Comparison of the Effects of Platelet Rich Fibrin and Platelet Rich Plasma on Experimentally Induced Tendon Injury in Rabbits Treated with Methylprednisolone

The aim of this study is to compare the effects of PRP and PRF on tendon injuries treated with methylprednisolone. In this context, the histopathological and immunohistochemical effects of PRP and PRF on tendon healing were evaluated. The study included 30 New Zealand rabbits (15 females and 15 males) with varying weights (1.5-3 kg) and ages (1-3 years). The experimental groups were designated as the steroid control group (Group B, n=10), the steroid+PRP group (Group C, n=10), and the steroid+PRF group (Group D, n=10). Additionally, the control tissues from a simultaneous study served as the empty control group (Group A). On the 14th postoperative day, a section encompassing the tenotomy site was excised from the area via incision. Healing was observed to be better in Groups C and D compared to Groups A and B. In Group A, inflammatory cell infiltration, primarily consisting of macrophages and polymorphonuclear leukocytes, along with a small number of lymphocytes and foreign-body giant cells, was higher than in all other groups. Group B exhibited less inflammatory cell infiltration compared to Group A. Additionally, hyperemia, hemorrhage, necrosis, new vessel formation, and fibroblasts of varying shapes and orientations were noted in Groups A and B. In contrast, cell infiltration was significantly lower in Groups C and D, while vascularization, fibroblast activity, and collagen density were higher. Collagen fibers were observed more regular bundles forms in Groups C and D compared to the control groups. The findings suggest that the combination of PRP or PRF with systemic methylprednisolone can effectively enhance tendon healing by modulating inflammatory responses, reducing adhesions, and supporting the formation of a well-organized extracellular matrix.