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Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback
YIJOM-4252; No of Pages 8
Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx https://doi.org/10.1016/j.ijom.2019.07.012, available online at https://www.sciencedirect.com
Clinical Paper Orthognathic Surgery
Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback
H. J. Yang1,2, Y.-E. Jung2, I. J. Kwon3, J.-Y. Lee2, S. J. Hwang1,2,4 1
Orthognathic Surgery Center, Seoul National University Dental Hospital, Republic of Korea; 2 Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Republic of Korea; 3Department of Oral and Maxillofacial Surgery, Soonchunhyang University Bucheon Hospital, Republic of Korea; 4Dental Research Institute, Seoul National University, Republic of Korea
H. J. Yang, Y. -E. Jung, I. J. Kwon, J. -Y. Lee, S. J. Hwang: Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback. Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx. ã 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Abstract. This study used three-dimensional computed tomography and polysomnography to evaluate the effect of a large mandibular setback on the postoperative pharyngeal airway space and obstructive sleep apnoea (OSA). Twelve patients who underwent bimaxillary surgery for a mandibular setback movement of >9 mm were included in this study. Changes in the pharyngeal airway space and polysomnography parameters based on the surgical movements were analyzed. The median mandibular setback movement was 11.08 mm. The total pharyngeal, oropharyngeal, and hypopharyngeal volumes, and the retroglossal cross-sectional area were significantly decreased postoperatively (P = 0.006; P = 0.005; P = 0.012; P = 0.005, respectively). The apnoea–hypopnoea index (AHI) increased significantly after surgery (P = 0.021). There were significant positive correlations between the preoperative inferiorly located hyoid bone and both AHI and respiratory disturbance index (RDI) postoperative (P = 0.008 and P = 0.027) and between the postoperative inferiorly dislocated retropalatal level and both AHI and RDI postoperative (P = 0.002 and P = 0.014). Four patients (33.3%) developed new onset OSA postoperatively. Large mandibular setback movements significantly reduced the pharyngeal airway space in the setting of bimaxillary surgery (P = 0.006).
Mandibular setback surgery is typically performed to improve the functional and aesthetic characteristics of mandibular 0901-5027/000001+08
prognathism. However, mandibular setback surgery is thought to change the tongue position and narrow the pharyngeal
Key words: large mandibular setback; pharyngeal airway space; computed tomography; polysomnography; obstructive sleep apnoea. Accepted for publication 23 July 2019
airway space (PAS)1. The main concern with these pharyngeal dimensional changes is their potential to cause obstructive sleep
ã 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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apnoea (OSA)2. Since Guilleminault et al.3 reported two patients who developed OSA after mandibular setback surgery, many studies have investigated these postoperative consequences using lateral cephalograms, three-dimensional (3D) computed tomography (CT), and polysomnography (PSG)1,2,4–15. A few studies using CT have found that there is no decrease in the PAS8 or that there is an increase in the total PAS after bimaxillary surgery for mandibular setback movement13,14. In contrast, most other studies have shown that patients have a reduced oropharyngeal space, reduced cross-sectional area (CSA) posterior to the tongue and soft palate, or decreased width of the PAS after mandibular setback surgery7,13,15–17. Other groups have also speculated that mandibular setback surgery can induce OSA15,18. The most accurate method of diagnosing surgically-induced OSA is overnight PSG11,12,19. In the first study in which OSA was shown to develop after mandibular setback surgery, the diagnosis was made using postoperative PSG3. The number of previous studies that have evaluated pre- and postoperative PSG is limited due to its high cost and patient hesitance to participate in these paired evaluations in an unfamiliar laboratory environment4,11– 13,19,20 . It is logical to postulate that the further the mandible moves backward, the more the PAS will be reduced; therefore, the prevalence of OSA will be increased after mandibular setback surgery. This postulation is supported by a recent study that identified a correlation between the extent of the jaw movements and the change in airway measurement in the nasopharynx and oropharynx10. However, most studies evaluating PAS changes have been performed on patients with a small mean mandibular setback movement (<7 mm)11–13,19,20. In the report by Hasebe et al.4, where the mean extent of mandibular setback was 5.8 mm in the group that underwent bimaxillary surgery and 8.4 mm in the group that underwent bilateral sagittal split ramus osteotomy (BSSRO), two patients with a mandibular setback >12–13 mm developed postoperative OSA. As no previous studies on this subject have reported the outcomes following a large mean mandibular setback movement, it was hypothesized that the volume of the pharyngeal airway would decrease significantly after a large mandibular setback, resulting in an increase in the incidence of postoperative OSA. The aims of the study were to evaluate the effect of large mandibular setback movements
(>9 mm) on postoperative changes of PAS using 3D CT and to evaluate changes in PSG parameters associated with the occurrence of OSA. Materials and methods Patients
The investigators designed and implemented a prospective observational study including patients with severe mandibular prognathism undergoing bimaxillary surgery, who had no previous history of OSA based on the apnoea–hypopnoea index (AHI). The study design and reports followed the STROBE guidelines (Strengthening the Reporting of Observational Studies in Epidemiology). This study was approved by the Institutional Review Board of Seoul National University Dental Hospital (CRI12036). Patients who were anticipated to undergo bimaxillary surgery with a large extent of mandibular setback (during prediction tracing) underwent an overnight formal PSG in the sleep laboratory 1 month before and 6 months after surgery. For all patients, 3D CT images were acquired 1 month before (T0) and 4–6 months after surgery (T1). Patients with mandibular setback movements of >9 mm at B point at T1 were included in this study. Patients with a preoperative AHI 5 were excluded, while patients with a preoperative respiratory disturbance index (RDI) 5 and preoperative AHI < 5 were included. Patients were excluded if they only underwent BSSRO, had cleft palate or a craniofacial syndrome, had undergone previous orthognathic surgery (including genioplasty), or had any breathing disorder (including allergic rhinitis and inflammatory nasal/ nasopharyngeal mucosa). Patients who were on medications that are associated with sleep disturbance were also excluded. The mean body mass index (BMI) was measured 1 month before and 6 months after surgery. Overweight or obese patients, based on a BMI > 25 kg/m2 at the time of postoperative PSG, were also excluded to avoid the weight-associated effect of mandibular setback on the airway.
Surgery
Le Fort I osteotomy and BSSRO with/ without genioplasty were performed in all patients by a single surgeon. Bone trimming and excision in the ramus osteotomy region was performed as necessary for the setback21. The surgery always
included correction of the maxillary midline, canting, and yaw deviation. In addition, surgical planning for maxillary anteroposterior (A-P) movement and maxillary posterior impaction were performed after considering the patient’s anatomical status and his/her preference for an aesthetic facial profile. Evaluation of surgical movements
3D CT images were acquired using a CT scanner (Somatom Sensation 10; Siemens, Munich, Germany) with the following parameters: tube voltage of 120 kVp, tube current of 80 mAs, and slice thickness of 0.75 mm. Digital image files were exported in DICOM format (Digital Imaging and Communications in Medicine) and imported into OnDemand 3D software (Cybermed, Inc., Seoul, Korea). After reorienting to the Frankfort horizontal (FH) plane, sella (S), and nasion (N), the 3D images from T0 and T1 were superimposed automatically based on the maximum mutual information algorithm22,23. The preoperative and postoperative 3D positions of the reference points (A point, B point, posterior nasal spine (PNS), right and left lingula) were measured. Methodical errors for each reference point were calculated using the Dahlberg formula: S2 = Sd2/2n (d, the difference between repeatedly measured values; n, the number of double measurements). The maximum error for all reference points was 0.164 mm in the A-P direction and 0.272 mm vertically. Polysomnography evaluation
The standard recording parameters during PSG included the following: AHI (/h), RDI (/h), sleep onset (min), sleep efficiency (%), sleep stages 1 (%), 2 (%), and 3 (%), rapid eye movement sleep (REM) (%), and arousal index (/h). Arterial oxygen saturation (SaO2) was measured continuously using pulse oximetry. Evaluation of the pharyngeal airway
Digital image files from 3D CT were imported into Invivo Dental software (Anatomage, San Jose, CA, USA). The FH plane was constructed to reorient the 3D images. For two-dimensional analysis of the PAS, the pharyngeal airway of each patient was studied at three levels (Fig. 1). The largest transverse width (TW), A-P length, and CSA were measured at these levels. After defining two reference lines (x-axis, i.e. the line tangential to the inferior portion of the sella turcica and parallel
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Fig. 1. Analysis of the airway on computed tomography. Three airway levels (dotted lines, a–c) and reference planes (solid lines) were used to divide the airway into three regions (e–g). The airway levels are parallel to the Frankfort horizontal (FH) plane. The CV1, CV2, and CV4 planes are parallel to the FH plane through the most inferior point of each cervical vertebra. (a) Retro-PNS level; (b) retropalatal level, i.e. the level of the most posterior point of the soft palate; (c) retroglossal level, i.e. the level of the most posterior point of the tongue base; (d) the position of the hyoid bone (the most anterosuperior hyoid bone point); (e) nasopharynx between the PNS–Vp and CV1 plane; (f) oropharynx between the CV1 and CV2 planes; (g) hypopharynx between the CV2 and CV4 planes. PNS, posterior nasal spine; Vp, the most posterior part of the ala of vomer; x-axis, the line tangent to the inferior point of the sella turcica and parallel to the FH plane; y-axis, the line on nasion and perpendicular to x-axis.
to the FH plane; y-axis, i.e. the line perpendicular to the x-axis and passing through N), the relative positions of these three levels and the hyoid bone were determined (Fig. 1). In order to evaluate the airway volume, the threshold value was set at a range of 1024 to 600 Hounsfield units, where the pharyngeal airway could be effectively differentiated from the neighbouring soft tissue. The pharyngeal airway was divided into three regions, including the nasopharyngeal, oropharyngeal, and hypopharyngeal volumes. These regions were defined using the PNS and cervical vertebra (CV) references according to a previous report16 (Fig. 1). Statistical evaluation
The Kolmogorov–Smirnov test was performed to determine whether values had normal distributions. Accordingly, the surgical movements on CT, PSG vari-
ables, and the pharyngeal airway volume, length, and area were compared using the Wilcoxon matched-pairs signed-rank test. Spearman’s rank correlation coefficient was determined between the PSG variables, airway parameters, and surgical movement. P-values of <0.05 were considered statistically significant. Results
Twelve patients were included in this study. The mean age at surgery was 21.8 2.9 years. The median BMI preoperatively (21.1 kg/m2, range 17.8–25.2 kg/ m2) and postoperatively (20.8 kg/m2, range 17.8–24.6 kg/m2) were not statistically different. The patient demographic data are shown in Table 1. Surgical movements
The maxillary movement at A point (mean 0.65 mm, ranging from 1.23 mm back-
ward to 4.54 mm forward) was not statistically significant. The PNS showed significant superior and anterior movements. The median mandibular backward movements were 11.08 mm (range 9.61– 14.26 mm) at B point (P = 0.002) and 8.76 mm (range 4.80–14.82 mm) at the lingula (P = 0.002). There were significant backward and upward movements at B point (P = 0.002 and P = 0.023, respectively) and the lingula (P = 0.002 and P = 0.010, respectively) (Table 2). Polysomnography measurement
PSG evaluation showed that the postoperative sleep quality was disturbed compared to the preoperative sleep quality. Two patients showed mild sleep apnoea with RDI scores of 5.9 and 9.1 before surgery. After surgery, seven patients had increased RDI scores. Five patients had mild sleep apnoea with RDI scores of 5.3–14.8. Four of these five patients de-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Table 1. Patient demographic data.
