[Study on the changes in the upper airway following osteotomy for the mandibular prognathism]

This study was designed to compare pre-operation, immediate post-operation and over 6 month's follow-up for the mandibular prognathism in order to investigate the changes in the upper airway following mandibular osteotomy. The subjects were 18 patients. Their lateral cephalograms were taken pre-operatively, immediate post-operatively and over 6 months after operation and traced and analysed based on 10 selected items. The following conclusions were reached. 1) The downward displacement of the hyoid bone was recognized right after operation. (P less than 0.01) The hyoid bone tended to move to the original position in male group but not in female group. (P less than 0.01, P greater than 0.05) 2) The distance between the body of hyoid and posterior pharyngeal wall remained constant postoperatively (P greater than 0.05) 3) The distance between the body of hyoid and Menton was found to be shortened right after operation and remained constant thereafter. (P less than 0.01, P greater than 0.05) 4) The distance between the palate and the dorsum of tongue remained constant postoperatively. (P greater than 0.05) 5) The distance between the root of tongue and posterior pharyngeal wall was found to be shortened right after operation and remained constant thereafter. (P less than 0.01, P greater than 0.05) 6) APDI, SN-Pog, SNB and ANB remained constant during over 6 month's follow-up. (P greater than 0.05) 7) Relapse was found to show no correlation to other measurements.