Freehand Condyle-Positioning During Orthognathic Surgery: Postoperative Cone-Beam Computed Tomography Shows Only Minor Morphometric Alterations of the Temporomandibular Joint Position.

ABSTRACT

OBJECTIVES: Purpose of this study was to evaluate changes in the temporomandibular joint (TMJ) position after bilateral sagittal split osteotomy (BSSO) of the mandible by the help of pre- and postoperative cone-beam computed tomography (CBCT) images. MATERIALS AND METHODS: A collective of n = 78 patients was investigated between 2009 and 2011 before and after BSSO of the mandible in mono- or bimaxillary orthognathic surgery procedures. No intraoperative fixation of the condyles was administered. CBCT scans were performed in all patients before and immediately after surgery with the KaVo 3DeXam device in the position of terminal occlusion. Subsequently, all scans were analyzed by help of the eXam Vision program and the ImageJ image processing software. Alterations of the TMJs were quantified by determining pre- to postoperative differences of the intercondylar distance, the mandibular angle on both sides, and the condylar angles in the transversal plane. RESULTS: The difference between pre- and postoperatively ascertained values was minimal (means lateral condylar distance -0.17  mm; distance of condylar centers -0.32  mm; medial condylar distance -0.49  mm; left mandibular angle +1.06°; right mandibular angle +2.06°; condylar angles in relation to a reference line left -2.93, right -0.75; angle of cutting +3.42). There is no apparent tendency toward a positional change in any of the 3 examined planes. Between bi- and monomaxillarily operated patients there was no difference either, except for the osteotomy plane. CONCLUSIONS: A 3-dimensional analysis of CBCT data of the TMJ seems to be appropriate to determine the condylar position pre- and postoperatively. Performed by an experienced orthognathic surgeon, BSSO of the mandible does not effectuate any relevant changes of the TMJ-position, thus making an intraoperative condyle-fixation unnecessary.