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Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2014.10.021, available online at http://www.sciencedirect.com
Research Paper Orthognathic Surgery
Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis S. M. Gokce, S. Gorgulu, U. Karacayli, H. S. Gokce, B. Battal: Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis. Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx. # 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Abstract. The aims of this study were to evaluate volumetric changes in the nasal cavity (NC) and pharyngeal airway space (PAS) after Le Fort I maxillary distraction osteogenesis (MDO) using a three-dimensional (3D) simulation program, and to determine the effects of MDO on respiratory function during sleep with polysomnography (PSG). 3D computed tomography images were obtained and analyzed before surgery (T0) and at a mean 8.2 1.2 months postsurgery (T1) (SimPlant-OMS software) for 11 male patients (mean age 25.3 5.9 years) with severe skeletal class III anomalies related to maxillary retrognathia. The simulation of osteotomies and placement of distractors were performed on stereolithographic 3D models. NC and PAS were segmented separately on these models for comparison of changes between T0 and T1. PSG including the apnoea–hypopnoea index (AHI), sleep efficiency, sleep stages (weakness, stages 1–4, and rapid eye movement (REM)), and mean lowest arterial O2 saturation were obtained at T0 and T1 to investigate changes in respiratory function during sleep. MDO was successful in all cases as planned on the models; the average forward movement at A point was 10.2 mm. Increases in NC and PAS volume after MDO were statistically significant. These increases resulted in significant improvement in sleep quality. PSG parameters changed after MDO; AHI and sleep stages weakness, 1, and 2 decreased, whereas REM, stages 3 and 4, sleep efficiency, and mean O2 saturation increased.
The use of distraction osteogenesis (DO) for the treatment of craniomaxillofacial anomalies has become popular over the past 10 years.1,2 Corpus, ramus, premaxillary, and maxillary DO are the most successful and widely used techniques 0901-5027/000001+07
for the correction of congenital class III malocclusions when rigid fixation techniques are insufficient.2,3 With rigid placement of the distractors, distraction forces may be transmitted to insufficient bone, and due to the anatomy of the region,
S. M. Gokce1, S. Gorgulu2, U. Karacayli3, H. S. Gokce4, B. Battal5 1
Department of Orthodontics, Medipol University, Mega Hospitals Complex, Bagcilar, Istanbul, Turkey; 2Department of Orthodontics, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey; 3Department of Oral and Maxillofacial Surgery, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey; 4Department of Prosthodontics, Medipol University, Mega Hospitals Complex, Bagcilar, Istanbul, Turkey; 5 Department of Radiology, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey
Key words: Le Fort I; distraction osteogenesis; 3D imaging; nasal cavity; PAS; polysomnography. Accepted for publication 29 October 2014
difficulties are often encountered, especially in maxillary distractions.4 Due to the experience gained with extraoral distractors, intraoral sub-periosteal distractors were developed and are now being used successfully.4
# 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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This study was approved by the institutional ethics committee and informed consent
0.018* 0.016* 0.083 0.017* 0.018* 0.018* Z = 2375 t = 2401 t = 1732 t = 2379 t = 2366 t = 2366 1.34 1.11 0.20 1.34 876.6 796.3
Test statisticsa
13.68 9.29 0.43 9.71 3635.7 2009.7
Mean difference
SD
14.1% 7.3% 2.49 82.06 80.06 2.75 31,824.9 32,362.2 1.21 81.07 79.07 1.24 27,001.9 26,626.2 0.69 0.53 0.53 0.81 2607.4 3101.0
Lower bound
Upper bound
2 82 80 2 29,236 29,312
Median
1.85 81.57 79.57 2.00 29,413.4 29,494.2
Mean
11 72 80 8 25,413 27,318 9.83 73.66 80.75 6.55 27,925.5 30,158.2
Upper bound Lower bound
15.01 70.90 79.24 8.87 23,629.8 24,810.8
95% CI for mean SD
After surgery (T1)
Median 95% CI for mean SD
3.71 1.49 0.81 1.25 2322.4 2890.9 11.83 72.28 80.00 7.71 25,777.7 27,484.5
T0–T1 T0–T1% increase
Mean
All CT examinations were performed before surgery (T0) and at >6 months after distraction (T1) using a 64 detector CT scanner (Aquilion 64; Toshiba Medical Systems, Otawara, Japan), with the subjects in supine position. Scan parameters were as follows: 120 kV, 150 mA, 400 ms rotation time, slice thickness of 6 months postsurgery (mean 8.2 1.2 months). The patients had severe skeletal class III anomalies due to maxillary retrognathia (mean sella–nasion–A point angle (SNA) 72.28 1.498, A point–nasion–B point angle (ANB) 7.71 1.258), an excessive overjet (mean increased negative 11.83 3.71 mm), an anterior and/or posterior cross-bite, and normal mandibular development (sella–nasion–B point angle (SNB) 80.00 0.818) (Table 1). Since all patients were adult with mandibular growth and mandibular complex structure that was normal, and all had excessive negative overjet, treatment with MDO was preferred over conventional Le Fort I osteotomy and rigid fixation to avoid the risk of potential relapse.
