Bimaxillary distraction technique for the correction of postankylotic asymmetry a unidirectional versus a bidirectional device

Abstract

The bimaxillary distraction (BMD) technique was originally introduced for the correction of facial asymmetry in hemifacial microsomia cases. Later, efforts were made to use the same technique for the treatment of asymmetric postankylotic deformities. This technique includes Lefort I osteotomy, oblique osteotomy along the angle of the mandible, followed by intermaxillary fixation to allow for the simultaneous distraction of both arches using a single distraction device fixed across the mandibular osteotomy. The technique primarily aims to correct the facial asymmetry with preservation of the preoperative compensated dental occlusion. Previous clinical studies have established the superiority of the technique in the correction of postankylotic asymmetry. Unfortunately, they did not investigate two important parameters: first, the criteria for the selection of the distraction device. Furthermore, they assessed the three-dimensional asymmetry in a single transverse plan and ignored both the anteroposterior and the vertical component of the deformity. This study was carried out to estimate the three-dimensional changes in the maxillofacial skeleton that could be achieved using the BMD technique using unidirectional versus bidirectional extraoral distraction devices. Aim

This study was carried out to investigate the mechanism of distraction movements in the (BMD) technique and hence aid the selection of a distraction device. Patients and methods

This preliminary study included six patients with facial asymmetry secondary to unilateral ankylosis of the temporomandibular joint (TMJ). The patients were divided into two groups: group I was treated using a unidirectional distraction device and group II was treated using a bidirectional device. All the patients were subjected to preoperative and postoperative assessments using study casts, direct soft tissue measurements, and plain radiographs (panorama PA and lateral cephalometry). Results and conclusions

The BMD technique led to successful correction of facial asymmetry in postankylotic deformity with minimal occlusal changes. Unidirectional devices resulted in better correction of facial height and less correction of the facial midline. However, the bidirectional device facilitated centralization of the chin with limited elongation of the mandibular ramus.