Patient
Sex
Age (years)
Anteroposterior movement (mm)a A point
1 2 3 4 5 6 7 8 9 10 11 12
M M F F F M F M M F M F
30 23 22 21 19 22 21 22 22 20 22 18
0.86 1.37 0.66 0.32 0.64 2.22 0.16 1.28 1.23 1.19 4.54 2.16
B point 10.60 12.88 12.06 12.29 10.36 9.61 13.79 14.26 11.56 10.02 10.34 9.91
Vertical movement (mm)a A point
PNS
0.62 0.61 0.48 0.27 1.66 4.69 3.66 1.08 1.38 3.51 3.64 0.17
3.41 4.92 3.25 0.15 8.41 10.21 5.39 2.34 1.65 0.86 7.47 4.23
Volumetric change of pharynx (mm3)
9713 5162 5007 3177 196 176 561 3073 2702 9321 203 3251
Preoperative PSG
Postoperative PSG
AHI (/h)
RDI (/h)
BMI (kg/m2)
AHI (/h)
RDI (/h)
BMI (kg/m2)
0.3 2 0.2 0.5 0 1.3 0.2 0.2 2.9 1.4 0.5 0.2
0.3 2 1.6 1.2 0 1.8 1.4 3.1 9.1 4.6 5.9 1.7
20.7 24.2 21.8 19.8 23.6 25.2 18.9 18.9 21.5 23.6 17.8 19.3
1.4 8.2 0.3 0.2 0.3 6.3 0 7 5.2 2.1 1 0
2.1 14.6 0.3 0.4 2.3 11.2 0.3 14.8 12.5 5.3 2.8 0.3
20.8 24.6 22.1 19.8 21.6 23.4 17.9 18.9 20.8 24.0 17.8 18.5
AHI, apnoea hypopnoea index; BMI, body mass index; F, female; M, male; PNS, posterior nasal spine; PSG, polysomnography; RDI, respiratory disturbance index. a Negative value of anteroposterior movement, backward movement; negative value of vertical movement, downward movement. Table 2. Surgical movements in the skeletal reference points following bimaxillary surgery for mandibular setback movement.
A point (mm) B point (mm) PNS (mm) Lingula (mm)
Anteroposterior Vertical Anteroposterior Vertical Anteroposterior Vertical Anteroposterior Vertical
Surgical movementa Median (min, max)
P-valueb
0.65 ( 1.23, 4.54) 0.38 ( 3.51, 4.69) 11.08 ( 14.26, 9.61) 2.13 ( 5.01, 15.21) 1.02 ( 0.39, 7.27) 3.82 ( 0.15, 10.21) 8.76 ( 14.82, 4.80) 4.36 ( 4.52, 9.01)
0.136 0.530 0.002** 0.023* 0.005** 0.003** 0.002** 0.010*
PNS, posterior nasal spine. a In horizontal movement: positive value, forward movement; negative value, backward movement. In vertical movement: positive value, upward movement; negative value, downward movement. b Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05, **P < 0.01.
veloped OSA after surgery (Table 1). The median RDI increased from 1.8 (range 0– 9.1) to 2.6 (range 0.3–14.8) from pre- to postoperative, but the difference was not significant (Table 3). All of the patients had normal AHI values before surgery. Postoperatively, nine patients had increased AHI scores, while four developed mild sleep apnoea with AHI scores >5 (Table 1). The median AHI increased significantly from 0.4 (range 0–2.9) to 1.2 (range 0–8.2) (P = 0.021) from preto postoperative, although the BMI did not change significantly. Sleep efficiency decreased significantly after surgery by a median 4.4%, ranging from 29.5% to 5.5% (P = 0.034) (Table 3). Pharyngeal airway measurements
The total (P = 0.006), oropharyngeal (P = 0.005), and hypopharyngeal (P = 0.012) volumes all decreased significantly. Although there was no significant change in the PAS at the retro-PNS and retropalatal levels, the CSA and A-P
length at the retroglossal level decreased significantly by a median 82.1 mm2 (range 234.1 to 33.3 mm2, P = 0.005) and 2.5 mm (range 22.5 to 3.9 mm, P = 0.034), respectively. The hyoid bone was also displaced backward by 5.4 mm (range 2.0 to 10.7 mm) (P = 0.006) (Table 4). Correlations among surgical movements, pharyngeal airway measurements, and PSG variables
Patient age was positively correlated with postoperative AHI and AHI score change P = 0.025; rs = 0.635, (rs = 0.640, P = 0.027, respectively). In addition, the postoperative SaO2 was negatively correlated with patient age (rs = 0.759, P = 0.004). However, all of the patients in this study were in their late teens and early 20s, except for one patient. The preoperative pharyngeal airway volume was not correlated with postoperative AHI, RDI, or changes in the AHI and RDI. In contrast, postoperative SaO2 and the change between the pre- and postop-
erative SaO2 were negatively correlated with the total pharyngeal airway volume preoperative (rs = 0.651, P = 0.022; rs = 0.661, P = 0.027, respectively). In addition, the change between pre- and postoperative SaO2 showed a negative correlation with preoperative nasopharyngeal volume (rs = 0.744, P = 0.009). This result indicates that postoperative SaO2 is likely to be lower in patients with a large preoperative PAS than in those with a smaller preoperative PAS. The preoperative vertical position of the retropalatal level was positively correlated with the RDI score change (rs = 0.615, P = 0.033). In other words, the postoperative RDI increased more in patients with a lower preoperative vertical position of the retropalatal level than in those with a higher preoperative retropalatal level. In addition, an inferiorly located hyoid bone preoperative was positively correlated with RDI and AHI scores postoperative P = 0.027; rs = 0.719, (rs = 0.634, P = 0.008, respectively), as well as with the change in AHI score (rs = 0.753,
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Table 3. Results of polysomnography.
AHI (/h) RDI (/h) Sleep onset (min) Sleep efficiency (%) NREM sleep Stage 1 (%) Stage 2 (%) Stage 3 (%) REM sleep (%) SaO2 (%) Arousal index (/h) BMI (kg/m2)
Preoperative Median (min, max)
Postoperative Median (min, max)
Surgical change Median (min, max)
P-valuea
0.4 (0, 2.9) 1.8 (0, 9.1) 14.0 (3.0, 88.5) 88.7 (59.0, 96.1)
1.2 (0, 8.2) 2.6 (0.3, 14.8) 11.3 (0.5, 95.5) 81.1 (52.3, 96.4)
0.6 ( 0.3, 6.8) 1.3 ( 3.1, 12.6) 0 ( 25.0, 37.0) 4.4 ( 29.5, 5.5)
0.021* 0.182 1.000 0.034*
8.0 (4.3, 18.6) 56.5 (47.2, 78.6) 17.3 (3.1, 27.0) 18.0 (4.7, 31.1) 98 (97, 99) 7.7 (2.4, 17.6) 21.1 (17.8, 25.2)
8.1 (4.3, 24.1) 58.9 (42.2, 72.8) 14.5 (0.1, 31.9) 17.7 (0, 27.7) 98.0 (97, 100) 8.7 (3.7, 18.5) 20.8 (17.8, 24.6)
0.2 ( 8.0, 10.0) 0.6 ( 10.3, 12.0) 3.9 ( 13.4, 18.7) 0.3 ( 14.0, 22.5) 0 ( 1, 3) 0.6 ( 9.3, 12.0) 0 ( 2.0, 0.4)
0.689 0.583 0.286 0.695 0.739 0.906 0.138
AHI, apnoea–hypopnoea index; BMI, body mass index; NREM, non-rapid eye movement sleep; RDI, respiratory disturbance index; REM, rapid eye movement sleep; SaO2, arterial oxygen saturation. a Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05.
Table 4. Results of pharyngeal airway measurements.