Before surgery (T0)
There are few reports on the use of internal distraction in the facial skeleton region.5,6 The advantages of internal devices are that they are less conspicuous and more tolerable to the patient. However, the design and installation of internal maxillary distraction osteogenesis (MDO) devices are difficult. To advance the maxilla to a predetermined position, it is critical to locate the distractors parallel to each other on both sides of the maxilla.6 Once the device is fixed, the vector of motion cannot be changed. So, presurgical projection on a three-dimensional (3D) stereolithographic (SLA) model is crucial to identify the distraction vector.5,6 Only a few studies have attempted to explore the effect of Le Fort I osteotomy on the pharyngeal airway space (PAS) in class III malocclusions.7–11 Harada et al.7 found increases in both nasopharyngeal depth and velar length after MDO. Mochida et al.8 showed that MDO in cleft lip and palate (CLP) patients led to an increase in the upper airway and a decrease in nasal resistance that remained stable even after 1 year. Aksu et al.9 found that anterior movement of the maxilla associated with MDO resulted in significant increases in posterior, superoposterior, and middle airway spaces in adult CLP patients. The distraction procedure not only changes the volume of bone tissue, but also modifies the surrounding structures such as the nasal cavity (NC).11 The anatomical and aesthetic aspects of DO are crucial, but the importance of functional consequences might overcome these aspects.12,13 Efforts to improve occlusion and facial aesthetics, and consequently the patient’s quality of life, may have the opposite effect.13 Creating upper airway resistance as a result of surgical procedures could influence respiration.12 Although the pharynx is voluntarily dilated when the patient is awake, there may be trouble during sleep. The single-night sleep study with full polysomnography (PSG) is a useful examination for evaluating, detecting, and quantifying respiratory impairment and can be performed safely in a variety of clinical situations.13 In the light of these facts, a hypothesis has been proposed that the volume of the NC and PAS increase after Le Fort I MDO and that the dentomaxillofacial changes accompanying MDO may have an effect on sleep respiratory function.
P-value
Gokce et al.
Table 1. Dentofacial, nasal cavity, and pharyngeal airway space volume changes between T0 and T1.
2
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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3D evaluation of the airway after Le Fort I MDO
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Fig. 1. Example of a stereolithographic model used for planning and preparation before surgery.
Fig. 2. 3D volumetric reconstruction and analysis of the nasal cavity at T0 and T1.
Fig. 3. The borders of the 3D pharyngeal airway space at T0 (green) and T1 (red). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
distractor positioning and incision lines for simulation before the actual operation were carried out on the SLA models; the plates of the distractor were fitted properly and marked on the SLA model for transfer to the operating area (Fig. 1). The NC and PAS were segmented on the 3D virtual models. The pre- and
post-treatment virtual models of the segmented regions were evaluated and compared. NC segments were restricted by the ostium of the paranasal sinuses, posterior airway, and nostrils (Fig. 2).14 The borders of the PAS were formed from the following: (1) anterior: a vertical plane through the distal margin of the vomer,
soft palate, base of the tongue, and anterior wall of the pharynx; (2) posterior: posterior wall of the pharynx; (3) lateral: the lateral walls of the pharynx; (4) upper: the roof of the nasopharynx; and (5) lower: a plane passing through the upper border of the larynx perpendicular to the sagittal plane (Fig. 3).15
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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4
Gokce et al. All variables were recorded on a computerized system. Sleep parameters were recorded on a 32-channel polygraph (SomnoStar Alpha Series 4; SensorMedics Corp., Yorba Linda, CA, USA). Sleep respiratory information, including the apnoea–hypopnoea index (AHI), sleep efficiency, sleep stages (weakness, stages 1, 2, 3, and 4, and rapid eye movement (REM)), and mean lowest arterial O2 saturation, was used for the data analysis.13 According to the PSG test results obtained before surgery, five of the 11 patients did not have any problem related with airway obstruction or snoring during sleep (AHI < 5). Six patients were diagnosed as simple snorers (AHI < 5); no patient was diagnosed with obstructive sleep apnoea syndrome (OSAS) at T0.
Surgical procedure
With a classic and complete high Le Fort I osteotomy under general anaesthesia, down-fracture and complete mobilization of the maxillary segment was performed in all patients by the same surgeon of the department of maxillofacial surgery. Insertion of the device was started with the fixing of titanium miniplates (MODUS; Medartis, Basel, Switzerland) to the zygomatic buttresses and maxillary segment below the osteotomy line bilaterally, as simulated previously on the SLA model. Distraction cylinders (MODUS, MDO1.5; Medartis, Basel, Switzerland) were placed on the miniplates. After the activation and direction of the distractors were approved, the device was anchored to the miniplates. After a 7-day latency period, distraction was performed at a rate of 0.5 mm twice a day for approximately 20 days. Distraction was continued until the elimination of the negative overjet and including 1-mm overtreatment. The patients underwent a consolidation period of 60 days with the distractors in place. Following the consolidation phase, the distractors were removed under local anaesthesia.
differences between the original and repeated measurements at the 0.05 level (P > 0.05).
Results
MDO was comfortable for the patients; its application was easy due to the position of the intraoral activating rod and it was removed after the consolidation period. No infection, dislocation, or device breakages occurred, and no lesions were encountered around the oral tissues during the distraction period. After MDO, skeletal alterations and occlusion at T1 were found to be compatible with the 3D simulation and SLA model, as visualized using the software.
Skeletal and volumetric measurements Statistical analysis
The descriptive analysis of preoperative and postoperative measurements was performed using SPSS 12.0.1 for Windows (SPSS Inc., Chicago, IL, USA). All pre- and post-treatment variables were compared with the paired-samples t-test, except for overjet and AHI, which did not pass the formal normality test (KolNon-parametric mogorov–Smirnov). variables were compared with the Wilcoxon signed-rank test. P-values of 6 months after MDO. Airflow was monitored through oral and nasal thermistors and cannulae adapted for this purpose. The mean lowest arterial O2 saturation was measured continuously by pulse oximetry using a finger probe. Body position was assessed continuously both with a closed-circuit camera and with a body position sensor.
The measured mean sagittal bone gain parallel to the skull base at A point was 10.2 mm (range 7.5–16.2 mm). As a result of the advancement of the maxillary complex, the mean negative overjet increased significantly from 11.83 3.71 mm to 1.85 0.69 mm (P < 0.05). The mean value of the SNA angle increased significantly from 72.28 1.498 to 81.57 0.538 (P < 0.05), but the mean change in SNB angle was not statistically significant (P > 0.05). The average value of the ANB angle changed from 7.71 1.258 to 2.00 0.818 and this change was significant (P < 0.05). The of NC (T0 volume 25,777.7 2322.4 mm3 to T1 29,413.4 2607.4 mm3) and the volume of PAS (T0 27,484.5 2890.9 mm3 to T1 29,494.2 3101.0 mm3) increased significantly (P < 0.05) (Fig. 4; Table 1).
