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CRANIOMAXILLOFACIAL DEFORMITIES/COSMETIC SURGERY
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Effects of Le Fort I Osteotomy on the Nasopharyngeal Airway—6-Month Follow-Up Mohammed Almuzian, BDS, MScOrtho, MScHCA, DClinDentOrtho,* Anas Almukhtar, BDS, MScOrtho,y Xiangyang Ju, BEng, PhD,z Ali Al-Hiyali, BDS, MScOMFS,x Philip Benington, BDS, MSc,k and Ashraf Ayoub, BDS, MDS, PhD{
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Purpose:
The literature discussing the impact of a single Le Fort I osteotomy on nasopharyngeal airways is limited. This study assessed the volumetric changes in the nasopharyngeal airway after a single Le Fort I osteotomy and explored the correlation between these changes and 3-dimensional surgical movements of the upper jaw.
Materials and Methods:
This retrospective study was conducted in 40 patients who had undergone a single Le Fort I (maxillary advancement with or without impaction) to correct Class III malocclusion from maxillary hypoplasia. Preoperative (T1) and 6-month postoperative (T2) cone-beam computed tomographic (CBCT) scans of these patients were used for analysis. Maxillary surgical movements and volumetric changes in the nasopharyngeal airway were measured. The reproducibility of the measurements was evaluated using paired t tests and intraclass correlation coefficients. The Wilcoxon test and Pearson correlation coefficient were applied to evaluate the importance of volumetric changes in the nasopharyngeal airway space and assess the correlations of these changes to the maxillary surgical movements. Six patients were excluded from the study owing to major differences (>5 ) in their head and neck posture between the T1 and T2 CBCT scans. The errors of the repeated measurements were insignificant (P > .05), with a high level of agreement (r = 0.99; P < .05) between the repeated digitization of the landmarks. There was a statistically significant impact of a Le Fort I osteotomy on the right maxillary sinus (decreased by 17.8%) and the lower retropalatal space (expanded by 17.3%; P < .05). The correlation between the change in airway volume and the magnitude of surgical maxillary movements was moderate (r = .4). Similarly, there was a moderate correlation between changes in the upper nasopharynx and those in the hypopharynx.
Results:
Conclusion:
The single Le Fort I osteotomy was found to increase the retroglossal airway volume. This could be important for the treatment of obstructive sleep apnea in patients with maxillary deficiency. A long-term follow-up assessment of a larger sample with a functional assessment of airway would be beneficial to confirm these findings. Ó 2015 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1-12, 2015
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*Department of Orthodontics, Glasgow Dental Hospital & School,
Address correspondence and reprint requests to Dr Almuzian:
Glasgow, UK.
Department of Orthodontics, Glasgow Dental Hospital and School,
yPostgraduate Student, Glasgow University Medical School, MVLS
378 Sauchiehall Street, Glasgow, UK; e-mail: dr_muzian@hotmail.
College, Glasgow Dental Hospital & School, Glasgow, UK.
com
zMedical Devices Unit, NHS Greater Glasgow and Clyde,
Received February 23 2015
Glasgow, UK. xPostgraduate Student, Glasgow Dental Hospital & School,
Ó 2015 American Association of Oral and Maxillofacial Surgeons
Glasgow, UK.
0278-2391/15/00907-6
Accepted June 26 2015
kConsultant Orthodontist, Glasgow Dental Hospital & School,
http://dx.doi.org/10.1016/j.joms.2015.06.172
Glasgow, UK. {Professor, Department of Oral and Maxillofacial Surgery, Glasgow Dental Hospital & School, Glasgow, UK.
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LE FORT I OSTEOTOMY AND NASOPHARYNGEAL AIRWAY
Table 1. POINTS AND LANDMARKS
Point
Definition
A ANS
Deepest (most posterior) midline point on the curvature between the ANS and the prosthion Tip of the bony anterior nasal spine at the inferior margin of the piriform aperture in the midsagittal plane (often used to define the anterior end of the palatal plane) Basion; most anterior inferior point on the margin of the foramen magnum in the midsagittal plane Second cervical vertebra Superoposterior extremity of the odontoid process of the C2 Most anteroinferior point of the body of the third cervical vertebra Most superior point of the crista galli Tangent point at the superoposterior extremity of the odontoid process of the C2 Most inferoposterior point on the body of the C2 Most inferoposterior point on the body of the fourth cervical vertebra Most superior point of the odontoid process of C2 Lowest point on the left inferior orbital margin Most superior point of the outline of the left external auditory meatus (anatomic porion) Most posterior point of the left lateral pterygoid plate as viewed on the coronal section Most lateral point in the left frontozygomatic suture Nasion; junction of the nasal and frontal bones at the most posterior point on the curvature of the bridge of the nose Most posterior point on the bony hard palate in the midsagittal plane Prosthion; most anterior inferior point of the alveolar bone crest of the maxillary incisors Lowest point on right inferior orbital margin Most posterior point of right lateral pterygoid plate as viewed in the coronal section Most lateral point in the right frontozygomatic suture Sella; center of the hypophyseal fossa (sella turcica) Midpoint of line between the sella and basion Most posterior point of the middle of the soft palate
Ba C2 C2sp (or C2od) C3ai Cg Cv2ig Cv2ip Cv4ip Cvod LOr Lpo LtLtPtg Lzyg N PNS Pr ROr RtLtPtg Rzyg S So Spip
Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
The impact of corrective jaw surgery on the upper airway spaces depends on the type of operation, the amount and direction of the skeletal movements, and a patient’s age, gender, and variations. Mandibular setback surgery results in a decrease in airway patency; therefore, bimaxillary osteotomy is indicated for the correction of large anteroposterior discrepancies.1-5 Rhinomanometric techniques to measure nasal airway resistance have shown that maxillary impaction increases alar width, with a subsequent decrease in nasal airway resistance.6,7 Another study based on 2-dimensional cephalometric analysis has proved that maxillary advancement meaningfully increases dimensions of the airway.8 The lack of information on the impact of a Le Fort I osteotomy on 3-dimensional measurements of the nasopharyngeal airway inspired this study. The study assessed assess volumetric changes in the nasal cavity, maxillary sinus, and oropharyngeal airway after a Le Fort I osteotomy and investigated the correlation between these changes and surgical maxillary movements.
