Observation of Osseous Healing After Intraoral Vertical Ramus Osteotomy: Focus on Computed Tomography Values

Positional changes in the mandibular proximal segment after intraoral vertical ramus osteotomy: Surgery-first approach versus conventional approach

Objective

To compare postoperative positional changes in the mandibular proximal segment between the conventional orthognathic surgery (CS) and the surgery-first approach (SF) using intraoral vertical ramus osteotomy (IVRO) in patients with Class III malocclusion.

Methods

Thirty-eight patients with skeletal Class III malocclusion who underwent bimaxillary surgery were divided into two groups according to the use of preoperative orthodontic treatment CS group (n = 18) and SF group (n = 20). Skeletal changes in both groups were measured using computed tomography before (T0), 2 days after (T1), and 1 year after (T2) the surgery. Three-dimensional (3D) angular changes in the mandibular proximal segment, condylar position, and maxillomandibular landmarks were assessed.

Results

The mean amounts of mandibular setback and maxillary posterior impaction were similar in both groups. At T2, the posterior portion of the mandible moved upward in both groups. In the SF group, the anterior portion of the mandible moved upward by a mean distance of 0.9 ± 1.0 mm, which was statistically significant (p < 0.001). There were significant between-group differences in occlusal changes (p < 0.001) as well as in overjet and overbite. However, there were no significant between-group differences in proximal segment variables.

Conclusions

Despite postoperative occlusal changes, positional changes in the mandibular proximal segment and the position of the condyles were similar between CS and SF, which suggested that SF using IVRO achieved satisfactory postoperative stability. If active physiotherapy is conducted, the proximal segment can be adapted in the physiological position regardless of the occlusal changes.

Effect of low-intensity pulsed ultrasound after intraoral vertical ramus osteotomy

OBJECTIVE

The present study investigated the effect of low-intensity pulsed ultrasound (LIPUS) on long-term osseous healing of the cleavage space between bone fragments after intraoral vertical ramus osteotomy (IVRO).

STUDY DESIGN

Patients undergoing IVRO were randomly assigned to the LIPUS group (n = 12) or the control group (n = 9) after surgery. LIPUS treatments were applied daily to the cleavage space between bone fragments for 3 weeks. We observed 3-dimensional quantitative color mapping of the whole mandible created by computed tomography (CT) data at 1 month, 6 months, and 1 year postoperatively. On the basis of CT values, the color grades were classified as D1 to D5 by using the Misch criteria. We then calculated mean CT values and rated each color grade in different selection ranges.

RESULTS

The mean CT values of the LIPUS group were significantly higher than those of the control group at 1 month, 6 months and 1 year postoperatively (P < .01). The color grades of the cleavage between bone fragments increased from D5 to D1 over time.

CONCLUSIONS

Our results indicated that LIPUS promoted osseous healing after IVRO, thus improving bone density and offering clinical benefits.

Rotation tendency of the posteriorly displaced proximal segment after vertical ramus osteotomy

Intraoral Vertical Ramus Osteotomy (IVRO) is one of the operative techniques used for orthognathic surgery. The aim of this study was to assess the posterior displacement of the proximal segment in patients undergoing IVRO at 1-year follow-up. In total, 52 hemimandibles from 26 patients who underwent IVRO in whom the proximal segment was posteriorly displaced without overlap with the distal segment at immediate post-operation (Imm) (30 cases, experimental group), and 26 patients in whom the proximal segment was not posteriorly displaced with overlap with the distal segment (Imm) (22 cases, control group) under three-dimensional computed tomography (3D CT) were included in the study. To analyze the movement of segments, the positions of the mid condyle point (MCP) and angle of condyle line (Con) were determined and the movement of the ramus angle (posterior edge of proximal segments) was measured at the proximal segment. Regression of the proximal segment in sagittal direction of the MCP was observed in both groups and all directions of the ramus angle in the experimental group, and only sagittal direction in the control group. In conclusion, posterior displacement of the proximal segment after IVRO showed tendency to regress its original position.

Changes in the computed tomography (pixel) value of mandibular ramus bone and fixation screws after sagittal split ramus osteotomy

The purpose of this retrospective study was to evaluate the changes in computed tomography (CT) values of ramus bone and screws after sagittal split ramus osteotomy (SSRO) setback surgery. The subjects were 64 patients (128 sides) who underwent bilateral SSRO setback surgery. They were divided into six groups according to the fixation plate type used and the use or not of self-setting α-tricalcium phosphate (Biopex): group 1: titanium plate and screws; group 2: titanium plate and screws with Biopex; group 3: poly-l-lactic acid (PLLA) plate and screws; group 4: PLLA plate and screws with Biopex; group 5: uncalcined and unsintered hydroxyapatite particles and poly-l-lactic acid (uHA/PLLA) plate and screws; group 6: PLLA/uHA plate and screws with Biopex. CT values (pixel values) of the lateral cortex, medial cortex, osteotomy site, and screws were measured preoperatively, immediately after surgery, and 1 year postoperatively using horizontal CT images at the mandibular foramen taken parallel to the Frankfort horizontal plane. There were significant differences in the time-course change of pixel values for the lateral cortex (P<0.0001) and the osteotomy site (P<0.0001) among the six groups. This study suggests that the fixation plate type and use of bone alternative material may affect bone quality during the process of bone healing after SSRO.

Unilateral mandibular advancement with bilateral intraoral vertical ramus osteotomy

Intraoral vertical ramus osteotomy (IVRO) is an effective surgical procedure that is used for the correction of mandibular prognathism. However, application of IVRO for mandibular advancement has been limited because of the instability of the proximal segments caused by the gap between the distal and proximal segments. We report a case of unilateral mandibular advancement with bilateral IVRO for the correction of facial asymmetry. This case shows possible application of bilateral IVRO for unilateral mandibular advancement without any means of fixation.