Table 2. Polysomnography parameter changes between T0 and T1. T1
T0 Mean
AHI Sleep efficiency (%) Sleep stage weakness (%) Sleep stage 1 (%) Sleep stage 2 (%) Sleep stage 3 (%) Sleep stage 4 (%) REM (%) Mean O2 saturation (%)
3.34 80.2 13.24 7.22 73.88 5.12 10.02 5.12 90.67
SD
1.82 2.67 3.01 2.98 6.12 1.9 2.27 2.72 3.52
95% CI Lower bound
Upper bound
1.02 79.32 10.77 5.99 68.34 3.02 9.11 4.04 84.25
4.25 90.15 16.68 11.23 78.22 8.76 12.84 7.27 94.16
Mean
2.95 93.88 7.23 4.02 64.23 8.16 14.34 12.11 96.28
SD
1.11 4.65 2.31 1.25 4.11 2.91 3.26 3.83 3.82
T0–T1 95% CI
Lower bound
Upper bound
0.89 85.86 5.12 2.21 59.37 5.04 11.46 10.02 92.59
6.34 98.21 10.54 6.23 67.39 11.64 18.35 16.45 99.17
Mean difference
SD
Test statisticsa
P-value
0.4 13.66 6.02 3.01 9.65 3.04 4.32 6.99 5.61
1.73 4.64 2.78 1.13 3.12 1.75 2.53 2.41 3.11
Z = 0.835 t = 10654 t = 5466 t = 3154 t = 8371 t = 6845 t = 3478 t = 5912 t = 5214
0.095 0.001** 0.0012** 0.04* 0.001** 0.0013** 0.001** 0.0011** 0.001**
SD, standard deviation; CI, confidence interval; AHI, apnoea–hypopnoea index; REM, rapid eye movement. a Z represents the Wilcoxon signed-rank test result; t represents the paired-sample t-test result. * P < 0.05. ** P < 0.01.
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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3D evaluation of the airway after Le Fort I MDO
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Fig. 4. 3D volumetric superimposition images of the nasal cavity (upper left) and pharyngeal airway space (lower left) at T0–T1, and 3D volumetric reconstruction of the total nasal cavity and pharyngeal airway space presented on lateral view for T0 (purple, red) and T1 (yellow, green) periods. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
Polysomnography measurements
Discussion
According to the PSG evaluation, the postoperative sleep quality of the subjects was improved at T1 when compared with T0 (Table 2). Six of the 11 subjects were habitual snorers preoperatively (AHI < 5); this habitual snoring decreased, and a satisfactory improvement in sleep quality was declared by all patients at T1. The mean AHI score decreased from 3.34 1.82 to 2.95 1.11, however this change was not significant (P > 0.05). Sleep efficiency improved significantly from 80.2 2.67% to 93.88 4.65% after surgery (P < 0.01). In all patients, sleep stages weakness, 1, and 2 were reduced after MDO (mean 6.02 2.78%, P < 0.01; difference 3.01 1.13%, P < 0.05; 9.65 3.12%, P < 0.01, respectively) and the insufficient stages 3 and 4 and REM scores were significantly increased at T1 (mean difference 3.04 1.75%, 4.32 2.53%, 6.99 2.41%, respectively; all and P < 0.01). Mean O2 saturation values during sleep increased significantly from 90.67 3.52% to 96.28 3.82% after MDO (P < 0.01).
Patients with severe maxillary hypoplasia constitute one of the groups of patients who are difficult to treat with traditional orthodontic and surgical techniques.4 DO is an option for patients who have previously been treated by conventional osteotomies at Le Fort levels or autogenous bone graft techniques and for relapse cases.16 The DO technique can be applied to the growing patient,3,5 and during application, the associated soft tissues also progress in accordance with the new bone tissue generated by DO.5 The expanded skeletal and soft tissues together form a functional matrix, which provides stability against relapse when compared with conventional orthognathic surgery.11 From a search of the literature, it was found that maxillary advancement with Le Fort I DO has been performed particularly in patients with craniofacial deformities such as CLP.8,9,17–22 The results of the present study were thus compared to those of the above-mentioned studies. Swennen et al.17 reported the successful application of the DO technique on two 13-year-old CLP patients with severe skeletal class III.
Wong et al.18 and Wang et al.19 reported that intraoral Le Fort I distractors are appropriate for CLP patients and those with a severe maxillary deficiency because of the risk of relapse. Wang et al.19 repeated their measurements at 6 months after MDO and reported no relapse despite a mean maxillary advancement of 11.3 mm. Kessler et al.20 reported that the results of midface DO treatment were stable at 12 months and 24 months after treatment. Singh et al.21 demonstrated that during the first 6 months following MDO in adult CLP patients, the maxilla relapse was approximately 30%; however at 6 months post-distraction, the relapse was negligible. In the present study, the follow-up period ranged from 6 to 9.5 months; MDO was successful in all cases, resulting in a mean 10.2 mm sagittal bone gain at A point. The internal MDO device was easily tolerated by all patients and the short-term outcome of treatment showed a satisfactory improvement. The optimal latency period, rhythm, and rate of MDO are yet to be determined. Adherence to a latency period of 5–7 days and distraction rhythm and rate of 0.5 mm
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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Gokce et al.
