Experimental research on the effects of hyperbaric oxygen on open tibial fracture coupled with seawater immersion in rabbits

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Objective To investigate the effects of HBO on open tibial fracture coupled with seawater immersion in rabbits and the possible mechanism involved. Methods Forty-eight New Zealand rabbits were selected and randomly divided into the HBO group and the control group, each consisting of 24 animals. The animals of both groups were inflicted with unilateral open tibial fracture. The injured limbs were immersed in artificial seawater for 3 hours, and then had wound suture and internal fracture fixation after debridement. The animals in the HBO group was immediately treated with HBO, once a day for a succession of 2 weeks, whereas the animals in the Control group were left there untreated. At week 4, 8 and 12 after injury, the animals were sacrificed and samples (8 limbs from each group) were collected for further study. The repair of the fractured tissues of both groups was compared by radiography, histology and immunohistochemistry. Results (1) Histopathology was performed by HE staining. At week 12 after injury, for the animals in the HBO group, osseous callus could universally be seen in the fracture zone, cell components were basically mature bone cells, and the infiltration of inflammatory cells could scarcely be seen, while for the animals in the Control group, mixed bone callus could mainly be noted in the fracture zone, but cartilage cells were still visible, and a small scale of inflammatory cell infiltration could also be observed.(2)Immunohistochemistry revealed that vascular endothelial growth factor (VEGF) was mainly expressed in the cytoplasm of osteoblast, chondrocytes and osteocyte, and significant changes could be seen at different time points. At week 4 after injury, the expression levels of the two groups were the highest. At week 8 and 12 after injury, the expression levels all gradually dropped to a relatively low level. At week 4 and 8 after injury, the expression level of the HBO group was obviously stronger than that of the Control group(P 0.05). (3)Radiographic imaging was performed for the detection of callus grayscale in the fracture zone. At week 12 after injury, the average value of callus grayscale in the fracture zone for the animals of the HBO group was (190.58 ± 7.52), while that of the Control group was (144± 8.11). Statistically significance was shown, when comparisons were made between the 2 groups (P 0.05). Conclusions In the treatment of open bone fracture coupled with seawater immersion, HBO could alleviate inflammatory reaction and reperfusion injury, enhance the proliferation of tissue cells, and was beneficial to the healing of bone fracture. For this reason, this regimen was a practical method for the repair of open bone fracture coupled with seawater immersion. Key words: Seawater immersion; Open fracture; Hyperbaric oxygen