Objective We aimed to study the pathology underlying traumatic temporomandibular joint ankylosis (TMJA). Study Design Specimens from 10 patients with traumatic TMJA were categorized using the Sawhney classification and were decalcified and stained with hematoxylin-eosin, alcian blue/periodic acid-Schiff, alizarin red, and Masson stains. Immunostaining with anti-CD34 antibody was performed. Computed tomography and pathologic findings were compared. Results Ankylosed areas consisted of fibrocartilaginous tissues. Bone formation occurred by osteophyte extension from the osteochondral surface toward the mass center. Endochondral ossification and osteophyte proliferation, alone or simultaneously, participated in bony ankylosis. Sequestra in the cartilaginous ankylosis preferentially formed bony bridges. Newly formed capillaries participated in ossification from the bony surface of the bone-cartilage junction; bone formed around the capillaries. Osteoclasts were present at the capillary tips. Conclusions Types II and III were cartilaginous-bony ankylosis, with similar components. Bony traumatic TMJA was formed by osteophyte proliferation and endochondral ossification.
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