The effect of altered head and tongue posture on upper airway volume based on a validated upper airway analysis-An MRI pilot study.

OBJECTIVE: To determine the influence of altered head or tongue posture on upper airway (UA) volumes using MRI imaging based on a new objective and validated UA evaluation protocol. SETTING AND SAMPLE POPULATION: One supine CBCT and five sagittal MRI scans were obtained from ten subjects in different head and tongue positions: (a) supine neutral head position (NHP) with the tongue in a natural resting position with the tip of the tongue in contact with the lingual aspect of the lower incisors (TRP); (b) head extension with TRP; (c) head flexion with TRP; (d) NHP with the tip of the tongue in contact with the posterior edge of the hard palate (THP); and (e) NHP with the tip of the tongue in contact with the floor of the mouth in contact with the caruncula sublingualis. MATERIAL AND METHODS: Based on a validated CBCT UA analysis, the retropalatal, oropharyngeal and the corresponding total volumes were measured from each MRI scan. Wilcoxon signed-rank test was applied to determine the statistically significant difference in mean volume between the baseline head and tongue posture (NHP with TRP) and the other postures. RESULTS: Five females and five males with a mean age of 46.5 ± 13.7 years volunteered for this pilot study. UA volumes, particularly the oropharyngeal volume, increased significantly with head extension and NHP with THP and decreased significantly with head flexion. CONCLUSION: Altered head and tongue posture proved to affect UA volumes, thus representing confounding variables during three-dimensional radiographic image acquisition.

Two-Year Postoperative Upper Airway Cone-Beam Computed Tomographic Outcomes Based on a Verified Upper Airway Analysis Following Bimaxillary Orthognathic Surgery.

PURPOSE: Upper airway (UA) assessment after orthognathic surgery should rely on a verified method of UA analysis. Therefore, the authors applied a new validated UA evaluation method to determine the effect of bimaxillary surgery (BMS) on UA parameters and hyoid bone and epiglottis displacement evaluated immediately and 2 years after surgery. MATERIALS AND METHODS: A retrospective cohort study was implemented of patients without obstructive sleep apnea who had undergone BMS for maxillomandibular deficiencies. A new validated UA cone-beam computed tomographic (CBCT) analysis, based on stable anatomic landmarks, was applied to CBCT scans acquired before initiation of treatment (T0), immediately after surgery (T1), and 2 years postoperatively (T2). A quality assessment was performed before analysis. The primary predictor variable consisted of time points during treatment (T0, T1 and T2), and UA volumes, cross-sectional area (CSA), and hyoid bone and epiglottis displacement were the outcome variables. Descriptive statistics and t test were performed and the P value was set at .05. RESULTS: Fifty patients (16 men and 34 women) with a mean age of 25.7 ± 8.2 years at time of surgery were included. CBCT scans were acquired at T0 (20 ± 9 months before surgery), T1 (14 ± 2 days after surgery), and T2 (30 ± 6 months after surgery). Immediately after surgery (T1 vs T0), BMS resulted in a statistically relevant UA volume increase of 26%. At 2-year follow-up (T2 vs T0), UA volume showed a statistically relevant increase by 20%. CSA increased by approximately 26 and 19% (P < .001) at T1 versus T0 and T2 versus T0, respectively. Two years after surgery, epiglottis displacement was 2 mm (P < .001) and hyoid bone displacement was 3 mm (P < .001) in a cranial direction and hyoid bone anterior displacement measured 3 mm (P < .001). CONCLUSIONS: Based on an objective, standardized, and validated CBCT UA analysis, BMS was associated with increased UA volume and CSA measures evaluated immediately and 2 years after surgery.

A new simple three-dimensional method to characterize upper airway in orthognathic surgery patient.

OBJECTIVES: To develop and validate a new reproducible 3D upper airway analysis based on skeletal structures not involved in the modification, which occur during orthognathic surgery. METHODS: From retrospective cohort of orthognathic surgically treated patients, pre- and postsurgical CBCT-scans of 10 post-pubertal patients were randomly selected. Two operators identified the landmarks, calculated the airway volumes, cross sections and linear measurements on the 10 scans twice at two different time intervals. Statistical analysis included test for normal distribution, technical error measurements, and intra- and inter-observers reliability. RESULTS: Intra- and inter-observer reliability was excellent for volumes and cross sections. The entire data sets exhibited normal distribution. Technical error of measurements showed an error in the range of 1.6 to 10.2% for volume, 1.6 to 12.2% for cross-sectional measurements, and 0.3 to 2.5% for linear measurements. No systematic errors were detected. CONCLUSIONS: This new proposed definition of upper airway boundaries was shown to be technical feasible and tested to be reliable in measuring upper airway in patients undergoing orthognathic surgery.

Effect of Head and Tongue Posture on the Pharyngeal Airway Dimensions and Morphology in Three-Dimensional Imaging: a Systematic Review.

OBJECTIVES: Natural head position is recommended to be optimal at cone-beam computed tomography acquisition. For standardization purposes in control of treatment outcome, it is clinically relevant to discuss, if a change of posture from natural head position may have an effect on the pharyngeal airway dimensions and morphology, during computed tomography, cone-beam computed tomography or magnetic resonance imaging acquisition. This was the aim of the present literature review study for purposes of valid evidence, which was hypothesized, to be present. MATERIAL AND METHODS: This systematic literature review has been registered in PROSPERO database with following number: CRD42015024567. A systematic literature search performed in PubMed, Embase and Cochrane was carried out in order to evaluate if the effect of human head or tongue posture has an effect on upper airway dimensions and morphology in CT, CBCT or MRI. Study quality assessment was performed. Predictor variable was head and tongue posture. Endpoints were numerical values of upper airway dimensions and morphology. RESULTS: Overall 1344 articles (Embase 1063, PubMed 269, and Cochrane 12) resulted in four included publications. Quality assessments revealed poor quality and low-level evidence by 46 - 67% of the maximum achievable score. Heterogeneous methodology made a meta-analysis impossible, consequently a narrative synthesis was performed. CONCLUSIONS: Limited, poor quality and low evidence level literature is available on the effect of head posture on upper airway dimensions and morphology in three-dimensional imaging. Valid evidence requires a standardized method of head and tongue posture during image acquisition in future studies.