Biomechanical assessment of unilateral sagittal split ramus osteotomy: a finite element analysis

Background: Some mandibular asymmetries may be candidates for a unilateral sagittal split osteotomy (USSO), such as unilateral condylar hyperplasia and post-traumatic malocclusions. However, there is insufficient data on the stresses generated on the condyle resulting from this procedure. We aimed to assess the biomechanical properties of the mandible following USSO. Methods: This was a modeling study, and a computed tomography (CT) scan of a fully dentate 20-year-old man was obtained from the database of the Oral and Maxillofacial Radiology Department. A threedimensional (3D) finite element model of a mandible was constructed. Variations of USSO were simulated on the model depending on the amount of midline displacement while the models were fixed with plates and screws. Masticatory and occlusal loads were loaded on each model and the stresses and dis-placement amounts were calculated and compared within groups. Results: We found an increase in displacement in the USSO models with more rotational forces. The stresses around the condyle and fixation area were also increased, and these stresses increased with an increased amount of midline deviation. Conclusions: We concluded that USSO procedures carry increased stress on the condyle and fixation. Therefore, the use of this technique should be limited while considering the consequences of the increased stress.