Nomogram based on MRI features and clinical indicators for predicting the risk of limited mouth opening in patients with temporomandibular disorders.

BACKGROUND: Limited mouth opening (LMO) is a cardinal manifestation of temporomandibular disorders (TMD). The prognostic value of magnetic resonance imaging (MRI) features for predicting LMO remains insufficiently defined. We aimed to systematically analyse MRI characteristics alongside clinical indicators in patients with TMD, identify independent predictors of LMO, and develop and validate an interpretable, clinically actionable nomogram. METHODS: In this single-centre retrospective study, we included 584 consecutive patients clinically diagnosed with TMD according to the Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD), who underwent MRI evaluation between January 2022 and December 2024, yielding 755 temporomandibular joints (TMJ). LMO was defined as maximum mouth opening (MMO) < 35 mm. Clinical features (age, sex) and MRI features (lesion side, disc position, disc morphology/signal/perforation, bilaminar zone tear, joint space, joint effusion, condylar movement, bony changes, lateral pterygoid muscle) were recorded. Candidate predictors were screened by univariable logistic regression and entered into multivariable logistic regression to identify independent predictors. A nomogram and risk-score model were constructed accordingly. The area assessed discrimination under the receiver-operating characteristic curve (AUC), model fit and calibration were evaluated using the Hosmer-Lemeshow test and calibration plots; clinical utility was examined with decision curve analysis (DCA). RESULTS: Multivariate analysis revealed age, anterior disc displacement without reduction (ADDwoR), disc signal, and joint space as independent predictors of LMO. The resulting nomogram achieved an AUC of 0.762 (95% CI, 0.727-0.798), outperforming any single predictor or alternative combined model (AUC = 0.659; 95% CI, 0.617-0.700). The Hosmer-Lemeshow test and calibration plots indicated close agreement between the predicted and observed risks, and DCA demonstrated a positive net benefit across a broad range of clinically relevant thresholds. CONCLUSIONS: Age, ADDwoR, abnormal disc signal, and abnormal joint space jointly characterize the risk of LMO in the TMD. The proposed nomogram shows solid discrimination, calibration, and clinical utility, supporting first-visit risk stratification and individualized management. Prospective multicenter-centre studies with external validation are warranted to confirm generalizability.