Radiological and Histological Assessment of the Regeneration of Experimental Fractures of Critical Length, Treated with Hydroxyapatite Alone and in Combination with Autologous PRP-gel

Abstract

The aim of this study was to evaluate the effect of autologous platelet-rich plasma (PRP) gel combined with nanohydroxyapatite (HA) on bone regeneration in critical-sized diaphyseal defects in rabbits. Fourteen clinically healthy adult New Zealand White rabbits were divided into two groups: control (HA only, n=7) and experimental (HA+PRP, n=7). Standardized defects were created in the radius (≥1.5× bone diameter), and radiological, histological, histochemical, and immunohistochemical analyses were performed on days 30, 60, and 90 post-surgery. Radiographically, the PRP group demonstrated earlier bone bridge formation and complete defect filling by day 90, with significantly higher healing coefficients (0.64 vs 0.21; p<0.05). Histological evaluation revealed accelerated callus maturation and active osteogenesis with organized bone marrow in the PRP group, whereas the HA group showed incomplete union and persistent fibrous tissue. Immunohistochemical staining (CD34) confirmed neovascularization and hematopoietic precursor cell proliferation in the PRP-treated defects. The combined use of nanohydroxyapatite and PRP gel significantly enhanced osteoregeneration and shortened healing time in critical-sized bone defects.