Materials and Methods Q11
The sample size for this study was calculated using the Researcher’s Tool Kit Calculator, which indicated
that a cohort of 32 patients would produce a confidence level of 95% and a statistical power of 50%. Therefore, it was decided to recruit 40 patients to overcome the potential exclusion of some cases. The study was approved by the West of Scotland research Q12 ethics service (reference, 12/WS/0133). The inclusion criteria were as follows: 1. Caucasian male and female patients 16 to 45 years old who had a Le Fort I osteotomy (maxillary advancement with or without impaction) to correct the underlying Class III malocclusion. 2. No previous tonsillar, nasal, adenoid, head or neck surgery. 3. No major variation in the head and craniocervical orientation between the preoperative (T1) and postoperative (T2) cone-beam computed tomographic (CBCT) scans. 4. No previous orthodontic expansion or mandibular orthognathic surgical procedure. Surgery was carried out by the same surgeon and the orthodontic treatment was carried out by various clinicians, ranging from consultants to specialist trainees, in the Glasgow Dental Hospital and School (GDHS; Glasgow, UK). All patients underwent presurgical
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Table 2. LINES AND PLANES
Line and Plane ANSV plane
C2sp/V plane C3ai/H plane Cg-Cvod plane CVT plane
Epi/FH plane
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LF plane LOrH plane Orbital plane PAL PNSH plane PNSV plane PNSV plane Ptg plane SN plane Spip/FH plane SPPFH plane TH plane TV plane Z plane
Definition Perpendicular plane to true horizontal plane passing through the nasion in the lateral view; if the midpalatine split extends to involve the anterior nasal spine, then the most posterior anterior nasal spine is considered Defined by the frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra Plane parallel to the Frankfort horizontal plane passing through the most anteroinferior point of the body of the third cervical vertebra Line connecting the crista galli and the superoposterior extremity of the odontoid process of the second cervical vertebra Line passing through the tangent point at the superoposterior extremity of the odontoid process of the second cervical vertebra and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra Plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the entrance of the esophagus; technically by the plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the most anteroinferior point of the body of the fourth cervical vertebra (C4ai/H plane) Left Frankfort; line connecting left orbit and left porion points True horizontal plane tangent to the lowest point on the left inferior orbital margin Line connecting right orbit and left orbit Line through the tangent point at the superoposterior extremity of the odontoid process of the second cervical vertebra and the most inferoposterior point on the body of the second cervical vertebra Plane parallel to the Frankfort horizontal plane passing through the posterior nasal spine and extending to the posterior wall of the pharynx Perpendicular to true horizontal plane passing through the posterior nasal spine; if the midpalatine split extends to involve the posterior nasal spine, then the most posterior end of the palate is considered True vertical plane passing through the posterior nasal spine Line connecting the most posterior points of the left and right lateral pterygoid plate as viewed in the coronal section Plane representing a line connecting the sella to the nasion Plane parallel to the Frankfort horizontal plane passing through the most posterior point of the middle of the soft palate Sagittal plane perpendicular to the Frankfort horizontal plane passing through the lateral walls of the maxillary sinus True horizontal; a reference line constructed by drawing a line perpendicular to the true vertical line True vertical; a reference line constructed perpendicular to the floor Zygomatic; line connecting the most lateral points on the right and left frontozygomatic suture
Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015. Table 3. CEPHALOMETRIC ANGLES
Angle Lordosis Pitch angle (P angle) Roll angle (R angle) Yaw angle (Y angle)
Definition Measured by the mean of the SN-PAL and CVT-NS angles (Fig 1A) Inner angle of the intersection of the SN and TH planes; represents the change in head orientation in the sagittal plane (cranial base inclination angle; Fig 1A) Inner angle of the intersection of the Z and TH planes; represents change in head orientation in the frontal plane (Fig 1B) Represents change in head orientation in the mediolateral plane, measured by right (Cg-CvodRtLtPtg)and left (Cg-Cvod-LtPtg) angles (Fig 1C)
Abbreviations: Cg-Cvod-LtLtPtg, angle formed by the most superior point of the crista galli, the most superior point of the odontoid process of the second cervical vertebra, and the most posterior point of the left lateral pterygoid plate as viewed in the coronal section; Cg-Cvod-RtLtPtg, angle formed by the most superior point of the crista galli, the most superior point of the odontoid process of the second cervical vertebra, and the most posterior point of the right lateral pterygoid plate as viewed in the coronal section; CVT-NS angle, angle formed by the line through and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra and the line connecting the nasion to the sella; SN-PAL angle, angle formed by the line connecting the sella and nasion and the line through the tangent point at the superoposterior extremity of the odontoid process of and the most inferoposterior point on the body of the second cervical vertebra; TH plane, true horizontal plane; Z plane, zygomatic plane. Q3 Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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FIGURE 1. Head and craniocervical orientation angles. A, Pitch and lordosis angle. B, Roll angle. C, Yaw angle. CVT-NS angle, angle formed by the line through and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra and the line connecting the nasion to the sella; P angle, pitch angle; R angle, roll angle; SN-PAL angle, angle formed by the line connecting the sella and nasion and the line through the tangent point at the superoposterior extremity of the odontoid process of and the most inferoposterior point on the body of the Q1 second cervical vertebra; Y angle, yaw angle. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015. FLA 5.2.0 DTD YJOMS56897_proof 15 July 2015 8:55 pm CE AH
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FIGURE 2. Standardized orientation technique. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
orthodontic treatment using upper and lower fixed appliances, with or without dental extractions. Two CBCT scans were acquired for each patient: immediately before the Le Fort I osteotomy (T1) and 6 months after surgery (during or after orthodontic
treatment; T2). All CBCT scans were taken at the GDHS using an iCAT scanner (Imaging Sciences International, Hatfield, PA) by a trained radiographer. Patients were required to take off any spectacles or jewelry, keep their eyes gently closed, and keep their
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FIGURE 3. Superimposition on cranial-base technique. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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15-18
Table 4. ANATOMIC BOUNDARIES OF AIRWAY SPACES
Boundaries Volume of Interest Lower nasal cavity Upper nasopharynx Upper oropharynx Retroglossal space Hypopharynx Maxillary sinus*
Anteriorly
Posteriorly
Superiorly
Inferiorly
Medially
Laterally
NSV plane PNSV plane PNSV plane PNSV plane PNSV plane
PNSV plane C2sp/V plane C2sp/V plane C2sp/V plane C2sp/V plane
LOrH plane LOrH plane PNSH plane Spip/FH plane C3ai/H plane
Inferior nasal wall PNSH plane Spip/FH plane C3ai/H plane Epi/FH plane
Nasal septum N/A N/A N/A N/A
Lateral nasal wall SPPFH SPPFH SPPFH SPPFH
Abbreviations: C2sp/V, frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra; C3ai/H, plane parallel to the Frankfort horizontal plane passing through the most anteroinferior point of the body of the third cervical vertebra; Epi/FH, plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the entrance of the esophagus; LOrH, true horizontal plane tangent to the lowest point on the left inferior orbital margin; N/A, not applicable; NSV, true horizontal plane passing through the posterior nasal spine; PNSH, plane parallel to Frankfort horizontal plane passing through the posterior nasal spine and extending to the posterior wall of the pharynx; PNSV, perpendicular to true horizontal plane passing through the posterior nasal spine (if the midpalatine split extends to involve the posterior nasal spine, then the most posterior end of the palate is considered); Spip/FH, plane parallel to the Frankfort horizontal plane passing through the most posterior point of the middle of the soft palate; SPPFH, sagittal plane perpendicular to the Frankfort horizontal plane passing through the lateral walls of the maxillary sinus. * All sinus cavities were included to the level of the LOrH plane superiorly and their minimum constricted openings with the adjacent nasal and paranasal cavities circumferentially. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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teeth in centric occlusion. They also were instructed to keep their lips and tongue in a normal relaxed position during the scan. For each scan, the patient was positioned with the Frankfort plane parallel to the floor (natural head position).9 An extended field of view of 22 cm was used to capture the facial skeleton from the glabella to the angle between the chin and the throat. The Digital Imaging and Communications in Medicine (DICOM) data for the T1 and T2 CBCT scans were imported and displayed using OnDemand3D software (Cybermed Inc, Seoul, Korea). Based on the reported validity of 3-dimensional cephalometric assessments,10,11 the head posture and craniocervical inclination (lordosis) were measured on each CBCT scan taken at T1 and T2. Points, planes, and angles used in this study are presented in Tables 1 to 3 and Figure 1. Four angular measurements (pitch, roll, yaw, and craniocervical angle) were recorded to the nearest degree. The first 3 angular measurements correspond to head posture and the latter measurement corresponds to lordosis. Patients were excluded if the change in head posture or lordosis was greater than 5 between the T1 and T2 scans, because such changes have an important influence on nasopharyngeal airway measurements.12-14 Each T1 CBCT scan was digitally oriented so that the plane of the pterygoid plate, left Frankfort horizontal plane, and zygomatic plane were parallel to the true horizontal plane, and the data were saved as a new T1 (NT1) scan (Fig 2). The T2 CBCT scan was superimposed on the corresponding NT1 scan, using the ante-
rior and posterior cranial bases as stable structures, and saved as a new T2 (NT2) scan (Fig 3). This allowed a standardized segmentation and eliminated the effect of positional error on segmentation. Using the NT1 and NT2 scans, the airway boundaries were determined, segmented, and measured using the ITK-SNAP software package (http://www.itksnap.org; Table 4, Fig 4).15-18 The manufacturer’s instructions for Q16 Q15 use of the ITK software package was followed.19 The measurement of the volume of the lower nasal cavity was limited to the respiratory space of the nasal cavity to minimize the inclusion of the paranasal sinuses and their related hiatuses. The retropalatal space was subdivided into upper (URP) and lower (LRP) retropalatal spaces by the frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra (C2sp/V plane). If the odontoid process of the second cervical vertebra was located superior to the C2sp/V plane, then the entire segment was considered part of the LRP space.15,16,20 Regarding the inferior boundaries of the hypopharynx (HP) space, if the epiglottis was positioned halfway across the HP, then a second volume measurement was added to include this area or volume within the region of interest. All volumetric measurements were carried out by 1 examiner and repeated after 1 week, and the 2 sets of measurements were compared to validate the reproducibility of the landmarks used for segmentation of the airway space boundaries. The magnitude of the maxillary skeletal movements was measured using the Maxilim software package
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FIGURE 4. Airway space volumetric measurement and segmentation using ITK-SNAP. A, Saggital view. B, Coronal view. (Fig 4 continued on next page.) Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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(Medicim NV, Mechelen, Belgium). Several markers were identified and digitized directly on the DICOM slices of the NT1 and NT2 scans. For maxillary surgical movements, orthogonal distances were recorded to the 3 common reference planes. The net movements were calculated as the differences between the NT1 and NT2 landmark positions in the X, Y, and Z planes (Fig 5). STATISTICAL ANALYSIS
The distribution of the sample data was assessed using the Kolmogorov-Smirnov test, which showed non-Gaussian distribution for most parameters. The Friedman test and Wilcoxon rank sum test (P < .05) were applied to determine a statistical difference owing to age or gender and to evaluate the importance of volumetric changes in the nasopharyngeal spaces secondary to a Le Fort I osteotomy.
