Abstract

Critical-sized bone defects remain a major challenge in orthopedic surgery due to limited spontaneous healing and the drawbacks of conventional grafting techniques. This study evaluated the regenerative potential of autologous advanced platelet-rich fibrin (A-PRF), Nano-hydroxyapatite (NHA), and their combination in a canine tibial defect model. Twelve adult dogs received bilateral 10 mm defects in the proximal third of the tibial diaphysis and were randomized into four groups: control (saline), A-PRF alone, NHA alone, and a combination of A-PRF and NHA. Bone regeneration was assessed radiographically and histologically at 2, 4, 8, and 12 weeks postoperatively. The A-PRF + NHA group showed the most rapid and complete healing, with early callus formation evident by week 4 and nearly complete radiographic bridging by week 12. In contrast, NHA alone produced moderate regeneration, while A-PRF alone was largely comparable to controls, indicating limited efficacy without structural support. Histological analysis confirmed these findings: the combination group exhibited extensive early osteoid deposition, followed by transition to organized lamellar bone and marrow-like tissue by week 12. Quantitative collagen content peaked in this group at week 4 (64.03 ± 1.44%), declining by week 12 (20.99 ± 2.50%), suggesting active remodeling and mineralization. These results demonstrate that combining A-PRF with NHA yields a synergistic effect, enhancing both early matrix formation and structural maturation. This autologous, biocompatible, and cost-effective approach holds promise as a viable alternative to traditional grafting methods for treating critical-sized bone defects.

Key words: Advanced Platelet rich fibrin; A-PRF; Nano-hydroxyapatite; tibial bone defect.