| Objective: A new type of bone graft material was constructed by combining calcium phosphate cement (CPC) with bone morphogenetic protein (BMP). In order to evaluate the feasibility to use this material to repair avascular necrosis of femoral head (ANFH) in clinic. The ability of CPC was compared with CPC/BMP in bone defects reconstruction of ANFH by animal experiments. Methods: The model of bone defect of ANFH was established in the left femoral head in 24 rabbits, of which 12 defects were implanted with CPC/BMP composites, 12 implanted with CPC. Put CPC solid phase powder (9.0g) and BMP (60mg) into mortar and grind the mixed powder sufficiently. keep the mixed powder in 4 degree centigrade refrigerator. All left hip joints were operated. After exposing hip joint, drill hole between femoral head and neck with 3.5mm aiguille. Get rid of 50% cancellus of femoral head with little curette. Put a piece of gauze which dipped in 95% alcohol into the hole and keep 30min. mix CPC solidification liquid with CPC solid phase powder or CPC/BMP mixed powder, then plant the materials into the bone defects of ANFH respectively. Press the materials 2min with finger. After solidification stitch the incision in order. The specimens were harvested separately at the end of 3 and 12 weeks after operation. In order to observe the formation of new bone and the degradation process of the materials, a series of examinations were carried out including of radiograph, histomorphology, transmission electron microscope (TEM), the results of CPC group and CPC/BMP group were compared on the same condition. Results: All the animals survived after operation, and no reactions of toxicity were found. The 12th week there was a joint dislocation in CPC group, the rests found no obvious abnormity. Activity degrees of the hip joints were good. The shape of the femoral heads were as usual, so were the articular surfaces. In CPC group, the 3rd week there was no obvious phenomenon of new bone formation. The 12th week there was lots of new bone. In CPC/BMP group, the 3rd week there was no obvious phenomenon of new bone formation either, but there was cartilage tissue between material and host bone. The 12th week there was a great lot of new bone. Radiograph: In CPC group, the 3rd week the material was developed clearly, CPC was not obvious degradation. The 12th week the density of the material decreased, the volume decreased. But the volume was still bigger than CPC/BMP group of the same period. In CPC/BMP group the 3rd week there showed vague image between host bone and material. The 12th week the image of new bone was distinct, the density of the material decreased, the degradation of the material was obvious and the volume decreased evidently. Histomorphology: There was no avascular necrosis of bone or cartilage in every group. In CPC group the 3rd week CPC did not decrease evidently, new bone formed on the surface of CPC. some infantile osteocytes could be found. The 12th week CPC decreased evidently, there were interspaces between material and new bone in some areas. New bone interlaced reticularly. Infantile osteocytes could be found. In CPC/BMP group the 3rd week infantile osteocytes and much new bone could be found, CPC was decomposed to some parts. The 12th week CPC was dispersed, new bone invaded the material, new bone and CPC enwrapped each other. But infantile osteocytes were not more than CPC group of the same period. Transmission electron microscopy: In CPC group the 3rd week some osteoblasts invaded the material, some cells protruded cell projections. But only few osteoblasts could be found. The rough endoplasmic reticulum (rER) did not swell evidently. The 12th week CPC granule density decreased, some osteoblasts could be found. The cell nucleus was round, rERs swelled. There was the phenomenon of mitochondrion cavitation and mitochondrion crest rupturing. In CPC/BMP group the 3rd week many priosteoblasts and osteoblasts invaded the material. More rERs were found. The 12th week many os... |
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