Introduction
This study aimed to evaluate the follow-up observation of patients with obstructive sleep apnea treated with maxillomandibular advancement (MMA) procedure with or without genial tubercle advancement (GTA).
Methods
A total of 25 patients (mean age 37.1 ± 17.3 years) were included in the study. Cone-beam computed tomography scans were taken before treatment; after presurgical orthodontic treatment; immediately after MMA procedure; and follow-up visit. All Digital Imaging and Communications in Medicine files were analyzed using the Dolphin 3D Imaging software program (Dolphin Imaging and Management Solutions, Chatsworth, Calif) to determine the total airway volume (TAV), airway area (AA), and minimal cross-sectional area (MCA). Dolphin 3D voxel-based superimposition was used to determine the amount of skeletal advancement with MMA and changes after surgery.
Results
Significant increase in TAV, AA, and MCA was found with MMA treatment (40.6%, 28.8%, and 56.4%, respectively, P <0.0001). Smaller but significant decrease in TAV, AA, and MCA was found during a follow-up visit (20.0%, 9.7%, and 26.8%, respectively, P <0.0001) giving a net increase of TAV, AA and MCA (35.8%, 27.1%, and 45.9%, respectively). No significant differences were found in any of the airway measurements with or without the GTA procedure. The average forward movements of the maxilla, mandible, and chin were 6.6 mm, 8.2 mm, and 11.4 mm, respectively. A relapse of less than 1 mm was found in each of the variables during the follow-up period. No correlation was found between the magnitudes of skeletal advancement and the change in oropharyngeal airway space (OPAS).
Conclusions
Significant increase in OPAS can be expected with MMA surgery with or without GTA procedure in patients diagnosed with obstructive sleep apnea. A partial loss in OPAS was found during the follow-up visit. The surgical movements were found to be stable, with less than 1 mm of relapse during the follow-up period, which was not clinically significant.
Highlights
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MMA procedure is effective in treatment of patients with sleep apnea.
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A significant increase in oropharyngeal space can be obtained with MMA.
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Maxillomandibular advancement is stable with <1 mm of skeletal relapse.
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There was no difference in airway volume with maxillomandibular advancement with or without genioplasty.
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No correlation was found between skeletal advancement and change in airway space.
Obstructive sleep apnea syndrome (OSAS) is a sleep-related breathing disorder, characterized by disrupted snoring and repetitive upper airway obstructions. It results in a continuum of changes in upper airway resistance, reduced blood oxygen levels, fragmentation of sleep, snoring, daytime fatigue, and hypersomnia which often lead to occupational disability and behavioral changes.
Successfully treating patients with OSAS remains a challenge among all dental and medical specialists. Continuous positive airway pressure is considered the therapeutic mainstay for OSAS. However, more than 50% of patients are intolerant and reject the therapy within the first few months after initiation. Other treatments for OSAS aimed at enlarging the upper airway while decreasing airway collapsibility include mandibular positioning devices and surgical reduction of the pharyngeal soft tissues. , However, mandibular positioning devices are removable appliances and have compliance limitations, and patients still seek alternative treatment options, including upper airway surgery.
The severity of OSAS is not the only determinant of candidacy for maxillomandibular advancement (MMA); these patients often require detailed evaluation and counseling before MMA is selected as a treatment option. Waite et al first described the MMA technique was a procedure for the treatment of patients with OSAS. It was performed by a combination of LeFort I and bilateral sagittal split osteotomies procedures, which moved both jaws anteriorly. This procedure leads to the anterior repositioning of the soft palate, tongue, and pharyngeal tissues. MMA is currently considered to be the most effective craniofacial surgical technique for treating OSAS in adults. It is beneficial in terms of the increased total volume of the upper airway size, improved oximetry indicators, and better quality of life measured on the Epworth sleepiness scale. Genial tubercle advancement (GTA) is often performed concomitantly with MMA for esthetic purposes. Body mass index (BMI), age, severity of OSAS, airway space, amount of skeletal advancement and relapse of MMA have been reported as clinical factors predictive of surgical success for treatment of patients with OSAS.
