[Establishment of a mouse model of traumatic temporomandibular joint ankylosis]

Objective: A C57/BL6 mouse model of traumatic temporomandibular joint ankylosis (TTMJA) was established through composite trauma to lay the foundation for studying the pathophysiology of TTMJA. Methods: This study was conducted from January 2024 to February 2025. Forty-two 4-weeks old C57/BL6 mice, numbered 1 to 42, are randomly assigned to a control group (n=21) and an experimental group (n=21) using a computer-generated random number sequence. The experimental group undergoes modeling surgery on the left temporomandibular joint (TMJ), while the control group is routinely raised without special treatment. At 12 weeks post-surgery, the TMJ complex of both groups is assessed via body weight and mouth opening measurements, gross observation, micro-CT, and histological staining to evaluate model establishment. Results: At 12 weeks post-operation, in the experimental group, the body weight of mice [(27.75±1.08) g] did not show a significant difference compared with that of the control group [(30.80±0.29) g](t=0.54,P=0.610). The maximum vertical passive mouth opening [(1.70±0.26) mm] in the experimental group was significantly lower than that in the control group [(3.43±0.21) mm](t=8.92,P<0.001). Gross observation indicated that the right TMJ structure of the experimental-group mice was normal, while irregular hyperplasia occurred in the left TMJ complex. Micro-CT revealed that at 12 weeks post-operation, the right joint structure of the experimental-group mice was normal, with regular condyles and glenoid fossae. On the left side, a large amount of bone hyperplasia occurred on the lateral side of the joint in the condyles and glenoid fossae, forming two irregular bone masses, and there was an uncalcified radiolucent zone between the bone masses. In histological staining, no new cartilage or bone tissue was observed in the left joint space of the control-group mice, and the articular disc structure was normal. In the experimental-group mice, obvious new cartilage and calcified bone tissue were visible on the lateral side of the left joint space. A bone bridge was formed between the condyles and glenoid fossae, the articular disc structure disappeared, and bony ankylosis occurred. Conclusions: In this experiment, a TTMJA model of C57/BL6 mice was initially established by removing the articular disc and damaging part of the fibrous cartilage of the glenoid fossae and condyles, providing an experimental platform for further research on the pathogenesis of TTMJA.