The relationship between disc morphology and condylar bone marrow edema in adolescent patients with anterior disc displacement with reduction: a retrospective cross-sectional study

BACKGROUND: Temporomandibular disorders (TMD) are relatively common among adolescents, with anterior disc displacement with reduction (ADDwR) being the most prevalent subtype. Current research has primarily focused on assessing disc position; however, the morphological characteristics of the disc in adolescent ADDwR patients and their association with early degenerative changes in the condyle, such as bone marrow edema (BME), remain underexplored. Therefore, this study aims to utilize 3.0T MRI to compare disc morphology and condylar bone marrow signals between adolescent ADDwR patients and a comparison group, as well as to further investigate the potential relationship between disc morphology and early condylar bone alterations. METHODS: We conducted a retrospective cross-sectional study on 84 participants: 44 in the ADDwR group and 40 in the comparison group without TMD (headache patients with no clinical or MRI signs of TMD). Independent two-sample t-tests, Mann-Whitney U tests, chi-square tests, or Fisher's exact tests were used for intergroup comparisons. The association between posterior band thickness and BME was assessed using the Mann-Whitney U test (with rank-biserial correlation as effect size). Firth logistic regression was used to identify factors independently associated with BME. RESULTS: The ADDwR and comparison groups were comparable in age and sex distribution (both p > 0.05). The ADDwR group showed more frequent disc deformation, thicker posterior band, and higher occurrence of condylar BME and joint effusion than the comparison group (all p < 0.001). In the ADDwR group, patients with BME had greater posterior band thickness than those without BME (median 3.70 mm vs. 3.20 mm; Mann-Whitney U = 276.5, p < 0.001; rank-biserial correlation r = 0.44). In multivariable Firth logistic regression adjusting for age, sex, disc deformation, and joint effusion, posterior band thickness was the only factor independently associated with condylar BME (OR per 0.1 mm increase = 1.64, 95% CI: 1.16-2.32, p = 0.0049). None of the other covariates reached statistical significance. CONCLUSION: Adolescent ADDwR patients present with abnormalities in both articular disc morphology and condylar bone marrow signals. Posterior band thickening is independently associated with condylar BME. These cross-sectional findings are hypothesis-generating; prospective studies are needed to determine whether posterior band measurement could help identify patients at risk of developing BME.