Pseudoankylosis - Uncommon Bony Fusion Between the Coronoid Process and Zygomatic Bone

Abstract

Introduction: Extraarticular disorders of various causes associated with a restriction of mandibular movement are summarized under pseudo-ankylosis. This clinical case report of a bony fusion between the zygomatic bone and the coronoid process documents the need for precise clinical and radiological diagnosis. Once diagnosed, surgical resection is the treatment of choice. Case report: A 43-year-old female patient presented in Freetown/Sierra Leone on board the hospital ship "Global Mercy" of the American aid organization Mercy Ships with a suspected diagnosis of "left temporomandibular joint ankylosis". A clinical examination revealed a restricted mouth opening of less than 5 mm and a bony distension of the left zygoma. It was reported that the mouth-opening impairment had been present for ten years. Further CT diagnostics revealed a bony fusion between the left zygoma and the coronoid process caused by a large osteoma. Bony resection of the osteoma was performed through a combined intra- and extraoral approach. After resection, a spontaneous mouth opening of 25 mm could be achieved intraoperatively. After an uncomplicated postoperative course, the patient was discharged with stable wound conditions and a mouth opening of 30 mm. Discussion(s): The diagnosis of "pseudo-ankylosis" can include various extraarticular neurogenic, psychogenic, and genetic diseases as well as tumors. In the case of bony changes, idiopathic hyperplasia of the coronoid process, Jacobson's disease, and osteomas of the coronoid process must be differentiated in the differential diagnosis. Only the early detailed clinical and radiological diagnosis of bony fusions ultimately points the way to the correct diagnosis of "pseudo-ankylosis".Copyright © 2025