Positional stability following intentional posterior ostectomy of the distal segment in bilateral sagittal split ramus osteotomy for correction of mandibular prognathism

Purpose: In order to minimize post-operative relapse after mandibular setback using bilateral sagittal split ramus osteotomy, we have recently tried a technique, i.e. intentional ostectomy of the posterior part of the distal segment. The aim of this study was to evaluate the effects of this technique on the frequencies and extent of post-operative relapse.

Patients: This study was based on 61 cases of mandibular prognathism. The traditional sagittal split was performed in 24 cases (average age: 22.0+/-3.8) as a control group and the technique of additional distal ostectomy was used in the other 37 cases (average age: 23.2+/-3.2) as a test group.

Methods: Horizontal and vertical changes in the position of the body of the mandible were measured to determine the amount of long-term post-operative relapse. The amount of relapse was compared between groups and the statistical significance of the differences was evaluated.

Results: The relapse index of the test group was significantly lower than that of the control group in the 6- and 12-month post-operative periods (p>0.005). The horizontal relapse index and facial length relapse index of the test group were lower than those of the control group 12 months post-operatively (p<0.05).

Conclusion: This method should be considered as a useful method to maximise long-term post-operative stability.