Experimental Study On Treatment Of Early Avascular Necrosis Of Femoral Head In Rabbit With Core Decompression Combined With VEGF

Objective: The mechanism and effection of vascular endothelial growth factor(VEGF) was investigated in avascular necrosis of femoral head of rabbits by being associated with core decompression.The new method of treating avascular necrosis of femoral head in early stage was explored with VEGF in clinics.Methods: 34 adult New Zealand rabbits were divided into three groups randomly.Group A of 10 rabbits as animal model group,the other two groups were 12 rabbits respectively.The B group of 12 rabbits was performed core decompression .The C group of 12 rabbits was performed core decompression associated with VEGF.Two femoral heads of every rabbits were studied in the experiment.The femoral head were refrigerated with liquefided nitrogen for 3 minutes.Nothing had done in group A.After being rewarmed. The femoral heads in group B and group C were drilled from the posterior medical aspect of the collum femoris down to the articular cartilage .Group C was implanted the gelatin sponge combined with VEGF in the drilled channel.In group B,only the gelatin sponge was implanted. In group A,femoral head specimens were obtained 3,7 days,2,4,6 and 8 weeks after operation.In group B and group C, the specimens were obtained 2,4,6 and 8 weeks after operation.All of the specimens were examined by radiograph,microscope and tissue image analysis.Angiogenesis of the repairing tissue in the femoral head was compred with at 2 weeks and 4 weeks after operation,New bone formation in the edge of the bone defect was compared with at 2 weeks and 8 weeks after operation.Finally ,the statistical analysis was made.Results:1 X-ray examination:Group A,at 3 days ,the shape and the density of the femoral head was normal.At 2 weeks ,the density was heightened slightly;At 4 weeks ,the trabeculae were normal. At 6 weeks,the density was higher.the disorder of the bone trabeculae could be observed.At 8 weeks ,cystic degeneration, the density was higher than before.In group B and group C,the manifestation of the area outside of defect area was consistent with guoup A.At 2 weeks,the density of defect area is low and the density of the brim of defect area was heightened. the bone density of defect area in group C was higher than those in group B.In group C,the trabeculae could be observed in the defect area. 2 In Group A,three days later after freezing ,osteocyte,chondrocyte and bone marrow were necrotic,and trabeculae kept intact,empty lacunae increased.The minimum of the empty lacunae rate was 58%.The maximum of the empty lacunae rate was 89%. After two weeks,repair process began.Cartilage repair came from two sources.One source which chondrocyte presented spindle shape was from synovial membrance and femoral head ligment .The other sourse was located in the zone of proliferation of cartilage, which chondrocyte presented roundness or oval shape.Two weeks later after freezing ,new-formed bone either appeared in the intertrabecular space or covered the dead trabeculae.At 8 weeks, new-formed bone increased,in the meantimes,a part of dead trabeculae became thin,irregular or broken.In group B, two weeks later after operation,angiogenesis appeared, gelatin sponge could be observed in the center of the drilled hole.Only a few amount of osteoblasts were in the drilled hole.With the time going,at 8 weeks, the drilled hole were full of marrow.In group C, Two weeks later after operation, there were also some new-formed bone appearing around the drilled hole,but there were a large amount of osteoblasts appearing on the gelatin sponge in the bone defects.angiogenesis in the femoral head were more abundant than in group B.At 4 weeks, the drilled hole were full of angiogenesis ,and new-formed trabeculae appeared.At 6weeks,bone marrow appeared and the drilled hole were full of bone trabeculae.At 8 weeks, the bone was repairing and bone marrow formed in the intertrabecular space.The trabeculae area percentage in group C had no statistically significance difference compared with group B at 2 weeks and 8 weeks.The femoral head in group C showed a significant increase in angiogenesis compared with group B 2 weeks and 4 weeks after operation.Conclusions: 1 The animal model of avascular necrosis of the femoral head can be established with modified liquid nitrogen method.2 VEGF can augment angiogenesis of bone tissue and improve microcirculation of necrotic femoral head. 3 VEGF may be beneficial to the reparative process of necrosis of the femoral head.