twice a day has been shown to generate new bone with a 4–6-week consolidation period.18 In the current study, the same protocol was performed, but with a consolidation period of 60 days. MDO is usually done after mandibular growth has ceased in order to prevent relapse.22 In this study, the dentofacial and pharyngeal growth of the subjects were complete and only male subjects were included to eliminate the gender factor in PAS.13,23 The CT technique is a valuable tool for investigating 3D changes in hard and soft tissues in terms of volume, which twodimensional (2D) radiographs cannot provide. Spiral CT to obtain 3D data was done using standard scanning protocols, and this method is reproducible, non-invasive, shows detailed hard and soft tissue anatomy, and allows comparison of 3D distances, accurate volume measurement, and orthogonal airway assessment.24 A change in body posture has an effect on PAS due to the postural effects of the tongue. A supine CT thus provides more physiological information since it is obtained in the usual sleeping posture.25 All CT scans used in the present study were obtained in supine position to minimize the effect on PAS due to body and head postures changes. Accurate planning of the osteotomies and distraction device positioning is crucial. Internal distraction devices offer a low-profile design and intraoral activation, which is an advantage in the adolescent patient who is concerned about appearance. Drawbacks are multi-vector limitation and difficulty in parallel and symmetric distractor placement.18 Using 3D virtual simulation and with the preparations made on the SLA models prior to surgery, parallel adaptation of the distractors to the bone tissue was easy during surgery and minimized the surgical operation time. To our knowledge, the present study is the first to evaluate the volumetric changes in NC and PAS using spiral CT-based 3D software and to evaluate functional changes using PSG after MDO in class III patients. As known, the maxillary bone forms the base of the NC and together with the palatal bone and the soft palate forms the front wall of the nasopharynx. Thus, changes in maxillary bone structure will inevitably affect these anatomical cavities.13,14 Gorgulu et al.14 found a significant NC volume increase after rapid palatal expansion. Gokce et al.13 evaluated alterations to the PAS after bimaxillary orthognathic surgery and reported that the nasopharynx
and oropharynx cavities expanded and moved forward together with the maxillary structures; the laryngopharynx contracted and moved backwards with the mandible due to the mandibular setback. Lee et al.26 showed an increase in volume of the nasopharynx and oropharynx and a decrease in volume of the laryngopharynx after bimaxillary orthognathic surgery using cone beam CT. Mochida et al.8 reported significant airway changes in CLP patients after a mean 12.4 mm of maxillary advancement. Xu et al.10 reported a 64.4% enlargement of the upper airway in patients after a mean 20 mm of midface advancement. Jakobsone et al.27 showed a 13–21% increase in PAS at the nasopharyngeal level after maxillary advancement. Aksu et al.9 reported a 30% PAS increase at the posterior, superoposterior, and middle airway space levels after a mean 8.7 mm of MDO. In our study, the total volumes of the NC and PAS increased by 14.1% and 7.3%, respectively (Table 1), and enlargement of the upper airway space was confirmed due to protrusion of the maxillary complex. In the comparison of the pre- and postsurgery 3D images, the NC volume was enlarged forward together with the anterior maxillary bone and surrounding soft tissues. In the superimposed 3D PAS images, it was found that the soft palate and uvula accompanied the protrusion of the maxillary bone. Therefore, the oropharynx and nasopharynx appear to be relocated in the forward direction (Fig. 4). After MDO, the volume of the superior and middle part of the PAS increased and the inferior part of the PAS remained stable. The mean percentage volume enlargement of these related sites was more than 10% after DO. It is concluded that the forward movement of these structures, which form the front wall of the oropharynx and nasopharynx, are the main cause of the PAS volume increase. Analysis of the PSG results showed great improvements after MDO. The frequency of snoring in six habitual snorer patients without OSA decreased markedly. In all patients, respiratory conditions during sleep were greatly improved. The stages weakness, 1, and 2 decreased, whereas REM and stages 3 and 4 increased after surgery. The current findings are in agreement with the results of a previous study by this group,13 which demonstrated bimaxillary orthognathic surgery to significantly improve sleep quality in class III patients by increasing the nasopharyngeal and velopharyngeal airways. In conclusion, after Le Fort I MDO, the volumes of the NC and PAS increased
significantly. This change led to a relaxation of the physiological flow of air through the PAS to the lungs, resulting in a significant improvement in sleep quality according to the PSG parameters. Further, the preparations made on the SLA models and the planning of surgery by virtual simulation before surgery simplified the work of the surgeons during the operation and increased the operation success. Funding
None. Competing interests
None declared. Ethical approval
The Ethics Committee of Gulhane Military Medical Academy in Ankara, Turkey approved this study (number 1491-97309/1539). Patient consent
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maxillary hypoplasia. J Craniofac Surg 2007;18:1209–15. Marsan G, Vasfi KS, Oztas E, Cura N, Susal Z, Emekli U. Oropharyngeal airway changes following bimaxillary surgery in class III female adults. J Craniomaxillofac Surg 2009;37:69–73. Abramson ZR, Susarla S, Tagoni JR, Kaban L. Three-dimensional computed tomographic analysis of airway anatomy. J Oral Maxillofac Surg 2010;68:363–71. 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. 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 3-dimensional conebeam computed tomography. J Oral Maxillofac Surg 2012;70:2867–75. 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 2011;139:e369–76.
