Evaluation of reproduced 3D TMJ movement in preoperative patients with facial asymmetry using 3D CT image and tracking camera system

Abstract

Purpose: This study applied three-dimensional analysis to assess the condylar movement in preoperative patients with facial asymmetry using a simulation system with a 3-dimensional computed tomography (3D CT) image and tracking camera system.

Methods: Mandibular movement was simulated in pre-orthognathic surgery patients (n=26) using skull CT data and a position tracking camera system. The mandibular midline shift (MMS) was measured in posteroanterior cephalometric radiographs of patients. Patients were divided into two groups: Group I included patients with severe facial asymmetry (MMS≥4°). Group II consisted of patients with slight facial asymmetry or symmetric face shapes (MMS<4°). Group I was divided into two subgroups

deviated side and non-deviated side. Mandibular movements were analyzed three-dimensionally. The intra-articular distance between the condyle and glenoid fossa was recorded and compared between Group I and Group II. The differences between the right and left axial condylar angles and anteroposterior positions were measured.

Results: The average condylar path length per one cycle in Group I (55.01±17.97) was longer than in Group II (44.38±13.67). The maximum linear distance in Group I (16.71±6.80) was longer than in Group II (13.05±5.92), and the difference between bilateral sides was significantly larger in Group I (p <0.05). The average intra-articular distance between condyle and glenoid fossa was shorter in Group I than Group II, especially at the lowest point (p < 0.05). The difference between the right and the left axial condylar angles was significantly larger in Group I than Group II (p <0.05) and the anteroposterior condylar position difference was slightly larger in Group I. Conclusion: We determined that the range of temporomandibular joint (TMJ) movement is related to the severity of facial asymmetry and is impacted by the affected side. We propose that the reduced joint space may cause TMJ overloading in severe facial asymmetry, which can lead to internal TMJ derangement. Because TMJ movement is influenced by disc position and other pathologic changes, further studies using MRI data will be needed.