The Pearson correlation coefficient was applied to assess the correlation between volumetric changes and the magnitude of surgical maxillary movement in 3 planes of space as a result of a Le Fort I osteotomy.
Results Six patients were excluded from the study because of a major difference ($5 ) in head and neck posture between the T1 and T2 CBCT scans. There was no statistically significant difference between the repeated volumetric measurements (P > .05), with a high level of agreement (r = 0.99; P < .05; Table 5). The main surgical movement of the maxilla was an anterior shift of 6.42 1.51 mm (range, 3.43 to 8.5 mm). This also was associated with a mild vertical impaction of 0.65 0.28 mm (range, 0.07 to 2.27 mm) more on the right side (mean, 0.82 0.32 mm; range,
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FIGURE 4 (cont’d). C, Axial view. D, Virtual model representation of nasopharyngeal airway spaces. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
0.1 to 2.9 mm) than on the left side (mean, 0.47 0.24 mm; range, 0.03 to 1.63 mm), with a mild mediolateral rotation of 0.86 0.44 mm (range, 0.2 to 1.73 mm; Table 6). Table 7 presents the volumetric changes of the nasopharyngeal airway spaces secondary to a Le Fort I Osteotomy. The right maxillary sinus (RMS) was significantly decreased by 17.8%, whereas the LRP was significantly expanded by 17.3% (P < .05). Genderrelated changes were not detected in this study (Friedman test, P = .4452). The correlation between the change in the volume of airway space and the magnitude of surgical maxillary movements was mild (r = 0.4; Table 8). Similarly, there was a weak correlation between the volumetric changes at different levels of the nasopharyngeal
airway space, except between the upper nasopharynx (UNP) and the URP (correlation coefficient, 0.53; Table 9). Q18
Discussion This study relied on an internal reference structure during segmentation that would not be affected by occlusal settling or orthodontic movement between the T1 and T2 CBCT scans. This is one of the explanations for the differences between the results of this study and other published data that have relied on dental reference points.17 Park et al17 used cervical vertebral levels to subdivide the airway space, but this was prone to errors because it relied on the patient’s head and neck posture during CBCT scanning.
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FIGURE 5. Skeletal movement measurement using Maxilim software. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
Changes in the head and neck posture owing to the effect of surgery or projectional scanning errors would affect the pharyngeal airway volume and crosssectional measurements.12,21-23 This source of error was detected in this study by measuring the angles of head orientation and neck lordosis at T1 and T2; approximately 10% of patients showed major changes in head and neck posture and were excluded. This study used 2 distinguishing methodologies. First, it assessed the effects of a single Le Fort I osteotomy on the nasopharyngeal airway space. Second, segmentation of the nasopharyngeal space allowed
changes at different levels to be quantified because each anatomic segment is related to a specific problem. Hernandez-Alfaro et al16 found a statistical expan- Q19 sion in total pharyngeal airway space (37.7%). This is dissimilar from the findings of the present study, which could be due to the fact that the entire airway space was considered and measured as a single unit, rather than in segments. With regard to volumetric changes in levels of the nasal cavity, the LNC was Q20 decreased by one tenth of its preoperative volume. This could be due to the combined maxillary vertical impaction, which decreases the effective volume of
Table 5. REPRODUCIBILITY OF VOLUMETRIC MEASUREMENTS
Wilcoxon signed rank test, P < .05 ICC
LMS
RMS
LNC
UNP
URP
LRP
RG
HP
0.742
0.945
0.438
0.156
0.375
0.250
0.383
0.844
0.999
1.000
0.999
1.000
1.000
1.000
1.000
1.000
Abbreviations: HP, hypopharynx; ICC, intraclass correlation coefficient; LMS, left maxillary sinus; LNC, ---; LRP, lower Q4 retropalatal space; RG, ---; RMS, right maxillary sinus; UNP, upper nasopharynx; URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
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Table 6. DEGREE OF MAXILLARY SURGICAL MOVEMENTS
Table 8. CORRELATION BETWEEN CHANGE IN VOLUME OF AIRWAY SPACE AND MAGNITUDE OF SURGICAL SKELETAL MOVEMENT
Mean SD Minimum Maximum Net anteroposterior movement Net vertical movement Right-side vertical movement Left-side vertical movement Net mediolateral movement
6.42 1.51
3.43
8.5
0.65 0.28 0.82 0.32
0.07 0.1
2.27 2.9
0.47 0.24
0.03
1.63
0.86 0.44
0.2
1.73
LMS RMS LNC UNP URP LRP RG HP
Abbreviation: SD, standard deviation. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
Q21
the LNC and disguises the effect of maxillary advancement. Although the changes were not statistically meaningful, they were similar to the findings of Pourdanesh et al.23 The ratio of the RG space at T1 to T2 was approximately 4:6, with approximately 15% of volumetric expansion after the Le Fort I osteotomy. An anatomically based explanation is that the superior attachments of the palatoglossus muscle were displaced anteriorly secondary to maxillary advancement with subsequent anterior displacement of the tongue and expansion of the RG airway volume.24 Because the main pathophysiology of obstructive sleep apnea and hypopnea (OSAH) is that the tongue falls backward and blocks the RG airway space during sleep, the Le Fort I osteotomy might be an alternative option for treatment of OSAH in patients with maxillary hypoplasia. Moreover, there was a decrease in the volume of the 2 maxillary sinuses, specifically the volume of the
Anteroposterior Movement
Vertical Movement
Mediolateral Movement
0.020 0.039 0.128 0.018 0.053 0.044 0.12 0.032
0.014 0.030 0.100 0.082 0.047 0.104 0.184 0.007
0.040 0.030 0.041 0.069 0.022 0.088 0.226 0.025
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right maxillary sinus; UNP, upper nasopharynx; URP, Q6 upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
RMS, which was decreased to one fifth of its preoperative value. This can be explained by the differential impaction of the right and left sides of the maxilla to correct occlusal canting as a result of the dominance of the right facial half.25-28 This assumption requires a larger sample in which a Le Fort I osteotomy is performed to correct the underlying asymmetry. Although the main objective of the study was to assess the impact of Le Fort I maxillary advancement on the nasopharyngeal airway, minor simultaneous surgical movements in the vertical or medial and vertical directions were unavoidable. The study showed a weak correlation between the volumetric changes at different levels of the upper airway tract and the magnitude of maxillary surgical movement. However, there was a moderate positive correlation between changes in the volume of the
Table 7. VOLUMETRIC CHANGES IN NASOPHARYNGEAL AIRWAY SPACES SECONDARY TO LE FORT I OSTEOTOMY
T1 Airway Space LMS RMS LNC UNC RG URP LRP HP
T2
Mean
SD
Mean
SD
Percentage of Volumetric Changes, (T2 T1)/T1 100
Wilcoxon Signed Rank Test, P < .05
9,705.6 10,471.6 7,917.2 6,640.2 2,000.7 8,534.1 8,605.2 3,863.6
2,482.1 3,488.6 1,452.5 2,661.6 3,227.0 7,738.0 4,684.9 2,180.9
9,511.7 8,606.2 7,189.2 7,311.7 1,704.6 9,053.8 10,089.6 3,243.5
