TMJ MRI structural features and horizontal condylar angle across a seven-type disc-condyle classification.

Area of Science:

• Radiology
• Orthodontics
• Biomedical Engineering

Background:

• Limited comprehensive MRI evaluation of TMJ disc displacement using a unified classification.
• Previous studies focused on individual structural markers, neglecting a holistic approach.

Purpose of the Study:

• To characterize MRI structural features and horizontal condylar angle (HCA) within a seven-type disc-condyle classification.
• To evaluate associations and discriminatory performance for anterior disc displacement (ADD) and ADD without reduction (ADDwoR).

Main Methods:

• Retrospective cross-sectional study of 568 TMJ sides from 310 patients.
• Classification into normal disc position (NDP), ADD with reduction (ADDwR), or ADD without reduction (ADDwoR).
• Assessment of disc deformation, condylar position, morphology, osseous status, and HCA using GEE models and ROC analysis.

Main Results:

• ADD joints exhibited greater disc deformation, condylar abnormalities, and higher HCA compared to NDP joints.
• HCA, posterior condylar position, and osseous status were independently associated with ADD.
• Disc deformation, condylar morphology, osseous status, and anterior condylar position were associated with ADDwoR; HCA was not.

Conclusions:

• TMJ disc displacement involves coordinated abnormalities in disc and condyle structures.
• The seven-type framework allows refined MRI-based structural stratification.
• HCA is a complementary marker, not a standalone diagnostic threshold.