Transverse Displacement and Angulation of the Proximal Segment After Mandibular Setback by Means of Bilateral Intraoral Vertico-Sagittal Ramus Osteotomy

PurposeThe purpose of this study was to assess the transverse displacement and angulation of the proximal segment after a bilateral intraoral vertico-sagittal ramus osteotomy (IVSRO) and its relation with mandibular setback.Patients and MethodsSixty patients were recruited into this study and underwent a mandibular setback with bilateral IVSRO with wire fixation. Posteroanterior and lateral cephalometric radiographs were obtained 1 month before and 1 month after surgery. The transverse displacement and angulation of the proximal segments after surgery were measured on posteroanterior radiographs, via the best-fit method. The correlation of the amount of mandibular setback with the amount of transverse displacement and angulation of proximal segment was also assessed.ResultsA statistically significant increase was seen in intergonial width (P < .001), and inter-ramus width (P < .001) with a mean of 2.25 mm (SD, 0.82) and 4.45 mm (SD, 1.18), respectively. Both the right and left ramus angles showed an increased angle on average: mean, 1.70° (SD, 0.91) and 1.43° (SD, 0.66), respectively. There was a statistically significant increase in both angles 1 month after surgery (P < .001). There was a statistically significant relation between the amount of mandibular body setback measured at B point and increase in intergonial width (P = .012, r = 0.45), inter-ramus width (P = .018, r = 0.42), left ramus angle (P = .007, r = 0.48), and right ramus angle (P = .008, r = 0.47).ConclusionsThis study suggested that IVSRO leads to an increase in intergonial width and inter-ramus width, as well as the outward angulation of the condylar fragment. In addition, there was a significant correlation between the amount of setback and intergonial width, inter-ramus width, and medial ramus angles.