Histological section of the bone defect. (A) Control group (Co) at two weeks. The black arrow indicates new bone trabeculae (BT). (B) Chitosan nanoparticle group(ChN) at two weeks, showing newBT. (C) Simvastatin group(Sim) at two weeks. The arrows indicate osteoblasts (OBs). (D) Combination of chitosan nanoparticles and simvastatin (ChSimN) at two weeks. The arrow shows new BT. (E) Co at four weeks, showing mature BT separated from the basal bone by a reversal line (RL), which is indicated by the arrow. (F) ChN at four weeks, showing mature bone. The arrow indicates a haversian canal (HC). (G) Sim group at four weeks, showing HC. (H) ChSimN at four weeks, showing HC. H&E × 10. Scale bar = 100 µm, n = 42.