Establishment Of Rabbit Model Of Avascular Necrosis Of Femoral Head In Children And Exploration For Pathogenesis

ObjectiveTo establish model of avascular necrosis of the femoral head in juvenile rabbits induced by glucocorticoid (GC), and detect the expression of glucocorticoid receptor (GR) in the femoral head. To explore the possible etiology of avascular necrosis of the femoral head in children.MethodsSixty New Zealand albino rabbits(50%female and50%male), two months old (1.4-1.7Kg) were randomly divided into2groups:steroid injection group (SIG) and control group (CG). The steroid injection group (n=48):Prednisolone acetate of7.5mg/kg was injected into each rabbit twice a week for eight weeks. The control group (n=12):Normal saline of0.30ml/kg was injected into each rabbit twice a week for eight weeks. X-ray and CT examination were performed at2,4,6, and8weeks after the first injection. Four rabbits of the steroid injection group and two of the control group were sacrificed after2,4,6weeks respectively, and the others were sacrificed after8weeks. The femoral head cartilage and the subcartilaginous bone were examined by histopathology and transmission electron microscope (TEM). The immunohistochemistry and image analysis were used to detect the expression of GR, TUNEL technology was used to inspect the apoptosis level of the bone cells and cartilage cells. According to Diagnosis adopted the diagnostic criteria for non-traumatic necrosis of femoral head from the Japan Association of osteonecrosis multi-center, the SIG was divided into disease group (DG) and non-disease group (NDG). The expression of GR were compared among DG, NDG and the CG, and the level of apoptosis of the femoral head bone cells were observed.Results1. According to the principle of non-traumatic necrosis of femoral head from the Japan Association of osteonecrosis multi-center7of31rabbits developed femoral head avascular necrosis in steroid injection group, the incidence is22.58%. 2. In SIG bone mineral density of femoral head was increased evenly and bone texture was disappeared. Epiphysis of femoral head was smaller and hip clearance was wider than CG. The height of epiphysis was also decreased. Along with the prolonged glucocorticoid given, symptoms were gradually increase.3. Bone trabeculae become sparser and thinner, some of them were fractured and irregular in SIG. Along with the prolonged glucocorticoid given, symptoms were gradually increased. At the end of8th week, there were statistical difference at proportion of bone trabeculae between SIG and CG (P<0.01). Osteocyte karyopyknosis, transformation and marginated were observed in DG. Compared with CG, NDG and normal side of DG, the empty lacunae were more in DG (P<0.01).4. Bone cells were shrinked, cell membrane were not integrity, organelle were undetected, karycotheca was broken and separated.chromatin was condensed and marginated.Lipid was found in some osteocytes.5. The expression of GR was detected in diseased side of articular cartilage in DG. The expression of GR was extremely low or undetectable in normal side of DG. NDG and CG (P<0.01).6. Apoptosis of femoral head cartilage cells and osteocyte was apparently in diseased side of DG compared with normal side of DG, NDG and CG.(P<0.01).Conclusion1. Simple gluteal injection of GC can lead to juvenile rabbits avascular necrosis of femoral head.2. GC and GR might play an important role in the onset and development of avascular necrosis of femoral head in juvenile rabbits.3. Apoptosis of femoral head cartilage cells and osteocyte could contribute to avascular necrosis of femoral head.