Address: Sila Mermut Gokce Department of Orthodontics Medipol University Mega Hospitals Complex Bagcilar 34214 Istanbul Turkey Tel.: +90 4447044; Fax: +90 212 4607070 E-mail: [email protected]
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx http://dx.doi.org/10.1016/j.ijom.2014.10.021, available online at http://www.sciencedirect.com
Research Paper Orthognathic Surgery
Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis S. M. Gokce, S. Gorgulu, U. Karacayli, H. S. Gokce, B. Battal: Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis. Int. J. Oral Maxillofac. Surg. 2014; xxx: xxx–xxx. # 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Abstract. The aims of this study were to evaluate volumetric changes in the nasal cavity (NC) and pharyngeal airway space (PAS) after Le Fort I maxillary distraction osteogenesis (MDO) using a three-dimensional (3D) simulation program, and to determine the effects of MDO on respiratory function during sleep with polysomnography (PSG). 3D computed tomography images were obtained and analyzed before surgery (T0) and at a mean 8.2 1.2 months postsurgery (T1) (SimPlant-OMS software) for 11 male patients (mean age 25.3 5.9 years) with severe skeletal class III anomalies related to maxillary retrognathia. The simulation of osteotomies and placement of distractors were performed on stereolithographic 3D models. NC and PAS were segmented separately on these models for comparison of changes between T0 and T1. PSG including the apnoea–hypopnoea index (AHI), sleep efficiency, sleep stages (weakness, stages 1–4, and rapid eye movement (REM)), and mean lowest arterial O2 saturation were obtained at T0 and T1 to investigate changes in respiratory function during sleep. MDO was successful in all cases as planned on the models; the average forward movement at A point was 10.2 mm. Increases in NC and PAS volume after MDO were statistically significant. These increases resulted in significant improvement in sleep quality. PSG parameters changed after MDO; AHI and sleep stages weakness, 1, and 2 decreased, whereas REM, stages 3 and 4, sleep efficiency, and mean O2 saturation increased.
The use of distraction osteogenesis (DO) for the treatment of craniomaxillofacial anomalies has become popular over the past 10 years.1,2 Corpus, ramus, premaxillary, and maxillary DO are the most successful and widely used techniques 0901-5027/000001+07
for the correction of congenital class III malocclusions when rigid fixation techniques are insufficient.2,3 With rigid placement of the distractors, distraction forces may be transmitted to insufficient bone, and due to the anatomy of the region,
S. M. Gokce1, S. Gorgulu2, U. Karacayli3, H. S. Gokce4, B. Battal5 1
Department of Orthodontics, Medipol University, Mega Hospitals Complex, Bagcilar, Istanbul, Turkey; 2Department of Orthodontics, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey; 3Department of Oral and Maxillofacial Surgery, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey; 4Department of Prosthodontics, Medipol University, Mega Hospitals Complex, Bagcilar, Istanbul, Turkey; 5 Department of Radiology, Dental Sciences Centre, Gulhane Military Medical Academy, Etlik, Ankara, Turkey
Key words: Le Fort I; distraction osteogenesis; 3D imaging; nasal cavity; PAS; polysomnography. Accepted for publication 29 October 2014
difficulties are often encountered, especially in maxillary distractions.4 Due to the experience gained with extraoral distractors, intraoral sub-periosteal distractors were developed and are now being used successfully.4
# 2014 International Association of Oral and Maxillofacial Surgeons. Published by Elsevier Ltd. All rights reserved.
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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This study was approved by the institutional ethics committee and informed consent
0.018* 0.016* 0.083 0.017* 0.018* 0.018* Z = 2375 t = 2401 t = 1732 t = 2379 t = 2366 t = 2366 1.34 1.11 0.20 1.34 876.6 796.3
Test statisticsa
13.68 9.29 0.43 9.71 3635.7 2009.7
Mean difference
SD
14.1% 7.3% 2.49 82.06 80.06 2.75 31,824.9 32,362.2 1.21 81.07 79.07 1.24 27,001.9 26,626.2 0.69 0.53 0.53 0.81 2607.4 3101.0
Lower bound
Upper bound
2 82 80 2 29,236 29,312
Median
1.85 81.57 79.57 2.00 29,413.4 29,494.2
Mean
11 72 80 8 25,413 27,318 9.83 73.66 80.75 6.55 27,925.5 30,158.2
Upper bound Lower bound
15.01 70.90 79.24 8.87 23,629.8 24,810.8
95% CI for mean SD
After surgery (T1)
Median 95% CI for mean SD
3.71 1.49 0.81 1.25 2322.4 2890.9 11.83 72.28 80.00 7.71 25,777.7 27,484.5
T0–T1 T0–T1% increase
Mean
All CT examinations were performed before surgery (T0) and at >6 months after distraction (T1) using a 64 detector CT scanner (Aquilion 64; Toshiba Medical Systems, Otawara, Japan), with the subjects in supine position. Scan parameters were as follows: 120 kV, 150 mA, 400 ms rotation time, slice thickness of 6 months postsurgery (mean 8.2 1.2 months). The patients had severe skeletal class III anomalies due to maxillary retrognathia (mean sella–nasion–A point angle (SNA) 72.28 1.498, A point–nasion–B point angle (ANB) 7.71 1.258), an excessive overjet (mean increased negative 11.83 3.71 mm), an anterior and/or posterior cross-bite, and normal mandibular development (sella–nasion–B point angle (SNB) 80.00 0.818) (Table 1). Since all patients were adult with mandibular growth and mandibular complex structure that was normal, and all had excessive negative overjet, treatment with MDO was preferred over conventional Le Fort I osteotomy and rigid fixation to avoid the risk of potential relapse.
Before surgery (T0)
There are few reports on the use of internal distraction in the facial skeleton region.5,6 The advantages of internal devices are that they are less conspicuous and more tolerable to the patient. However, the design and installation of internal maxillary distraction osteogenesis (MDO) devices are difficult. To advance the maxilla to a predetermined position, it is critical to locate the distractors parallel to each other on both sides of the maxilla.6 Once the device is fixed, the vector of motion cannot be changed. So, presurgical projection on a three-dimensional (3D) stereolithographic (SLA) model is crucial to identify the distraction vector.5,6 Only a few studies have attempted to explore the effect of Le Fort I osteotomy on the pharyngeal airway space (PAS) in class III malocclusions.7–11 Harada et al.7 found increases in both nasopharyngeal depth and velar length after MDO. Mochida et al.8 showed that MDO in cleft lip and palate (CLP) patients led to an increase in the upper airway and a decrease in nasal resistance that remained stable even after 1 year. Aksu et al.9 found that anterior movement of the maxilla associated with MDO resulted in significant increases in posterior, superoposterior, and middle airway spaces in adult CLP patients. The distraction procedure not only changes the volume of bone tissue, but also modifies the surrounding structures such as the nasal cavity (NC).11 The anatomical and aesthetic aspects of DO are crucial, but the importance of functional consequences might overcome these aspects.12,13 Efforts to improve occlusion and facial aesthetics, and consequently the patient’s quality of life, may have the opposite effect.13 Creating upper airway resistance as a result of surgical procedures could influence respiration.12 Although the pharynx is voluntarily dilated when the patient is awake, there may be trouble during sleep. The single-night sleep study with full polysomnography (PSG) is a useful examination for evaluating, detecting, and quantifying respiratory impairment and can be performed safely in a variety of clinical situations.13 In the light of these facts, a hypothesis has been proposed that the volume of the NC and PAS increase after Le Fort I MDO and that the dentomaxillofacial changes accompanying MDO may have an effect on sleep respiratory function.
