The present study was to investigate the relationship between the post-operative area of the gonial region (lateral and frontal) and post-operative relapse.

Thirty-seven patients, treated for mandibular prognathism were followed with serial lateral cephalograms [pre-operatively (T1), immediately after surgery (T2), and at least 2 years post-operatively (T3)]. The surgical changes (T21), post-operative stability (T32) and 2-year surgical change (T31) were evaluated by the Student's t-test. Pearson's correlation coefficient analysis was used to determine the correlations between the cephalometric parameters. Multiple linear regression analysis was used to assess the association between the risk factors and post-operative relapse.

The immediate post-operative changes (T21), mean setback of the Me was 12.3 mm and the frontal gonial area (T2) was increased by 138.7 mm². The final post-operative changes (T31), lateral gonial area was significantly reduced by 190.5 mm².

Relapse was significantly correlated with the amount of setback. However, changes in the area of the gonial region (lateral and frontal) showed weak correlation with relapse. Multiple regression analysis also showed poor predictability of relapse. In conclusion, the results of this study showed that significant changes in the area of the gonial region (lateral and frontal) did not affect the maintenance of post-operative stability.