Quantitative analysis of disc-condyle movement following disc repositioning operation by arthroscopic for Bi-ADD patients.

Background: 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).

Methods: 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.

Results: 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.

Conclusions: 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.