Predisposing conditions for condylar sag after intraoral vertical ramus osteotomy.

Intraoral vertical ramus osteotomy (IVRO) is used to treat mandibular prognathism and temporomandibular disorders. However, the improvement of temporomandibular disorders after IVRO is considered to be due to the anterior and downward movement of the mandibular condyle, which may lead to condylar sag, and in the worst case, condylar luxation. In this retrospective cohort study, we examined factors potentially associated with condylar sag. Univariate analysis indicated that condylar sag was significantly associated with the following factors: magnitude of setback (P = 0.001), less than 3 mm setback (P < 0.001), presence of temporomandibular joint (TMJ) symptoms (P = 0.002), Wilkes classification (P = 0.039), occlusal cant correction ≥ 2 mm (P = 0.018), and mandibular condyle deformation (P < 0.001). Setback magnitude (P = 0.032) and TMJ symptoms (P = 0.007) remained significant in the multivariate analysis. In the receiver operating characteristic curve, the setback magnitude cut-off value for condylar sag after IVRO was 3.25 mm. Thus, the incidence of condylar sag after IVRO is increased with a smaller setback magnitude (≤ 3.25 mm) and the presence of TMJ symptoms. These factors should be evaluated by surgeons during treatment planning for IVRO to estimate condylar sag, and it may be possible to predict the risk of condylar luxation.

Anterior relapse or posterior drift after intraoral vertical ramus osteotomy.

This study aimed to evaluate the factors contributing to postoperative anterior relapse or posterior drift of the distal segment after intraoral vertical ramus osteotomy. A retrospective cohort study was conducted which included 31 patients who underwent setback surgery for mandibular prognathism by the intraoral vertical ramus osteotomy technique. Uni- and multivariate analyses were performed to determine the association of potential explanatory variables (sex, age, magnitude of setback, differences in setback magnitude between sides (right/left), duration of splint use, Angle's classification of malocclusion, mandibular angle, and tightness of occlusion of the molars) with positional changes in the distal segment. The setback magnitude was only significant factor affecting (P = 0.015) for posterior drift, with significant posterior in setback magnitudes of less than 7.25 mm. Posterior drift after intraoral vertical ramus osteotomy is less likely if setback magnitude exceeds 7.25 mm. For setbacks less than 7.25 mm, posterior drift should either be carefully corrected postoperatively, or an alternative surgical technique should be used. The setback magnitude showed a significant association with the risk of posterior drift following intraoral vertical ramus osteotomy, and the determined cut-off value may serve as a predictor for postoperative outcomes.

Effects of the changes in the condylar long axis angle and condylar position on temporomandibular symptoms after intraoral vertical ramus osteotomy: a preliminary study.

OBJECTIVE: This study was conducted to characterize the effects of the changes in the condylar long axis and position on temporomandibular symptoms with respect proximal segment position after intraoral vertical ramus osteotomy (IVRO). STUDY DESIGN: Twenty Japanese patients with diagnosed jaw deformity underwent IVRO without internal fixation. Long-term changes in condylar long axis and position were assessed during postoperative follow-up examinations by using computed tomography, and t tests were performed for comparison. In addition, changes in temporomandibular symptoms were examined. RESULTS: The degree of axial rotation of the proximal segment changed significantly when the proximal segment was located laterally. Downward changes in condylar position significantly differed when the proximal segment was located posterolaterally. Forward changes in condylar position significantly differed when the proximal segment was located laterally; moreover, when the proximal segment was located laterally, temporomandibular symptoms disappeared. CONCLUSIONS: Lateral location of the proximal segment may be an important factor in the positive effects of IVRO, with respect to temporomandibular symptoms.