Three-Dimensional CT Analysis of Airway Volume Following RME Treatment

Rapid maxillary expansion (RME) is an orthopedic procedure prescribed for treatment of crossbites and transverse maxillary deficiencies. RME reportedly increases nasal width and volume, thereby lessening nasal resistance and improving nasal respiration. Objectives: The purpose of this preliminary report of a retrospective 3-dimensional study, utilizing computer tomography, was to determine if RME causes a significant change in the maxillary sinuses, nasal cavity, nasopharynx, oropharynx, hypopharynx, soft palate area, and soft tissue thickness of the airway. Methods: Following reliability studies, volumetric and soft tissue thickness parameters were compared using spiral CTs of 10 patients taken as preliminary and 3 month retention records following rapid maxillary expansion. Intraclass correlations (ICC) were performed on duplicate measures of 10 CTs. Comparisons between the pre and post RME measurements were made using nonparametric signed rank tests. Spearman correlation coefficients were calculated to evaluate the association between the pre-RME measurements and the changes as well as correlations among the volume, area, and thickness measurements. Statistical significance was set at P < 0.05. Results: ICC values were >0.91 for all reliability measures. Only nasal cavity volume changed significantly (increase = 2578±3500mm3). Changes in soft palate area and soft tissue thickness (CV3ia) were related to the starting values - subjects with larger initial values showed less change. Statistically significant positive correlations were obtained between changes in nasopharynx volume and soft tissue thickness (CV4ia), hypopharynx volume and soft tissue thickness (CV4ia), soft palate area and soft tissue thickness (AA), soft tissue thickness (AA) and soft tissue thickness (CV3sa), and soft tissue thickness (CV2) and soft tissue thickness (CV3ia). A statistically significant negative correlation was obtained between changes in nasal cavity volume and soft palate area. Conclusion: In this preliminary report, RME increases nasal cavity volume. The significance of other measures might change with increased sample number.