A Comparative Study of the Changes in Condylar Position after Mandibular Setback Using Bilateral Sagittal Split Ramus Osteotomy Between Surgery-After and Surgery-First Orthognathic Surgery
This study included 20 skeletal class III malocclusion patients without facial asymmetry who underwent bilateral sagittal split ramus osteotomy (BSSRO) for mandibular setback from January 2010 to January 2012 (SAOS group 10 patients, SFOS group 10 patients).
3D computed tomographic images of the facial bone that were taken before the surgery, 1 week after the surgery, and 6 months after surgery were converted to 3D images with OnDemand3DTM program. After creating 3D images, the length and angle of the condyles to the axial plane, frontal plane, and sagittal plane were measured. Change of each indexes were analyzed statistically by noting periodical changes in each group and periodical changes between each group using 2 way RMANOVA (Repeated measure ANOVA) and pairwise comparison, and the relationship between amount of changes in each index and amount of mean setback were evaluated using Pearson's correlation analysis.
Results of this study are as follows:
1. The amounts of mean setback were 8.7 ± 2.3 mm in SAOS group and 9.0 ± 3.6 mm in SFOS group.
2. Except for left condyles of SFOS group, the angle between sagittal plane and the axial line for condylar head in both condyles of both groups slightly decreased at the post-op 1 week and 6 months (p < 0.05).
3. There were no significant differences in perpendicular distance between sagittal plane and the most medial point of condylar head in both condyles of both groups at the post-op 1 week, but except for right condyles of SAOS group, the distance in both condyles of both groups slightly decreased at the post-op 6 months(p < 0.05).
4. There were no significant differences in all indexes on frontal and sagittal plane in both condyles of both groups at the post-op 1 week and 6 months except for the perpendicular distance between axial plane and most superior point of condyle head in the left condyles of both groups.
5. There were no significant differences in the values of all indexes in both condyles between SAOS & SFOS group at the same periods.
6. There were no significant differences between amount of change in each indexes and mean amount of setback in SAOS & SFOS group (p < 0.05).
These results indicate that there was no significant difference in the postoperative condylar positional change between SFOS and SAOS group after the mandibular setback by BSSRO in the mandibular prognathism patients.
References
1. Hackney FL, Van Sickels JE, Nummikoski PV: Condylar displacement and temporomandibular joint dysfunction following bilateral sagittal split osteotomy and rigid fixation. J Oral Maxillofac Surg 47:223-227, 1989.
2. Alfaro F, Martinez R, Coral A, Escriche C: "Surgery First”in Bimaxillary Orthognathic Surgery. J Oral Maxillofac Surg 69:e201-e207, 2011.