| Objectives:To establish a reliable and approximated to pathological changes of known human femoral head osteonecrosis rabbit model of osteonecrosis of the femoral head (ONFH) by a novel liquid nitrogen freezing method.Methods:Twenty-one New Zealand white rabbits have been recruited in this study. Gluteus muscles were bluntly separated aseptically and the bilateral round ligaments of femur were cut off and the femoral heads were exposed. Thereafter, medical cotton stickers were dipped with liquid nitrogen and the weight loading area of bilateral femoral heads cartilage were frozen by three times alteration of freezing and rewarming. The rabbits were randomly selected and the femoral heads were examined through X-ray photography at3,7days,2,4,6,8weeks post-operation. Then The femoral heads of the model were taken by surgery and examined by gross morphology. Immediately after being routinely embedded in paraffin, complete serial sections of femoral heads were cut and stained with H&E, then the histopathology of the sections were observed under macroscopy and light microscope, respectively.Results:X-ray photography showed that the femoral heads were not distinct changes at3,7days. The bone density of femoral heads increased at2weeks, and was not uniform at4weeks post-refrigeration. After6weeks, the femoral heads presented irregular shape, marginal lucent area and began to collapse. Then obviously collapsed joint surface, widened joint space, and blurred epiphyseal plate were observed at8weeks post-refrigeration. Gross morphology manifestly demonstrated a aggravating cartilage and bone injury of femoral heads with time elapsed. Histopathologic results showed that necrosis of chondrocytes and osteocytes occurred at3days after freezing, and empty osteocyte lacunae appeared apparently at7days. Defected articular cartilage, engorged small vessels in the subchondral area, severed and disarranged bone trabeculae could be observed after2weeks. Articular cartilage exfoliation, adipocytes necrosis, and fibroplasias in medullary cavity appeared at4weeks. Collapse of femoral heads happened and fibrosis bones creeping substitution were visible at6weeks. Depository growth of new bone could be seen and cells dwelled in epiphyseal plate become crushing and deformation at8weeks.Conclusions:The novel rabbit model of ONFH by liquid nitrogen freezing method presented here posses lower trauma, approximated to pathological changes of human ONFH, and could be used in ONFH therapeutic related studies including stem cell transplantation in the future. |