2,468.2 3,427.4 2,306.7 2,434.1 2,091.0 4,039.1 5,590.3 1,939.1
2.0 17.8 9.2 10.1 14.8 6.1 17.3 16.1
.408 .015 .109 .162 .5186 .1627 .013 .501
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right maxillary sinus; SD, standard deviation; T1, preoperative; T2, 6 months postoperative; UNC, ---; UNP, upper nasopharynx; Q5 URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176
Table 9. CORRELATION BETWEEN VOLUMETRIC CHANGES AT DIFFERENT LEVELS OF THE UPPER AIRWAY TRACT
LMS RMS LNC UNP URP LRP RG HP
LMS
RMS
LNC
UNP
URP
LRP
RG
HP
1.000 0.073 0.145 0.084 0.333 0.350 0.398 0.013
1.000 0.040 0.384 0.336 0.073 0.137 0.167
1.000 0.063 0.218 0.009 0.036 0.145
1.000 0.532 0.326 0.205 0.419
1.000 0.114 0.362 0.151
1.000 0.038 0.301
1.000 0.008
1.000
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right Q7 maxillary sinus; UNP, upper nasopharynx; URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
Q22
UNP and URP spaces, which is due to the close anatomic relation of these airway spaces. These findings differ from those of Sears et al,18 probably because the design of the present study was limited to cases that had a Le Fort I osteotomy only. Although the outcomes of this study showed that the applied technique in quantifying the airway volume was sensitive and reliable, its specificity in measuring airway functionality needs to be assessed clinically. The authors acknowledge that one of the limitations of this study is the short-term follow-up, which was limited to 6 months after surgery. A future comparative clinical study with long-term follow-up would be beneficial to support changes in the nasopharyngeal airway spaces after a Le Fort I osteotomy. Further applications of the ITK-SNAP software package could be used to gauge the size of the bony cleft defect and the success of alveolar bone grafting in patients with cleft lip and roof of the mouth. The Le Fort I osteotomy was found to increase the retroglossal airway volume and the right maxillary antrum. This could be important for the treatment of OSAH in patients with maxillary deficiency. A longterm follow-up study in a larger sample with functional assessment of the airway would be beneficial to confirm these findings.
References 1. Kawamata A, Fujishita M, Ariji Y, et al: Three-dimensional computed tomographic evaluation of morphologic airway changes after mandibular setback osteotomy for prognathism. Oral Surg Oral Med Oral Path Oral Radiol, Endodont 89:278, 2000 2. Liukkonen M, V€ah€atalo K, Peltom€aki T, et al: Effect of mandibular setback surgery on the posterior airway size. Int J Adult Orthodon Orthognath Surg 17:41, 2001 3. Chen F, Terada K, Hua Y, et al: Effects of bimaxillary surgery and mandibular setback surgery on pharyngeal airway measurements in patients with Class III skeletal deformities. Am J Orthod Dentofacial Orthop 131:372, 2007 4. Greco JM, Frohberg U, Van Sickels JE: Long-term airway space changes after mandibular setback using bilateral sagittal split osteotomy. Int J Oral Maxillofac Surg 19:103, 1990
5. Muto T, Yamazaki A, Takeda S, et al: Effect of bilateral sagittal split ramus osteotomy setback on the soft palate and pharyngeal airway space. Int J Oral Maxillofac Surg 37:419, 2008 6. Guenthner TA, Sather AH, Kern EB: The effect of Le Fort I maxillary impaction on nasal airway resistance. Am J Orthod 85:308, 1984 7. Turvey TA, Hall DJ, Warren DW: Alterations in nasal airway resistance following superior repositioning of the maxilla. Am J Orthod 85:109, 1984 8. Jakobsone G, Stenvik A, Espeland L: The effect of maxillary advancement and impaction on the upper airway after bimaxillary surgery to correct Class III malocclusion. Am J Orthod Dentofacial Orthop 139:e369, 2011 9. Solow B, Tallgren A: Natural head position in standing subjects. Acta Odontol 29:591, 1971 10. Gribel BF, Gribel MN, Fraz~ao DC, et al: Accuracy and reliability of craniometric measurements on lateral cephalometry and 3D measurements on CBCT scans. Angle Orthod 81:26, 2010 11. de Oliveira AE, Cevidanes LH, Phillips C, et al: Observer reliability of three-dimensional cephalometric landmark identification on cone-beam computerized tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 107:256, 2009 12. Shelton RL, Bosma JF: Maintenance of the pharyngeal airway. J Appl Physiol 17:209, 1962 13. Muto T, Takeda S, Kanazawa M, et al: The effect of head posture on the pharyngeal airway space (PAS). Int J Oral Maxillofac Surg 31:579, 2002 14. Stepovich ML: A cephalometric positional study of the hyoid bone. Am J Orthod 51:882, 1965 15. Chang Y, Koenig LJ, Pruszynski JE, et al: Dimensional changes of upper airway after rapid maxillary expansion: A prospective cone-beam computed tomography study. Am J Orthod Dentofacial Orthop 143:462, 2013 16. Hernandez-Alfaro F, Guijarro-Martınez R, Mareque-Bueno J: Effect of mono- and bimaxillary advancement on pharyngeal airway volume: Cone-beam computed tomography evaluation. J Oral Maxillofac Surg 69:e395, 2011 17. Park SB, Kim YI, Son WS, et al: 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 41:87, 2012 18. Sears CR, Miller AJ, Chang MK, et al: Comparison of pharyngeal airway changes on plain radiography and cone-beam computed tomography after orthognathic surgery. J Oral Maxillofac Surg 69:e385, 2011 19. Ibanez L, Schroeder W, Ng L, et al: The ITK Software Guide; 2003 Q23 20. Lenza MG, Lenza MD, Dalstra M, et al: An analysis of different approaches to the assessment of upper airway morphology: A CBCT study. Orthod Craniofac Res 13:96, 2010 21. Huggare J: Natural head position recording on frontal skull radiographs. Acta Odontol 47:105, 1989 22. Cevidanes L, Oliveira AE, Motta A, et al: Head orientation in CBCT-generated cephalograms. Angle Orthod 79:971, 2009
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LE FORT I OSTEOTOMY AND NASOPHARYNGEAL AIRWAY
23. Pourdanesh F, Sharifi R, Mohebbi A, et al: Effects of maxillary advancement and impaction on nasal airway function. Int J Oral Maxillofac Surg 41:1350, 2012 24. Goodday R, Bourque S: Subjective outcomes of maxillomandibular advancement surgery for treatment of obstructive sleep apnea syndrome. J Oral Maxillofac Surg 70:417, 2012 25. Bj€ ork A, Bj€ ork L: Artificial deformation and cranio-facial asymmetry in ancient Peruvians. J Dent Res 43:353, 1964
26. Woo T: On the asymmetry of the human skull. Biometrika 324, 1931 Q24 27. Arvystas MG, Antonellis P, Justin AF: Progressive facial asymmetry as a result of early closure of the left coronal suture. Am J Orthod 87:240, 1985 28. Almuzian M, Adai K: Computerised frontal symmetry analysis of Iraqi adults with Class I normal occlusion. Al-Rafedeen Dent J 12: 27, 2002
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Effects of Le Fort I Osteotomy on the Nasopharyngeal Airway—6-Month Follow-Up Mohammed Almuzian, BDS, MScOrtho, MScHCA, DClinDentOrtho,* Anas Almukhtar, BDS, MScOrtho,y Xiangyang Ju, BEng, PhD,z Ali Al-Hiyali, BDS, MScOMFS,x Philip Benington, BDS, MSc,k and Ashraf Ayoub, BDS, MDS, PhD{
Q26
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Purpose:
The literature discussing the impact of a single Le Fort I osteotomy on nasopharyngeal airways is limited. This study assessed the volumetric changes in the nasopharyngeal airway after a single Le Fort I osteotomy and explored the correlation between these changes and 3-dimensional surgical movements of the upper jaw.
