In this study, we employed both rigid and flexible fixation following femur fracture to investigate the potential impact of flexible fixation on bone healing and shaping by comparing the bone volume/total volume (BV/TV) in rat models of femur fracture under different mechanical loading conditions, and we explored the mechanism by comparing the SHH and CXCL12 levels of femur fracture model in rats under different fixation strengths and stress environments. The gene discussed is CXCL12; the disease is femur fracture.