Continuous detrimental activity of intra-articular fibrous scar tissue in correlation with posttraumatic ankle osteoarthritis

Posttraumatic osteoarthritis is primarily characterized by articular cartilage destruction secondary to trauma or fracture events. Even while intra-articular scar tissue can be observed following ankle fractures, little is known about its nature and molecular events linking its biological activity and cartilage deterioration. Here, we investigated scar tissue's histological and molecular characteristics, and its relationship with localized articular cartilage alterations consistent with early osteoarthritic degeneration. Intra-articular scar tissues from sixty-two patients who underwent open reduction internal fixation for ankle fracture were obtained at hardware removal time (6–44 months after fracture). Histological analysis demonstrated that scar tissue has the nature of fibrosis with fibrous tissue hyperplasia, fibroblast proliferation, and chondrometaplasia. These fibrous scar tissues showed overexpressed pro-inflammatory cytokines and high mRNA expression levels of osteoarthritis-related markers (cytokines, chemokines, and enzymes) compared to the normal synovium. Furthermore, those transcriptional levels were significantly correlated with the grade of talar chondral degeneration. Our findings suggest that following an ankle fracture, the intra-articular fibrous scar tissue exhibits high catabolic and inflammatory activity, which has a long-lasting negative impact correlated to cartilage deterioration in the development of posttraumatic osteoarthritis.