Objective     To establish a simple

reproductive and standardized method for mouse femur critical bone defect for research in tissue engineering.       Methods      Anatomic data of mouse femur were obtained through measurement in order to guide the operation. Thirty 2 to 3 months old FVB/N mice were randomly divided into 3 experimental groups

each group with 10 mice. Their right femur were inflicted to make a defect in sizes of for 1

2 and 2.5 mm respectively after the mice were fixed in our self-designed fixation equipment. Bone defect healing process was assessed by plain X-ray filming and histological observation.       Results      X-ray film and histological observation confirmed that the bone defect at the size of 1 mm was restored by the self-repairing mechanism in 3 months after operation

but no such repair were found in the defect of 2 and 2.5 mm groups. Satisfactory models were created in 89.7% experimental mice.      Conclusion       Mouse femur critical defect model can be established through our self-designed fixation equipment. Bone defect in size of 2 mm and more in mouse femur can not heal up spontaneously even in 3 months after operation. This defect model has high repeatability and can be used for the related research in tissue engineering as standard animal models.