A Cephalometric Study on Changes in Pharyngeal Airway Space, Tongue and Hyoid Bone Positions Following the Surgical Correction of Mandibular Prognathism

ABSTRACT

PURPOSE: This study was aimed at measuring the changes in the hyoid bone position, tongue position, and pharyngeal airway space in subjects with mandibular setback osteotomies. METHODS: Twenty patients were evaluated retrospectively for their changes in pharyngeal airway space, tongue and hyoid bone positions. All patients underwent surgical mandibular setback using bilateral sagittal split osteotomies. The cephalometric analysis was performed preoperatively, and 1 week, 3-6 months, and 1 year postoperatively. RESILT The hyoid bone moved inferiorly and posteriorly immediately after surgery, and it returned to the preoperative position during follow-up period. The nasopharyngeal airway space was not significantly changed after surgery. A considerable decrease in the oropharyngeal and hypopharyngeal airway spaces following mandibular setback surgery was found. The upper and lower tongue was posteriorly repositioned immediately after surgery. During follow-up period, the hypopharyngeal airway space and lower tongue posture returned to the preoperative positions, but the oropharyngeal airway space and upper tongue posture were not significantly changed. The position of pogonion remarkably changed to backward immediately after surgery, but slightly anterior advancement was found during follow-up period. CONCLUSION: Immediately after mandibular setback surgery, the oropharyngeal and hypopharyngeal airway spaces obviously decreased due to posterior and inferior repositions of the tongue and hyoid bone. During follow-up period, lower tongue and hyoid bone returned to the preoperative positions, it was related to advancement of the pogonion in this period. The narrowing of the oropharyngeal airway space and posterior movement of the upper tongue posture were relatively permanent after mandibular setback surgery. We suspected this phenomenon had an influence on maintaining the total volume of oral cavity against mandibular setback.