Three-Dimensional Computed Tomographic Analysis of Airway Anatomy

Pharyngeal airway changes in Class III patients treated with double jaw orthognathic surgery--maxillary advancement and mandibular setback

PURPOSE

The pharyngeal airway may change after skeletal movement in patients who have undergone orthognathic surgery. The aim of this study was to evaluate the skeletal and pharyngeal airway changes in subjects with a Class III facial pattern who underwent double-jaw surgery (maxillary advancement and mandibular setback).

MATERIALS AND METHODS

The present retrospective study assessed preoperative (T0), 2- to 4-month postoperative (T1), and 6- to 12-month postoperative (T2) radiographs of subjects with a Class III facial pattern treated at São Lucas Hospital (Porto Alegre, Brazil) using imaging software (Dolphin Imaging 3D 11.5). Five measurements of the pharyngeal airway space (nasopharynx; upper, middle, and lower oropharynges; hypopharynx) were evaluated and correlated with the skeletal movement of the jaws (lines perpendicular to the Frankfurt horizontal plane passing through the nasion point to points A and B). The Student t test for paired samples was used to assess the presence of significant differences between the intervals, and the Spearman correlation coefficient was used to assess the significant correlation existing between the skeletal movement and the pharyngeal airway changes. The results were considered at a maximum level of significance of 5% (P < .05).

RESULTS

In the sample of 58 subjects (38 female and 20 male, 18 to 48 years old), measurements of the nasopharynx, upper oropharynx, and middle oropharynx increased, whereas measurements of the lower oropharynx and hypopharynx decreased during these periods (T0 to T1, T0 to T2). Decreases from T1 to T2 in the measurements of the nasopharynx and upper oropharynx were also identified. A correlation between the jaw movements and the change in airway measurement was found between the line perpendicular to the Frankfurt horizontal plane passing through the nasion point to point A and the nasopharynx and between the line perpendicular to the Frankfurt horizontal plane passing through the nasion point to point B and the lower oropharynx for T0 to T1 and T0 to T2.

CONCLUSIONS

A correlation between skeletal movements and changes in the measurements of pharyngeal airway was found between maxillary advancement and the nasopharynx, with proportions of 102.8% and 85.5% in the short and medium terms, respectively, and between mandibular setback and the low oropharynx, with proportions of 44.8% and 43.5% in the short and medium terms. A correlation for pharyngeal airway measurements was found between those located anatomically near each other, showing the importance of the pharyngeal muscles in this relation.

Bimaxillary 'rotation advancement' procedures in patients with obstructive sleep apnea: a 3-dimensional airway analysis of morphological changes

The aim of this retrospective three dimensional (3D) computed tomographic analysis was to investigate the morphological airway changes in 17 obstructive sleep apnea (OSA) patients following bimaxillary rotation advancement procedures. Morphological changes of the nasal cavity and naso-, oro- and hypopharynx were analysed separately, as were the total airway changes using nine parameters of airway size and four of shape. The Wilcoxon test was used to compare airway changes and the intraclass correlation coefficient to qualify inter-observer reliability. Following bimaxillary advancement and anti-clockwise maxillary rotation, the total airway volume and the lateral dimension of the cross-sectional airway increased significantly. The total length of the airway became shorter (p<0.05). Remarkable changes were seen in the oropharynx: the length, volume, cross-sectional area (CSA), antero-posterior and medio-lateral distance changed (p<0.05). This combined with a significant 3D change in the shape of the airway from round to elliptical. The average cross-sectional oropharyngeal area was nearly doubled, the minimal CSA increased 40%, and the hyoid bone was located more anterior and superior. Inter-examiner reliabilities were high (0.89). 3D airway analysis aids the understanding of postoperative pathophysiological changes in OSA patients. The airway became shorter, more voluminous, medio-laterally wider, and more compact and elliptical.

Surgical treatment modality for facial esthetics in an obstructive sleep apnea patient with protrusive upper lip and acute nasolabial angle

For patients with severe obstructive sleep apnea syndrome (OSAS), maxillomandibular advancement (MMA) offers a good treatment option by physically expanding the skeletal framework. However, facial esthetics can be aggravated by MMA in patients with OSAS who have a normally positioned maxilla, a protrusive upper lip, and an acute nasolabial angle. Therefore, surgical treatment planning should be customized according to diverse skeletodental and soft-tissue patterns to produce a favorable change in facial esthetics and sleep function in patients with OSAS. In this case report, good treatment results were achieved in a young female patient with OSAS and skeletal Class II, a normally positioned maxilla, a protrusive upper lip, and acute nasolabial angle by impaction of the maxilla, autorotation/advancement of the mandible, and advancement of the chin. A customized flowchart for surgical treatment planning in OSAS that considers facial esthetics was suggested.

