Changes in tongue and hyoid positions, and posterior airway space following mandibular setback surgery

The postural response of the tongue after mandibular setback is clinically important for maintaining normal respiration. Although the hyoid bone moves progressively to adapt physiologically to the altered orofacial configuration following such surgery, it is not clear whether repositioning of the hyoid has an effect on the pharyngeal airway. In the present study, postoperative changes in hyoid position and pharyngeal airway space were assessed retrospectively in patients who had undergone mandibular setback surgery.

Digitized lateral cephalograms from 30 mandibular setback surgery cases taken preoperatively, and 1 month and more than 1 year postoperatively, were used to examine pharyngeal airway morphology and the position of hyoid bone.

A significant downward movement of the hyoid bone was found 1 month after surgery, while the pharyngeal airway dimensions at the tongue were maintained. More than 1 year after surgery, the hyoid position returned to its original position, resulting in a significant decrease in retrolingual airway dimension.

The results indicate that mandibular setback causes airway narrowing late after surgery, while the early postoperative airway dimension is maintained. Long-term observations should be performed because of the changes of oropharyngeal configuration following mandibular setback.