Preliminary application of radioimmunoscintigraphy with 99Tcm labelled anti-fibrin monoclonal antibody (SZ-63) in experimental steroid-induced osteonecrosis in rabbits

Objective: To evaluate the feasibility of radioimmunoscintigraphy of steroid-induced osteonecrosis with 99Tcm labelled monoclonal antibody against human fibrin (SZ-63) and to explore the mechanisms postulated in the pathogenesis of steroid-induced osteonecrosis. Methods: Experimental steroid-induced osteonecrosis was produced by intravenous horse serum combined with intraperitoneal high-dose of dexamethasone in 14 healthy adult rabbits, and then radioimmunoscintigraphy with 99Tcm-SZ-63 was performed. The acquired images were analyzed in comparison with histopathological findings. The other 5 healthy adult rabbits received injection of normal saline instead of horse serum or steroids were used as control. Results: The histopathological observation showed that 10 of 14 model rabbits (71.43%) had osteonecrosis in the femoral head (osteonecrosis group) and no osteonecrosis signs were found in the remaining 4 model rabbits (28.57%, non-osteonecrosis group) and either in the control group. In the osteonecrosis group, the radioactivity uptake increased markedly in both ends of the femur, especially in the femoral head 4 h after injection of 99Tcm-SZ-63. No abnormal signs were observed in both the non-osteonecrosis group and the control group. The radioactivity ratios of femoral head to trunk were 2.16 +- 0.35, 1.68 +- 0.29 and 1.57 +- 0.12 in osteonecrosis group, non-osteonecrosis group and control group, respectively. There was statistical difference between the former two groups (P < 0.05) but no difference between the latter two groups (P > 0.05). Conclusions: Steroid-induced osteonecrosis is correlative to thrombosis. Radioimmunoscintigraphy with 99Tcm-SZ-63 could specifically detect in vivo thrombosis of the steroid-induced osteonecrosis in the rabbit models, and it may provide a great potential of early noninvasive diagnosis of osteonecrosis and screening high-risk group of steroid-induced osteonecrosis