Three-dimensional computed tomography analysis of airway volume changes after rapid maxillary expansion

INTRODUCTION

In this retrospective study with 3-dimensional computed tomography, we evaluated airway volume, soft-palate area, and soft-tissue thickness changes before and after rapid maxillary expansion in adolescents. Another purpose was to determine whether rapid maxillary expansion caused changes in the palatal and mandibular planes and facial height.

METHODS

The sample comprised 20 patients who were treated with rapid maxillary expansion. Spiral tomographs were taken before and 3 months after treatment. Reliability studies were performed, and then volumetric, soft-palate area, soft-tissue thickness, and cephalometric parameters were compared on the tomographs. Intraclass correlations were performed on the reliability measurements. Before and after rapid maxillary expansion measurements were compared by using Wilcoxon signed rank tests. Spearman correlation coefficients were used to evaluate the associations among the airway volume, soft-palate area, soft-tissue thickness, and cephalometric measurements. Significance was accepted at P ≤0.05 for all tests.

RESULTS

Intraclass correlation coefficients were ≥0.90 for all reliability measures. Significant increases from before to after rapid maxillary expansion were found in nasal cavity and nasopharynx volumes, and for the measurements of MP-SN, S-PNS, N-ANS, ANS-Me, and N-Me. Significant positive correlations existed between changes in PP-SN and N-ANS, and ANS-Me and N-Me.

CONCLUSIONS

Rapid maxillary expansion causes significant increases in nasal cavity volume, nasopharynx volume, anterior and posterior facial heights, and palatal and mandibular planes.

Three-dimensional airway evaluation in 387 subjects from one university orthodontic clinic using cone beam computed tomography

OBJECTIVE

To determine the linear, volumetric, and cross-sectional area measurements in a large sample of subjects seeking treatment in a university clinic of orthodontics.

MATERIALS AND METHODS

Cone-beam computed tomography (CBCT) scans from 387 patients were analyzed retrospectively. All scans were loaded into the 3dMDvultus program (Atlanta, Ga) for airway analysis using automated segmentation. Gender, age, height, weight, airway length, volume, and area of maximum constriction were collected.

RESULTS

The rostrocaudal length of the airway increased with age until the age of 15 years in female subjects but continued to increase in male subjects and ranged from 44 to 88 mm over the period of 8 to 18 years of age with the gender data combined. The volume of the airway increased through the entire 11-year age range from 2000 mm(3) to 27,000 mm(3). The rate of airway volume increased at a slower rate in female than in male subjects. The smallest cross-sectional area increased with age ranging from 20 to 250 mm(2) but at a slower rate with female subjects, while male subjects demonstrated a more exponential increase after the age of 13 years.

CONCLUSIONS

The human airway increases in length and volume during a rapid period of craniofacial growth in patients between the ages of 8 and 18 years, and the site of maximum cross-sectional area constriction can vary.

Cone beam computed tomography evaluation of changes in the naso-maxillary complex associated with two types of maxillary expanders

OBJECTIVE

To test the hypothesis that there were no differences in the skeletal and dental effects of banded vs bonded expanders when evaluated using cone beam computed tomography (CBCT).

MATERIALS AND METHODS

The experimental sample consisted of 23 patients: 13 (seven male, six female; mean age  =  12.6 ±1.8 years) and 10 (five male, five female; mean age  =  13.5 ± 2.1 years) treated with banded and bonded maxillary expanders, respectively. CBCT images were taken at T1 (pretreatment) and T2 (immediately after expansion) to evaluate the changes in the naso-maxillary complex. Relationships between and within groups were assessed using analysis of variance. If the results were significant, post hoc t-tests were used to determine where the significant differences occurred.

RESULTS

Regardless of the appliance, the maxilla was expanded equally at the level of the canines and first and second premolars. At the level of the first molars, more dental tipping and alveolar bending were evident in the banded expander group. Both appliances equally increased the skeletal and soft tissue dimensions of the nasal cavity and maxillary sinus volume. The posterior airway volume did not significantly change with either method of expansion.

CONCLUSIONS

The hypothesis was rejected. Both appliances expanded the maxilla similarly. However, in the banded group, more dental tipping and alveolar bending occurred at the level of the first molars. Maxillary expansion affected the palatal suture and demonstrated anterior and posterior skeletal widening of the nasal cavity, with corresponding soft tissue changes and increased airway volume.

