Abstract: Objective To establish developmental dysplasia of the hip (DDH) animal model treated by sartorius iliac flap with epiphysis, explore the expression and significance of bone morphogenetic proteins-2 (BMP-2) and its mRNA during repair process. Methods A unilateral acetabular bone defect animal model was established with 48 Japanese white rabbits, and then the rabbits were divided into two groups.Rabbits in experimental group were treated by sartorius epiphyseal iliac flap, and rabbits in control group did not receive any related therapy.The general gait and hip motion were observed at 1, 2, 4 and 8 weeks after operation.Then they were sacrificed and their acetabular bone and cartilage tissues were taken for HE staining.The expression of BMP-2 and its mRNA were measured by Western Blot and Real-Time PCR, respectively. Results The hip motion of rabbits in control group recovered slowly, and they were still limping at 8 weeks after operation.Meanwhile, rabbits in experimental group recovered gradually and walked nearly normally at 8 weeks after operation.In control group, bone defects were found under acetabular cartilage.The morphology of cartilage cell was normal at 1 week after operation.At 2 weeks after operation, the acetabular cartilage layer showed uneven thickness and it lasted to 8 weeks after operation.Acetabular cartilage cells showed signs of degeneration or necrosis at 4 weeks postoperatively.In experimental group, it showed an obvious gap between flap cartilage and acetabular cartilage at 1 week after surgery.The distance between these two cartilages became shorter at 2, 4 weeks after surgery.At 8 weeks after surgery, the flap cartilage and acetabular cartilage almost fused together.The expression levels of BMP-2 and BMP-2 gene were consistent in acetabulum.In control group, it showed a low expression of BMP-2 and no significant changes over time.In experimental group, the expression of BMP-2 increased gradually over time.The BMP-2 expression was significantly higher when compared with control group since 2 weeks after surgery and it reached the peak at 4 weeks postoperatively. Conclusion The iliac flap cartilage and acetabular cartilage has fused together in the rabbits of experimental group.The epiphyseal iliac flap increases the expression of BMP-2 in acetabulum and the increasing expression of BMP-2 may participate in the physiological process of repairing dysplasia of acetabular cartilage.