P-value
Gokce et al.
Table 1. Dentofacial, nasal cavity, and pharyngeal airway space volume changes between T0 and T1.
2
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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3D evaluation of the airway after Le Fort I MDO
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Fig. 1. Example of a stereolithographic model used for planning and preparation before surgery.
Fig. 2. 3D volumetric reconstruction and analysis of the nasal cavity at T0 and T1.
Fig. 3. The borders of the 3D pharyngeal airway space at T0 (green) and T1 (red). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
distractor positioning and incision lines for simulation before the actual operation were carried out on the SLA models; the plates of the distractor were fitted properly and marked on the SLA model for transfer to the operating area (Fig. 1). The NC and PAS were segmented on the 3D virtual models. The pre- and
post-treatment virtual models of the segmented regions were evaluated and compared. NC segments were restricted by the ostium of the paranasal sinuses, posterior airway, and nostrils (Fig. 2).14 The borders of the PAS were formed from the following: (1) anterior: a vertical plane through the distal margin of the vomer,
soft palate, base of the tongue, and anterior wall of the pharynx; (2) posterior: posterior wall of the pharynx; (3) lateral: the lateral walls of the pharynx; (4) upper: the roof of the nasopharynx; and (5) lower: a plane passing through the upper border of the larynx perpendicular to the sagittal plane (Fig. 3).15
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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Gokce et al. All variables were recorded on a computerized system. Sleep parameters were recorded on a 32-channel polygraph (SomnoStar Alpha Series 4; SensorMedics Corp., Yorba Linda, CA, USA). Sleep respiratory information, including the apnoea–hypopnoea index (AHI), sleep efficiency, sleep stages (weakness, stages 1, 2, 3, and 4, and rapid eye movement (REM)), and mean lowest arterial O2 saturation, was used for the data analysis.13 According to the PSG test results obtained before surgery, five of the 11 patients did not have any problem related with airway obstruction or snoring during sleep (AHI < 5). Six patients were diagnosed as simple snorers (AHI < 5); no patient was diagnosed with obstructive sleep apnoea syndrome (OSAS) at T0.
Surgical procedure
With a classic and complete high Le Fort I osteotomy under general anaesthesia, down-fracture and complete mobilization of the maxillary segment was performed in all patients by the same surgeon of the department of maxillofacial surgery. Insertion of the device was started with the fixing of titanium miniplates (MODUS; Medartis, Basel, Switzerland) to the zygomatic buttresses and maxillary segment below the osteotomy line bilaterally, as simulated previously on the SLA model. Distraction cylinders (MODUS, MDO1.5; Medartis, Basel, Switzerland) were placed on the miniplates. After the activation and direction of the distractors were approved, the device was anchored to the miniplates. After a 7-day latency period, distraction was performed at a rate of 0.5 mm twice a day for approximately 20 days. Distraction was continued until the elimination of the negative overjet and including 1-mm overtreatment. The patients underwent a consolidation period of 60 days with the distractors in place. Following the consolidation phase, the distractors were removed under local anaesthesia.
differences between the original and repeated measurements at the 0.05 level (P > 0.05).
Results
MDO was comfortable for the patients; its application was easy due to the position of the intraoral activating rod and it was removed after the consolidation period. No infection, dislocation, or device breakages occurred, and no lesions were encountered around the oral tissues during the distraction period. After MDO, skeletal alterations and occlusion at T1 were found to be compatible with the 3D simulation and SLA model, as visualized using the software.
Skeletal and volumetric measurements Statistical analysis
The descriptive analysis of preoperative and postoperative measurements was performed using SPSS 12.0.1 for Windows (SPSS Inc., Chicago, IL, USA). All pre- and post-treatment variables were compared with the paired-samples t-test, except for overjet and AHI, which did not pass the formal normality test (KolNon-parametric mogorov–Smirnov). variables were compared with the Wilcoxon signed-rank test. P-values of 6 months after MDO. Airflow was monitored through oral and nasal thermistors and cannulae adapted for this purpose. The mean lowest arterial O2 saturation was measured continuously by pulse oximetry using a finger probe. Body position was assessed continuously both with a closed-circuit camera and with a body position sensor.
The measured mean sagittal bone gain parallel to the skull base at A point was 10.2 mm (range 7.5–16.2 mm). As a result of the advancement of the maxillary complex, the mean negative overjet increased significantly from 11.83 3.71 mm to 1.85 0.69 mm (P < 0.05). The mean value of the SNA angle increased significantly from 72.28 1.498 to 81.57 0.538 (P < 0.05), but the mean change in SNB angle was not statistically significant (P > 0.05). The average value of the ANB angle changed from 7.71 1.258 to 2.00 0.818 and this change was significant (P < 0.05). The of NC (T0 volume 25,777.7 2322.4 mm3 to T1 29,413.4 2607.4 mm3) and the volume of PAS (T0 27,484.5 2890.9 mm3 to T1 29,494.2 3101.0 mm3) increased significantly (P < 0.05) (Fig. 4; Table 1).