Volume Total (mm3) Nasopharynx (mm3) Oropharynx (mm3) Hypopharynx (mm3) Retro-PNS level A-P length (mm) TW (mm) CSA (mm2) Retropalatal level A-P length (mm) TW (mm) CSA (mm2) Vertical position (mm) Retroglossal level A-P length (mm) TW (mm) CSA (mm2) Vertical position (mm) Hyoid bone position A-P (mm) Vertical (mm)
Preoperative Median (min, max)
Postoperative Median (min, max)
Surgical change Median (min, max)
P-valuea
22,981 (19,303, 32,430) 8132 (4174, 11,082) 5956 (3591, 9513) 9060 (6841, 12,636)
21,128 (12,419, 23,463) 7512 (4744, 9456) 4476 (3061, 5482) 8451 (4614, 10,534)
3125 ( 9713, 561) 360 ( 3668, 2885) 1413 ( 4031, 159) 1954 ( 4753, 821)
0.006** 0.433 0.005** 0.012*
20.6 (4.2, 28.8) 27.5 (13.4, 30.7) 449.7 (43.4, 631.2)
23.2 (14.5, 26.9) 26.7 (21.9, 29.6) 486.8 (323.3, 572.3)
0.7 ( 12.3, 22.7) 1.0 ( 7.2, 14.3) 12.4 ( 231.6, 528.0)
0.695 0.480 0.638
9.5 (3.8, 15.1) 20.9 (12.9, 26.4) 152.4 (39.6, 252,9) 61.1 (47.1, 68.4)
9.1 (6.8, 12.4) 19.1 (11.3, 23.4) 137.8 (79.6, 196.6) 59.0 (54.1, 73.4)
0.8 ( 4.3, 6.0) 1.7 ( 6.5, 4.8) 30.2 ( 87.7, 89.5) 0.4 ( 9.1, 9.5)
0.388 0.213 0.272 0.754
13.9 (5.0, 31.6) 26.8 (10.0, 32.0) 276.4 (138.1, 425.2) 79.2 (72.9, 98.8)
10.5 (7.0, 13.8) 24.5 (15.3, 29.5) 178.9 (122.4, 264.3) 82.5 (72.3, 100.8)
2.5 ( 22.5, 3.9) 0.5 ( 12.2, 14.5) 82.1 ( 234.1, 33.3) 2.5 ( 15.7, 10.7)
0.034* 0.388 0.005** 0.239
35.3 (25.3, 45.2) 100.3 (76.4, 132.6)
38.6 (30.5, 50.9) 102.2 (71.1, 121.7)
5.4 ( 2.0, 10.7) 3.7 ( 45.1, 20.1)
0.006** 0.308
A-P, anteroposterior; CSA, cross-sectional area; PNS, posterior nasal spine; TW, transverse width. a Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05, **P < 0.01.
P = 0.005). Postoperative AHI and RDI scores increased in patients with a low preoperative vertical hyoid bone position (Table 5). Patients with an inferiorly dislocated retropalatal level after surgery had poor sleep quality. The vertical position of the retropalatal level was positively correlated with postoperative AHI and RDI P = 0.002; rs = 0.683, (rs = 0.800, P = 0.014, respectively). In addition, postoperative vertical position of the retropalatal level was positively correlated with changes in AHI and RDI (rs = 0.851, P = 0.000; rs = 0.636, P = 0.026, respectively). Similarly, postoperative vertical
position of the retroglossal level was positively correlated with changes in AHI and RDI (rs = 0.673, P = 0.017; rs = 0.594, P = 0.042, respectively) (Table 5).
Discussion
It was hypothesized that pharyngeal airway volume would decrease significantly after correction of a large mandibular setback of >9 mm, which would increase the postoperative incidence of new OSA. Although there was no significant change in RDI, AHI increased significantly from pre- to postoperative. Four of the 12
patients (33.3%) developed mild OSA (both RDI and AHI) after surgery. The first reported cases of postoperative OSA occurred in two women in their 40 s after mandibular setback movements of 7 mm and 10 mm3. Another study of 22 patients reported that only two patients with large mandibular setbacks >12– 13 mm developed mild OSA postoperatively4. A third study involving 40 patients described an obese male patient who developed OSA after 10.1 mm backward movement12. These five cases were presented as case reports, or as special cases. However, no clinical studies have investigated the development of OSA following
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Table 5. Correlations between PSG variables and pharyngeal airway measurementsa. Pharyngeal airway measurements Preoperative Volume
Pearson correlation
Total Nasopharynx Oropharynx Hypopharynx
Retro-PNS level
CSA
Retropalatal level
CSA Vertical position
Retroglossal level
CSA Vertical position
Hyoid bone position
A-P Vertical
Postoperative Volume
Total Nasopharynx Oropharynx Hypopharynx
Retro-PNS level
CSA
Retropalatal level
CSA Vertical position
Retroglossal level
CSA Vertical position
Hyoid bone position
A-P Vertical
Changes between preoperative and postoperative PSG
Postoperative PSG AHI
RDI
SaO2
AHI
RDI
SaO2
rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value
0.365 0.243 0.007 0.983 0.144 0.656 0.302 0.340 0.151 0.640 0.165 0.609 0.361 0.248 0.186 0.563 0.453 0.140 0.186 0.563 0.719** 0.008
0.211 0.510 0.190 0.554 0.127 0.695 0.218 0.495 0.070 0.828 0.296 0.351 0.401 0.196 0.007 0.983 0.500 0.098 0.063 0.845 0.634* 0.027
0.651* 0.022 0.453 0.139 0.461 0.132 0.187 0.561 0.385 0.217 0.347 0.270 0.335 0.287 0.442 0.150 0.088 0.787 0.149 0.645 0.404 0.193
0.333 0.291 0.007 0.983 0.144 0.656 0.329 0.296 0.140 0.664 0.175 0.586 0.529 0.077 0.102 0.753 0.487 0.108 0.287 0.365 0.753** 0.005
0.336 0.286 0.210 0.513 0.000 1.000 0.098 0.762 0.259 0.417 0.063 0.846 0.615* 0.033 0.182 0.572 0.245 0.443 0.175 0.587 0.517 0.085
0.661* 0.027 0.744** 0.009 0.372 0.260 0.101 0.767 0.555 0.076 0.492 0.124 0.420 0.198 0.130 0.702 0.077 0.821 0.029 0.933 0.208 0.540
rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value
0.084 0.795 0.274 0.389 0.032 0.922 0.340 0.279 0.439 0.154 0.102 0.753 0.800** 0.002 0.189 0.555 0.575 0.050 0.204 0.526 0.309 0.329
0.056 0.862 0.373 0.232 0.063 0.845 0.437 0.156 0.521 0.082 0.141 0.662 0.683* 0.014 0.218 0.495 0.535 0.073 0.021 0.948 0.204 0.524
0.072 0.823 0.175 0.586 0.118 0.715 0.027 0.934 0.008 0.981 0.053 0.869 0.762** 0.004 0.030 0.925 0.347 0.270 0.396 0.202 0.209 0.513
0.035 0.914 0.207 0.519 0.070 0.829 0.385 0.216 0.455 0.137 0.011 0.974 0.851** 0.000 0.336 0.285 0.673* 0.017 0.256 0.422 0.333 0.291
0.014 0.966 0.014 0.966 0.077 0.812 0.308 0.331 0.559 0.059 0.070 0.829 0.636* 0.026 0.434 0.159 0.594* 0.042 0.210 0.513 0.266 0.404
0.280 0.404 0.541 0.086 0.319 0.340 0.043 0.899 0.183 0.589 0.188 0.579 0.521 0.100 0.150 0.660 0.328 0.324 0.227 0.502 0.077 0.821
AHI, apnoea–hypopnoea index; A-P, anteroposterior; CSA, cross-sectional area; PNS, posterior nasal spine; PSG, polysomnography; RDI, respiratory disturbance index; SaO2, arterial oxygen saturation. a Statistical analyses were conducted using Spearman’s rank correlation coefficient; *P < 0.05, **P < 0.01.
large mean mandibular setback. The present study is novel in reporting the incidence rate of postoperative OSA, PSG parameter scores, and PAS changes after large mandibular setback. In recent decades, changes in the airway space after mandibular setback surgery have attracted increasing attention2,4– 11,14,16–18,20,24–27 . Most studies have shown that the oropharynx and hypopharynx narrow significantly after mandibular setback2,4,7,9,11,13,14,17,19. On the other
hand, it has been reported that the airway volume is significantly increased in bimaxillary surgery with maxillary advancement and mandibular setback27. Airway narrowing is considered a predisposing factor for OSA11,15,18. In the present study, the total pharyngeal, oropharyngeal, and hypopharyngeal volumes, as well as the retroglossal CSA were significantly reduced after surgery. The relationship between the extent of jaw movements and the PAS change is
unclear. Becker et al. identified a correlation between the extent of jaw movements and changes in airway measurements at the nasopharynx and oropharynx10. In contrast, there was no correlation in the present study, or in that performed by Kim et al.15. OSA-related sleep parameters are influenced by several variables. There was a significant positive correlation between an inferiorly located hyoid bone preoperative, as well as inferiorly dislocated retro-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Large mandibular setback and OSA palatal and retroglossal levels postoperative, and postoperative RDI and AHI (and/ or changes in the RDI and AHI). However, different from our hypothesis, there was no significant correlation between the extent of mandibular setback and AHI or RDI after surgery. Therefore, there is still no clear evidence that mandibular setback surgery causes OSA. Guilleminault et al.3 described two patients who underwent mandibular setback and subsequently developed OSA. Snoring in both patients worsened, and their RDI also increased significantly after surgery. Foltan et al.7 investigated the effect of bimaxillary surgery with maxillary advancement (4.44 mm) and mandibular setback (4.96 mm) on ventilation during sleep using a comparison of the presurgical and postsurgical PSG and pulmonary function test results. The authors concluded that orthognathic surgery worsened the breathing function during sleep. Foltan et al.20 also reported significantly increased RDI and AHI, as well as decreased SaO2 after bimaxillary surgery (maxillary advancement 5.9 mm, mandibular setback 4.1 mm). Hasebe et al.4 reported that two patients were diagnosed with mild OSA 6 months after large mandibular setback surgery (13.7 mm and 12.6 mm). In another study from the same institution, AHI did not significantly change after surgery in both the one-jaw and bimaxillary surgery groups (maximum mandibular setback 4.9 mm)12. In contrast, two studies showed opposite results. Sleep quality and efficiency in the PSG evaluation improved significantly after bimaxillary surgery (maxillary advancement 4.5 mm or 5.2 mm; mandibular setback 6.4 mm or 6.5 mm)11,13. The pharyngeal airway undergoes changes according to the extent and direction of surgical movement. In order to minimize the worsening of the facial profile, alternative surgical techniques (including a modified surgical method combined with bimaxillary anterior segmental osteotomy26 and maxillary expansion with mandibular anterior segment osteotomy28) have been introduced. The mandibular setback, combined with maxillary advancement, can reduce the extent of mandibular setback and consequently increase PSA11,13. Therefore, it is more favourable to minimize the postoperative reduction of the airway than to perform mandible surgery alone2,9. Moreover, different patient preferences must be considered, because the extent and direction of surgical movement can greatly influence the aesthetics of the facial profile.
