ObjectiveImplantation the rhBMP-2/PLGA carrying poly microspheres to subchondral bone of the ANFH models to research the mechanism and function of therapeutic effect of the rhBMP-2/PLGA sustained-release microspheres with core decompression in the treatment of rabbit avascular necrosis of the femoral head, Provide a theoretical basis for clinical ,exploring a new method for early stage ANFH.Methods①The rhBMP-2/PLGA microspheres were prepared using W/O/W solvent evaporation method. Detecte morphology of the microspheres, the drug loading and the efficiency of encapsulation and in vitro release behaviors put ossification test to detect it’s osteogenesis.②Make the ANFH models:adopt the classic methed:46 adult NewZealand white rabbits were randomly divided into four groups:A,control group(n=10);B model group(n=120);C coredecompression group(n=12);D core decompression with rhBMP-2/PLGA sustained-release microsphere group(n=12).The rabbits in the last three groups were inject with 10ml/kg equine horse serum into ear-vein.three weeks later they were inject with 6ml/kg horse serum into ear-vein again.And then,after two weeks they were inject with 45mg/kg methylprednisolone sodium succinate 3 times(three days every time) also through ear-vein. The control group breadde normally.③Zoopery:the C、D group were operated with core depression.and after the core depression the D group were implanted with 3mg rhBMP-2 microspheres and then using the autoallergic bone to fill the hole. Group A and B give none disposal.12 weeks after the operation execute the rabbits we observed the necrossis of samples through X-ray and pathological section and The immunohistochemistry study for rabbit VEGF.Result1、About the rhBMP-2/PLGA microspheres: the entrapment rate of the microspheres carrying rhBMP-2 is (37.52±4.31)% and the wear rate is (5.12±1.32)%,the microsphere releasing rhBMP-2 have a breaking through,there are 40% rhBMp-2 were released in the first 7days and then the releasing rate is stable. About 90% rhBMP-2 were released in the later 42 days.2、Succeed modeling the early stage ANFH models :The surface of the femoral head in the modeling groups are complete no collapse were seen. there is red congestive on the surface and easy to cut, the cortex is thin. hematoxylin and eosin stain: The empty cartilage cell lacunae are rising and the numbers of blood vessel under cartilage reduced X ray showed osteoporosis appeared the bone density reduced.3、The effect of rhBMP-2/PLGA delayde release microspheres to the early stage ANFH:(1)All the surface of the femoral head in the four groups are and complete no collapse were seen. The femoral head in group A are smooth and hard the surface are white ; there is red congestive on the surface of the B group dark and easy to cut, the cortex is thin. The femoral head in the C group were light white, it is easier cut than A group but harder than B gpoup. The D group were nearly normal in every asbect.(2)The X-ray: the bone density in the B group are significantly less than A group. The density of group C are stronger than group but still less than group A. Group D are significantly stronger than group B and nearly normal.(3) Hematoxylin and eosin stain: the empty cartilage cell lacunae in group B and C are increased significantly than group A.the B group are more than group C.and D group shows significantly degraded than group B(p<0.05). The numbers of blood vessel under cartilage in group B was significantly reduced than group A,while group C was increased but less than group D, the D group increased significantly compared with group B (p<0.05).(4) 8 weeks after the operation the immunohistochemistry study for rabbit collagen typeⅠshows group B made the lightest color ,while group C was made a deeper color than B group,the D group the deeper color than group A (p<0.05).CONCLUSION1. Early stage avascular necrosis of the femoral head model was successfully established in rabbits.2. It is indicated that core decompression with rhBMP-2/PLGA could significantly enhance bone tissue angiogenesis. Repair of osteonecrosis could be ameliorated accordingly,thus providing a potential method in the treatment of the femoral head necrosis.