Traumatic and Non-traumatic Osteonecrosis in the Femoral Head of a Rabbit Model

Abstract

Osteonecrosis of the femoral head is an idiopathic, debilitating and progressive disease. A number of traumatic or non-traumatic animal models have been reported for research on osteonecrosis. This study was performed to compare the efficacy of femoral head osteonecrosis in rabbits by traumatic and non-traumatic methods. Twenty-seven New Zealand White rabbits were divided into three experimental groups, nine heads each. Two groups were surgically induced into osteonecrosis; a steel cerclage wire was ligated tightly around the neck of the right femoral head (Group W), and the femoral neck was tied with a cerclage wire in the same way as in the W group, and burned by attachment of an electrode tip to the wire and then the wire was removed (Group B). The other group was induced into osteonecrosis with a single intra-muscular injection of 20 mg/kg methyl-prednisolone acetate single injection (Group M). In the control group, the left femoral head of animals in group W and B was used. After two weeks, rabbits were sacrificed and the femoral head and neck were collected. Osteonecrosis of the femoral head was evaluated by radiography, histology and immunohistology methods. Osteonecrosis lesions in the femoral head were identified in traumatic models of groups W and B. Cartilage degeneration in the superficial layer and TUNEL positive cells in the femoral head were detected more in Group B than in Group W. These findings revealed that short-term induced osteonecrosis of the femoral head was effectively achieved by cautery around the femoral neck.

Keywords: animal model; bone; cartilage; osteonecrosis; rabbit.

Figure 1

Digital radiograghic appearances of the normal (A) and osteonecrotic (B) femoral head. Radiodensity is increased in the osteonecrotic femoral head. No collapse or change was observed in femoral head sphericity.

Figure 2

Histology of the epiphyseal region in the femoral head (H&E stain). Magnification ×400. A. Normal femoral head in the control group shows well stained nuclei of osteocytes and hematopoietic tissue, and normal trabecular bone and bone marrow. B. Osteonecrotic lesions in the femoral head of group B. The osteonecrotic lucanae are empty. Necrotic cells were observed in intertrabecular spaces.

Figure 3

Histology of the epiphyseal cartilage region in the femoral head (Safranin O stain). Magnification ×400. A. Articular cartilage of the normal femoral head. B. Degenerated articular cartilage with fibrillation and loss of glycosaminoglycans of the femoral head in group B.

Figure 4

The average necrotic score of each group in trabecular bone and cartilage of the femoral heads. W group: wiring induced group, B group: burning induced group, M group: steroid induced group. Necrotic bone and cartilage changes were found to be significantly high in the W group and B group, compared with the control and M group (P<0.05).

Figure 5

TUNEL labeling of the epiphyseal trabecular bone in the femoral head. Magnification ×400. A. No TUNEL positive cells or bone marrow cells were observed in the normal femoral head of the control group. B. TUNEL positive cells were observed. The TUNEL reaction shows apoptotic bodies in osteocytes and bone marrow cells.