Quantification of the difference between 3D CT and plain radiograph for measurement of the position of medial unicompartmental knee replacements

The aim of this study was to quantify the differences in measurements obtained from 3D Computed Tomography and plain radiograph, for the positioning of the tibial component of the Oxford unicompartmental knee replacement. Post-operative 3D Computed Tomography data and plain radiographs (long antero-posterior (AP) and short lateral) were obtained for 28 knees of patients who had undergone medial unicompartmental knee replacement. Parameters of the orientation/positioning of the tibial component: Varus/valgus, posterior tibial slope and rotation were measured with both modalities. Bland-Altman plots were used to calculate the 1.96 standard deviation limits of agreement (LOA) between imaging modalities. Intra class correlation was used to assess inter-method and inter-rater reliability (>0.81 = very good reliability). Radiographs were less reliable in all parameters, when compared with 3D CT (intra class correlation coefficients: tibial rotation 0.94 vs 0.96, varus/valgus 0.76 vs 0.94, and posterior tibial slope 0.82 vs 0.92). The LOA were -4.9° to 3.4° for varus/valgus (bias -0.7°, one third >3° different); -4.9° to 0.1° for posterior tibial slope (bias -2.4°, one third >3° different); and -20.6° to 16.1° for rotation (bias -2.2°, one third >10° different). There was some disagreement between measurement by 3D Computed Tomography and plain radiograph for all three parameters of tibial component orientation, especially tibial rotation. This will be particularly relevant to research into the relationship between the accuracy of implant positioning/orientation and patient satisfaction/implant survival rates. This method offers a more reliable standard for the reporting of knee arthroplasty.

Airway volume for different dentofacial skeletal patterns

INTRODUCTION

Our objective was to evaluate the nasal passage (NP) and oropharyngeal (OP) volumes of patients with different dentofacial skeletal patterns.

METHODS

The study sample consisted of 140 patients (70 boys, 70 girls), divided into 3 groups as Class I (1 ≤ ANB ≤ 3), Class II (ANB > 3), and Class III (ANB < 1), and then further divided into 4 groups as SNA angle ≥ 80°, SNA angle <80°, SNB angle ≥78°, and SNB angle < 78° to evaluate how the positional changes in the maxilla and the mandible affect the OP and NP variables. Differences between groups were determined by using the Kruskal-Wallis test. Correlations between the variables were tested with the Spearman correlation coefficient. The linear multiple regression test was applied to create a model for the airway volumes separately.

RESULTS

The OP volume of the Class II subjects (n = 50) was significantly lower when compared with that of the Class I (n = 46) and Class III subjects (n = 44). The only statistically significant difference for NP volume was observed between the Class I and Class II groups. The mean OP airway volume of subjects with retruded mandibular positions was statistically significantly smaller when compared with the subjects with higher SNB angles. The area of the most constricted region at the base of the tongue (minAx) had a high potential in explaining the OP volume, whereas the NP volume models were not as successful as the OP counterpart. However, minAx was also entered into the NP volume equations as an explanatory variable.

CONCLUSIONS

The OP airway volumes of Class II patients were smaller when compared with Class I and Class III patients. It was observed that mandibular position with respect to cranial base had an effect on the OP airway volume. The only significant difference for the NP volume was between the Class I and Class II groups, with a smaller volume observed for the Class II group.

Comparison of pharyngeal airway changes on plain radiography and cone-beam computed tomography after orthognathic surgery

PURPOSE

The purpose of the present prospective study was to develop a 3-dimensional analysis of the airway using cone-beam computed tomography (CBCT) and to determine whether changes in the airway before and after orthognathic surgery correlate on 2-dimensional lateral cephalogram and 3-dimensional CBCT images.

MATERIALS AND METHODS

Patients requiring orthognathic surgery during 2004 to 2005 were recruited for the present study. Lateral cephalograms and CBCT scans were obtained at 3 points: preoperatively, within 1 month postoperatively, and after 6 months postoperatively. The nasopharynx, oropharynx, and hypopharynx were segmented on both the radiograph and the CBCT scan for each patient in a repeatable manner at each point. For the lateral cephalogram, linear measurements in the middle of each of the 3 segments were obtained. For the CBCT, volumetric measurements of each of the 3 segments were obtained. The intrarater variability was assessed, and Pearson's correlation was used to compare the 2 imaging modalities.

