Articular eminence inclination as a morphological marker for temporomandibular joint disc displacement: a dual-modality imaging analysis

Objective To investigate the association between the morphology of the articular eminence (AE) and mandibular fossa (MF) and the presence of temporomandibular joint (TMJ) disc displacement with reduction (DDwR) using cone-beam computed tomography (CBCT) and magnetic resonance imaging (MRI). Methods This retrospective cross-sectional study analyzed 60 TMJs from 30 patients with intra-articular disorders treated at two Vietnamese centers (2022–2024). MRI classified joints as DDwR or normal disc position (No DD). CBCT provided morphometric measurements: AE inclination (top-roof line [TR] and best-fit line [BF] angles), AE height and width, and MF width. Intra-observer reliability was assessed using the intraclass correlation coefficient (ICC). Group differences were tested using t-tests or Mann–Whitney U tests ( p < 0.05). Results MRI identified 50 DDwR joints (83.3%) and 10 No DD joints (16.7%). Measurement reliability was excellent (ICC = 0.86). AE inclination was significantly lower in DDwR joints (TR: 37.85 ± 7.13 ° vs. 46.44 ± 6.41 °, p = 0.001; BF: 53.80 ± 6.70 ° vs. 60.64 ± 7.16 °, p = 0.003). No significant differences were found for AE height (6.88 ± 1.51 mm vs. 6.91 ± 1.00 mm), AE width (9.37 ± 1.63 mm vs. 9.48 ± 1.54 mm), or MF width (15.24 ± 1.40 mm vs. 15.85 ± 1.00 mm) (all p > 0.05). Conclusion A flatter AE inclination is significantly associated with DDwR, challenging the traditional view that a steeper eminence predisposes to disc displacement. These findings suggest AE flattening may be a secondary change linked to degenerative remodeling. CBCT-based AE inclination assessment could aid in risk evaluation and early diagnosis of TMJ internal derangement.