Temporomandibular disorders (TMDs) refer to a group of conditions characterized by similar clinical symptoms, including pain in the temporomandibular joint (TMJ) and/or masticatory muscles, joint clicking, crepitus, and abnormal mandibular movement (Schiffman et al., 2014; Xiong et al., 2021). Anterior disc displacement (ADD) of the TMJ is one of the most common subtypes of TMDs, typically presenting with joint pain, clicking, and limited mouth opening (Schiffman et al., 2014). ADD can be further classified as anterior disc displacement with reduction (ADDwR) and anterior disc displacement without reduction (ADDWoR), depending on whether the disc returns to its normal position during the maximal mouth opening (Schiffman et al., 2014). While ADD affects both adults and adolescents, it is particularly common in adolescents, especially those with dentofacial deformities (Ikeda et al., 2014). Subchondral cortical bone formation begins around ages 12–14, with full condylar development occurring by ages 21–22 (Lei et al., 2013). During this period, the condyle is less able to adapt to abnormal mechanical stress caused by conditions such as ADD compared to fully developed condyles (Huang et al., 2020). Condylar cartilage serves as one of a growth centers for the mandible, and untreated ADD during adolescence can result in condylar resorption, disrupting condylar development and leading to severe dentofacial deformity (Zhuo et al., 2015). Previous studies indicated that untreated unilateral ADD might cause mandibular deviation, while bilateral ADD could result in skeletal Class II malocclusion, characterized by mandibular retrusion and anterior open bite (Zhuo et al., 2015; Dong et al., 2021a). Early diagnosis and treatment are therefore crucial for young patients with ADD in preventing further damage to the articular cartilage and condylar morphology.

Treatment for ADD includes both conservative and surgical therapies. Conservative therapies, such as behavioral education, medication, muscle relaxants, and occlusal splints, may help alleviate symptoms. Occlusal splints may also prevent condylar resorption, but their effectiveness in supporting condylar development remain uncertain (Lei et al., 2019; Wänman and Marklund, 2020). Articular disc repositioning is one of the surgical therapies for ADDwoR, typically performed via arthroscopic or open disc repositioning. Studies have frequently reported new bone formation in the condyles of adolescent ADDwoR patients after surgery, which effectively promotes condylar height increase and corrects dentofacial deformities (Zhu et al., 2019; Dong et al., 2021a; Zhang et al., 2024). However, due to the curved anatomical shape of the condylar head, disc position after surgery is not always consistent. Regarding disc repositioning, current views advocate for overcorrection the disc to the 1–2 o'clock position on the condyle to minimize the risk of postoperative recurrence. (He et al., 2015; Liu et al., 2019; Zhang et al., 2024). In cases where the disc is overcorrected, bone remodeling may exhibit a regional distribution, with new bone formation being more pronounced on the posterior slope and less on the anterior slope of the condyle (Dong et al., 2021a). A preliminary study using multimodal image registration techniques observed differences in bone remodeling areas when the disc was positioned in an overcorrected versus non-overcorrected position after surgery (Tang et al., 2023). Postoperative outcomes such as increased condylar degeneration or excessive, uneven bone remodeling are undesirable. The relationship between the disc's sagittal position and condylar bone remodeling remains unclear, with limited evidence on whether repositioning to different locations leads to varying remodeling patterns.

A retrospective cohort study was designed and implemented to quantitatively and qualitatively assess condylar bone remodeling data across different groups. This study intends to analyze whether differences in the sagittal position of the disc after surgical repositioning affect the outcomes of condylar bone remodeling, offering potential insights into optimizing surgical outcomes. The null hypothesis posited that surgical positioning of the disc in different locations will not result in differences in the amount and location of postoperative condylar bone remodeling.