results (Fig. 2C) (Yang and Hwang, 2012). If the size of the bone defect exceeded 3 mm, interpositional bone graft was needed because bone recovery would be inadequate (Ueki et al., 2011). Lack of long-term stability may be due to insufficient bone contact at the osteotomy site, which prevents primary bone healing (Jünger et al., 2003). The Le Fort I inclined osteotomy is a modified technique designed to obtain direct bone contact after MD (Yang and Hwang, 2012). The lateral wall of the nasal cavity is osteotomized in the superiorposterior direction by changing the inclination of the reciprocating saw. The bony height at the piriform aperture area can be increased with this technique. Direct bone contact can be most effectively obtained by clockwise maxillary rotation accomplished with anterior downward movement and simultaneous posterior impaction (Yang and Hwang, 2012). When the Le Fort I inclined osteotomy was performed for MD in our previous study, the amount of vertical relapse at point A was 0.96 ± 0.70 mm (34.4%) of the 2 to 4 mm MD and 0.68 ± 1.04 mm (12.5%) of the 4 mm or more MD (Yang and Hwang, 2012). The results seem to be more stable than those obtained for MD using conventional Le Fort I osteotomy, which showed a greater than 40% tendency for vertical relapse, with 2 to 4 mm maxillary downward movement and less than 20% tendency with 4 mm or more MD (Proffit et al., 2007). If total setback of the maxilla is performed concurrently with MD, direct bone contact may be impractical in Le Fort I inclined osteotomy (Yang and Hwang, 2012). If direct bone contact is not achieved, it may be helpful to perform interpositional bone graft with hydroxyapatite and autogenous bone graft and fixation using a rigid plate (Perez et al., 1997). Perez et al. reported an average 28.2% vertical relapse in patients undergoing Le Fort I MD of an average 4.6 mm (Perez et al., 1997). We performed autogenous bone graft in patients without direct bone contact after MD. The amount of MS is determined by final occlusion. In addition, the anterior and posterior position of the chin is appropriately controlled by moving the posterior maxilla vertically. Many studies have identified several contributing factors for skeletal relapse after mandibular setback surgery, indicating that the causes of skeletal
MRA
4. Discussion
.339 .072 .202 .292 .153 .428 .316 .094 .423* .022 .459* .012 1
p < 0.001), and amount of MD at U1 (r ¼ 0.397, p ¼ 0.033). Postoperative CCWR of the mandible also has a significant association with mandibular forward (r ¼ 0.505, p ¼ 0.005) and upward (r ¼ 0.489, p ¼ 0.007) relapse (Table 6). In maxillary vertical relapse, skeletal relapse at point A showed a significant correlation with surgical increase in MPA (r ¼ 0.509, p ¼ 0.005), while it showed no statistical correlation with other relapse variables. Conversely, vertical dental relapse at U1 showed a significant correlation only with postoperative increase in SNB (r ¼ 0.469, p ¼ 0.010), anterior relapse at point B (r ¼ 0.403, p ¼ 0.030), and decrease in MPA (r ¼ 0.420, p ¼ 0.023). Similarly, the horizontal dental relapse at U1 showed a significant correlation with postoperative increase in SNB (r ¼ 0.601, p ¼ 0.001) and anterior relapse at point B (r ¼ 0.581, p < 0.001). The greater the amount of MS and the larger intraoperative CWR of the PS was, the greater U1 protruded labially postoperatively (r ¼ 0.438, p ¼ 0.017; r ¼ 0.592, p < 0.001, respectively) (Table 6).
5
.936*** <.001 .609*** <.001 .036 .852 1
H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
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H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
Fig. 2. Schematic drawing of pushing and rebounding action in MD with MS. (A) Before surgery. (B) Surgical movement of MD with MS. MD and MS together causes vertical bone step (yellow asterisk). Intraoperative CWR of the PS due to adjustment of the inferior borders of the PS and the DS. (C) Immediately after surgery. Le Fort I inclined osteotomy leads to a direct bone contact after MD due to the beveled bone surface at the piriform aperture area (black circle). (D) Postoperative relapse. CCWR of the mandible and skeletal (vertical) and dental (vertical and horizontal) relapse of the maxilla are observed. (E) One year after surgery.
