Glenoid fossa changes following orthognathic surgery

Objectives
Glenoid fossa morphology may change following orthognathic surgery and may subsequently affect skeletal stability and functionality, however hardly documented. Hence, the purpose of this study was to evaluate the morphological change of the glenoid fossa two years after bimaxillary surgery.

Materials and Methods
A case series was performed including subjects diagnosed with maxillary and/or mandibular growth disturbances, who underwent bimaxillary surgery between March 2012 and November 2017. Study variables were gender, age and postoperative condylar resorption. Subjects were sampled evenly within subgroups with and without postoperative condylar resorption. The outcome variable, three-dimensional morphological change of the glenoid fossa was calculated as surface distance in mm between superimposed pre- and postsurgical (two years) cone-beam computed tomography, and were spatially divided into four regions. Evaluation of glenoid fossa changes of more than one voxel (> 0.3 mm) and comparison of subjects with and without postoperative condylar resorption were performed by one-sample and unpaired t-tests, respectively.

Results
Twenty subjects (sixteen female; mean age 27.6 years) with class II malocclusion and maxillomandibular retrognathia were included. The glenoid fossa changes (0.36 mm) were significant (p = 0.021), and significantly larger in subjects with condylar resorption than in those without in the anterior-lateral (0.40 mm vs. 0.27 mm, p = 0.021) and anterior-medial fossa region (0.48 mm vs. 0.26 mm, p = 0.015).

Conclusion
Significant morphological fossa changes were found two years after orthognathic surgery, and subjects with postoperative condylar resorption showed a significantly higher degree of morphological change in the anterior glenoid fossa than subjects without. Glenoid fossa remodeling is believed to be one of three adaptive processes in the TMJ, which contributes to the position of the mandible. Therefore, it is highly relevant to take glenoid fossa remodeling into consideration, e.g. when evaluating maxillomandibular growth disturbances or the outcome of orthognathic surgical treatment.