Etiology of Temporomandibular Joint Ankylosis Secondary to Condylar Fractures: The Role of Concomitant Mandibular Fractures

Purpose: The purpose of the study was to explore the association between condylar fractures and temporomandibular joint (TMJ) ankylosis in a sample from 1 hospital in China. Patients and Methods: All patients treated for post-traumatic TMJ ankylosis in a 5-year period at Peking University, School of Stomatology, who had sufficient information available were included. Demographic information and details of their original injury and resultant ankylosis were tabulated and analyzed by descriptive statistics. Results: Twenty-five patients with 40 ankylosed joints met the inclusion criteria (15 were bilateral). The majority of patients were male, and ranged from 5 to 52 years of age with a mean of 23 years. Twenty-five of 40 cases were the result of a sagittal fracture of the condyle, where the medial pole was fractured off. Nineteen ankylosed joints (47.5%) showed lateral or superolateral displacement of the lateral aspect of the ramus/condylar process. Sixteen of 25 patients (64%) had fractures of the mandible other than condylar fractures located in the anterior mandible that were often untreated or not properly reduced. Fifty percent of the patients had widening of face or crossbites. Conclusions: The results of this study indicate that the combination of an intracapsular fracture with concomitant widening of the mandible leads to the lateral pole of the condyle or the condylar stump to become displaced laterally or superolaterally in relation to the zygomatic arch, where it fuses. Proper treatment of the anterior mandibular fracture(s) may help prevent the development of TMJ ankylosis in such patients.