Most Korean and East Asian patients with mandibular prognathism have a small nose and protruding upper lip. Therefore, most patients do not prefer maxillary advancement, which can lead to a more protrusive upper lip and upturned nose. We frequently use a surgical option with clockwise rotation of the maxillomandibular complex with maxillary posterior impaction for an aesthetic facial profile29. However, this maxillary posterior impaction should be carefully applied in patients with a small retropalatal airway, because superior movement of the tongue can push the soft palate and severely narrow the airway at this level. In this study, the A-P length, TW, and CSA at the retropalatal level tended to decrease after surgery. In contrast, at the retro-PNS level, the A-P length, TW, and CSA tended to increase postoperatively (Table 4). If patients can accept that facial aesthetics can be of secondary importance to deep sleep without any disorder, it is better to avoid this clockwise rotation of the maxillomandibular complex (with preservation of the prognathic chin, or slight improvement with setback genioplasty and contouring surgery) for the PAS. In this study, the mean maxillary A-P movement was <1 mm. There was a significant reduction in the oropharyngeal and hypopharyngeal volumes and the retroglossal CSA, with 33.3% occurrence of newly developed OSA after surgery. Therefore, maxillary advancement to reduce the mandibular setback movements is strongly recommended. It is crucial that the surgeon and patient communicate about the balance between correcting severe mandibular prognathism and ensuring sound respiratory function without postoperative OSA. This study is distinctive in that it only included patients with a large mandibular setback of >9 mm to evaluate the possibility of newly developed OSA postoperatively. However, it was limited by a small sample size of patients with severe mandibular prognathism who underwent PSG and 3D facial CT twice. Another study limitation is the shortterm evaluation of postoperative sleep parameters. Furthermore, other contributing factors were not investigated, such as alcohol consumption and mandibular setback movement, which can contribute to OSA. Further larger studies including the use of a questionnaire are needed to substantiate the study findings and to provide a more accurate assessment of the effect of mandibular setback on PAS and the development of OSA.
7
In this study, it was found that the total pharyngeal, oropharyngeal, and hypopharyngeal volumes and the retroglossal CSA were significantly reduced after bimaxillary surgery with large mandibular setback movements. New mild OSA developed postoperatively in four of the 12 patients according to both RDI and AHI scores. Surgeons must be aware of this potential surgical consequence. Therefore, mandibular setbacks that are large in extent should be reduced by maxillary advancement as much as possible. Funding
This research was supported by grant number 04-2011-0048 from the Seoul National University Dental Hospital Research Fund, Republic of Korea. Competing interests
The authors have no financial interests to declare with regard to the content of this article. Ethical approval
This study was approved by the Institutional Review Board of Seoul National University Dental Hospital (CRI12036). Patient consent
Patient consent was not required. Acknowledgements. The authors would like to thank Professor Shin-Jae Lee of the Department of Orthodontics at the School of Dentistry, Seoul National University for his statistical advice.
References 1. Muto T, Yamazaki A, Takeda S, Sato Y. Effect of bilateral sagittal split ramus osteotomy setback on the soft palate and pharyngeal airway space. Int J Oral Maxillofac Surg 2008;37:419–23. 2. Mattos CT, Vilani GN, Sant’Anna EF, Ruellas AC, Maia LC. Effects of orthognathic surgery on oropharyngeal airway: a metaanalysis. Int J Oral Maxillofac Surg 2011;40:1347–56. 3. Guilleminault C, Riley R, Powell N. Sleep apnea in normal subjects following mandibular osteotomy with retrusion. Chest 1985;88:776–8. 4. Hasebe D, Kobayashi T, Hasegawa M, Iwamoto T, Kato K, Izumi N, Takata Y, Saito C. Changes in oropharyngeal airway and respiratory function during sleep after orthog-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
YIJOM-4252; No of Pages 8
8
Yang et al.
5.
6.
7.
8.
9.
10.
11.
12.
13.
nathic surgery in patients with mandibular prognathism. Int J Oral Maxillofac Surg 2011;40:584–92. Chen F, Terada K, Hanada K, Saito I. Predicting the pharyngeal airway space after mandibular setback surgery. J Oral Maxillofac Surg 2005;63:1509–14. Kawakami M, Yamamoto K, Fujimoto M, Ohgi K, Inoue M, Kirita T. Changes in tongue and hyoid positions, and posterior airway space following mandibular setback surgery. J Craniomaxillofac Surg 2005;33:107–10. Foltan R, Hoffmannova J, Donev F, Vlk M, Sedy J, Kufa R, Bulik O. The impact of Le Fort I advancement and bilateral sagittal split osteotomy setback on ventilation during sleep. Int J Oral Maxillofac Surg 2009;38:1036–40. Jakobsone G, Neimane L, Krumina G. Twoand three-dimensional evaluation of the upper airway after bimaxillary correction of class III malocclusion. Oral Surg Oral Med Pathol Oral Radiol Endod Oral 2010;110:234–42. Hong JS, Park YH, Kim YJ, Hong SM, Oh KM. Three-dimensional changes in pharyngeal airway in skeletal class III patients undergoing orthognathic surgery. J Oral Maxillofac Surg 2011;69:e401–8. Becker OE, Avelar RL, Goelzer JG, Dolzan Ado N, Haas Jr OL, De Oliveira RB. Pharyngeal airway changes in class III patients treated with double jaw orthognathic surgery—maxillary advancement and mandibular setback. J Oral Maxillofac Surg 2012;70:e639–47. Gokce SM, Gorgulu S, Gokce HS, Bengi AO, Karacayli U, Ors F. Changes in posterior airway space, pulmonary function and sleep quality, following bimaxillary orthognathic surgery. Int J Oral Maxillofac Surg 2012;41:820–9. Uesugi T, Kobayashia T, Hasebea R, Ikeb M, Saito C. Effects of orthognathic surgery on pharyngeal airway and respiratory function during sleep in patients with mandibular prognathism. Int J Oral Maxillofac Surg 2014;43:1082–90. Gokce SM, Gorgulu S, Gokce HS, Bengi AO, Karacayli U, Ors F. Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3dimensional simulation and modeling program. Am J Orthod Dentofacial Orthop 2014;146:477–92.
14. Lee Y, Chun YS, Kang N, Kim M. Volumetric changes in the upper airway after bimaxillary surgery for skeletal class III malocclusions: a case series study using 3dimensional cone-beam computed tomography. J Oral Maxillofac Surg 2012;70:2867– 75. 15. Kim HS, Kim GT, Kim S, Lee JW, Kim EC, Kwon YD. Three-dimensional evaluation of the pharyngeal airway using cone-beam computed tomography following bimaxillary orthognathic surgery in skeletal class III patients. Clin Oral Investig 2016;20:915–22. 16. Park SB, Kim YI, Son WS, Hwang DS, Cho BH. Cone-beam computed tomography evaluation of short- and long-term airway change and stability after orthognathic surgery in patients with class III skeletal deformities: bimaxillary surgery and mandibular setback surgery. Int J Oral Maxillofac Surg 2012;41:87–93. 17. Kawamata A, Fujishita M, Ariji Y, Ariji E. Three-dimensional computed tomographic evaluation of morphologic airway changes after mandibular setback osteotomy for prognathism. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:278–87. 18. Chen F, Terada K, Hua Y, Saito I. Effects of bimaxillary surgery and mandibular setback surgery on pharyngeal airway measurements in patients with class III skeletal deformities. Am J Orthod Dentofacial Orthop 2007;131:372–7. 19. Lee UL, Oh H, Min SK, Shin JH, Kang YS, Lee WW, Han YE, Choi YJ, Kim HJ. The structural changes of upper airway and newly developed sleep breathing disorders after surgical treatment in class III malocclusion subjects. Medicine (Baltimore) 2017;96: e6873. 20. Foltan R, Hoffmannova J, Pavlikova G, Hanzelka T, Klima K, Horka E, Adamek S, Sedy J. The influence of orthognathic surgery on ventilation during sleep. Int J Oral Maxillofac Surg 2011;40:146–9. 21. Kim MJ, Kim SG, Park YW. Positional stability following intentional posterior ostectomy of the distal segment in bilateral sagittal split ramus osteotomy for correction of mandibular prognathism. J Craniomaxillofac Surg 2002;30:35–40. 22. Choi JH, Mah J. A new method for superimposition of CBCT volumes. J Clin Orthod 2010;44:303–12. 23. Lee JH, Kim MJ, Kim SM, Kwon OH, Kim YK. The 3D CT superimposition method
24.
25.
26.
27.
28.
29.
using image fusion based on the maximum mutual information algorithm for the assessment of oral and maxillofacial surgery treatment results. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:167–74. Enacar A, Aksoy AU, Sencift Y, Haydar B, Aras K. Changes in hypopharyngeal airway space and in tongue and hyoid bone positions following the surgical correction of mandibular prognathism. Int J Adult Orthodon Orthognath Surg 1994;9:285–90. Eggensperger N, Smolka W, Iizuka T. Longterm changes of hyoid bone position and pharyngeal airway size following mandibular setback by sagittal split ramus osteotomy. J Craniomaxillofac Surg 2005;33:111–7. Goh YH, Lim KA. Modified maxillomandibular advancement for the treatment of obstructive sleep apnea: a preliminary report. Laryngoscope 2003;113:1577–82. Havron AG, Aronovich S, Shelgikar AV, Kim HL, Conley RS. 3D Airway changes using CBCT in patients following mandibular setback surgery maxillary advancement. Orthod Craniofac Res 2019;22 (Suppl 1):30–5. Han JJ, Hong DH, Hwang SJ. Maxillary expansion and mandibular setback surgery with and without mandibular anterior segment osteotomy to correct mandibular prognathism with obstructive sleep apnea. J Craniofac Surg 2017;28:723–30. Ghosh A, Ray A. Converting a bi-jaw surgery to a single-jaw surgery: posterior maxdentoalveolar intrusion with illary microimplants to avoid the need of a maxillary surgery in the surgical management of skeletal class III vertical malocclusion. APOS Trends Orthodontics 2016;6:218–27.
