Fig. 4

Van Gieson staining. Group a at the 2nd week: the bone stump was neat, the fibrous tissue proliferated, multinucleated cells were seen around (black arrow), the cell was infiltrated, and the bone was absorbed; no obvious signs of infection (LM × 40). Group b at the 2nd week: the fibrous tissue was connected with the host bone (black arrow), a large number of cells were infiltrated (green arrow), and no obvious signs of infection (LM × 40). Group c at the 2nd week: neovascularization and fibrous tissue grew into the material were less than that in group d (green arrow), the bone stump was neat, and there were no obvious signs of infection (LM × 40). Group d at the 2nd week: neovascularization and fibrous tissue grew into the material, a large number of cells were infiltrated (green arrow), and no obvious signs of infection (LM × 40). Group a at the 4th week: bone resorption and remodeling (green arrow) were observed around the bone stump (black arrow), and VG staining showed that large bone formation areas gradually closed the medullary cavity (black arrow) (LM × 40). Group b at the 4th week: the autogenous bone was closely connected with the host bone (black arrow), surrounded by a large number of blue fibrous callus (black arrow) and red stained bone callus (green arrow) (LM × 40). Group c at the 4th week: more blood vessels and fibrous tissue grew into the material (red arrow), there was a little bone formation (green arrow), and there was a fibrous connective tissue between the material and host bone (yellow arrow) (LM × 40). Group d at the 4th week: more blood vessels and fibrous tissue grew into the material, the new bone tissue was found in the pores (red arrow), and collagen was distributed along the surface of the material (green arrow) (LM × 40). Group a at the 8th week: the bone texture is clear in the bone stump area (black arrow), and the orientation of the trabecular bone in the area of bone resorption and remodeling section was irregular (green arrow) (LM × 40). Group b at the 8th week: the autologous bone marrow cavity is recanalized (black arrow), the orientation of bone trabecula was irregular (green arrow), and there was an obvious difference between the host bone and autologous bone (white arrow) (LM × 40). Group c at the 8th week: the collagen was formed on the surface of the material (green arrow) (LM × 40). Group c at the 8th week: the collagen was formed on the surface of the material (red arrow) (LM × 40). Group d at the 8th week: the new bone increased gradually from the two ends of the defect into the material, there was a red staining of the bone tissue (green arrow) and cell distribution along the surface of the material (yellow arrow) (LM × 40). Group a at the 12th week: the medullary cavity closure (black arrow) and bone continuity were good (green arrow) (LM × 40). Group b at the 12th week: autologous bone marrow cavity is recanalized, visible bone resorption and reconstruction were observed, the orientation of bone trabecula was regular (black arrow) (LM × 40). Group c at the 12th week: in the pores, the number of bone formation tissue was increased (green arrow), along the surface of the material distribution, increased blood vessels, and collagen deposition around the blood vessels (red arrow) (LM × 40). Group d at the 12th week: the number of the new bone was increased than before, the material occupied was reduced, the orientation of bone trabecula was irregular, the osteoblasts were active (green arrow), and the material and new bone were connected closely (LM × 40). Group a at the 24th week: multinucleated cell aggregation around the medullary cavity of bone adjacent side (green arrow), bone resorption and remodeling; the orientation of bone trabecula was regular (black arrow) (LM × 40). Group b at the 24th week: the cortical bone structure was clear, and the orientation of bone trabecula was regular (green arrow) (LM × 40). Group c at the 24th week: the materials’ occupied space was reduced, the pores were filled with new bone tissue (green arrow), the material and new bone were connected closely (black arrow), and the orientation of bone trabecula was irregular (LM × 40). Group d at the 24th week: all the materials were absorbed, the orientation of bone trabecula was regular, the calcification was good, and the reconstruction of the medullary cavity was complete (black arrow) (LM × 40)