Effects of a single condylar neck fracture without condylar cartilage injury on traumatic heterotopic ossification around the temporomandibular joint in mice

Objectives. In this study, we tried to explore the effects of a single condylar neck fracture without condylar cartilage injury during the pathogenesis process of traumatic heterotopic ossification around the temporomandibular joint (THO-TMJ). Study Design. One-month-old C57 BL/6 J male mice were divided into 2 groups. In group 1, condylar cartilage was partially removed in the right joint to induce THO. In group 2, a single fracture on the condylar neck was created using small scissors. The condylar head was repositioned to its original place if any displacement occurred. The phenotypes were observed using gross observation, micro-computed tomography, and histologic examination. Results. The results showed obvious hyperplasia in the right condyle in group 1, with ectopic bones and cartilage in the periarticular region. In group 2, the surface of condyle was smooth, but the size of the right condylar head became smaller. Conclusions. Taking these findings together, we concluded that it is condylar cartilage injury, and not a single condylar neck fracture without condylar cartilage injury, that contributes to the development of THO-TMJ.