Address: Soon Jung Hwang Department of Oral and Maxillofacial Surgery School of Dentistry Seoul National University 101 Daehakro Jongno-gu 03080 Seoul Republic of Korea Tel.: +82 2 2072 3061 Fax: +82 2 766 4948 E-mail: [email protected]
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx https://doi.org/10.1016/j.ijom.2019.07.012, available online at https://www.sciencedirect.com
Clinical Paper Orthognathic Surgery
Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback
H. J. Yang1,2, Y.-E. Jung2, I. J. Kwon3, J.-Y. Lee2, S. J. Hwang1,2,4 1
Orthognathic Surgery Center, Seoul National University Dental Hospital, Republic of Korea; 2 Department of Oral and Maxillofacial Surgery, School of Dentistry, Seoul National University, Republic of Korea; 3Department of Oral and Maxillofacial Surgery, Soonchunhyang University Bucheon Hospital, Republic of Korea; 4Dental Research Institute, Seoul National University, Republic of Korea
H. J. Yang, Y. -E. Jung, I. J. Kwon, J. -Y. Lee, S. J. Hwang: Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback. Int. J. Oral Maxillofac. Surg. 2019; xxx: xxx–xxx. ã 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Abstract. This study used three-dimensional computed tomography and polysomnography to evaluate the effect of a large mandibular setback on the postoperative pharyngeal airway space and obstructive sleep apnoea (OSA). Twelve patients who underwent bimaxillary surgery for a mandibular setback movement of >9 mm were included in this study. Changes in the pharyngeal airway space and polysomnography parameters based on the surgical movements were analyzed. The median mandibular setback movement was 11.08 mm. The total pharyngeal, oropharyngeal, and hypopharyngeal volumes, and the retroglossal cross-sectional area were significantly decreased postoperatively (P = 0.006; P = 0.005; P = 0.012; P = 0.005, respectively). The apnoea–hypopnoea index (AHI) increased significantly after surgery (P = 0.021). There were significant positive correlations between the preoperative inferiorly located hyoid bone and both AHI and respiratory disturbance index (RDI) postoperative (P = 0.008 and P = 0.027) and between the postoperative inferiorly dislocated retropalatal level and both AHI and RDI postoperative (P = 0.002 and P = 0.014). Four patients (33.3%) developed new onset OSA postoperatively. Large mandibular setback movements significantly reduced the pharyngeal airway space in the setting of bimaxillary surgery (P = 0.006).
Mandibular setback surgery is typically performed to improve the functional and aesthetic characteristics of mandibular 0901-5027/000001+08
prognathism. However, mandibular setback surgery is thought to change the tongue position and narrow the pharyngeal
Key words: large mandibular setback; pharyngeal airway space; computed tomography; polysomnography; obstructive sleep apnoea. Accepted for publication 23 July 2019
airway space (PAS)1. The main concern with these pharyngeal dimensional changes is their potential to cause obstructive sleep
ã 2019 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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apnoea (OSA)2. Since Guilleminault et al.3 reported two patients who developed OSA after mandibular setback surgery, many studies have investigated these postoperative consequences using lateral cephalograms, three-dimensional (3D) computed tomography (CT), and polysomnography (PSG)1,2,4–15. A few studies using CT have found that there is no decrease in the PAS8 or that there is an increase in the total PAS after bimaxillary surgery for mandibular setback movement13,14. In contrast, most other studies have shown that patients have a reduced oropharyngeal space, reduced cross-sectional area (CSA) posterior to the tongue and soft palate, or decreased width of the PAS after mandibular setback surgery7,13,15–17. Other groups have also speculated that mandibular setback surgery can induce OSA15,18. The most accurate method of diagnosing surgically-induced OSA is overnight PSG11,12,19. In the first study in which OSA was shown to develop after mandibular setback surgery, the diagnosis was made using postoperative PSG3. The number of previous studies that have evaluated pre- and postoperative PSG is limited due to its high cost and patient hesitance to participate in these paired evaluations in an unfamiliar laboratory environment4,11– 13,19,20 . It is logical to postulate that the further the mandible moves backward, the more the PAS will be reduced; therefore, the prevalence of OSA will be increased after mandibular setback surgery. This postulation is supported by a recent study that identified a correlation between the extent of the jaw movements and the change in airway measurement in the nasopharynx and oropharynx10. However, most studies evaluating PAS changes have been performed on patients with a small mean mandibular setback movement (<7 mm)11–13,19,20. In the report by Hasebe et al.4, where the mean extent of mandibular setback was 5.8 mm in the group that underwent bimaxillary surgery and 8.4 mm in the group that underwent bilateral sagittal split ramus osteotomy (BSSRO), two patients with a mandibular setback >12–13 mm developed postoperative OSA. As no previous studies on this subject have reported the outcomes following a large mean mandibular setback movement, it was hypothesized that the volume of the pharyngeal airway would decrease significantly after a large mandibular setback, resulting in an increase in the incidence of postoperative OSA. The aims of the study were to evaluate the effect of large mandibular setback movements
(>9 mm) on postoperative changes of PAS using 3D CT and to evaluate changes in PSG parameters associated with the occurrence of OSA. Materials and methods Patients
The investigators designed and implemented a prospective observational study including patients with severe mandibular prognathism undergoing bimaxillary surgery, who had no previous history of OSA based on the apnoea–hypopnoea index (AHI). The study design and reports followed the STROBE guidelines (Strengthening the Reporting of Observational Studies in Epidemiology). This study was approved by the Institutional Review Board of Seoul National University Dental Hospital (CRI12036). Patients who were anticipated to undergo bimaxillary surgery with a large extent of mandibular setback (during prediction tracing) underwent an overnight formal PSG in the sleep laboratory 1 month before and 6 months after surgery. For all patients, 3D CT images were acquired 1 month before (T0) and 4–6 months after surgery (T1). Patients with mandibular setback movements of >9 mm at B point at T1 were included in this study. Patients with a preoperative AHI 5 were excluded, while patients with a preoperative respiratory disturbance index (RDI) 5 and preoperative AHI < 5 were included. Patients were excluded if they only underwent BSSRO, had cleft palate or a craniofacial syndrome, had undergone previous orthognathic surgery (including genioplasty), or had any breathing disorder (including allergic rhinitis and inflammatory nasal/ nasopharyngeal mucosa). Patients who were on medications that are associated with sleep disturbance were also excluded. The mean body mass index (BMI) was measured 1 month before and 6 months after surgery. Overweight or obese patients, based on a BMI > 25 kg/m2 at the time of postoperative PSG, were also excluded to avoid the weight-associated effect of mandibular setback on the airway.
Surgery
Le Fort I osteotomy and BSSRO with/ without genioplasty were performed in all patients by a single surgeon. Bone trimming and excision in the ramus osteotomy region was performed as necessary for the setback21. The surgery always
included correction of the maxillary midline, canting, and yaw deviation. In addition, surgical planning for maxillary anteroposterior (A-P) movement and maxillary posterior impaction were performed after considering the patient’s anatomical status and his/her preference for an aesthetic facial profile. Evaluation of surgical movements
3D CT images were acquired using a CT scanner (Somatom Sensation 10; Siemens, Munich, Germany) with the following parameters: tube voltage of 120 kVp, tube current of 80 mAs, and slice thickness of 0.75 mm. Digital image files were exported in DICOM format (Digital Imaging and Communications in Medicine) and imported into OnDemand 3D software (Cybermed, Inc., Seoul, Korea). After reorienting to the Frankfort horizontal (FH) plane, sella (S), and nasion (N), the 3D images from T0 and T1 were superimposed automatically based on the maximum mutual information algorithm22,23. The preoperative and postoperative 3D positions of the reference points (A point, B point, posterior nasal spine (PNS), right and left lingula) were measured. Methodical errors for each reference point were calculated using the Dahlberg formula: S2 = Sd2/2n (d, the difference between repeatedly measured values; n, the number of double measurements). The maximum error for all reference points was 0.164 mm in the A-P direction and 0.272 mm vertically. Polysomnography evaluation
The standard recording parameters during PSG included the following: AHI (/h), RDI (/h), sleep onset (min), sleep efficiency (%), sleep stages 1 (%), 2 (%), and 3 (%), rapid eye movement sleep (REM) (%), and arousal index (/h). Arterial oxygen saturation (SaO2) was measured continuously using pulse oximetry. Evaluation of the pharyngeal airway
Digital image files from 3D CT were imported into Invivo Dental software (Anatomage, San Jose, CA, USA). The FH plane was constructed to reorient the 3D images. For two-dimensional analysis of the PAS, the pharyngeal airway of each patient was studied at three levels (Fig. 1). The largest transverse width (TW), A-P length, and CSA were measured at these levels. After defining two reference lines (x-axis, i.e. the line tangential to the inferior portion of the sella turcica and parallel
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Large mandibular setback and OSA
3
Fig. 1. Analysis of the airway on computed tomography. Three airway levels (dotted lines, a–c) and reference planes (solid lines) were used to divide the airway into three regions (e–g). The airway levels are parallel to the Frankfort horizontal (FH) plane. The CV1, CV2, and CV4 planes are parallel to the FH plane through the most inferior point of each cervical vertebra. (a) Retro-PNS level; (b) retropalatal level, i.e. the level of the most posterior point of the soft palate; (c) retroglossal level, i.e. the level of the most posterior point of the tongue base; (d) the position of the hyoid bone (the most anterosuperior hyoid bone point); (e) nasopharynx between the PNS–Vp and CV1 plane; (f) oropharynx between the CV1 and CV2 planes; (g) hypopharynx between the CV2 and CV4 planes. PNS, posterior nasal spine; Vp, the most posterior part of the ala of vomer; x-axis, the line tangent to the inferior point of the sella turcica and parallel to the FH plane; y-axis, the line on nasion and perpendicular to x-axis.
to the FH plane; y-axis, i.e. the line perpendicular to the x-axis and passing through N), the relative positions of these three levels and the hyoid bone were determined (Fig. 1). In order to evaluate the airway volume, the threshold value was set at a range of 1024 to 600 Hounsfield units, where the pharyngeal airway could be effectively differentiated from the neighbouring soft tissue. The pharyngeal airway was divided into three regions, including the nasopharyngeal, oropharyngeal, and hypopharyngeal volumes. These regions were defined using the PNS and cervical vertebra (CV) references according to a previous report16 (Fig. 1). Statistical evaluation
The Kolmogorov–Smirnov test was performed to determine whether values had normal distributions. Accordingly, the surgical movements on CT, PSG vari-
ables, and the pharyngeal airway volume, length, and area were compared using the Wilcoxon matched-pairs signed-rank test. Spearman’s rank correlation coefficient was determined between the PSG variables, airway parameters, and surgical movement. P-values of <0.05 were considered statistically significant. Results
Twelve patients were included in this study. The mean age at surgery was 21.8 2.9 years. The median BMI preoperatively (21.1 kg/m2, range 17.8–25.2 kg/ m2) and postoperatively (20.8 kg/m2, range 17.8–24.6 kg/m2) were not statistically different. The patient demographic data are shown in Table 1. Surgical movements
The maxillary movement at A point (mean 0.65 mm, ranging from 1.23 mm back-
ward to 4.54 mm forward) was not statistically significant. The PNS showed significant superior and anterior movements. The median mandibular backward movements were 11.08 mm (range 9.61– 14.26 mm) at B point (P = 0.002) and 8.76 mm (range 4.80–14.82 mm) at the lingula (P = 0.002). There were significant backward and upward movements at B point (P = 0.002 and P = 0.023, respectively) and the lingula (P = 0.002 and P = 0.010, respectively) (Table 2). Polysomnography measurement
PSG evaluation showed that the postoperative sleep quality was disturbed compared to the preoperative sleep quality. Two patients showed mild sleep apnoea with RDI scores of 5.9 and 9.1 before surgery. After surgery, seven patients had increased RDI scores. Five patients had mild sleep apnoea with RDI scores of 5.3–14.8. Four of these five patients de-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Table 1. Patient demographic data.
