Histological and ultrastructural changes in steroid-induced necrosis of the femoral head in adult rabbits

ABSTRACT

BACKGROUND:

Femoral head necrosis can be induced in adult rabbits when a large dose of steroid has been used for a long time. However, the pathogenesis of steroid-induced femoral head necrosis needs further study.

To probe into the mechanism of the disease by light microscope and transmission microscope from morphological perspective based on the model of femoral head necrosis in rabbits.

A randomized controlled observation.

Laboratory of Morphology; Teaching and Research Division of Pathology; Laboratory of Surgery, Weifang Medical College.MATERIALS The experiment was carried out at the Experimental Center of Morphology, Weifang Medical College, between March 2002 and March 2003. Totally 40 adult New Zealand white rabbits were randomly divided into control group (n=10), dexamethasone group (n=10) and horse serum group (n=20).

Control group was given intravenous injection of normal saline of 10 mL/(kg·d) for 7 consecutive days. Dexamethasone group was given intramuscular injection of dexamethasone of 10 mL/(kg ·d)for 7consecutive days. Horse serum group was given intravenous administration of horse serum of 10 mL/kg; 3 weeks later the same volume of horse serum was injected once again, followed intramuscular injection of dexamethasone of 10 mL/(kg·d)for 7 consecutive days. Inferior sections of cartilage of the femoral head necrosis in the experimental animals were obtained 5 and 10weeks later, and then histological and ultrastructural changes were observed under the light microscope and transmission microscope.MAIN OUTCOME

① Histo-morphological observation of the animals in each group. ② Ultrastructural changes.

All the experimental animals survived and entered the result analysis. ① Histo-morphological observation The cells of inferior sections of cartilage of the femoral head necrosis of the experimental animals in control group were arranged regularly and had a small volume of elliptical bone cells. The cell body was located at bone lacuna, blood vessel arranged well in the medullary cavity of bone. Lesion haracteristics of femoral head in dexamethasone group and horse serum group were similarHematopoietic adipose in the medullary cavity of bone was significantly decreased while fat adipose obviously increased; bone trabecula of metaphysis and the inferior sections of cartilage of femoral head were found with ered, and so was the bone nucleus. The number of lacuna of bone was increased. ② Ultrastructural changes Normal bone cells in control group were elliptical, located at bone lacuna. Nucleus was at one end of the cell with complete karyotheca and many mitochondria in the cytoplasm. In dexamethasone group and horse serum group there were lipid droplets in the osteocytes, narrowed blood capillary in the medullary cavity of bone and injured vascular endothelial cells.

Corticotropin can induce necrosis of femoral head; the hormone causes accumulated fat adipose in the medullary cavity of bone.The increased internal pressure in the medullary cavity leads to ischemia of femoral head, thus inducing the necrosis of osteocytes.