Materials and Methods:
This retrospective study was conducted in 40 patients who had undergone a single Le Fort I (maxillary advancement with or without impaction) to correct Class III malocclusion from maxillary hypoplasia. Preoperative (T1) and 6-month postoperative (T2) cone-beam computed tomographic (CBCT) scans of these patients were used for analysis. Maxillary surgical movements and volumetric changes in the nasopharyngeal airway were measured. The reproducibility of the measurements was evaluated using paired t tests and intraclass correlation coefficients. The Wilcoxon test and Pearson correlation coefficient were applied to evaluate the importance of volumetric changes in the nasopharyngeal airway space and assess the correlations of these changes to the maxillary surgical movements. Six patients were excluded from the study owing to major differences (>5 ) in their head and neck posture between the T1 and T2 CBCT scans. The errors of the repeated measurements were insignificant (P > .05), with a high level of agreement (r = 0.99; P < .05) between the repeated digitization of the landmarks. There was a statistically significant impact of a Le Fort I osteotomy on the right maxillary sinus (decreased by 17.8%) and the lower retropalatal space (expanded by 17.3%; P < .05). The correlation between the change in airway volume and the magnitude of surgical maxillary movements was moderate (r = .4). Similarly, there was a moderate correlation between changes in the upper nasopharynx and those in the hypopharynx.
Results:
Conclusion:
The single Le Fort I osteotomy was found to increase the retroglossal airway volume. This could be important for the treatment of obstructive sleep apnea in patients with maxillary deficiency. A long-term follow-up assessment of a larger sample with a functional assessment of airway would be beneficial to confirm these findings. Ó 2015 American Association of Oral and Maxillofacial Surgeons J Oral Maxillofac Surg -:1-12, 2015
Q10
*Department of Orthodontics, Glasgow Dental Hospital & School,
Address correspondence and reprint requests to Dr Almuzian:
Glasgow, UK.
Department of Orthodontics, Glasgow Dental Hospital and School,
yPostgraduate Student, Glasgow University Medical School, MVLS
378 Sauchiehall Street, Glasgow, UK; e-mail: dr_muzian@hotmail.
College, Glasgow Dental Hospital & School, Glasgow, UK.
com
zMedical Devices Unit, NHS Greater Glasgow and Clyde,
Received February 23 2015
Glasgow, UK. xPostgraduate Student, Glasgow Dental Hospital & School,
Ó 2015 American Association of Oral and Maxillofacial Surgeons
Glasgow, UK.
0278-2391/15/00907-6
Accepted June 26 2015
kConsultant Orthodontist, Glasgow Dental Hospital & School,
http://dx.doi.org/10.1016/j.joms.2015.06.172
Glasgow, UK. {Professor, Department of Oral and Maxillofacial Surgery, Glasgow Dental Hospital & School, Glasgow, UK.
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LE FORT I OSTEOTOMY AND NASOPHARYNGEAL AIRWAY
Table 1. POINTS AND LANDMARKS
Point
Definition
A ANS
Deepest (most posterior) midline point on the curvature between the ANS and the prosthion Tip of the bony anterior nasal spine at the inferior margin of the piriform aperture in the midsagittal plane (often used to define the anterior end of the palatal plane) Basion; most anterior inferior point on the margin of the foramen magnum in the midsagittal plane Second cervical vertebra Superoposterior extremity of the odontoid process of the C2 Most anteroinferior point of the body of the third cervical vertebra Most superior point of the crista galli Tangent point at the superoposterior extremity of the odontoid process of the C2 Most inferoposterior point on the body of the C2 Most inferoposterior point on the body of the fourth cervical vertebra Most superior point of the odontoid process of C2 Lowest point on the left inferior orbital margin Most superior point of the outline of the left external auditory meatus (anatomic porion) Most posterior point of the left lateral pterygoid plate as viewed on the coronal section Most lateral point in the left frontozygomatic suture Nasion; junction of the nasal and frontal bones at the most posterior point on the curvature of the bridge of the nose Most posterior point on the bony hard palate in the midsagittal plane Prosthion; most anterior inferior point of the alveolar bone crest of the maxillary incisors Lowest point on right inferior orbital margin Most posterior point of right lateral pterygoid plate as viewed in the coronal section Most lateral point in the right frontozygomatic suture Sella; center of the hypophyseal fossa (sella turcica) Midpoint of line between the sella and basion Most posterior point of the middle of the soft palate
Ba C2 C2sp (or C2od) C3ai Cg Cv2ig Cv2ip Cv4ip Cvod LOr Lpo LtLtPtg Lzyg N PNS Pr ROr RtLtPtg Rzyg S So Spip
Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
The impact of corrective jaw surgery on the upper airway spaces depends on the type of operation, the amount and direction of the skeletal movements, and a patient’s age, gender, and variations. Mandibular setback surgery results in a decrease in airway patency; therefore, bimaxillary osteotomy is indicated for the correction of large anteroposterior discrepancies.1-5 Rhinomanometric techniques to measure nasal airway resistance have shown that maxillary impaction increases alar width, with a subsequent decrease in nasal airway resistance.6,7 Another study based on 2-dimensional cephalometric analysis has proved that maxillary advancement meaningfully increases dimensions of the airway.8 The lack of information on the impact of a Le Fort I osteotomy on 3-dimensional measurements of the nasopharyngeal airway inspired this study. The study assessed assess volumetric changes in the nasal cavity, maxillary sinus, and oropharyngeal airway after a Le Fort I osteotomy and investigated the correlation between these changes and surgical maxillary movements.
