Structural characteristics of the temporomandibular joint in rotational disc displacement: a retrospective cross-sectional study based on MRI

Temporomandibular disorders (TMD) are common conditions affecting the temporomandibular joint (TMJ). While anterior disc displacement (ADD) has been extensively studied, rotational disc displacement (RDD) remains understudied. MRI can provide a detailed evaluation of TMJ structure, making it possible to assess changes in TMJ structure in RDD patients. A total of MR images of 462 TMJ (231 patients) were retrospectively recruited from our dataset, including 116 ADD with reduction (ADDwR) and 114 RDD with reduction (RDDwR), as well as 232 normal control TMJs. The parameters of TMJ based on MRI included disc dimensions, condylar dimensions, joint spaces, horizontal condylar angle, and glenoid fossa inclination. Multivariable multinomial generalized estimating equations (GEE) with ADDwR as the reference identify the parameters of TMJ associated with RDDwR. The RDDwR group showed higher prevalence of joint clicking ( P < 0.05) and numerically higher prevalence of mouth opening limitation( P = 0.072), while there was no difference in pain compared to ADDwR groups. Multivariable GEE analysis identified intermediate zone thickness (OR = 1.843), anterior band thickness (OR = 1.420), mediolateral diameter (OR = 0.838), anterior joint space (OR = 0.598), and superior joint space (OR = 0.509) as independent factors associated with RDDwR (all P < 0.05). Compared with the ADDwR group, the TMJ of the RDDwR group showed thickening of the middle and anterior zones, reduction of ML, and reduction of the anterior and superior joint spaces. They may be associated with their clinical symptoms. The identified structural parameters of TMJ may serve as candidate quantitative imaging biomarkers for the assessment of the treatment response and prognosis in RDDwR patients.