This study aimed to assess the location of disc and the movement characteristic of disc–condyle following disc repositioning operation by bilateral arthroscopic (Bi–ADRO).

The consecutive patients enrolled, who received magnetic resonance imaging (MRI), 84 patients were included. 31 patients distributing in group N diagnosed as non–ADD. 53 patients, with 87 joints diagnosed with anterior disc displacement without reduction (ADDWoR) assigned to the surgical group (group A), who underwent the Bi–ADRO, with postoperative follow–ups at 1 (A_1M), 3 (A_3M), and 6 (A_6M) months. The statistical analysis was IBM SPSS Statistics v.27.0, p<0.05 was considered significant.

1. The group N showed a significant increase in painless maximum vertical opening (MVO) compared to baseline measurements (p < 0.05). The group A₀ demonstrated significantly lower MVO than the group N (p < 0.001). Statistically significant differences in MVO were observed across all A_0–6M follow–up intervals compared to baseline (p < 0.05). 2. 1) In the coronal view, rare disc displacement was showed in group N, whereas discs were invisible in A₀; partially visible in A_6M, with lateral displacement 11/42, which can be seen at the disc–condyle angle of –29.14°±32.49°. 2) In the sagittal view, disc–condyle angles between group N and A₀, A_6M in both closed and opening were significantly different (p < 0.001). 3) Significant differences were observed in mobility between group N and A₀, A_6M (p < 0.001). 3. Postoperative changes in disc–condyle angles and mobility over time: 1) In the coronal view, disc visibility improved, with persistent lateral displacement. 2) In the sagittal view, disc–condyle angles increased over time, while the rate of increase diminished. 3) Mobility progressively increased in the groups A_1M∼6M, with significant intergroup differences (p < 0.05). 4. The changes of disc–condyle angle over time were negatively correlated with the surgical disc position: closed: p < 0.001, r=–0.508; p < 0.001, r=–0.522; opening: p < 0.05, r=–0.212; p < 0.05, r=–0.232.

Following ADRO, progressive restoration of MVO was observed. Bi–ADRO improved disc position, with sagittal repositioning being more pronounced than coronal. Sagittal disc position exhibited anterior displacement over time; disc movement was predominantly vertical, while condylar primarily sagittal. The most pronounced changes in disc–condyle mobility occurred at 3 months. The 0°∼–60° are favorable disc–repositioned because of optimal mobility and have the potential to be recommended.