Ankylosis of the Coronoid Process to the Zygomatic Bone: A Case Report and Review of the Literature

Purpose: Extra-articular temporomandibular bony ankylosis between the zygomatic bone and coronoid process is a rare condition. Currently, there are fewer than 40 cases reported in the English-language literature. The aim of this study was to report a case of zygomatico-coronoid ankylosis with surgical intervention and a literature review. Materials and Methods: Through a PubMed search from 1946 to February 2018, using the terms (“extra-capsular” OR “zygomatico-coronoid” OR “extra-articular”) AND (“ankylosis”), 61 articles were initially identified. After screening, manual reviewing, and including additional articles through reviews of the reference lists, 26 reports (33 patients) were included in the analysis. Results: Patients' age ranged from 12 to 71 years (mean, 36.62 yr; standard deviation, 16.24 yr). The gender composition of patients was male (n = 20; 60.6%), female (n = 12; 36.4%), and unknown (n = 1; 0.3%), with a clear male predominance. The etiologies were trauma (n = 25; 75.8%), infection (n = 3; 9.1%), surgical complication (n = 4; 12.1%), and radiotherapy for maxillary cancer (squamous cell carcinoma; n = 1; 3.0%). The treatment options were surgical intervention through an intraoral approach (n = 19; 57.6%), an extraoral approach (n = 10; 30.3%), and intraoral and extraoral approaches (n = 2; 6.1%) and nonsurgical intervention (n = 2; 6.1%). Conclusion: Zygomatico-coronoid ankylosis is a possible cause of mouth-opening limitation, particularly in relation to facial trauma. However, it can be easily overlooked because of the rarity of zygomatico-coronoid ankylosis and the attention focused on the joint. Surgical intervention is regarded as a good treatment to improve mouth-opening limitation.