Ultrastructural study on adhesions in internal derangement of the temporomandibular joint

Purpose: This study examined the ultrastructural characteristics of adhesions in the upper joint compartment of temporomandibular joint (TMS). Materials and Methods: Tissue biopsy specimens of adhesions were obtained during arthroscopic operation on 36 joints in 22 patients with internal derangement OD). The biopsy specimens were examined by light and transmission electron microscopy. Results: Adhesions were grossly divided into two types based on arthroscopic observation: 1) a band-like type, which connected the articular fossa and TMJ disc, and 2) a pseudowall-like type, which faced the synovial fluid and was lined by articular tissue. Two types of collagen arrangement were observed at the electron microscopic level: orderly arranged collagen bundles and randomly arranged collagen bundles. Orderly arranged collagen bundles were prominent in the band-like adhesions. In pseudowall-like adhesions, mainly the randomly arranged collagen bundles were seen. However, in some dense fiber parts, orderly arranged collagen bundles also were observed. In other pseudowall-like adhesions, only orderly arranged collagen bundles were seen. Elastic fibers were abundant in some pseudowall-like adhesions with randomly arranged collagen bundles. There were no elastic fibers in the band-like adhesions, some dense fiber parts of the pseudowall-like adhesion, pseudowall-like adhesions consisting of only orderly arranged collagen bundles, and in the synovial membrane. Conclusion: The different arrangement of collagen fibers and presence or absence of elastic fibers were observed in the two types of adhesions. These findings sewed to show that extracellular components correspond to a dysfunction involving an ID of TMJ.