CLINICAL ANALYSIS OF GONIAL ANGLE CHANGE AFTER ORTHOGNATHIC SUGERY IN PATIENTS WITH THE MANDIBULAR PROGNATHISM

Kwon, Yeong Ho; Jang, Hyun Jung; Lee, Sang Han

Abstract

Predictional study for lateral change between pre- and post-orthognathic surgery has been emphasized mainly on anterior area of lateral profile; upper lip, lower lip and chin et al. So interest for lateral profile change has been less in posterior area of lateral profile and literature analyzing gonial angle change is rare. The purpose of this study is to make prediction for gonial angle change possible and to offer somewhat treatment guidance for gonial angle to be improved by investigating overall gonial angle change between pre- and post-orthognathic surgery and inquiring into factors influencing on pattern of gonial angle change. For this study 35 patients were selected retrospectively. Lateral cephalometric radiographs were taken in just pre-op time, pod 1 day, pod 1 year. They were analyzed and gonial angles were measured. The results were as follows: 1. Gonial angle at pod 1 day was decreased about 9.3degreesthan pre-op and gonial angle at pod 1 year was increased about 4.0degreesthan pod 1 day. So gonial angle at pod 1 year was decreased about 5.3degreesthan pre-op gonial angle(p<0.01). 2. Mean pre-op gonial angle was 129.4degrees, showing significantly high value than normal and mean gonial angle at pod 1 year was 124.1degrees, showing value near to normal. 3. Mean gonial angle change between pre-op and pod 1 year was decreased about 5.4degrees in female and 5.3degreesin male. There was no statistically significant difference between male and female(p>0.05). 4. Principal factor influencing on decreased gonial angle in gonial angle change between pre-op and pod 1 year was amount of mandibular setback. 5. Principal factor influencing on increased gonial angle in gonial angle change between pod 1 day and pod 1 year was % horizontal relapse, and it was thought that resorption and bone remodelling on posterior area in mandibular distal segment also were related to increased gonial angle. 6. It is thought that sagittal split ramus osteotomy in mandibular prognathic patients with high value of gonial angle is effective to improvement of gonial angle, and in patients who have normal range of gonial angle and are required with excessive mandibular setback, short lingual cut method, additional resection of posterior margin of distal segment, Obwegeser II method will be considerd. 7. More prudent operation and careful post-op management will be responsible for maintenance of post-operative stable gonial angle.