Chitosan-augmented advanced platelet rich fibrin improves the regeneration of superficial digital flexor tendon gap tenorrhaphy in donkeys (Equus Asinus)

Abstract Background Tendon healing remains a formidable challenge in equine rehabilitation as injured tendons are healed by a fibrotic scar that exhibits compromised biomechanical characteristics. The objectives were to evaluate the regenerative effectiveness of autologous advanced platelet rich fibrin (A-PRF) and chitosan (Ch) for repairing the superficial digital flexor tendon (SDFT) following gap tenorrhaphy in a prospective, blinded, randomized, controlled experimental study carried out on 18 male donkeys based on clinical, ultrasonographic, and histopathological interpretations. These animals were allocated according to the gap-filled biomaterials into three groups (n = 6 each): the control group, the PRF group, and the PRF/Ch group. Results The addition of A-PRF, both alone or with chitosan, led to significant (P < 0.05) and marked changes compared to those in the control group. Both the PRF and PRF/Ch groups exhibited normal clinical index scores, characterized by a comfortable attitude with neither swelling, pain, nor lameness, after the recovery of normal tendon ultrasonographic characteristics (echogenicity, alignment, thickness, shape, and gliding properties) and histologic features. The addition of chitosan to A-PRF in the PRF/Ch group significantly (P < 0.05) reduced the SDFT thickness, intratendinous edema, inflammatory cell infiltration, and vascularization. Conclusion The combination of both A-PRF and chitosan could represent an innovative and effective approach for enhancing SDFT healing outcomes, offering promising improvements in the field of equine rehabilitation.