Effects of hyperbaric oxygen therapy on open tibial fractures in rabbits after transient seawater immersion

To explore the effect and mechanism of hyperbaric oxygen (HBO₂) therapy of open tibial fractures in rabbits after transient seawater immersion.Forty-eight (48) New Zealand rabbits were randomly and averagely divided into an HBO₂ therapy group (Group A) and a control group (Group B). All rabbits were subjected to unilateral open tibial fractures, while immersed in artificial seawater (20-22 °C) for three hours prior to debridement and external fixation. Group A was treated with HBO₂ at 2 atmospheres absolute (ATA) for 50 minutes once daily for two weeks; Group B received postoperative routine treatments only. The fracture zone in each group was compared by radiological, histological and immunohistochemical examinations.In Group A, bony callus and mature osteocytes without infiltration of inflammatory cells were observed in the fracture zone. Vascular endothelial growth factor (VEGF) was expressed mainly in the cytoplasm of osteoblasts, chondrocytes and osteocytes, and exhibited significant changes at different time points. The gray value of bony callus in Group A was 190.58 ± 7.52; that of Group B was 144 ± 8.11. Difference between the groups was statistically significant (P ⟨ 0.01). The content of malondialdehyde (MDA) in Group A was significantly lower than Group B (P ⟨ 0.01), and the activity of superoxide dismutase (SOD) in Group A was higher than Group B (P ⟨ 0.01) at four weeks. There were no significant differences in MDA content and SOD activity between groups at eight and 12 weeks.HBO₂ treatment of open tibial fractures in seawater can reduce the inflammatory reaction and reperfusion injury, and promote osteocytic proliferation and fracture healing.