[Relationship between the bone mass and the expressions of vascular endothelial growth factor, basic fibroblast growth factor, and bone morphogenetic protein 2 mRNA in avascular necrosis of femoral head].

OBJECTIVE

To study the expression changes of vascular endothelial growth factor (VEGF), basic fibroblast growth factor (bFGF), and bone morphogenetic protein 2 (BMP-2) in femoral neck fracture, traumatic, and non-traumatic avascular necrosis of femoral head (ANFH), and to study the relationship between the expressions of VEGF, bFGF, BMP-2 mRNA and bone mass so as to explore the pathogenesis of ANFH and provide the experimental basis for individual treatment of ANFH.

METHODS

Femoral head specimens were obtained from 59 donors undergoing total hip replacement, including 22 cases of traumatic ANFH (group A, 13 cases of Ficat stage III and 9 cases of Ficat stage IV), 19 cases of non-traumatic ANFH (group B, 11 cases of Ficat stage III and 8 cases of Ficat stage IV; 10 cases of steroid-induced ANFH, 7 cases of alcoholic ANFH, and 2 cases of unexplained ANFH), and 18 cases of fresh femoral neck fracture (group C). There was no significant difference in the general data among 3 groups (P > 0.05). The bone mineral density (BMD) at weight-bearing area of the femoral head was measured with dual energy X-ray absorptiometry. The pathological changes were observed by using optical microscope and scanning electron microscope. The percentage of empty bone lacuna and the percentage of trabecular bone area were calculated. The expressions of VEGF, bFGF, and BMP-2 mRNA in femoral head were detected by use of in-situ hybridization technique.

RESULTS

The BMD in groups A and B were significantly lower than that in group C (P < 0.05), and there was significant difference between group A and group B (P < 0.05). In the necrosis area of groups A and B, the bone trabecula was rarefactive and not of integrity, with a great number of empty bone lacuna. In healthy area, more fiber hyperplasia was observed in group A, the proliferated and hypertrophic fat cells in the medullary cavity in group B. Scanning electron microscope showed that many osteocytes underwent fatty degeneration and necrosis, and that the proliferation of fat cells in bone matrix was observed in groups A and B. While in group C, the femoral head had intact articular cartilage and intact bone trabeculae, and osteocytes were clearly seen. The percentage of empty bone lacuna was significantly higher (P < 0.05) and the percentage of trabecular bone area was significantly lower (P < 0.05) in groups A and B than group C; and there was significant difference in the percentage of empty bone lacuna between groups A and B (P < 0.05). The expressions of VEGF, bFGF, and BMP-2 mRNA were significantly lower in groups A and B than group C (P < 0.05), and the expressions of BMP-2 and bFGF mRNA in group A were significantly higher than those in group B (P < 0.05). There were positive linear correlation between the expressions of VEGF mRNA, bFGF mRNA, BMP-2 mRNA and the BMD and percentage of trabecular bone area, respectively. While there were significantly negative correlation between the expressions of VEGF mRNA, bFGF mRNA, BMP-2 mRNA and percentage of empty bone lacuna.

CONCLUSION

The repair capacity of local femoral head in traumatic ANFH is stronger than that in non-traumatic ANFH. The expressions of VEGF mRNA, bFGF mRNA, and BMP-2 mRNA decline in traumatic and nontraumatic ANFH.