Establishing rabbit model of osteonecrosis of the femoral head by intraosseous liquid nitrogen freezing method

Abstract

Objective To establish the rabbit model of osteonecrosis of the femoral head (ONFH) by intraosseous liquid nitrogen freezing method. Methods One side femoral head of eighteen New Zealand rabbits was randomly selected for establishing the rabbit models of ONFH by intraosseous liquid nitrogen freezing method, and the another side as normal controls. After 2, 4, and 8 weeks after operation, gross, radiological and histopathological observations were observed. Results The normal side of the femoral head had no abnormal changes, and the number of empty bone lacunae accounted for (11.02±1.56)%. On the experimental side, X-ray showed that the femoral head density increased at the 2nd week. At 4th week, the cystic changes were seen and bone density increased. At 8th week, the bone density of the femoral head was uneven, and mild collapse of weight bearing area was found in 2 femoral heads. Histopathologically, at 2nd week, hematopoietic tissue decreased, bone trabecular necrosis and bone marrow focal necrosis, and empty bone lacunae increased significantly [(73.33±7.21)%] in the femoral heads. At 4th week, trabecular bone thinning and derangement were found, empty bone lacunae increased significantly [(81.52±7.35)%], and fibrous tissues were seen in the femoral heads. At 8th week, the necrotic area in the femoral head was significantly increased, trabecular bone became thinner, sparse and broken, and a large number of empty lacunae [(88.13±8.12)%] were seen. There were some hyperplastic connective tissue in the necrotic area, and repaired reaction in the peripheral of the necrotic area. There was no damage and stripping of the cartilage surface of the femoral head. On the experimental side, osteonecrosis appeared in the femoral heads. At 2nd, 4th, and 8th week, the lacunae count was significantly greater on the experimental side than that of the normal side (t2nd week=12.168, P2nd week=0.007; t4th week=13.048, P4th week=0.006; t8th week=13.048, P8th week=0.006). Conclusion Establishing the rabbit models of ONFH with intraosseous liquid nitrogen freezing method is simple and easy, which can simulate clinical early stage of ONFH and suitable for the standardizational treatment study. Key words: Liquid nitrogen freezing; Osteonecrosis of the femoral head; Models, animal; Rabbit