Reliability and Validity of a Newly Proposed Classification System for Adult Condylar Fractures of the Mandible

The study aimed to systematically compare the reliability and validity of the Simplified Classification of Mandibular Condylar Fractures in Adults and the Lindahl classification in the imaging diagnosis of adult condylar fractures, assess the clinical feasibility of the new system, and provide a methodological basis for its clinical application. A sample database composed of 846 patients with 1095 sides with fresh adult mandibular condylar fracture was established. From this database, 300 sides were selected by stratified proportional sampling as the fracture classification sample, and 50 sides as the reproducibility test sample. Three senior oral and maxillofacial trauma physicians, after unified training, independently diagnosed the samples using the Simplified Classification and the Lindahl classification, and re-diagnosed the reproducibility test sample after 6 months. Evaluation indicators included intrarater reliability, inter-rater reliability, diagnostic consistency, and coverage rate. For the Lindahl classification, the mean intrarater Kappa value was 0.763, and the inter-rater Kappa value was 0.504. The coverage rate was 99.2% for the primary classification (fracture level) and 96.0% for the secondary classification (displacement and relation to the articular fossa). The mean diagnostic consistency rate was 72.9%. For the Simplified Classification, the mean intrarater Kappa value was 0.830, and the inter-rater Kappa value was 0.665. The coverage rate was 100% for the primary classification (fracture level) and 99.8% for the secondary classification (types I-IV). The mean diagnostic consistency rate was 82.9%. Compared with the Lindahl classification, the Simplified Classification demonstrates better stability in repeated diagnoses, advantages in defining fracture levels and describing comminuted fractures, and effectively improves classification consistency and coverage. However, difficulties exist in classifying comminuted fractures extending from the condylar neck to the base without involving the condylar head, which can be improved through supplementary definitions.