Table 2. Polysomnography parameter changes between T0 and T1. T1
T0 Mean
AHI Sleep efficiency (%) Sleep stage weakness (%) Sleep stage 1 (%) Sleep stage 2 (%) Sleep stage 3 (%) Sleep stage 4 (%) REM (%) Mean O2 saturation (%)
3.34 80.2 13.24 7.22 73.88 5.12 10.02 5.12 90.67
SD
1.82 2.67 3.01 2.98 6.12 1.9 2.27 2.72 3.52
95% CI Lower bound
Upper bound
1.02 79.32 10.77 5.99 68.34 3.02 9.11 4.04 84.25
4.25 90.15 16.68 11.23 78.22 8.76 12.84 7.27 94.16
Mean
2.95 93.88 7.23 4.02 64.23 8.16 14.34 12.11 96.28
SD
1.11 4.65 2.31 1.25 4.11 2.91 3.26 3.83 3.82
T0–T1 95% CI
Lower bound
Upper bound
0.89 85.86 5.12 2.21 59.37 5.04 11.46 10.02 92.59
6.34 98.21 10.54 6.23 67.39 11.64 18.35 16.45 99.17
Mean difference
SD
Test statisticsa
P-value
0.4 13.66 6.02 3.01 9.65 3.04 4.32 6.99 5.61
1.73 4.64 2.78 1.13 3.12 1.75 2.53 2.41 3.11
Z = 0.835 t = 10654 t = 5466 t = 3154 t = 8371 t = 6845 t = 3478 t = 5912 t = 5214
0.095 0.001** 0.0012** 0.04* 0.001** 0.0013** 0.001** 0.0011** 0.001**
SD, standard deviation; CI, confidence interval; AHI, apnoea–hypopnoea index; REM, rapid eye movement. a Z represents the Wilcoxon signed-rank test result; t represents the paired-sample t-test result. * P < 0.05. ** P < 0.01.
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
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Fig. 4. 3D volumetric superimposition images of the nasal cavity (upper left) and pharyngeal airway space (lower left) at T0–T1, and 3D volumetric reconstruction of the total nasal cavity and pharyngeal airway space presented on lateral view for T0 (purple, red) and T1 (yellow, green) periods. (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of the article.)
Polysomnography measurements
Discussion
According to the PSG evaluation, the postoperative sleep quality of the subjects was improved at T1 when compared with T0 (Table 2). Six of the 11 subjects were habitual snorers preoperatively (AHI < 5); this habitual snoring decreased, and a satisfactory improvement in sleep quality was declared by all patients at T1. The mean AHI score decreased from 3.34 1.82 to 2.95 1.11, however this change was not significant (P > 0.05). Sleep efficiency improved significantly from 80.2 2.67% to 93.88 4.65% after surgery (P < 0.01). In all patients, sleep stages weakness, 1, and 2 were reduced after MDO (mean 6.02 2.78%, P < 0.01; difference 3.01 1.13%, P < 0.05; 9.65 3.12%, P < 0.01, respectively) and the insufficient stages 3 and 4 and REM scores were significantly increased at T1 (mean difference 3.04 1.75%, 4.32 2.53%, 6.99 2.41%, respectively; all and P < 0.01). Mean O2 saturation values during sleep increased significantly from 90.67 3.52% to 96.28 3.82% after MDO (P < 0.01).
Patients with severe maxillary hypoplasia constitute one of the groups of patients who are difficult to treat with traditional orthodontic and surgical techniques.4 DO is an option for patients who have previously been treated by conventional osteotomies at Le Fort levels or autogenous bone graft techniques and for relapse cases.16 The DO technique can be applied to the growing patient,3,5 and during application, the associated soft tissues also progress in accordance with the new bone tissue generated by DO.5 The expanded skeletal and soft tissues together form a functional matrix, which provides stability against relapse when compared with conventional orthognathic surgery.11 From a search of the literature, it was found that maxillary advancement with Le Fort I DO has been performed particularly in patients with craniofacial deformities such as CLP.8,9,17–22 The results of the present study were thus compared to those of the above-mentioned studies. Swennen et al.17 reported the successful application of the DO technique on two 13-year-old CLP patients with severe skeletal class III.
Wong et al.18 and Wang et al.19 reported that intraoral Le Fort I distractors are appropriate for CLP patients and those with a severe maxillary deficiency because of the risk of relapse. Wang et al.19 repeated their measurements at 6 months after MDO and reported no relapse despite a mean maxillary advancement of 11.3 mm. Kessler et al.20 reported that the results of midface DO treatment were stable at 12 months and 24 months after treatment. Singh et al.21 demonstrated that during the first 6 months following MDO in adult CLP patients, the maxilla relapse was approximately 30%; however at 6 months post-distraction, the relapse was negligible. In the present study, the follow-up period ranged from 6 to 9.5 months; MDO was successful in all cases, resulting in a mean 10.2 mm sagittal bone gain at A point. The internal MDO device was easily tolerated by all patients and the short-term outcome of treatment showed a satisfactory improvement. The optimal latency period, rhythm, and rate of MDO are yet to be determined. Adherence to a latency period of 5–7 days and distraction rhythm and rate of 0.5 mm
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Gokce et al.
