Transverse displacement and angulation of the proximal segment after mandibular setback by means of bilateral intraoral vertico-sagittal ramus osteotomy

Abstract

Purpose: The 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 methods: Sixty 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.

Results: A 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).

Conclusions: This 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.