Mandibular condylar displacement and the associated factors following intraoral vertical ramus osteotomy

Objective: In intraoral vertical ramus osteotomy (IVRO), the proximal and distal bony segments are not fixed rigidly and thus mandibular condyles are easily displaced. Since there have been only a few reports which examined any factors relating to the condylar displacement and mobility, we aimed to analyze the change in position over time through IVRO and elucidate the associated clinical factors. Methods: A retrospective study included 100 condyles in 50 patients. The Schüller's radiographs and posteroanterior cephalograms collected at the determined 6 time points were analyzed. The condylar head position was defined using X-Y coordinates. The amount of condylar displacement, the height of articular eminence and the ramus angulation were measured. The clinical information such as patient's age, sex, operation time, setback quantity, TMJ noise or pain and surgical methods (1 or 2 jaw surgeries) was collected. Statistical analyses concerning the postoperative condylar displacement was performed. Results: The most of condyles showed the significant anterior and inferior shift immediately after surgeries which displacement had been restored over time and mostly resolved in one-year after surgery. We found some positive correlations of the amount of operative condylar displacement with setback quantity, the ramus angulation changes and the height of the articular eminence. The significant differences were found in the items of TMJ noise and surgical method. The recovery amount of condyles was significantly different in the surgical methods. Conclusion: Our study provides the detail radiographic data of condyles and some associated factors to which attention should be paid when performing IVRO.