RESULTS

A total of 20 patients scheduled for orthognathic surgery were recruited for the present study. Of the 20 patients, 13 were female and 7 were male. The mean age at surgery was 23.85 years (range 14 to 43). Of the 20 patients, 6 underwent maxillary advancement only, 8 underwent mandibular advancement with or without genioplasty, and 6 underwent 2-jaw surgery or mandibular setback. We examined the entire cohort without separation into procedure or examination point and found a weak, but statistically significant, correlation between the linear and volume measurements in the nasopharyngeal and oropharyngeal regions but not in the hypopharyngeal region (r = 0.43, P < .002; r = 0.49, P < .0002; r = 0.16, P = .26, respectively). The maxillary advancement group (n = 6) demonstrated a correlation between the linear and volume measurements in the nasopharyngeal region (r = 0.53, P = .03). The mandibular advancement with or without genioplasty group (n = 8) showed a correlation in the nasopharyngeal and oropharyngeal regions (r = 0.55, P < .02, and r = 0.46, P = .05, respectively). For the combination/setback procedures (n = 6), a correlation was found in the oropharyngeal region (r = 0.64, P < .01). All other comparisons between the linear and volume measurements did not correlate. Additionally, no correlations were found between the linear and volumetric change in airway size between 6 months postoperatively and preoperatively, except for the oropharyngeal region (r = 0.67, P < .01).

CONCLUSION

We present a method of measuring the airway that could be used for both 2-dimensional and 3-dimensional images. It includes segmentation of the pharyngeal airway into its nasopharyngeal, oropharyngeal, and hypopharyngeal components. Correlations were found between the linear and volumetric measurements of the segmented airway in patients who had undergone orthognathic surgery; however, the correlations were generally weak.

Cephalometric predictors of therapeutic response to multilevel surgery in patients with obstructive sleep apnea

PURPOSE

The present study investigated whether cephalometric measurements can predict the therapeutic efficacy of multilevel phase I surgery for patients with obstructive sleep apnea (OSA).

PATIENTS AND METHODS

Among 210 patients with OSA who underwent multilevel phase I surgery, 85 were recruited on the basis of the baseline polysomnography, body mass index, and lateral cephalogram recordings. The patients were divided into 2 groups according to the degree of change in the apnea-hypopnea index before and 6 months after multilevel surgery: good responders (>50% decrease in apnea-hypopnea index) and poor responders (0% to 50% decrease or increase in apnea-hypopnea index). Cephalometric analysis was performed to identify the relevant variables, with division into 5 compartments: craniofacial, soft palate, tongue, hyoid bone, and upper airway variables.

RESULTS

In the craniofacial compartment, poor responders represented skeletal Class II with a more retrognathic mandible, and a hyperdivergent vertical pattern with a larger mandibular plane angle, longer lower facial height, and steeper occlusal plane than good responders. In the upper airway compartment, poor responders had narrower middle and inferior airway spaces and a longer upper airway length than good responders. No significant differences were found in the soft palate, tongue, and hyoid measurements between the 2 groups.

CONCLUSION

Some preoperative cephalometric measurements were verified retrospectively to predict the therapeutic response to the multilevel surgery in patients with OSA. This study would contribute not only to establishing selective criteria for the surgical approach to patients with OSA in ear-nose-throat practice but also in deciding on the referral to orthodontists or maxillofacial surgeons.

Three-dimensional changes in pharyngeal airway in skeletal class III patients undergoing orthognathic surgery

PURPOSE

It has often been hypothesized that mandibular setback surgery causes narrowing of the pharyngeal airway. We examined whether the pharyngeal airway narrowed after orthognathic surgery in patients undergoing either mandibular setback surgery or bimaxillary surgery and whether the amount of narrowing of the pharyngeal airway was any different after mandibular setback surgery or bimaxillary surgery.

MATERIALS AND METHODS

Cone-beam computed tomography scans were obtained for 21 patients who were assigned to either mandibular setback surgery or bimaxillary surgery. The anteroposterior dimension, lateral width, cross-sectional area, and volume of each subject's pharyngeal airway were measured before and after surgery.

RESULTS

The pharyngeal airway showed significant narrowing after both mandibular setback surgery and bimaxillary surgery. The amount of change in the anteroposterior dimension and cross-sectional area on the posterior nasal spine plane and the length of the pharyngeal airway showed significant differences between the 2 groups.

CONCLUSION

The amount of narrowing of the pharyngeal airway was smaller in patients undergoing bimaxillary surgery than in the patients undergoing mandibular setback surgery.