Cephalometric study of the upper airway in surgically corrected class III skeletal deformity.

Abstract

Changes in the upper airway after surgical correction of Class III skeletal dentofacial deformity were investigated by measurement of the cephalometric radiographs of 70 Class III subjects before surgery and 6 months after surgery. Comparison of the results with those of a normal group of 74 subjects without deformity or surgery was also carried out. Gender dimorphism in measurements and type of surgery performed were taken into account. Results showed that postoperatively the soft palate and hyoid bone were posteriorly displaced in men, the oropharyngeal, hypopharyngeal, and minimal airway depth were reduced, but in women, the minimal depth was not reduced. In the mandibular setback group, men showed posterior movement of the tongue base, with decrease in minimal airway depth. In the maxillary advancement group, nasopharyngeal depth increased in both genders. In the bimaxillary surgery group, the soft palate moved posteriorly and the tongue occupied a larger proportion of the airway in both genders. The hyoid was displaced backwards in women, while men showed a decrease in both oropharyngeal and minimal airway depth. In comparison with normal subjects, postoperative measurements indicated that the soft palate was reduced in length, thickness, and area, and the base of the tongue was more posterior. Minimal pharyngeal depth was reduced in both genders. After mandibular setback, the tongue base was more posterior and the hypopharyngeal depth was reduced. The bimaxillary surgery group also demonstrated a more posterior tongue base but without reduction of the hypopharyngeal depth. The mandibular setback group should be most at risk of obstructive sleep apnea, but compensatory changes in soft palate morphology may explain the low occurrence in practice.