Materials and Methods Q11
The sample size for this study was calculated using the Researcher’s Tool Kit Calculator, which indicated
that a cohort of 32 patients would produce a confidence level of 95% and a statistical power of 50%. Therefore, it was decided to recruit 40 patients to overcome the potential exclusion of some cases. The study was approved by the West of Scotland research Q12 ethics service (reference, 12/WS/0133). The inclusion criteria were as follows: 1. Caucasian male and female patients 16 to 45 years old who had a Le Fort I osteotomy (maxillary advancement with or without impaction) to correct the underlying Class III malocclusion. 2. No previous tonsillar, nasal, adenoid, head or neck surgery. 3. No major variation in the head and craniocervical orientation between the preoperative (T1) and postoperative (T2) cone-beam computed tomographic (CBCT) scans. 4. No previous orthodontic expansion or mandibular orthognathic surgical procedure. Surgery was carried out by the same surgeon and the orthodontic treatment was carried out by various clinicians, ranging from consultants to specialist trainees, in the Glasgow Dental Hospital and School (GDHS; Glasgow, UK). All patients underwent presurgical
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Table 2. LINES AND PLANES
Line and Plane ANSV plane
C2sp/V plane C3ai/H plane Cg-Cvod plane CVT plane
Epi/FH plane
Q2
LF plane LOrH plane Orbital plane PAL PNSH plane PNSV plane PNSV plane Ptg plane SN plane Spip/FH plane SPPFH plane TH plane TV plane Z plane
Definition Perpendicular plane to true horizontal plane passing through the nasion in the lateral view; if the midpalatine split extends to involve the anterior nasal spine, then the most posterior anterior nasal spine is considered Defined by the frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra Plane parallel to the Frankfort horizontal plane passing through the most anteroinferior point of the body of the third cervical vertebra Line connecting the crista galli and the superoposterior extremity of the odontoid process of the second cervical vertebra Line passing through the tangent point at the superoposterior extremity of the odontoid process of the second cervical vertebra and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra Plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the entrance of the esophagus; technically by the plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the most anteroinferior point of the body of the fourth cervical vertebra (C4ai/H plane) Left Frankfort; line connecting left orbit and left porion points True horizontal plane tangent to the lowest point on the left inferior orbital margin Line connecting right orbit and left orbit Line through the tangent point at the superoposterior extremity of the odontoid process of the second cervical vertebra and the most inferoposterior point on the body of the second cervical vertebra Plane parallel to the Frankfort horizontal plane passing through the posterior nasal spine and extending to the posterior wall of the pharynx Perpendicular to true horizontal plane passing through the posterior nasal spine; if the midpalatine split extends to involve the posterior nasal spine, then the most posterior end of the palate is considered True vertical plane passing through the posterior nasal spine Line connecting the most posterior points of the left and right lateral pterygoid plate as viewed in the coronal section Plane representing a line connecting the sella to the nasion Plane parallel to the Frankfort horizontal plane passing through the most posterior point of the middle of the soft palate Sagittal plane perpendicular to the Frankfort horizontal plane passing through the lateral walls of the maxillary sinus True horizontal; a reference line constructed by drawing a line perpendicular to the true vertical line True vertical; a reference line constructed perpendicular to the floor Zygomatic; line connecting the most lateral points on the right and left frontozygomatic suture
Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015. Table 3. CEPHALOMETRIC ANGLES
Angle Lordosis Pitch angle (P angle) Roll angle (R angle) Yaw angle (Y angle)
Definition Measured by the mean of the SN-PAL and CVT-NS angles (Fig 1A) Inner angle of the intersection of the SN and TH planes; represents the change in head orientation in the sagittal plane (cranial base inclination angle; Fig 1A) Inner angle of the intersection of the Z and TH planes; represents change in head orientation in the frontal plane (Fig 1B) Represents change in head orientation in the mediolateral plane, measured by right (Cg-CvodRtLtPtg)and left (Cg-Cvod-LtPtg) angles (Fig 1C)
Abbreviations: Cg-Cvod-LtLtPtg, angle formed by the most superior point of the crista galli, the most superior point of the odontoid process of the second cervical vertebra, and the most posterior point of the left lateral pterygoid plate as viewed in the coronal section; Cg-Cvod-RtLtPtg, angle formed by the most superior point of the crista galli, the most superior point of the odontoid process of the second cervical vertebra, and the most posterior point of the right lateral pterygoid plate as viewed in the coronal section; CVT-NS angle, angle formed by the line through and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra and the line connecting the nasion to the sella; SN-PAL angle, angle formed by the line connecting the sella and nasion and the line through the tangent point at the superoposterior extremity of the odontoid process of and the most inferoposterior point on the body of the second cervical vertebra; TH plane, true horizontal plane; Z plane, zygomatic plane. Q3 Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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FIGURE 1. Head and craniocervical orientation angles. A, Pitch and lordosis angle. B, Roll angle. C, Yaw angle. CVT-NS angle, angle formed by the line through and tangent to the superoposterior extremity of the odontoid process of the second cervical vertebra and the line connecting the nasion to the sella; P angle, pitch angle; R angle, roll angle; SN-PAL angle, angle formed by the line connecting the sella and nasion and the line through the tangent point at the superoposterior extremity of the odontoid process of and the most inferoposterior point on the body of the Q1 second cervical vertebra; Y angle, yaw angle. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015. FLA 5.2.0 DTD YJOMS56897_proof 15 July 2015 8:55 pm CE AH
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FIGURE 2. Standardized orientation technique. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
orthodontic treatment using upper and lower fixed appliances, with or without dental extractions. Two CBCT scans were acquired for each patient: immediately before the Le Fort I osteotomy (T1) and 6 months after surgery (during or after orthodontic
treatment; T2). All CBCT scans were taken at the GDHS using an iCAT scanner (Imaging Sciences International, Hatfield, PA) by a trained radiographer. Patients were required to take off any spectacles or jewelry, keep their eyes gently closed, and keep their
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ALMUZIAN ET AL
FIGURE 3. Superimposition on cranial-base technique. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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LE FORT I OSTEOTOMY AND NASOPHARYNGEAL AIRWAY
15-18
Table 4. ANATOMIC BOUNDARIES OF AIRWAY SPACES
Boundaries Volume of Interest Lower nasal cavity Upper nasopharynx Upper oropharynx Retroglossal space Hypopharynx Maxillary sinus*
Anteriorly
Posteriorly
Superiorly
Inferiorly
Medially
Laterally
NSV plane PNSV plane PNSV plane PNSV plane PNSV plane
PNSV plane C2sp/V plane C2sp/V plane C2sp/V plane C2sp/V plane
LOrH plane LOrH plane PNSH plane Spip/FH plane C3ai/H plane
Inferior nasal wall PNSH plane Spip/FH plane C3ai/H plane Epi/FH plane
Nasal septum N/A N/A N/A N/A
Lateral nasal wall SPPFH SPPFH SPPFH SPPFH
Abbreviations: C2sp/V, frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra; C3ai/H, plane parallel to the Frankfort horizontal plane passing through the most anteroinferior point of the body of the third cervical vertebra; Epi/FH, plane parallel to the Frankfort horizontal plane connecting the base of the epiglottis to the entrance of the esophagus; LOrH, true horizontal plane tangent to the lowest point on the left inferior orbital margin; N/A, not applicable; NSV, true horizontal plane passing through the posterior nasal spine; PNSH, plane parallel to Frankfort horizontal plane passing through the posterior nasal spine and extending to the posterior wall of the pharynx; PNSV, perpendicular to true horizontal plane passing through the posterior nasal spine (if the midpalatine split extends to involve the posterior nasal spine, then the most posterior end of the palate is considered); Spip/FH, plane parallel to the Frankfort horizontal plane passing through the most posterior point of the middle of the soft palate; SPPFH, sagittal plane perpendicular to the Frankfort horizontal plane passing through the lateral walls of the maxillary sinus. * All sinus cavities were included to the level of the LOrH plane superiorly and their minimum constricted openings with the adjacent nasal and paranasal cavities circumferentially. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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teeth in centric occlusion. They also were instructed to keep their lips and tongue in a normal relaxed position during the scan. For each scan, the patient was positioned with the Frankfort plane parallel to the floor (natural head position).9 An extended field of view of 22 cm was used to capture the facial skeleton from the glabella to the angle between the chin and the throat. The Digital Imaging and Communications in Medicine (DICOM) data for the T1 and T2 CBCT scans were imported and displayed using OnDemand3D software (Cybermed Inc, Seoul, Korea). Based on the reported validity of 3-dimensional cephalometric assessments,10,11 the head posture and craniocervical inclination (lordosis) were measured on each CBCT scan taken at T1 and T2. Points, planes, and angles used in this study are presented in Tables 1 to 3 and Figure 1. Four angular measurements (pitch, roll, yaw, and craniocervical angle) were recorded to the nearest degree. The first 3 angular measurements correspond to head posture and the latter measurement corresponds to lordosis. Patients were excluded if the change in head posture or lordosis was greater than 5 between the T1 and T2 scans, because such changes have an important influence on nasopharyngeal airway measurements.12-14 Each T1 CBCT scan was digitally oriented so that the plane of the pterygoid plate, left Frankfort horizontal plane, and zygomatic plane were parallel to the true horizontal plane, and the data were saved as a new T1 (NT1) scan (Fig 2). The T2 CBCT scan was superimposed on the corresponding NT1 scan, using the ante-
rior and posterior cranial bases as stable structures, and saved as a new T2 (NT2) scan (Fig 3). This allowed a standardized segmentation and eliminated the effect of positional error on segmentation. Using the NT1 and NT2 scans, the airway boundaries were determined, segmented, and measured using the ITK-SNAP software package (http://www.itksnap.org; Table 4, Fig 4).15-18 The manufacturer’s instructions for Q16 Q15 use of the ITK software package was followed.19 The measurement of the volume of the lower nasal cavity was limited to the respiratory space of the nasal cavity to minimize the inclusion of the paranasal sinuses and their related hiatuses. The retropalatal space was subdivided into upper (URP) and lower (LRP) retropalatal spaces by the frontal plane perpendicular to the Frankfort horizontal plane passing through the superoposterior extremity of the odontoid process of the second cervical vertebra (C2sp/V plane). If the odontoid process of the second cervical vertebra was located superior to the C2sp/V plane, then the entire segment was considered part of the LRP space.15,16,20 Regarding the inferior boundaries of the hypopharynx (HP) space, if the epiglottis was positioned halfway across the HP, then a second volume measurement was added to include this area or volume within the region of interest. All volumetric measurements were carried out by 1 examiner and repeated after 1 week, and the 2 sets of measurements were compared to validate the reproducibility of the landmarks used for segmentation of the airway space boundaries. The magnitude of the maxillary skeletal movements was measured using the Maxilim software package
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FIGURE 4. Airway space volumetric measurement and segmentation using ITK-SNAP. A, Saggital view. B, Coronal view. (Fig 4 continued on next page.) Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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(Medicim NV, Mechelen, Belgium). Several markers were identified and digitized directly on the DICOM slices of the NT1 and NT2 scans. For maxillary surgical movements, orthogonal distances were recorded to the 3 common reference planes. The net movements were calculated as the differences between the NT1 and NT2 landmark positions in the X, Y, and Z planes (Fig 5). STATISTICAL ANALYSIS
The distribution of the sample data was assessed using the Kolmogorov-Smirnov test, which showed non-Gaussian distribution for most parameters. The Friedman test and Wilcoxon rank sum test (P < .05) were applied to determine a statistical difference owing to age or gender and to evaluate the importance of volumetric changes in the nasopharyngeal spaces secondary to a Le Fort I osteotomy.
