To investigate the correlation between the osseous structure of temporomandibular joint (TMJ) and three different status of anterior disc location, so that it could guide the clinical diagnosis further.

Fifty-two patients [46 females and 6 males, with an age of (27.8±8.3) years] who treated with MRI and cone beam CT, were recruited from the Temporomandibular Joint Specialist Clinic, The First Affiliated Hospital of Xinjiang Medical University, between March 2018 to December 2021. According to the radiographic findings of the level of anterior disc displacement (ADD) in TMJ, patients were divided into three groups: normal articular disc position (NADP, n=28 TMJs), anterior disc displacement with reduction (ADDWR, n=28 TMJs), and anterior disc displacement without reduction (ADDWoR, n=28 TMJs). In the light of the reconstructed three-dimensional model, ten representative morphological parameters including condylar volume (CV), condylar superficial area (CSA), fossa volume (FV), fossa superficial area (FSA), the proportion of the condylar volume in the articular fossa (CV%), the proportion of the condylar superficial area in the articular fossa (CSA%), superior joint space (SJS), anterior joint space (AJS), posterior joint space (PJS), and medial joint space (MJS), were measured respectively under one-way analysis of variance (ANOVA), Kruskal-Wallis Htest and receiver operator characteristic curve(ROC curve) analyses.

CV and CSA values varied significantly in the pathological progression from normal location to irreversible anterior displacement in TMJ. For CV value, NADP group [(1 834.90±667.67) mm³]>ADDWR group [(1 747.34±369.42) mm³]>ADDWoR group [(1 256.29±418.27) mm³] [t=4.31, P_{(NADP-ADDWoR)}<0.001; t=3.66, P_{(ADDWR-ADDWoR)}<0.001], for CSA value, NADP group [(859.27±216.01) mm²]>ADDWR group [(838.23±118.82) mm²]>ADDWoR group [(669.14±150.26) mm²] [t=4.27, P_{(NADP-ADDWoR)}<0.001; t=3.80, P_{(ADDWR-ADDWoR)}<0.001]. The difference of SJS value in NADP group [(2.22±0.88) mm], ADDWR group [(1.94±0.64) mm] and ADDWoR group [(1.45±0.57) mm], was statistically significant [t=4.11, P_{(NADP-ADDWoR)}<0.001; t=2.63, P_{(ADDWR-ADDWoR)}=0.010]. The results of MJS in NADP group [(5.03±1.41) mm], ADDWR group [(3.86±1.32) mm], and ADDWoR group [(4.91±1.65) mm] were significantly different [t=3.00, P_(NADP-ADDWR)=0.004; t=2.63, P_{(ADDWR-ADDWoR)}=0.009]. As calculated by the ROC curve analysis, CV, CSA and SJS showed that (AUC_CV=0.77, AUC_CSA=0.76; AUC_SJS=0.76) for the NADP and ADDWoR groups, and (AUC_CV=0.80; AUC_CSA=0.80; AUC_SJS=0.72) for the ADDWR and ADDWoR groups. While the diagnostic accuracy of MJS for the comparison in NADP versus ADDWR and ADDWR versus ADDWoR was respectively AUC_(NADP-ADDWR)=0.73, and AUC_{(ADDWR-ADDWoR)}=0.69.

CV, CSA, SJS, and MJS were significantly associated with the different disc displacement status, and the condyle in TMJ ADD exhibited three-dimensionally altered dimensions. They could be considered as promising biometric markers to diagnose the ADD status.

Temporomandibular joint; Temporomandibular disorders; Articular disc displacement; Three-dimensional cephalometrics; Diagnostic test