relapse are multifactorial (Mucedero et al., 2008; Jakobsone et al., 2011; Yang and Hwang, 2014). Among the various factors contributing to skeletal relapse, intraoperative CWR of the PS is considered a primary relapse factor in BSSRO for mandibular prognathism (Franco et al., 1989; Komori et al., 1989; Politi et al., 2004; Cho, 2007; Proffit et al., 2007; Yang and Hwang, 2014). Intraoperative CWR of the PS (2.9e5.4 ) and subsequent postoperative CCWR (0.9e3.5 ) of the mandible have been reported in previous studies (Mobarak et al., 2000; Politi et al., 2004; Jakobsone et al., 2011). When the PS is rotated clockwise, the masseter and temporal muscles attached to the PS are stretched. Rebound of the mandibular ramus to its original position is often accompanied by anterosuperior relapse of the mandible, especially when rigid fixation is performed (Franco et al., 1989; Yang and Hwang, 2014; Santos et al., 2017). In this study, strong relationships were revealed among CWR of the PS during surgery, postoperative CCWR
of the mandible, and mandibular forward and upward relapse during the postsurgical phase. CWR of the PS is influenced by several parameters, particularly vertical bone steps, which are height differences between the inferior border of the DS and PS when the DS is positioned in the final occlusal state (Yang and Hwang, 2014). The amount of vertical bone step is positively correlated with the amount of MS and MD (Yang and Hwang, 2014). Therefore, the relapse tendencies of the MMC after MD with MS have to be closely linked each other. The anterior relapse after MS was different according to the amount of MD. In this study, Group I with great MD, the intraoperative CWR and postoperative CCWR of the PS was greater than that of the Group II with small or no MD, while there was no significant difference of the amount of MS between Groups I and II. Consequently, the anterior relapse of the mandible was greater in Group I than in Group II despite the same amount of MS in Groups I and II.
Fig. 3. Lateral cephalograms taken at T0, T1 and T2 of a representative case. Tracings are superimposed between T0 and T1, T1 and T2.
Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022
H.J. Yang, S.J. Hwang / Journal of Cranio-Maxillo-Facial Surgery xxx (2018) 1e7
In Group I, the maxilla was repositioned inferiorly by 4.26 ± 1.49 mm at point A intraoperatively, and the amount of MS was 10.58 ± 5.42 mm at point B. The PSA of the mandible increased by 4.9 ± 3.0 as the maxilla moved downward and the DS moved backward (Fig. 2B). The mandible was rotated significantly counterclockwise by 2.3 ± 1.7 at the 1-year follow-up with anterior and superior relapse at point B. The maxilla showed vertical relapse by 0.86 ± 0.95 mm at point A. Because of the Le Fort I inclined osteotomy and direct bone contact with or without interpositional bone graft, the maxilla showed more stable skeletal progression. There was no significant change in horizontal direction, and there was a significant difference in vertical direction at the point A. However, vertical relapse of less than 1 mm suggests that the relapse may have resulted from bony remodeling during bone healing (Fig. 2) (Yang and Hwang, 2012). However, even if skeletal relapse was prevented, dental relapse was inevitable. As the mandible undergoes forward relapse, it collides with the maxillary incisors, which promotes significant relapse of U1 vertically and horizontally. The vertical relapse of U1 was 1.17 ± 1.11 mm upward, and the horizontal relapse was 1.68 ± 1.44 mm forward. This may cause difficulty during postoperative orthodontic treatment and aesthetic deterioration due to labial protrusion of the maxillary incisor (Figs. 2E and 3). 5. Conclusion Le Fort I inclined osteotomy is recommended to obtain direct bone contact when moving the maxilla inferiorly for more stable results. When MS and MD coexist, the PS should be fixed while maintaining vertical bone step to prevent CWR of the PS. CWR of the PS during surgery can lead to mandibular forward and upward relapse during the postsurgical phase, which can increase the labial inclination of the maxillary incisors. Because this study involves a small number of cases, further investigation with a larger number of patients may provide more information on predictable postoperative stability. Conflicts of interest The authors have no financial interests to declare in relation to the content of this article. Acknowledgements This study was supported by a grant (HI13C1491) from the Korea Health Technology R&D Project, Ministry of Health and Welfare, Republic of Korea. References Cho HJ: Long-term stability of surgical mandibular setback. Angle Orthod 77: 851e856, 2007 Chou JI, Fong HJ, Kuang SH, Gi LY, Hwang FY, Lai YC, et al: A retrospective analysis of the stability and relapse of soft and hard tissue change after bilateral sagittal split osteotomy for mandibular setback of 64 Taiwanese patients. J Oral Maxillofac Surg 63: 355e361, 2005 Dal Pont G: Retromolar osteotomy for the correction of prognathism. J Oral Surg Anesth Hosp Dent Serv 19: 42e47, 1961
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Please cite this article in press as: Yang HJ, Hwang SJ, Relapse related to pushing and rebounding action in maxillary anterior downgraft with mandibular setback surgery, Journal of Cranio-Maxillo-Facial Surgery (2018), https://doi.org/10.1016/j.jcms.2018.05.022