Objective： To investigate the effect of Huogu II Formula （活骨 II方 ） with medicinal guide Radix Achyranthis Bidentatae （Ach） on bone marrow stem cells （BMSCs） homing to necrosis area after osteonecrosis of the femoral head （ONFH） frozen by liquid nitrogen in rabbit as well as to explore the mechanism of prevention and treatment for ONFH. Methods： The animal model of ONFH was established by liquid nitrogen frozen on the rabbit left hind leg. Forty-eight Japanese White rabbits were randomly assigned to sham-operated group, model group, Huogu II group, and Huogu II plus Ach group, with 12 rabbits in each. During the course of ONFH animal model establishment, all rabbits were subcutaneously injected with recombinant human granulocyte colony-stimulating factor [rhG-CSF, 30 μg/（kg.day） for continuous 7 days]. Meanwhile, normal saline and decoction of the two formulae were administrated by gavage, respectively. White blood cells （WBC） were counted in peripheral blood before and after injection of rhG-CSF. Materials were drawn on the 2rid and 4th weeks after model built; bone glutamine protein （BGP） and bone morphogenetic protein 2 （BMP2） levels in serum were tested. Histopathologic changes were observed by hematoxylin and eosin （HE） staining. BMP2 mRNA levels were detected with in situ hybridization （iSH） staining. 5-Bromo-2＇-deoxyuridine （BrdU） and stromal cell derived factor 1 （SDF-1） were measured by immunohistochemical assay in femoral head of the left hind leg. Results： Compared with the shamoperated group, the ratio of empty lacuna, serum BGP, and SDF-1 level in the model group increased significantly, and BMP2 in both serum and femoral head decreased significantly. However, in comparison with the model group, the empty lacuna ratio of Huogu II group and Huogu II plus Ach group decreased obviously in addition to the levels of serum BGP and BMP2, and the expressions of BMP2 mRNA, BrdU, and SDF-1 increased significantly. Above changes were particularly obv
