The effect of pre-emptive analgesia plus early weight-bearing treadmill training (EWBTT) on healing and motor function recovery of femoral shaft fracture is not clear.A total of 60 SD male rats were randomly allocated into 4 groups: group A (pre-emptive analgesia with EWBTT), group B (pre-emptive analgesia with delayed weight-bearing treadmill training, DWBTT), group C (pre-emptive analgesia with no weight-bearing), and group D (EWBTT with no pre-emptive analgesia). All rats were molded by internal fixation with Kirschner wire after right femoral shaft fracture. In groups A, B, and C, tramadol was intramuscularly injected 15 minutes before surgery. EWBTT was performed at day 1 postoperatively in groups A and D, and DWBTT was performed at day 14 postoperatively in group B. Oblique plate test was accomplished to assess hindlimb motor function recovery of rats in each group. Status of fracture healing was assessed through digital radiography (DR). Hematoxylin-eosin (HE) staining and immunohistochemistry of bone morphogenetic protein-2 (MBP-2) and vascular endothelial growth factor (VEGF) in callus were performed to explore fracture healing. The expression of BMP-2 and VEGF protein in quadriceps femoris muscle was detected by Western blot technique and mRNA expression of BMP-2 and VEGF in callus ascertained via reverse transcription-polymerase chain reaction (RT-PCR) technique.For oblique plate test, rats in group A outperformed those in groups B and C at all time points after operation. DR image revealed that large numbers of callus growth, blurred fracture line, and obvious continuous callus passing through the fracture line can be found in group A at day 28 postoperatively, which is the best healing status among all groups. HE staining of callus confirmed the optimal effect of healing for rats in group A. VEGF and BMP-2 expression by immunohistochemistry showed a significantly higher positive score for callus in group A while those in group C being the lowest at all time points postoperatively. Significantly higher expression level of VEGF and BMP-2 protein was detected in quadriceps femoris muscle from group A, which exceeded those in all other groups at all time points. RT-PCR testing proved the highest expression of BMP-2 and VEGF mRNA in callus of rats from group A, significantly higher than those of other groups.Both pre-emptive analgesia and EWBTT can effectively invoke the expression of VEGF and BMP-2 and promote recovery of hindlimb locomotor function in rats with femoral fracture, and the combination of them leads to more superior results.Copyright © 2023 Yunqiang Chen et al.