Three-dimensional quantification of post-surgical condylar displacement

Background: Condylar displacement following orthognathic surgery has been related to post-surgical relapse. Although postoperative changes in condylar position have been reported in previous studies, no study has precisely quantified these variations in three dimensions (3D). The development of cone beam computed tomography (CBCT) has enabled the accurate measurement of changes in condylar position in three planes of space (x, y, z). ❧ Purpose: To quantify, in 3D, the amount and direction of condylar displacement relative to the glenoid fossa after bi-maxillary surgery. ❧ Materials and Methods: The sample consisted of 17 patients undergoing orthognathic surgery treated consecutively by one surgeon. The pre-surgical and 2-week post-surgical CBCT DICOM files were collected for each patient. The regions of interest in the temporomandibular joint complex were segmented and the pre- and post surgical condyles were superimposed using the glenoid fossa as the reference structure. Condylar translation and rotation were compared before and after surgery for each patient in three planes of space. ❧ Results: The average condylar displacement was 0.78 mm on x plane, -3.80 mm on y and 0.14 mm on z plane. As for rotation, the average movement was 0.06° on x plane, 0.30° on y and -0.27 on z. The only statistically significant movements were translation on Y plane and rotation on Z plane. ❧ Conclusion: Minimal changes in condyle position do occur immediately after bi-maxillary surgery and it is possible to accurately assess the amount and direction of this displacement in 3D.