Bilateral pseudo-disc changes in a minipig model for unilateral anterior disc displacement of the temporomandibular joint.

PURPOSE: Current animal models of anterior disc displacement (ADD) of the temporomandibular joint (TMJ) have primarily been developed in small animals, using sutures or elastic bands to pull the disc anteriorly. These models often exhibit severe osteoarthritis (OA) and rapid progression to late-stage ADD, which do not accurately reflect the natural course of ADD in humans. This exploratory study aimed to establish a unilateral ADD-induced surgical protocol in a minipig model and evaluate the early changes of ADD. METHODS: Six Bama minipigs (12 joints) were divided into 3 groups: control group (CG), ADD experimental group (ADD-EG), and contralateral experimental group (CL-EG). Nickel-titanium coil springs were used to induce mild, sustained traction to anteriorly displace the TMJ discs. After a 5-week observation period, in-vivo magnetic resonance imaging (MRI) scans confirmed the anterior position of the TMJ discs. RESULTS: Micro-computed tomography showed minimal condylar bone changes, while histological analysis revealed mild OA-like condylar cartilage changes. MRI identified hypointense lesions posterior to the TMJ discs, indicative of pseudo-disc changes in the posterior attachments (PAs). Histological staining further confirmed chondroid metaplasia in the PAs surrounded by transitional zones in both ADD-EG and CL-EG. CONCLUSION: This study established a unilateral ADD minipig model using a nickel-titanium coil spring and identified bilateral chondroid metaplasia in the PAs, which may offer new perspectives for ADD therapies.