RESUMEN
Purpose@#The purpose of this article is to study the relationship of unintentionally extended split in the distal segment during the bilateral sagittal split ramus osteotomy (BSSRO) and skeletal relapse. @*Materials and Methods@#Twenty patients with mandibular prognathism were divided into two groups according to whether or not unintentionally extended split had occurred. Cone-beam computed tomography images were taken before surgery (T0), immediately after surgery (T1), and postoperatively at 6 months (T2). The stability was evaluated by measuring the change of Nasion perpendicular-Pogonion (N-Pog) distance.Result: Both groups showed mild advancement of Pog during follow-up. In both groups, the condyle head rotated inward and moved posterioinferiorly after surgery, but tended to return to their original position during follow-up. @*Conclusion@#There was no statistically significant difference between the two groups in mandible position. Moreover, the condylar position was stable. If it is difficult to proceed reduction of the unintentionally extended split, careful inspection should be performed to prevent subsequent complications during follow-up.