Repair Mechanism of the Triangular Fibrocartilage Complex (TFCC) in the Chronic Stage

The triangular fibrocartilage complex (TFCC) is essential for ulnar wrist stability, yet its avascular central region is conventionally considered incapable of spontaneous healing, relying solely on passive nutrient diffusion. This article presents a mechanistic hypothesis regarding the self-repair potential of the TFCC during chronic-stage rehabilitation. Based on a synthesis of anatomical, biomechanical, and cell-biological evidence, it is proposed that isometric ulnar deviation training may serve two interrelated functions. First, it strengthens the extensor carpi ulnaris (ECU) muscle, thereby unloading the TFCC and improving dynamic ulnar wrist stability. Second, mechanical loading activates ECU tendon fibroblasts to secrete key growth factors, including transforming growth factor $\beta$ (TGF-$\beta$) and insulin-like growth factor-1 (IGF-1). Owing to the close anatomical proximity between the ECU tendon and the TFCC, these factors could reach the adjacent avascular TFCC region via extracellular matrix (ECM) relay and exosome-mediated transport, establishing a local repair-promoting microenvironment. Compared with conventional rest-based management, this active training strategy could theoretically improve repair outcomes, increase the extent of healing and lower re-injury rates. Through systematic analysis of existing research, this paper provides a new theoretical framework and practical directions for rehabilitation of TFCC injuries.