The Pearson correlation coefficient was applied to assess the correlation between volumetric changes and the magnitude of surgical maxillary movement in 3 planes of space as a result of a Le Fort I osteotomy.
Results Six patients were excluded from the study because of a major difference ($5 ) in head and neck posture between the T1 and T2 CBCT scans. There was no statistically significant difference between the repeated volumetric measurements (P > .05), with a high level of agreement (r = 0.99; P < .05; Table 5). The main surgical movement of the maxilla was an anterior shift of 6.42 1.51 mm (range, 3.43 to 8.5 mm). This also was associated with a mild vertical impaction of 0.65 0.28 mm (range, 0.07 to 2.27 mm) more on the right side (mean, 0.82 0.32 mm; range,
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FIGURE 4 (cont’d). C, Axial view. D, Virtual model representation of nasopharyngeal airway spaces. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
0.1 to 2.9 mm) than on the left side (mean, 0.47 0.24 mm; range, 0.03 to 1.63 mm), with a mild mediolateral rotation of 0.86 0.44 mm (range, 0.2 to 1.73 mm; Table 6). Table 7 presents the volumetric changes of the nasopharyngeal airway spaces secondary to a Le Fort I Osteotomy. The right maxillary sinus (RMS) was significantly decreased by 17.8%, whereas the LRP was significantly expanded by 17.3% (P < .05). Genderrelated changes were not detected in this study (Friedman test, P = .4452). The correlation between the change in the volume of airway space and the magnitude of surgical maxillary movements was mild (r = 0.4; Table 8). Similarly, there was a weak correlation between the volumetric changes at different levels of the nasopharyngeal
airway space, except between the upper nasopharynx (UNP) and the URP (correlation coefficient, 0.53; Table 9). Q18
Discussion This study relied on an internal reference structure during segmentation that would not be affected by occlusal settling or orthodontic movement between the T1 and T2 CBCT scans. This is one of the explanations for the differences between the results of this study and other published data that have relied on dental reference points.17 Park et al17 used cervical vertebral levels to subdivide the airway space, but this was prone to errors because it relied on the patient’s head and neck posture during CBCT scanning.
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FIGURE 5. Skeletal movement measurement using Maxilim software. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
Changes in the head and neck posture owing to the effect of surgery or projectional scanning errors would affect the pharyngeal airway volume and crosssectional measurements.12,21-23 This source of error was detected in this study by measuring the angles of head orientation and neck lordosis at T1 and T2; approximately 10% of patients showed major changes in head and neck posture and were excluded. This study used 2 distinguishing methodologies. First, it assessed the effects of a single Le Fort I osteotomy on the nasopharyngeal airway space. Second, segmentation of the nasopharyngeal space allowed
changes at different levels to be quantified because each anatomic segment is related to a specific problem. Hernandez-Alfaro et al16 found a statistical expan- Q19 sion in total pharyngeal airway space (37.7%). This is dissimilar from the findings of the present study, which could be due to the fact that the entire airway space was considered and measured as a single unit, rather than in segments. With regard to volumetric changes in levels of the nasal cavity, the LNC was Q20 decreased by one tenth of its preoperative volume. This could be due to the combined maxillary vertical impaction, which decreases the effective volume of
Table 5. REPRODUCIBILITY OF VOLUMETRIC MEASUREMENTS
Wilcoxon signed rank test, P < .05 ICC
LMS
RMS
LNC
UNP
URP
LRP
RG
HP
0.742
0.945
0.438
0.156
0.375
0.250
0.383
0.844
0.999
1.000
0.999
1.000
1.000
1.000
1.000
1.000
Abbreviations: HP, hypopharynx; ICC, intraclass correlation coefficient; LMS, left maxillary sinus; LNC, ---; LRP, lower Q4 retropalatal space; RG, ---; RMS, right maxillary sinus; UNP, upper nasopharynx; URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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1009 1010 1011 1012 1013 1014 1015 1016 1017 1018 1019 1020 1021 1022 1023 1024 1025 1026 1027 1028 1029 1030 1031 1032 1033 1034 1035 1036 1037 1038 1039 1040 1041 1042 1043 1044 1045 1046 1047 1048 1049 1050 1051 1052 1053 1054 1055 1056 1057 1058 1059 1060 1061 1062 1063 1064
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Table 6. DEGREE OF MAXILLARY SURGICAL MOVEMENTS
Table 8. CORRELATION BETWEEN CHANGE IN VOLUME OF AIRWAY SPACE AND MAGNITUDE OF SURGICAL SKELETAL MOVEMENT
Mean SD Minimum Maximum Net anteroposterior movement Net vertical movement Right-side vertical movement Left-side vertical movement Net mediolateral movement
6.42 1.51
3.43
8.5
0.65 0.28 0.82 0.32
0.07 0.1
2.27 2.9
0.47 0.24
0.03
1.63
0.86 0.44
0.2
1.73
LMS RMS LNC UNP URP LRP RG HP
Abbreviation: SD, standard deviation. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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the LNC and disguises the effect of maxillary advancement. Although the changes were not statistically meaningful, they were similar to the findings of Pourdanesh et al.23 The ratio of the RG space at T1 to T2 was approximately 4:6, with approximately 15% of volumetric expansion after the Le Fort I osteotomy. An anatomically based explanation is that the superior attachments of the palatoglossus muscle were displaced anteriorly secondary to maxillary advancement with subsequent anterior displacement of the tongue and expansion of the RG airway volume.24 Because the main pathophysiology of obstructive sleep apnea and hypopnea (OSAH) is that the tongue falls backward and blocks the RG airway space during sleep, the Le Fort I osteotomy might be an alternative option for treatment of OSAH in patients with maxillary hypoplasia. Moreover, there was a decrease in the volume of the 2 maxillary sinuses, specifically the volume of the
Anteroposterior Movement
Vertical Movement
Mediolateral Movement
0.020 0.039 0.128 0.018 0.053 0.044 0.12 0.032
0.014 0.030 0.100 0.082 0.047 0.104 0.184 0.007
0.040 0.030 0.041 0.069 0.022 0.088 0.226 0.025
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right maxillary sinus; UNP, upper nasopharynx; URP, Q6 upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
RMS, which was decreased to one fifth of its preoperative value. This can be explained by the differential impaction of the right and left sides of the maxilla to correct occlusal canting as a result of the dominance of the right facial half.25-28 This assumption requires a larger sample in which a Le Fort I osteotomy is performed to correct the underlying asymmetry. Although the main objective of the study was to assess the impact of Le Fort I maxillary advancement on the nasopharyngeal airway, minor simultaneous surgical movements in the vertical or medial and vertical directions were unavoidable. The study showed a weak correlation between the volumetric changes at different levels of the upper airway tract and the magnitude of maxillary surgical movement. However, there was a moderate positive correlation between changes in the volume of the
