Effect of the timing of surgery on the fracture healing process and the expression levels of vascular endothelial growth factor and bone morphogenetic protein-2

The aim of the present study was to observe the effect of varying the timing of surgery on the fracture healing process and the expression levels of vascular endothelial growth factor (VEGF) and bone morphogenetic protein (BMP)-2 in rats. A total of 192 rats underwent closed femur fracture modelling. The rats underwent open reduction and internal fixation surgery 1, 3, 5, 7, 11 and 14 days subsequent to the fracture occurring. Immunohistochemical staining and analysis of the VEGF and BMP-2 expression levels were simultaneously conducted on bone from the fracture site of the rats on various days. The VEGF and BMP-2 expression levels at the fracture sites were higher and were maintained for a longer period of time in the 7- and 11-day surgery groups than in the other surgery groups and the rats that did not undergo surgery. The 5-day surgery group demonstrated a greater intensity in BMP-2 expression compared with the remaining surgery groups; however, no significant differences were identified between 1-day surgery and non surgery groups. In the 3-day surgery group, the expression levels VEGF and BMP-2 were low at each stage of the fracture-healing process and were lower compared with those observed in the non-surgery group. The timing of the surgical procedures affected the VEGF and BMP-2 expression levels at the fracture sites of the experimental rats and, the optimal time for performing surgery was identified to be within the first two weeks. However, surgery may not be conducive to fracture healing if it is performed within the first few days following fracture.