Patient
Sex
Age (years)
Anteroposterior movement (mm)a A point
1 2 3 4 5 6 7 8 9 10 11 12
M M F F F M F M M F M F
30 23 22 21 19 22 21 22 22 20 22 18
0.86 1.37 0.66 0.32 0.64 2.22 0.16 1.28 1.23 1.19 4.54 2.16
B point 10.60 12.88 12.06 12.29 10.36 9.61 13.79 14.26 11.56 10.02 10.34 9.91
Vertical movement (mm)a A point
PNS
0.62 0.61 0.48 0.27 1.66 4.69 3.66 1.08 1.38 3.51 3.64 0.17
3.41 4.92 3.25 0.15 8.41 10.21 5.39 2.34 1.65 0.86 7.47 4.23
Volumetric change of pharynx (mm3)
9713 5162 5007 3177 196 176 561 3073 2702 9321 203 3251
Preoperative PSG
Postoperative PSG
AHI (/h)
RDI (/h)
BMI (kg/m2)
AHI (/h)
RDI (/h)
BMI (kg/m2)
0.3 2 0.2 0.5 0 1.3 0.2 0.2 2.9 1.4 0.5 0.2
0.3 2 1.6 1.2 0 1.8 1.4 3.1 9.1 4.6 5.9 1.7
20.7 24.2 21.8 19.8 23.6 25.2 18.9 18.9 21.5 23.6 17.8 19.3
1.4 8.2 0.3 0.2 0.3 6.3 0 7 5.2 2.1 1 0
2.1 14.6 0.3 0.4 2.3 11.2 0.3 14.8 12.5 5.3 2.8 0.3
20.8 24.6 22.1 19.8 21.6 23.4 17.9 18.9 20.8 24.0 17.8 18.5
AHI, apnoea hypopnoea index; BMI, body mass index; F, female; M, male; PNS, posterior nasal spine; PSG, polysomnography; RDI, respiratory disturbance index. a Negative value of anteroposterior movement, backward movement; negative value of vertical movement, downward movement. Table 2. Surgical movements in the skeletal reference points following bimaxillary surgery for mandibular setback movement.
A point (mm) B point (mm) PNS (mm) Lingula (mm)
Anteroposterior Vertical Anteroposterior Vertical Anteroposterior Vertical Anteroposterior Vertical
Surgical movementa Median (min, max)
P-valueb
0.65 ( 1.23, 4.54) 0.38 ( 3.51, 4.69) 11.08 ( 14.26, 9.61) 2.13 ( 5.01, 15.21) 1.02 ( 0.39, 7.27) 3.82 ( 0.15, 10.21) 8.76 ( 14.82, 4.80) 4.36 ( 4.52, 9.01)
0.136 0.530 0.002** 0.023* 0.005** 0.003** 0.002** 0.010*
PNS, posterior nasal spine. a In horizontal movement: positive value, forward movement; negative value, backward movement. In vertical movement: positive value, upward movement; negative value, downward movement. b Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05, **P < 0.01.
veloped OSA after surgery (Table 1). The median RDI increased from 1.8 (range 0– 9.1) to 2.6 (range 0.3–14.8) from pre- to postoperative, but the difference was not significant (Table 3). All of the patients had normal AHI values before surgery. Postoperatively, nine patients had increased AHI scores, while four developed mild sleep apnoea with AHI scores >5 (Table 1). The median AHI increased significantly from 0.4 (range 0–2.9) to 1.2 (range 0–8.2) (P = 0.021) from preto postoperative, although the BMI did not change significantly. Sleep efficiency decreased significantly after surgery by a median 4.4%, ranging from 29.5% to 5.5% (P = 0.034) (Table 3). Pharyngeal airway measurements
The total (P = 0.006), oropharyngeal (P = 0.005), and hypopharyngeal (P = 0.012) volumes all decreased significantly. Although there was no significant change in the PAS at the retro-PNS and retropalatal levels, the CSA and A-P
length at the retroglossal level decreased significantly by a median 82.1 mm2 (range 234.1 to 33.3 mm2, P = 0.005) and 2.5 mm (range 22.5 to 3.9 mm, P = 0.034), respectively. The hyoid bone was also displaced backward by 5.4 mm (range 2.0 to 10.7 mm) (P = 0.006) (Table 4). Correlations among surgical movements, pharyngeal airway measurements, and PSG variables
Patient age was positively correlated with postoperative AHI and AHI score change P = 0.025; rs = 0.635, (rs = 0.640, P = 0.027, respectively). In addition, the postoperative SaO2 was negatively correlated with patient age (rs = 0.759, P = 0.004). However, all of the patients in this study were in their late teens and early 20s, except for one patient. The preoperative pharyngeal airway volume was not correlated with postoperative AHI, RDI, or changes in the AHI and RDI. In contrast, postoperative SaO2 and the change between the pre- and postop-
erative SaO2 were negatively correlated with the total pharyngeal airway volume preoperative (rs = 0.651, P = 0.022; rs = 0.661, P = 0.027, respectively). In addition, the change between pre- and postoperative SaO2 showed a negative correlation with preoperative nasopharyngeal volume (rs = 0.744, P = 0.009). This result indicates that postoperative SaO2 is likely to be lower in patients with a large preoperative PAS than in those with a smaller preoperative PAS. The preoperative vertical position of the retropalatal level was positively correlated with the RDI score change (rs = 0.615, P = 0.033). In other words, the postoperative RDI increased more in patients with a lower preoperative vertical position of the retropalatal level than in those with a higher preoperative retropalatal level. In addition, an inferiorly located hyoid bone preoperative was positively correlated with RDI and AHI scores postoperative P = 0.027; rs = 0.719, (rs = 0.634, P = 0.008, respectively), as well as with the change in AHI score (rs = 0.753,
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Large mandibular setback and OSA
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Table 3. Results of polysomnography.
AHI (/h) RDI (/h) Sleep onset (min) Sleep efficiency (%) NREM sleep Stage 1 (%) Stage 2 (%) Stage 3 (%) REM sleep (%) SaO2 (%) Arousal index (/h) BMI (kg/m2)
Preoperative Median (min, max)
Postoperative Median (min, max)
Surgical change Median (min, max)
P-valuea
0.4 (0, 2.9) 1.8 (0, 9.1) 14.0 (3.0, 88.5) 88.7 (59.0, 96.1)
1.2 (0, 8.2) 2.6 (0.3, 14.8) 11.3 (0.5, 95.5) 81.1 (52.3, 96.4)
0.6 ( 0.3, 6.8) 1.3 ( 3.1, 12.6) 0 ( 25.0, 37.0) 4.4 ( 29.5, 5.5)
0.021* 0.182 1.000 0.034*
8.0 (4.3, 18.6) 56.5 (47.2, 78.6) 17.3 (3.1, 27.0) 18.0 (4.7, 31.1) 98 (97, 99) 7.7 (2.4, 17.6) 21.1 (17.8, 25.2)
8.1 (4.3, 24.1) 58.9 (42.2, 72.8) 14.5 (0.1, 31.9) 17.7 (0, 27.7) 98.0 (97, 100) 8.7 (3.7, 18.5) 20.8 (17.8, 24.6)
0.2 ( 8.0, 10.0) 0.6 ( 10.3, 12.0) 3.9 ( 13.4, 18.7) 0.3 ( 14.0, 22.5) 0 ( 1, 3) 0.6 ( 9.3, 12.0) 0 ( 2.0, 0.4)
0.689 0.583 0.286 0.695 0.739 0.906 0.138
AHI, apnoea–hypopnoea index; BMI, body mass index; NREM, non-rapid eye movement sleep; RDI, respiratory disturbance index; REM, rapid eye movement sleep; SaO2, arterial oxygen saturation. a Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05.
Table 4. Results of pharyngeal airway measurements.
Volume Total (mm3) Nasopharynx (mm3) Oropharynx (mm3) Hypopharynx (mm3) Retro-PNS level A-P length (mm) TW (mm) CSA (mm2) Retropalatal level A-P length (mm) TW (mm) CSA (mm2) Vertical position (mm) Retroglossal level A-P length (mm) TW (mm) CSA (mm2) Vertical position (mm) Hyoid bone position A-P (mm) Vertical (mm)
Preoperative Median (min, max)
Postoperative Median (min, max)
Surgical change Median (min, max)
P-valuea
22,981 (19,303, 32,430) 8132 (4174, 11,082) 5956 (3591, 9513) 9060 (6841, 12,636)
21,128 (12,419, 23,463) 7512 (4744, 9456) 4476 (3061, 5482) 8451 (4614, 10,534)
3125 ( 9713, 561) 360 ( 3668, 2885) 1413 ( 4031, 159) 1954 ( 4753, 821)
0.006** 0.433 0.005** 0.012*
20.6 (4.2, 28.8) 27.5 (13.4, 30.7) 449.7 (43.4, 631.2)
23.2 (14.5, 26.9) 26.7 (21.9, 29.6) 486.8 (323.3, 572.3)
0.7 ( 12.3, 22.7) 1.0 ( 7.2, 14.3) 12.4 ( 231.6, 528.0)
0.695 0.480 0.638
9.5 (3.8, 15.1) 20.9 (12.9, 26.4) 152.4 (39.6, 252,9) 61.1 (47.1, 68.4)
9.1 (6.8, 12.4) 19.1 (11.3, 23.4) 137.8 (79.6, 196.6) 59.0 (54.1, 73.4)
0.8 ( 4.3, 6.0) 1.7 ( 6.5, 4.8) 30.2 ( 87.7, 89.5) 0.4 ( 9.1, 9.5)
0.388 0.213 0.272 0.754
13.9 (5.0, 31.6) 26.8 (10.0, 32.0) 276.4 (138.1, 425.2) 79.2 (72.9, 98.8)
10.5 (7.0, 13.8) 24.5 (15.3, 29.5) 178.9 (122.4, 264.3) 82.5 (72.3, 100.8)
2.5 ( 22.5, 3.9) 0.5 ( 12.2, 14.5) 82.1 ( 234.1, 33.3) 2.5 ( 15.7, 10.7)
0.034* 0.388 0.005** 0.239
35.3 (25.3, 45.2) 100.3 (76.4, 132.6)
38.6 (30.5, 50.9) 102.2 (71.1, 121.7)
5.4 ( 2.0, 10.7) 3.7 ( 45.1, 20.1)
0.006** 0.308
A-P, anteroposterior; CSA, cross-sectional area; PNS, posterior nasal spine; TW, transverse width. a Statistical analyses were conducted using the Wilcoxon signed-rank test; *P < 0.05, **P < 0.01.
