Anterior disc displacement without reduction: What happens after TMJ skeletal anchorage surgery? A retrospective cohort study.

Objective: This study aimed to investigate surgery-related changes in condylar height, disc length, disc displacement, and tissue thickness of the temporomandibular joint (TMJ) after skeletal anchorage surgery to obtain a better understanding of surgical outcomes and to provide useful information for treatment protocols.

Methods: This retrospective cohort study included 172 joints in 86 patients with unilateral anterior disc displacement without reduction (AddwoR), which were divided into an untreated group and an operation group. All patients had 2 magnetic resonance imaging records for measurement at the initial visit and follow-up visit respectively. The t-test was used to assess intra- and inter-group differences.

Results: In the untreated group, the changes in condylar height, disc length, and disc displacement on the AddwoR side were -0.98 mm, -0.11 mm and 0.74 mm, respectively. In the operation group, the changes in the condylar height, disc length, disc displacement and tissue thickness on the AddwoR side after anchorage surgery were 0.84 mm, 0.21 mm, -6.63 mm and -0.87 mm, respectively. A statistically significant difference was observed between the two groups.

Conclusions: The present study suggests that the condylar height and disc length of AddwoR without treatment tended to decrease with time. Additionally, TMJ skeletal anchorage surgery effectively reversed the decreases in condylar height and disc length. However, the findings suggest that TMJ anchorage surgery results in a decrease in tissue thickness. Preoperative tissue quality should be considered when planning surgical interventions to minimize the risk of tissue thinning.