twice a day has been shown to generate new bone with a 4–6-week consolidation period.18 In the current study, the same protocol was performed, but with a consolidation period of 60 days. MDO is usually done after mandibular growth has ceased in order to prevent relapse.22 In this study, the dentofacial and pharyngeal growth of the subjects were complete and only male subjects were included to eliminate the gender factor in PAS.13,23 The CT technique is a valuable tool for investigating 3D changes in hard and soft tissues in terms of volume, which twodimensional (2D) radiographs cannot provide. Spiral CT to obtain 3D data was done using standard scanning protocols, and this method is reproducible, non-invasive, shows detailed hard and soft tissue anatomy, and allows comparison of 3D distances, accurate volume measurement, and orthogonal airway assessment.24 A change in body posture has an effect on PAS due to the postural effects of the tongue. A supine CT thus provides more physiological information since it is obtained in the usual sleeping posture.25 All CT scans used in the present study were obtained in supine position to minimize the effect on PAS due to body and head postures changes. Accurate planning of the osteotomies and distraction device positioning is crucial. Internal distraction devices offer a low-profile design and intraoral activation, which is an advantage in the adolescent patient who is concerned about appearance. Drawbacks are multi-vector limitation and difficulty in parallel and symmetric distractor placement.18 Using 3D virtual simulation and with the preparations made on the SLA models prior to surgery, parallel adaptation of the distractors to the bone tissue was easy during surgery and minimized the surgical operation time. To our knowledge, the present study is the first to evaluate the volumetric changes in NC and PAS using spiral CT-based 3D software and to evaluate functional changes using PSG after MDO in class III patients. As known, the maxillary bone forms the base of the NC and together with the palatal bone and the soft palate forms the front wall of the nasopharynx. Thus, changes in maxillary bone structure will inevitably affect these anatomical cavities.13,14 Gorgulu et al.14 found a significant NC volume increase after rapid palatal expansion. Gokce et al.13 evaluated alterations to the PAS after bimaxillary orthognathic surgery and reported that the nasopharynx
and oropharynx cavities expanded and moved forward together with the maxillary structures; the laryngopharynx contracted and moved backwards with the mandible due to the mandibular setback. Lee et al.26 showed an increase in volume of the nasopharynx and oropharynx and a decrease in volume of the laryngopharynx after bimaxillary orthognathic surgery using cone beam CT. Mochida et al.8 reported significant airway changes in CLP patients after a mean 12.4 mm of maxillary advancement. Xu et al.10 reported a 64.4% enlargement of the upper airway in patients after a mean 20 mm of midface advancement. Jakobsone et al.27 showed a 13–21% increase in PAS at the nasopharyngeal level after maxillary advancement. Aksu et al.9 reported a 30% PAS increase at the posterior, superoposterior, and middle airway space levels after a mean 8.7 mm of MDO. In our study, the total volumes of the NC and PAS increased by 14.1% and 7.3%, respectively (Table 1), and enlargement of the upper airway space was confirmed due to protrusion of the maxillary complex. In the comparison of the pre- and postsurgery 3D images, the NC volume was enlarged forward together with the anterior maxillary bone and surrounding soft tissues. In the superimposed 3D PAS images, it was found that the soft palate and uvula accompanied the protrusion of the maxillary bone. Therefore, the oropharynx and nasopharynx appear to be relocated in the forward direction (Fig. 4). After MDO, the volume of the superior and middle part of the PAS increased and the inferior part of the PAS remained stable. The mean percentage volume enlargement of these related sites was more than 10% after DO. It is concluded that the forward movement of these structures, which form the front wall of the oropharynx and nasopharynx, are the main cause of the PAS volume increase. Analysis of the PSG results showed great improvements after MDO. The frequency of snoring in six habitual snorer patients without OSA decreased markedly. In all patients, respiratory conditions during sleep were greatly improved. The stages weakness, 1, and 2 decreased, whereas REM and stages 3 and 4 increased after surgery. The current findings are in agreement with the results of a previous study by this group,13 which demonstrated bimaxillary orthognathic surgery to significantly improve sleep quality in class III patients by increasing the nasopharyngeal and velopharyngeal airways. In conclusion, after Le Fort I MDO, the volumes of the NC and PAS increased
significantly. This change led to a relaxation of the physiological flow of air through the PAS to the lungs, resulting in a significant improvement in sleep quality according to the PSG parameters. Further, the preparations made on the SLA models and the planning of surgery by virtual simulation before surgery simplified the work of the surgeons during the operation and increased the operation success. Funding
None. Competing interests
None declared. Ethical approval
The Ethics Committee of Gulhane Military Medical Academy in Ankara, Turkey approved this study (number 1491-97309/1539). Patient consent
Not required. References 1. Stucki-McCormick SU, Mizrahi RD, Fox RM, Romo T. Distraction osteogenesis of the mandible using a submerged intraoral device: a report of three cases. J Oral Maxillofac Surg 1999;57:192–8. 2. Gulses A, Aydıntug YS, Sencimen M, Bayar GR, Acıkel C. Evaluation of the vitality levels of the teeth in the distracted segment in procedures of premaxillary distraction osteogenesis. Gulhane Med J 2012;54: 111–9. 3. Wiltfang J, Kessler P, Schultze-Mosgau S, Merten HA, Gu¨nther G. Continuous bone distraction with the help of a microhydraulic cylinder. Second international congress on cranial and facial bone distraction processes. Bologna: Monduzzi Editore; 1999 . p. 35–40. 4. Cohen SR, Rutrick RE, Burstein FD. Distraction osteogenesis of the human craniofacial skeleton: initial experience with a new distraction system. J Craniofac Surg 1995;6: 368–74. 5. Rachmiel A, Aizenbud D, Eleftheriou S, Peled M, Layfer D. Extraoral vs. intraoral distraction osteogenesis in the treatment of hemifacial microsomia. Ann Plast Surg 2000;45:386–94. 6. Gateno J, Engel ER, Teichgraeber JF, Yamaji KE, Xia JJ. A new Le Fort I internal distraction device in the treatment of severe maxillary hypoplasia. J Oral Maxillofac Surg 2005;63:148–54.
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Address: Sila Mermut Gokce Department of Orthodontics Medipol University Mega Hospitals Complex Bagcilar 34214 Istanbul Turkey Tel.: +90 4447044; Fax: +90 212 4607070 E-mail: [email protected]
Please cite this article in press as: Gokce SM, et al. Three-dimensional evaluation of nasal and pharyngeal airway after Le Fort I maxillary distraction osteogenesis, Int J Oral Maxillofac Surg (2014), http://dx.doi.org/10.1016/j.ijom.2014.10.021
