Long-term evaluation of the stability of reconstructed condyles by transport distraction osteogenesis

This retrospective longitudinal study evaluated the long-term stability of reconstructed condyles by transport distraction osteogenesis of the mandibular ramus in patients with unilateral temporomandibular joint (TMJ) ankylosis. 7 patients were followed up for 16-92 months (mean 39.4 months). The mean age of the patients at the time of distraction was 22.9 years (range 7-44 years). Maximal mouth opening and panoramic radiographs were recorded preoperatively, at the time of device removal and several years after removal of distraction device. At follow-up, cone beam CT images of the TMJ were obtained to confirm the changes of the reconstructed condyle. Absolute height (Co-Inc) and relative height (Co-Inc/Co-Go) of the reconstructed condyle and the asymmetric difference ratio (AR) were examined to assess the changes of condylar height and mandibular symmetry. The mean maximal mouth opening was stable during the period of follow-up. The mean absolute height and relative height of the reconstructed condyle decreased significantly (P<0.05). Although no significant difference was found, the mandibular asymmetry difference ratio increased by 16.7%. These results suggested that the heights of reconstructed condyles were not stable in the long-term, and the mandible tended to be asymmetrical.