Evaluation of effect of different bilateral sagittal ramus osteotomy techniques on interference between proximal and distal bony segments of facial asymmetry patients

Objective: During the orthognatic surgery for correction of facial asymmetry, there may be condyle distortions because of the interferences between the proximal and distal segments. The present study aims to evaluate the amount of bony interferences between mandibular proximal and distal segments by using a virtual surgical planning software programme. Materials-Methods: A retrospective chart review was conducted involving those who underwent mandibular orthognathic surgery and has virtual surgical planning software records. 12 patients were included in the present study. The same jaw movements of the virtual patients that were previously planned for the surgery, were simulated with four different osteotomy techniques. Dal Pont modification of sagittal split ramus osteotomy (SSRO), Hunsuck modification of SSRO, Posnick modification of SSRO and minimally invasive SSRO techniques were simulated for each patient on the virtual planning records. The volume of the interference between proximal and distal segments of the mandible and the angulation of the proximal segment due to these interferences were evaluated. Results: Dal Pont modification of SSRO demonstrated the highest bony interference between the proximal and distal segments of the mandibles. All the other osteotomy modifications resulted in lower interferences, however only the differences between Dal Pont modification-Posnick modification (p:0.008) and Dal Pont modification-minimally invasive SSRO technique (p:0.019) were statistically significant. Conclusion: In facial asymmetry, all surgical techniques were accompanied with bony interferences to some extent. To minimise this shortcoming, an osteotomy modification that decreases the split area can be utilised. Key words: Facial asymmetry, sagittal split ramus osteotomy, peripheral condylar sag, virtual planning