Do patients with different craniofacial patterns have differences in upper airway volume? A systematic review with network meta-analysis.

Background: Craniofacial skeletal discrepancies have been associated with upper airway dimensions.

Objective: To identify differences in upper airway volume across different sagittal and vertical skeletal patterns.

Search methods: Unrestricted literature searches in eight databases/registers for human studies until May 2023.

Selection criteria: Cross-sectional studies measuring upper airway volumes using three-dimensional imaging in healthy patients of different sagittal (Class I, Class II, and Class III) or vertical (normodivergent, hypodivergent, and hyperdivergent) craniofacial morphology.

Data collection and analysis: Duplicate independent study selection, data extraction, and risk of bias assessment. Random-effects frequentist network meta-analysis was performed followed by subgroup-analyses and assessment of the quality of clinical recommendations (confidence in effect estimates) with the CINeMA (Confidence in Network Meta-Analysis) approach.

Results: Seventy publications pertaining to 66 unique studies were included with 56 studies (5734 patients) contributing to meta-analyses. Statistically significant differences were found for total  pharyngeal airway volume, with Class II having decreased airway volume (-2256.06 mm3; 95% Confidence Interval [CI] -3201.61 to -1310.51 mm3) and Class III increased airway volume (1098.93 mm3; 95% CI 25.41 to 2172.45 mm3) compared to Class I. Significant airway volume reductions for Class II were localized mostly at the oropharynx, followed by the palatopharynx, and the glossopharynx. Significant airway volume increases for Class III were localized mostly at the oropharynx, followed by the intraoral cavity, and hypopharynx. Statistically significant differences according to vertical skeletal configuration were seen only for the oropharynx, where hyperdivergent patients had reduced volumes compared to normodivergent patients (-1716.77 mm3; 95% CI -3296.42 to -137.12 mm3). Airway differences for Class II and Class III configurations (compared to Class I) were more pronounced in adults than in children and the confidence for all estimates was very low according to CINeMA.

Conclusions: Considerable differences in upper airway volume were found between sagittal and vertical skeletal configurations. However, results should be interpreted with caution due to the high risk of bias, owing to the retrospective study design, inconsistencies in anatomic compartment boundaries used, samples of mixed children-adult patients, and incomplete reporting.

Clinical trial registration: PROSPERO (CRD42022366928).