Relationships among magnetic resonance imaging, histological findings, and IGF-I in steroid-induced osteonecrosis of the femoral head in rabbits.
OBJECTIVE
To study the relationships among magnetic resonance imaging (MRI), histological findings, and insulin-like growth factor-I (IGF-I) in steroid-induced osteonecrosis of the femoral head in rabbits.


METHODS
Thirty rabbits were randomly divided into experimental Group A (n=15) and control Group B (n=15). The 7.5 mg/kg (2 ml) of dexamethasone (DEX) and physiological saline (2 ml) were injected into the right gluteus medius muscle twice at one-week intervals in animals of Groups A and B, respectively. At 4, 8 and 16 weeks after obtaining an MRI, the rabbits were sacrificed and the femoral head from one side was removed for histological study of lacunae empty of osteocytes, subchondral vessels, and size of fat cells under microscopy, and the femoral head from the other side was removed for enzyme-linked immunoadsorbent assay (ELISA) for IGF-I.


RESULTS
At 4, 8 and 16 weeks after treatment, no necrotic lesions were detected in Group B, while they were detected in Group A. Light microscopy revealed that the fat cells of the marrow cavity were enlarged, subchondral vessels were evidently decreased, and empty bone lacunae were clearly increased. The IGF-I levels in Group A were significantly higher than those in Group B. At 8 weeks after the DEX injection, the MRI of all 20 femora showed an inhomogeneous, low signal intensity area in the femoral head, and at 16 weeks, the findings of all 10 femora showed a specific "line-like sign". The MRI findings of all femora in Group B were normal.


CONCLUSIONS
MRI is a highly sensitive means of diagnosing early experimental osteonecrosis of the femoral head. However, the abnormal marrow tissues appeared later than 4 weeks when the expression of IGF-I increased. This reparative factor has an early and important role in response to steroid-induced osteonecrosis of the femoral head, and provides a theoretical foundation for understanding the pathology and designing new therapies.
Division of Neurobiology and Physiology, Institute of Neuroscience, School of Medicine, Zhejiang University, Hangzhou 310058, China. genius1174@163.com
Xing-can
XC
Chen
Jian
J
Weng
Xue-qun
XQ
Chen
Ji-zeng
JZ
Du
Miao-ping
MP
Zhu
Yong-qing
YQ
Pan
Miao
M
Liu
D000818:Animals; D003907:Dexamethasone; D004195:Disease Models, Animal; D005271:Femur Head Necrosis / Q000139:chemically induced / Q000378:metabolism* / Q000473:pathology*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008279:Magnetic Resonance Imaging; D011817:Rabbits; D013256:Steroids
D013256:Steroids; D007334:Insulin-Like Growth Factor I; D003907:Dexamethasone