Cephalometric analysis of modifications of the pharynx due to maxillo-mandibular advancement surgery in patients with obstructive sleep apnea.

Cephalometry has been used to measure hard and soft facial tissues, as well as the pharyngeal air space for the diagnosis of obstructive sleep apnea (OSA). The changes occurring in the pharynx due to maxillo-mandibular advancement (MMA) have not been established or quantified. The objective of this study was to identify the anatomical changes of the pharynx and of hard tissues that occur in patients with OSA after MMA. 19 patients with a polysomnographic diagnosis of OSA were submitted to cephalometric analysis before and 6 months after surgery in order to evaluate the changes produced by MMA in the pharynx and soft tissues. Cephalometry was standardized in order to obtain descriptive measurements of the dimensions of the airways, the position of the hyoid bone, and maxilla-mandibular relations. The modifications of the pharynx due to MMA showed a significant relation obtained by cephalometry. For each millimeter of maxillary and mandibular bone advancement there was a 0.76mm increase in the retropalatal region and a 1.2mm increase in the pharynx in the retrolingual region. In addition, MMA promoted a significant repositioning of the hyoid bone in the cranial direction.