Abstract: Objective  To establish a reliable model to study osteoporotic nonunion. Methods  A total of 60 female rats were randomly divided into experimental group (n=45) and control group (n=15). The ovary of rats in the experimental group were resected, while equal volume of fat tissues around the ovary of rats in the control group were resected. After 12 weeks, 10 rats in either group were killed. Histochemical staining, serological indicator and mechanical strength of femur were used to identify the osteoporotic models. Then osteoectomy was operated in the other rats of the experimental group, with external fixators maintaining a 6mm critical defect. The model of osteoporotic nonunion was identified by histochemical staining and imaging observations. Results  Compared with the control group, mechanical strength of the femur had obviously decreased and NTX in the serum increased in the experimental group (P<0.05). The Results   of radiography and histology showed that the ends had been sealed by the woven bone, and connective tissues filled up the gap 12 weeks after osteoectomy. The external fixators were stable and could maintain the ends in the same horizontal plane.  Conclusion  The adjustable external fixator is stable enough to build a reliable animal model of the osteoporotic nonunion.

Key words: Osteoporosis, External fixator, Nonunion, Rat model