Hyoid position, pharyngeal airway and head posture in relation to relapse after the mandibular setback in skeletal Class III

Abstract

This study evaluates the process of relapse after mandibular setback surgery by an analysis of the role of craniofacial morphology, hyoid position, pharyngeal airway and head posture. Subjects examined were 62 patients who received the sagittal split ramus osteotomies (SSRO). Changes of the craniofacial and related structures were evaluated from the serial cephalograms up to 3 years after the surgery. Results indicated that mandibular relapse represented by Pg occurred mostly within 6 months after the surgery. A net setback of the mandible was 9.1 mm and the superior move was 1.7 mm, with a reduction of 7.2 mm in mandibular length, 4.2 mm in ramus height, 3.7 mm in posterior face height, 2.6 degrees in gonial angle, an increase of 2.9 degrees in mandibular plane angle (MPA) by the last examination. Hyoid bone moved backward and downward and head posture was raised. The forward relapse of Pg was correlated with the changes of ANB, MPA, ramus height and hyoid position. Only hyoid position was predictably correlated with mandibular morphology and head posture. These findings suggest that mandibular setback alters the relationship among the hyoid position, pharyngeal airway and the head posture. It might be critical, therefore, relapse is closely monitored and controlled before the full healing of fragments and new muscular balance is established.

Effect of Orthognathic Surgery on the Posterior Airway Space in Patients Affected by Skeletal Class III Malocclusion

“…However, an aspect of orthognathic surgery that is rarely evaluated is the effect of the skeletal movements on the pharyngeal airway. Changes in airway dimensions have been demonstrated after surgical repositioning of the mandible or maxilla [2][3][4][5][6][7][8][9][10][11][12][13][14][15].…”

“…The isolated mandibular setback has been the target of several studies. These studies reported a change in the position of the hyoid bone and reduction in the dimensions of the retrolingual and hypopharyngeal airway after mandibular setback surgery [3][4][5][6][7][8][9][10][11][12][13][14].…”

“…Liukkonen et al [3] also noted that the degree of postero-caudal (clockwise) rotation of the mandible during the setback, correlated to the degree of airway narrowing [3]. Some studies suggest that the changes are temporary as the tissues re-adapt, resulting in partial or total resolution [3,7,8,10,12]. However, most of the other studies showed that the airway changes are stable over the long term [4,5,9,11,12,14].…”

“…Some studies suggest that the changes are temporary as the tissues re-adapt, resulting in partial or total resolution [3,7,8,10,12]. However, most of the other studies showed that the airway changes are stable over the long term [4,5,9,11,12,14]. The study with the longest follow-up of 12 years showed that the decrease in the lower pharyngeal airway was stable but the upper and middle pharyngeal airway continued to decrease over the 12 years [18].…”

Avaliação da via aérea superior em pacientes Classe III submetidos à cirurgia ortognática – Revisão de Literatura

“…As alterações da VAS depois de cirurgia de recuo mandibular continuam controversas, com alguns estudos demonstrando que há uma diminuição das dimensões da VAS e outros mostrando que nenhuma alteração da VAS ocorre após esse tipo de cirurgia 5,10,11,12,13,14,16,18,19,21,22,23,24,25,26,27,28 . Os trabalhos em pacientes com deformidade dento-esqueléticos classe III submetidos à cirurgia ortognática demonstraram uma forte correlação entre a quantidade do movimento do recuo mandibular com o estreitamento da via aérea e alteração da posição do osso hióide.…”