Table 7. VOLUMETRIC CHANGES IN NASOPHARYNGEAL AIRWAY SPACES SECONDARY TO LE FORT I OSTEOTOMY
T1 Airway Space LMS RMS LNC UNC RG URP LRP HP
T2
Mean
SD
Mean
SD
Percentage of Volumetric Changes, (T2 T1)/T1 100
Wilcoxon Signed Rank Test, P < .05
9,705.6 10,471.6 7,917.2 6,640.2 2,000.7 8,534.1 8,605.2 3,863.6
2,482.1 3,488.6 1,452.5 2,661.6 3,227.0 7,738.0 4,684.9 2,180.9
9,511.7 8,606.2 7,189.2 7,311.7 1,704.6 9,053.8 10,089.6 3,243.5
2,468.2 3,427.4 2,306.7 2,434.1 2,091.0 4,039.1 5,590.3 1,939.1
2.0 17.8 9.2 10.1 14.8 6.1 17.3 16.1
.408 .015 .109 .162 .5186 .1627 .013 .501
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right maxillary sinus; SD, standard deviation; T1, preoperative; T2, 6 months postoperative; UNC, ---; UNP, upper nasopharynx; Q5 URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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1121 1122 1123 1124 1125 1126 1127 1128 1129 1130 1131 1132 1133 1134 1135 1136 1137 1138 1139 1140 1141 1142 1143 1144 1145 1146 1147 1148 1149 1150 1151 1152 1153 1154 1155 1156 1157 1158 1159 1160 1161 1162 1163 1164 1165 1166 1167 1168 1169 1170 1171 1172 1173 1174 1175 1176
Table 9. CORRELATION BETWEEN VOLUMETRIC CHANGES AT DIFFERENT LEVELS OF THE UPPER AIRWAY TRACT
LMS RMS LNC UNP URP LRP RG HP
LMS
RMS
LNC
UNP
URP
LRP
RG
HP
1.000 0.073 0.145 0.084 0.333 0.350 0.398 0.013
1.000 0.040 0.384 0.336 0.073 0.137 0.167
1.000 0.063 0.218 0.009 0.036 0.145
1.000 0.532 0.326 0.205 0.419
1.000 0.114 0.362 0.151
1.000 0.038 0.301
1.000 0.008
1.000
Abbreviations: HP, hypopharynx; LMS, left maxillary sinus; LNC, ---; LRP, lower retropalatal space; RG, ---; RMS, right Q7 maxillary sinus; UNP, upper nasopharynx; URP, upper retropalatal space. Almuzian et al. Le Fort I Osteotomy and Nasopharyngeal Airway. J Oral Maxillofac Surg 2015.
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UNP and URP spaces, which is due to the close anatomic relation of these airway spaces. These findings differ from those of Sears et al,18 probably because the design of the present study was limited to cases that had a Le Fort I osteotomy only. Although the outcomes of this study showed that the applied technique in quantifying the airway volume was sensitive and reliable, its specificity in measuring airway functionality needs to be assessed clinically. The authors acknowledge that one of the limitations of this study is the short-term follow-up, which was limited to 6 months after surgery. A future comparative clinical study with long-term follow-up would be beneficial to support changes in the nasopharyngeal airway spaces after a Le Fort I osteotomy. Further applications of the ITK-SNAP software package could be used to gauge the size of the bony cleft defect and the success of alveolar bone grafting in patients with cleft lip and roof of the mouth. The Le Fort I osteotomy was found to increase the retroglossal airway volume and the right maxillary antrum. This could be important for the treatment of OSAH in patients with maxillary deficiency. A longterm follow-up study in a larger sample with functional assessment of the airway would be beneficial to confirm these findings.
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5. Muto T, Yamazaki A, Takeda S, et al: Effect of bilateral sagittal split ramus osteotomy setback on the soft palate and pharyngeal airway space. Int J Oral Maxillofac Surg 37:419, 2008 6. Guenthner TA, Sather AH, Kern EB: The effect of Le Fort I maxillary impaction on nasal airway resistance. Am J Orthod 85:308, 1984 7. Turvey TA, Hall DJ, Warren DW: Alterations in nasal airway resistance following superior repositioning of the maxilla. Am J Orthod 85:109, 1984 8. Jakobsone G, Stenvik A, Espeland L: The effect of maxillary advancement and impaction on the upper airway after bimaxillary surgery to correct Class III malocclusion. Am J Orthod Dentofacial Orthop 139:e369, 2011 9. Solow B, Tallgren A: Natural head position in standing subjects. Acta Odontol 29:591, 1971 10. Gribel BF, Gribel MN, Fraz~ao DC, et al: Accuracy and reliability of craniometric measurements on lateral cephalometry and 3D measurements on CBCT scans. Angle Orthod 81:26, 2010 11. de Oliveira AE, Cevidanes LH, Phillips C, et al: Observer reliability of three-dimensional cephalometric landmark identification on cone-beam computerized tomography. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 107:256, 2009 12. Shelton RL, Bosma JF: Maintenance of the pharyngeal airway. J Appl Physiol 17:209, 1962 13. Muto T, Takeda S, Kanazawa M, et al: The effect of head posture on the pharyngeal airway space (PAS). Int J Oral Maxillofac Surg 31:579, 2002 14. Stepovich ML: A cephalometric positional study of the hyoid bone. Am J Orthod 51:882, 1965 15. Chang Y, Koenig LJ, Pruszynski JE, et al: Dimensional changes of upper airway after rapid maxillary expansion: A prospective cone-beam computed tomography study. Am J Orthod Dentofacial Orthop 143:462, 2013 16. Hernandez-Alfaro F, Guijarro-Martınez R, Mareque-Bueno J: Effect of mono- and bimaxillary advancement on pharyngeal airway volume: Cone-beam computed tomography evaluation. J Oral Maxillofac Surg 69:e395, 2011 17. Park SB, Kim YI, Son WS, et al: 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 41:87, 2012 18. Sears CR, Miller AJ, Chang MK, et al: Comparison of pharyngeal airway changes on plain radiography and cone-beam computed tomography after orthognathic surgery. J Oral Maxillofac Surg 69:e385, 2011 19. Ibanez L, Schroeder W, Ng L, et al: The ITK Software Guide; 2003 Q23 20. Lenza MG, Lenza MD, Dalstra M, et al: An analysis of different approaches to the assessment of upper airway morphology: A CBCT study. Orthod Craniofac Res 13:96, 2010 21. Huggare J: Natural head position recording on frontal skull radiographs. Acta Odontol 47:105, 1989 22. Cevidanes L, Oliveira AE, Motta A, et al: Head orientation in CBCT-generated cephalograms. Angle Orthod 79:971, 2009
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23. Pourdanesh F, Sharifi R, Mohebbi A, et al: Effects of maxillary advancement and impaction on nasal airway function. Int J Oral Maxillofac Surg 41:1350, 2012 24. Goodday R, Bourque S: Subjective outcomes of maxillomandibular advancement surgery for treatment of obstructive sleep apnea syndrome. J Oral Maxillofac Surg 70:417, 2012 25. Bj€ ork A, Bj€ ork L: Artificial deformation and cranio-facial asymmetry in ancient Peruvians. J Dent Res 43:353, 1964
26. Woo T: On the asymmetry of the human skull. Biometrika 324, 1931 Q24 27. Arvystas MG, Antonellis P, Justin AF: Progressive facial asymmetry as a result of early closure of the left coronal suture. Am J Orthod 87:240, 1985 28. Almuzian M, Adai K: Computerised frontal symmetry analysis of Iraqi adults with Class I normal occlusion. Al-Rafedeen Dent J 12: 27, 2002
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![[Horseshoe Le Fort I osteotomy].](/assets/img/hold.png)
