To observe capillary vessel changes in rabbits with hormone-induced avascular necrosis of femoral head and the possible mechanism involved in the treatment of the disorder with hyperbaric oxygen (HBO).

Forty-eight adult Japanese white rabbits were randomly divided into 2 groups: the experimental model group (n=36) and the control group (n=12). The animals in the experimental model group were injected with prednisolone acetate (10 mg/kg), twice a week and the animals in the control group were injected with physiological saline (2 ml) also twice a week for 6 weeks. Then, rabbits in experimental group were randomized into the HBO group (n=18) and the control group (n=18). The HBO group received HBO treatment for 6 weeks, while the control group was treated with normobaric air. Hemorrheology parameters, vascular endothelial growth factor (VEGF), changes in tissue pathology, as well as changes in radiographic imaging were detected at week 2, 4, 6, 8, 10 and 12 following experiment.

Features of hemorrheology for the model group deteriorated at weeks 2, 4 and 6. Endangium in the femoral head capillary vessel of the experimental group was disrupted, and there were thrombosis and osteoporosis in the femoral head. Optical microscopy revealed that the number of empty bone lacunae and fat cells increased, and some bone trabeculae were disrupted. Electron microscopy indicated that cell volume of the femoral head decreased and nuclei shrank, more osteocytes after necrosis occurred were dissolved into fragments. For the HBO treatment group, features of hemorrheology improved, and positive expressions of VEGF in large amounts could be detected in osteogenic cells and blood vessels on the surface of bone trabeculae in the femoral head, with the positive site being mainly located in endangium. Under optical microscope, repair of necrotic osteocytes could be found, and nascent osteocytes could be detected by transmission microscopy.

Large dosage of hormones could induce damage to endangium of capillary vessels, which might be an important reason for the necrosis of the femoral head in rabbits. HBO could promote the secretion of such cytokines as VEGF, accelerate revascularization and ossification, which might be an important theoretical evidence for the treatment of hormone-induced avascular necrosis of the femoral head by HBO.

Capillary vessel; Necrosis of femoral head; Hyperbaric oxygen; Vascular endothelial growth factor