Cephalometric imaging has been commonly used to assess the anatomy of the facial skeleton and upper airway. However, it is limited in its representation of 3-dimensional (3D) structures. Cone-beam computed tomography (CBCT) provides the ability to visualize the upper airway and perform 3D reconstructions. However, it should not be used to diagnose sleep apnea, because such imaging currently does not represent a proper risk assessment technique or screening method. When available, it may be used for monitoring or treatment planning. Three-dimensional imaging exposes patients to a lower radiation dose than conventional computed tomography and is a faster procedure. CBCT is a noninvasive, effective, and reliable technique for airway evaluation. CBCT can as well produce more accurate images without distortion and can be used to evaluate 3D skeletal changes via superimposition with the cranial base structure, which is not affected by surgery.
Although CBCT is the preferred method for evaluating oropharyngeal airway space (OPAS), few studies have compared the use of lateral cephalogram and CBCT in evaluating airway space. Moreover, there are few follow-up studies evaluating airway changes and skeletal stability of MMA for patients with OSAS.
This study aimed to determine the follow-up airway changes in patients with OSAS treated with MMA procedure with or without GTA. In addition, this study attempted to determine if there is a relationship between skeletal and airway changes in order to gain a better understanding of the stability after the MMA procedure.
Material and methods
This study was carried out on 25 subjects. The sample size for the study was predetermined using G∗Power (version 3.1, Faul, Erdfelder, Lang, & Buchner, Düsseldorf, Germany) for the repeated measures analysis of variance to detect a medium effect (d = 0.25) with statistical power at 0.80 and α = 0.05 significance level (actual power was 0.99).
This study was approved by the West Virginia University Institutional Review Board (protocol no. 1704532922). This was a retrospective study using existing scans selected from the database of 1 of the investigator’s (M.B.) orthodontics office, and permission was obtained from the office to use the records for the study.
The following criteria were considered in the selection of the subjects: patients who were 15 years or older, patients who were diagnosed with OSAS with polysomnography or airway constriction at 1 or more levels along with the posterior airway space, and patients with adequate radiographic documentation. Patients with a previous history of orthognathic or maxillofacial surgery and/or with craniofacial abnormalities were excluded from the study.
All patients underwent presurgical orthodontic phase for an average of 18 months. All patients received MMA surgery, but 15 (10 females and 5 males) of these patients underwent MMA with GTA. After surgery, all patients were followed for an average of 10 months.
The CBCT scans were taken before treatment (T1), after presurgical orthodontic treatment (T2), immediately after MMA procedure (T3), and follow-up visit (T4). Thus, T2 − T1 represented changes due to orthodontic treatment only, T3 − T2 represented changes due to MMA procedure, and T4 − T3 represented changes 10 months follow-up after surgery. Each patient served as his or her own control. During image acquisition, the patient was in a natural head posture and in a maximum interception position. All CBCT scans were taken using Kodak 9500 Cone Beam 3D System (Carestream Health, Rochester, NY) with the following settings: 10 mA, 90 kV, exposure time of 10.8 seconds, voxel size of 300 mm, axial slice thickness of 0.2 mm, and scanning area of 18 × 20.6 cm. All files were originated and kept as Digital Imaging and Communications in Medicine format files.
For measurements of OPAS, Dolphin (version 11.95, Dolphin Imaging and Management Solutions, Chatsworth, Calif) software was used to calculate the total airway volume (TAV), airway area (AA) and the minimal cross-sectional area (MCA) selected from predefined structures. The borders of OPAS were identified, similar as described in El and Palomo, between the palatal plane (ANS-PNS) superiorly extending to the posterior wall of the pharynx and the plane parallel to the palatal plane that passes from the most anterior-inferior point of the third cervical vertebrae and the base of the epiglottis inferiorly ( Fig 1 ). TAV, AA, and MCA measurements of the airway were then calculated by using a specific analysis tool in Dolphin ( Fig 2 ) for each patient at all time points ( Fig 3 ).
