An Experimental Study On Steroid-induced Avascular Necrosis Of Femoral Head Treated With Hyperbaric Oxygen In Rabbits

Objective To explore the pathogenesis of steroid-induced avascular necrosis of femoral head(ANFH) and the mechanism of treament of ANFH through hyperbaric oxygen(HBO) by producing and treating animal model of steroid-induced ANFH.Materials and methods 60 impubic Japanese rabbits were randomly devided into two groups:experimental group and control group.In experiment group, prednisolone was injected into mucle of each one in a dose of 10mg /kg body weighty times per week;in control, 2ml of salt water was injected into muscle of each one.Six weeks later,rabbits in experimental group were randomized to HBO group and control group.The control group was placed in the air,while HBO group receive HBO treatment,one time per day for two weeks as a period of treatment and three periods of treatment were completed.The hemorheological parameters,serum total cholesterol(TC) and triglyceride(TG) were determined at 2nd week ,4th week ,6th week, 8 th week and 12th week befor and after the treament. H.E staining,electron microscope examination and immunohistochemical staining for vascular endothelial growth factor(VEGF) were peformed on specimens of femoral head to observe pathological changes.Results At the end of 2nd week,4th week and 6th week, the serum TG and TC concentrations, blood viscosity in experiment group were higher than those in control group.Osteoporosis developed in experimental group.By light microscopy,empty lacunae increased and numbers of osteoblasts and subchondral sinusoids decreased in experimental group.Electron microscope examination showed that a proportion of osteocytes decreased in size with nuclei shrinking. Many osteocytes necrotized and becamed fragmented. Additionally,apoptotic osteocytes were observed and rate of osteocytes immunohistochemically positive for VEGF decreased.TG, TC, blood viscosity and plasma viscosity in HBO group decreased gradually.H.E staining indicated that osteoblast and osteoclast around trabecula of bones proliferated actively and fatty tissues reduced with hematopoiteic tissue regenerating.Electron microscopy examination exhibited existence of infantile osteocytes in trabecula of bones, sythensis of collagen fibers, newly-born capillaryvessels and increased rate of osteocytes positive for VEGF staining. Conclusions1 A large dose of hormone may produce avascular necrosis of femoral head in rabbits;2 Hyperviscosity and hemorheological parameters play an important role in the pathogenesis of avascularnecrosis of femoral head;3 Necrosis and apoptosis of osteocytes play a important role in the development and progression of ANFH;4 HBO may be helpful in the tissue repair of ANFH through increasing the oxygen tension in femoral head ,contributing to the formation of bypass circulation, improving local shortage of blood,increasing fibroblastic, osteoblastic and osteoclastic activities, enhancing the secretion of cytokines such as VEGF,which reaultingly expedite the healing of rabbit's necrotic femoral head.