P = 0.005). Postoperative AHI and RDI scores increased in patients with a low preoperative vertical hyoid bone position (Table 5). Patients with an inferiorly dislocated retropalatal level after surgery had poor sleep quality. The vertical position of the retropalatal level was positively correlated with postoperative AHI and RDI P = 0.002; rs = 0.683, (rs = 0.800, P = 0.014, respectively). In addition, postoperative vertical position of the retropalatal level was positively correlated with changes in AHI and RDI (rs = 0.851, P = 0.000; rs = 0.636, P = 0.026, respectively). Similarly, postoperative vertical
position of the retroglossal level was positively correlated with changes in AHI and RDI (rs = 0.673, P = 0.017; rs = 0.594, P = 0.042, respectively) (Table 5).
Discussion
It was hypothesized that pharyngeal airway volume would decrease significantly after correction of a large mandibular setback of >9 mm, which would increase the postoperative incidence of new OSA. Although there was no significant change in RDI, AHI increased significantly from pre- to postoperative. Four of the 12
patients (33.3%) developed mild OSA (both RDI and AHI) after surgery. The first reported cases of postoperative OSA occurred in two women in their 40 s after mandibular setback movements of 7 mm and 10 mm3. Another study of 22 patients reported that only two patients with large mandibular setbacks >12– 13 mm developed mild OSA postoperatively4. A third study involving 40 patients described an obese male patient who developed OSA after 10.1 mm backward movement12. These five cases were presented as case reports, or as special cases. However, no clinical studies have investigated the development of OSA following
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Table 5. Correlations between PSG variables and pharyngeal airway measurementsa. Pharyngeal airway measurements Preoperative Volume
Pearson correlation
Total Nasopharynx Oropharynx Hypopharynx
Retro-PNS level
CSA
Retropalatal level
CSA Vertical position
Retroglossal level
CSA Vertical position
Hyoid bone position
A-P Vertical
Postoperative Volume
Total Nasopharynx Oropharynx Hypopharynx
Retro-PNS level
CSA
Retropalatal level
CSA Vertical position
Retroglossal level
CSA Vertical position
Hyoid bone position
A-P Vertical
Changes between preoperative and postoperative PSG
Postoperative PSG AHI
RDI
SaO2
AHI
RDI
SaO2
rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value
0.365 0.243 0.007 0.983 0.144 0.656 0.302 0.340 0.151 0.640 0.165 0.609 0.361 0.248 0.186 0.563 0.453 0.140 0.186 0.563 0.719** 0.008
0.211 0.510 0.190 0.554 0.127 0.695 0.218 0.495 0.070 0.828 0.296 0.351 0.401 0.196 0.007 0.983 0.500 0.098 0.063 0.845 0.634* 0.027
0.651* 0.022 0.453 0.139 0.461 0.132 0.187 0.561 0.385 0.217 0.347 0.270 0.335 0.287 0.442 0.150 0.088 0.787 0.149 0.645 0.404 0.193
0.333 0.291 0.007 0.983 0.144 0.656 0.329 0.296 0.140 0.664 0.175 0.586 0.529 0.077 0.102 0.753 0.487 0.108 0.287 0.365 0.753** 0.005
0.336 0.286 0.210 0.513 0.000 1.000 0.098 0.762 0.259 0.417 0.063 0.846 0.615* 0.033 0.182 0.572 0.245 0.443 0.175 0.587 0.517 0.085
0.661* 0.027 0.744** 0.009 0.372 0.260 0.101 0.767 0.555 0.076 0.492 0.124 0.420 0.198 0.130 0.702 0.077 0.821 0.029 0.933 0.208 0.540
rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value rs P-value
0.084 0.795 0.274 0.389 0.032 0.922 0.340 0.279 0.439 0.154 0.102 0.753 0.800** 0.002 0.189 0.555 0.575 0.050 0.204 0.526 0.309 0.329
0.056 0.862 0.373 0.232 0.063 0.845 0.437 0.156 0.521 0.082 0.141 0.662 0.683* 0.014 0.218 0.495 0.535 0.073 0.021 0.948 0.204 0.524
0.072 0.823 0.175 0.586 0.118 0.715 0.027 0.934 0.008 0.981 0.053 0.869 0.762** 0.004 0.030 0.925 0.347 0.270 0.396 0.202 0.209 0.513
0.035 0.914 0.207 0.519 0.070 0.829 0.385 0.216 0.455 0.137 0.011 0.974 0.851** 0.000 0.336 0.285 0.673* 0.017 0.256 0.422 0.333 0.291
0.014 0.966 0.014 0.966 0.077 0.812 0.308 0.331 0.559 0.059 0.070 0.829 0.636* 0.026 0.434 0.159 0.594* 0.042 0.210 0.513 0.266 0.404
0.280 0.404 0.541 0.086 0.319 0.340 0.043 0.899 0.183 0.589 0.188 0.579 0.521 0.100 0.150 0.660 0.328 0.324 0.227 0.502 0.077 0.821
AHI, apnoea–hypopnoea index; A-P, anteroposterior; CSA, cross-sectional area; PNS, posterior nasal spine; PSG, polysomnography; RDI, respiratory disturbance index; SaO2, arterial oxygen saturation. a Statistical analyses were conducted using Spearman’s rank correlation coefficient; *P < 0.05, **P < 0.01.
large mean mandibular setback. The present study is novel in reporting the incidence rate of postoperative OSA, PSG parameter scores, and PAS changes after large mandibular setback. In recent decades, changes in the airway space after mandibular setback surgery have attracted increasing attention2,4– 11,14,16–18,20,24–27 . Most studies have shown that the oropharynx and hypopharynx narrow significantly after mandibular setback2,4,7,9,11,13,14,17,19. On the other
hand, it has been reported that the airway volume is significantly increased in bimaxillary surgery with maxillary advancement and mandibular setback27. Airway narrowing is considered a predisposing factor for OSA11,15,18. In the present study, the total pharyngeal, oropharyngeal, and hypopharyngeal volumes, as well as the retroglossal CSA were significantly reduced after surgery. The relationship between the extent of jaw movements and the PAS change is
unclear. Becker et al. identified a correlation between the extent of jaw movements and changes in airway measurements at the nasopharynx and oropharynx10. In contrast, there was no correlation in the present study, or in that performed by Kim et al.15. OSA-related sleep parameters are influenced by several variables. There was a significant positive correlation between an inferiorly located hyoid bone preoperative, as well as inferiorly dislocated retro-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
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Large mandibular setback and OSA palatal and retroglossal levels postoperative, and postoperative RDI and AHI (and/ or changes in the RDI and AHI). However, different from our hypothesis, there was no significant correlation between the extent of mandibular setback and AHI or RDI after surgery. Therefore, there is still no clear evidence that mandibular setback surgery causes OSA. Guilleminault et al.3 described two patients who underwent mandibular setback and subsequently developed OSA. Snoring in both patients worsened, and their RDI also increased significantly after surgery. Foltan et al.7 investigated the effect of bimaxillary surgery with maxillary advancement (4.44 mm) and mandibular setback (4.96 mm) on ventilation during sleep using a comparison of the presurgical and postsurgical PSG and pulmonary function test results. The authors concluded that orthognathic surgery worsened the breathing function during sleep. Foltan et al.20 also reported significantly increased RDI and AHI, as well as decreased SaO2 after bimaxillary surgery (maxillary advancement 5.9 mm, mandibular setback 4.1 mm). Hasebe et al.4 reported that two patients were diagnosed with mild OSA 6 months after large mandibular setback surgery (13.7 mm and 12.6 mm). In another study from the same institution, AHI did not significantly change after surgery in both the one-jaw and bimaxillary surgery groups (maximum mandibular setback 4.9 mm)12. In contrast, two studies showed opposite results. Sleep quality and efficiency in the PSG evaluation improved significantly after bimaxillary surgery (maxillary advancement 4.5 mm or 5.2 mm; mandibular setback 6.4 mm or 6.5 mm)11,13. The pharyngeal airway undergoes changes according to the extent and direction of surgical movement. In order to minimize the worsening of the facial profile, alternative surgical techniques (including a modified surgical method combined with bimaxillary anterior segmental osteotomy26 and maxillary expansion with mandibular anterior segment osteotomy28) have been introduced. The mandibular setback, combined with maxillary advancement, can reduce the extent of mandibular setback and consequently increase PSA11,13. Therefore, it is more favourable to minimize the postoperative reduction of the airway than to perform mandible surgery alone2,9. Moreover, different patient preferences must be considered, because the extent and direction of surgical movement can greatly influence the aesthetics of the facial profile.