For skeletal measurements, Dolphin 3D voxel-based superimposition method proposed by Bazina et al, was adopted to assess the skeletal changes and relapse after MMA. Dolphin, ITK-SNAP, an open-source software (version 3.2; http://www.itksnap.org ) and 3D Slicer (version 4.8; http://www.slicer.org ) imaging software programs were used. Three areas were selected to measure the differences between the 2 models at the T3 − T2 surgical period. The 3 areas were A-point, B-point, and Pogonion point ( Fig 4 ). After defining these areas, the absolute differences in millimeters between the 2 3D surfaces were then calculated by using the Mesh Statistics tool in 3D Slicer. Quantification of the differences was done by measuring the distance between the 2 surface models using closest-point color maps as well ( Fig 5 ). This process was performed and repeated for each patient at the T4 − T3 period as well to assess the relapse after the surgery.
Statistical analysis
The data collected were compiled in an Excel spreadsheet (Microsoft, Redmond, Wash) and transferred to SAS software (version 9.4, SAS Institute, Cary, NC) for statistical analysis. Descriptive analyses were conducted to get a basic understanding of the study sample. To determine the change in airway measurements between different time points, we used repeated measures analysis of variance analysis. Tukey’s test was followed to compare individual measurement means. The significant cutoff value for the Bonferroni correction test was set to 0.008 (0.05 per 6). We incorporated a paired t test to examine the significance of the advancement and relapse in skeletal change. We used Pearson correlation tests to evaluate the relationship between airway change and skeletal change. Intraclass correlation coefficients (ICC) were calculated to evaluate the reliability of the repeated measurements. All statistical tests were 2-sided, and P <0.05 was considered statistically significant.
Results
For error measurements, 15 subjects were analyzed by the same researcher a second time with a 2-week interval in between. ICC values were calculated to determine the reliability of measurements. The ICC values ranged from 0.94 to 0.98, indicating a high level of agreement between the 2 measurements.
A total of 25 Caucasians (18 females and 7 males) who were evaluated for OSAS and underwent MMA surgical treatment were included in the final study. The average age at the time of surgery was 37.1 years (range 15-62 years). Fifteen of these patients underwent MMA with GTA procedures.
For the subjects who completed the OSAS diagnosis with preoperative polysomnography (PSG), the preoperative average of the apnea-hypopnea index was 22.6 (range 5.0-72.9), and peripheral oxygen saturation was 87.4% (range 82%-95%). The preoperative BMI was 30.6 kg/m 2 (range 25.4-35.8).
The results showed no significant increase in TAV with a mean of 1305.08 mm 3 after the presurgical orthodontic phase. After the MMA procedure, TAV was increased by 9019.7 mm 3 in the T3 − T2 period, which represents a gain of 40.6% ( P <0.0001). During the follow-up period, a reduction of 3699.2 mm 3 , or a loss of 20.0%, was found after surgery (T4 − T3, P < 0.0001) ( Table I ).
| Variable | Time point | Mean | SD | P value | Mean change | Percentage change, % | ||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| T2 − T1 | T3 − T2 | T4 − T3 | T2 − T1 | T3 − T2 | T4 − T3 | T2 − T1 | T3 − T2 | T4 − T3 | ||||
| TAV, mm³ | T1 | 11886.1 | 976.4 | 0.34 | <0.0001 ∗ | <0.0001 ∗ | 1305.1 | 9019.7 | −3699.2 | 9.9 | 40.6 | −20.0 |
| T2 | 13191.2 | 962.7 | ||||||||||
| T3 | 22210.9 | 1198.4 | ||||||||||
| T4 | 18511.7 | 1344.2 | ||||||||||
| AA, mm 2 | T1 | 521.1 | 27.7 | 0.40 | <0.0001 ∗ | 0.020 | 37.8 | 225.7 | −69.5 | 6.8 | 28.8 | −9.7 |
| T2 | 558.8 | 28.1 | ||||||||||
| T3 | 784.5 | 31.2 | ||||||||||
| T4 | 715.0 | 32.1 | ||||||||||
| MCA, mm 2 | T1 | 122.2 | 14.6 | 0.99 | <0.0001 ∗ | 0.002 ∗ | 2.6 | 161.5 | −60.5 | 2.1 | 56.4 | −26.8 |
| T2 | 124.8 | 13.1 | ||||||||||
| T3 | 286.4 | 17.6 | ||||||||||
| T4 | 225.9 | 20.9 | ||||||||||
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