Changes in posterior airway space and hyoid bone position after surgical mandibular advancement

Objective: To evaluate cephalometric changes in posterior airway space (PAS) and in hyoid bone distance to mandibular plane (MP) 1-3 years after bilateral sagittal split osteotomy (BSSO). Material and methods: The sample consisted of 36 females and 16 males who underwent mandibular advancement by BSSO. To observe sagittal changes in PAS and in hyoid bone distance to MP both pre- and postoperative cephalograms were analyzed using WinCeph (R) 8.0 software. For the statistical analyses paired T-test and multivariate logistic regression models were used. Results: By the surgical-orthognathic treatment the sagittal dimension of PAS showed variable changes but it mainly diminished when the mandibular advancement exceeded 6mm. In most cases the hyoid bone moved superiorly by BSSO. Logistic regression models showed that males, patients with narrow PAS at the baseline, and those with counterclockwise rotation of the mandible by the treatment gained more increase in PAS. However, an increase in sagittal PAS dimension tended to relapse over time. Concerning the movement of the hyoid it was found that the more PAS increased the less hyoid moved superiorly. In males the change in hyoid position was more obvious than in females. Conclusion: Males, patients with narrow PAS at the baseline, and those whose mandible moved in the counterclockwise direction with moderate advancement gained more retrolingual airway patency by BSSO.