Most Korean and East Asian patients with mandibular prognathism have a small nose and protruding upper lip. Therefore, most patients do not prefer maxillary advancement, which can lead to a more protrusive upper lip and upturned nose. We frequently use a surgical option with clockwise rotation of the maxillomandibular complex with maxillary posterior impaction for an aesthetic facial profile29. However, this maxillary posterior impaction should be carefully applied in patients with a small retropalatal airway, because superior movement of the tongue can push the soft palate and severely narrow the airway at this level. In this study, the A-P length, TW, and CSA at the retropalatal level tended to decrease after surgery. In contrast, at the retro-PNS level, the A-P length, TW, and CSA tended to increase postoperatively (Table 4). If patients can accept that facial aesthetics can be of secondary importance to deep sleep without any disorder, it is better to avoid this clockwise rotation of the maxillomandibular complex (with preservation of the prognathic chin, or slight improvement with setback genioplasty and contouring surgery) for the PAS. In this study, the mean maxillary A-P movement was <1 mm. There was a significant reduction in the oropharyngeal and hypopharyngeal volumes and the retroglossal CSA, with 33.3% occurrence of newly developed OSA after surgery. Therefore, maxillary advancement to reduce the mandibular setback movements is strongly recommended. It is crucial that the surgeon and patient communicate about the balance between correcting severe mandibular prognathism and ensuring sound respiratory function without postoperative OSA. This study is distinctive in that it only included patients with a large mandibular setback of >9 mm to evaluate the possibility of newly developed OSA postoperatively. However, it was limited by a small sample size of patients with severe mandibular prognathism who underwent PSG and 3D facial CT twice. Another study limitation is the shortterm evaluation of postoperative sleep parameters. Furthermore, other contributing factors were not investigated, such as alcohol consumption and mandibular setback movement, which can contribute to OSA. Further larger studies including the use of a questionnaire are needed to substantiate the study findings and to provide a more accurate assessment of the effect of mandibular setback on PAS and the development of OSA.
7
In this study, it was found that the total pharyngeal, oropharyngeal, and hypopharyngeal volumes and the retroglossal CSA were significantly reduced after bimaxillary surgery with large mandibular setback movements. New mild OSA developed postoperatively in four of the 12 patients according to both RDI and AHI scores. Surgeons must be aware of this potential surgical consequence. Therefore, mandibular setbacks that are large in extent should be reduced by maxillary advancement as much as possible. Funding
This research was supported by grant number 04-2011-0048 from the Seoul National University Dental Hospital Research Fund, Republic of Korea. Competing interests
The authors have no financial interests to declare with regard to the content of this article. Ethical approval
This study was approved by the Institutional Review Board of Seoul National University Dental Hospital (CRI12036). Patient consent
Patient consent was not required. Acknowledgements. The authors would like to thank Professor Shin-Jae Lee of the Department of Orthodontics at the School of Dentistry, Seoul National University for his statistical advice.
References 1. Muto T, Yamazaki A, Takeda S, Sato Y. Effect of bilateral sagittal split ramus osteotomy setback on the soft palate and pharyngeal airway space. Int J Oral Maxillofac Surg 2008;37:419–23. 2. Mattos CT, Vilani GN, Sant’Anna EF, Ruellas AC, Maia LC. Effects of orthognathic surgery on oropharyngeal airway: a metaanalysis. Int J Oral Maxillofac Surg 2011;40:1347–56. 3. Guilleminault C, Riley R, Powell N. Sleep apnea in normal subjects following mandibular osteotomy with retrusion. Chest 1985;88:776–8. 4. Hasebe D, Kobayashi T, Hasegawa M, Iwamoto T, Kato K, Izumi N, Takata Y, Saito C. Changes in oropharyngeal airway and respiratory function during sleep after orthog-
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012
YIJOM-4252; No of Pages 8
8
Yang et al.
5.
6.
7.
8.
9.
10.
11.
12.
13.
nathic surgery in patients with mandibular prognathism. Int J Oral Maxillofac Surg 2011;40:584–92. Chen F, Terada K, Hanada K, Saito I. Predicting the pharyngeal airway space after mandibular setback surgery. J Oral Maxillofac Surg 2005;63:1509–14. Kawakami M, Yamamoto K, Fujimoto M, Ohgi K, Inoue M, Kirita T. Changes in tongue and hyoid positions, and posterior airway space following mandibular setback surgery. J Craniomaxillofac Surg 2005;33:107–10. Foltan R, Hoffmannova J, Donev F, Vlk M, Sedy J, Kufa R, Bulik O. The impact of Le Fort I advancement and bilateral sagittal split osteotomy setback on ventilation during sleep. Int J Oral Maxillofac Surg 2009;38:1036–40. Jakobsone G, Neimane L, Krumina G. Twoand three-dimensional evaluation of the upper airway after bimaxillary correction of class III malocclusion. Oral Surg Oral Med Pathol Oral Radiol Endod Oral 2010;110:234–42. Hong JS, Park YH, Kim YJ, Hong SM, Oh KM. Three-dimensional changes in pharyngeal airway in skeletal class III patients undergoing orthognathic surgery. J Oral Maxillofac Surg 2011;69:e401–8. Becker OE, Avelar RL, Goelzer JG, Dolzan Ado N, Haas Jr OL, De Oliveira RB. Pharyngeal airway changes in class III patients treated with double jaw orthognathic surgery—maxillary advancement and mandibular setback. J Oral Maxillofac Surg 2012;70:e639–47. Gokce SM, Gorgulu S, Gokce HS, Bengi AO, Karacayli U, Ors F. Changes in posterior airway space, pulmonary function and sleep quality, following bimaxillary orthognathic surgery. Int J Oral Maxillofac Surg 2012;41:820–9. Uesugi T, Kobayashia T, Hasebea R, Ikeb M, Saito C. Effects of orthognathic surgery on pharyngeal airway and respiratory function during sleep in patients with mandibular prognathism. Int J Oral Maxillofac Surg 2014;43:1082–90. Gokce SM, Gorgulu S, Gokce HS, Bengi AO, Karacayli U, Ors F. Evaluation of pharyngeal airway space changes after bimaxillary orthognathic surgery with a 3dimensional simulation and modeling program. Am J Orthod Dentofacial Orthop 2014;146:477–92.
14. Lee Y, Chun YS, Kang N, Kim M. Volumetric changes in the upper airway after bimaxillary surgery for skeletal class III malocclusions: a case series study using 3dimensional cone-beam computed tomography. J Oral Maxillofac Surg 2012;70:2867– 75. 15. Kim HS, Kim GT, Kim S, Lee JW, Kim EC, Kwon YD. Three-dimensional evaluation of the pharyngeal airway using cone-beam computed tomography following bimaxillary orthognathic surgery in skeletal class III patients. Clin Oral Investig 2016;20:915–22. 16. Park SB, Kim YI, Son WS, Hwang DS, Cho BH. Cone-beam computed tomography evaluation of short- and long-term airway change and stability after orthognathic surgery in patients with class III skeletal deformities: bimaxillary surgery and mandibular setback surgery. Int J Oral Maxillofac Surg 2012;41:87–93. 17. Kawamata A, Fujishita M, Ariji Y, Ariji E. Three-dimensional computed tomographic evaluation of morphologic airway changes after mandibular setback osteotomy for prognathism. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2000;89:278–87. 18. Chen F, Terada K, Hua Y, Saito I. Effects of bimaxillary surgery and mandibular setback surgery on pharyngeal airway measurements in patients with class III skeletal deformities. Am J Orthod Dentofacial Orthop 2007;131:372–7. 19. Lee UL, Oh H, Min SK, Shin JH, Kang YS, Lee WW, Han YE, Choi YJ, Kim HJ. The structural changes of upper airway and newly developed sleep breathing disorders after surgical treatment in class III malocclusion subjects. Medicine (Baltimore) 2017;96: e6873. 20. Foltan R, Hoffmannova J, Pavlikova G, Hanzelka T, Klima K, Horka E, Adamek S, Sedy J. The influence of orthognathic surgery on ventilation during sleep. Int J Oral Maxillofac Surg 2011;40:146–9. 21. Kim MJ, Kim SG, Park YW. Positional stability following intentional posterior ostectomy of the distal segment in bilateral sagittal split ramus osteotomy for correction of mandibular prognathism. J Craniomaxillofac Surg 2002;30:35–40. 22. Choi JH, Mah J. A new method for superimposition of CBCT volumes. J Clin Orthod 2010;44:303–12. 23. Lee JH, Kim MJ, Kim SM, Kwon OH, Kim YK. The 3D CT superimposition method
24.
25.
26.
27.
28.
29.
using image fusion based on the maximum mutual information algorithm for the assessment of oral and maxillofacial surgery treatment results. Oral Surg Oral Med Oral Pathol Oral Radiol 2012;114:167–74. Enacar A, Aksoy AU, Sencift Y, Haydar B, Aras K. Changes in hypopharyngeal airway space and in tongue and hyoid bone positions following the surgical correction of mandibular prognathism. Int J Adult Orthodon Orthognath Surg 1994;9:285–90. Eggensperger N, Smolka W, Iizuka T. Longterm changes of hyoid bone position and pharyngeal airway size following mandibular setback by sagittal split ramus osteotomy. J Craniomaxillofac Surg 2005;33:111–7. Goh YH, Lim KA. Modified maxillomandibular advancement for the treatment of obstructive sleep apnea: a preliminary report. Laryngoscope 2003;113:1577–82. Havron AG, Aronovich S, Shelgikar AV, Kim HL, Conley RS. 3D Airway changes using CBCT in patients following mandibular setback surgery maxillary advancement. Orthod Craniofac Res 2019;22 (Suppl 1):30–5. Han JJ, Hong DH, Hwang SJ. Maxillary expansion and mandibular setback surgery with and without mandibular anterior segment osteotomy to correct mandibular prognathism with obstructive sleep apnea. J Craniofac Surg 2017;28:723–30. Ghosh A, Ray A. Converting a bi-jaw surgery to a single-jaw surgery: posterior maxdentoalveolar intrusion with illary microimplants to avoid the need of a maxillary surgery in the surgical management of skeletal class III vertical malocclusion. APOS Trends Orthodontics 2016;6:218–27.
Address: Soon Jung Hwang Department of Oral and Maxillofacial Surgery School of Dentistry Seoul National University 101 Daehakro Jongno-gu 03080 Seoul Republic of Korea Tel.: +82 2 2072 3061 Fax: +82 2 766 4948 E-mail: [email protected]
Please cite this article in press as: Yang HJ, et al. Airway changes and prevalence of obstructive sleep apnoea after bimaxillary orthognathic surgery with large mandibular setback, Int J Oral Maxillofac Surg (2019), https://doi.org/10.1016/j.ijom.2019.07.012