ANIMAL MODELS

HISTOMORPHOMETRIC CHANGES OF BONE MARROW FAT CELLS IN CORTICOSTEROID-TREATED RABBITS WITH OSTEONECROSIS

Keita Miyanishi, Takuaki Yamamoto, Takahiko Irisa, Akihisa Yamashita, Seiya Jingushi, Yasuo Noguchi, Yukihide Iwamoto
Department of Orthopaedic Surgery, Graduate School of Medical Sciences, Kyushu University, Fukuoka Japan

This study was designed to determine whether the size of marrow fat cells differed between corticosteroid-treated rabbits with osteonecrosis and those without osteonecrosis. Forty-eight rabbits were intramusculary injected once with 20 mg/kg of methylprednisolone acetate, and 6 rabbits were injected once with physiologic saline as a control. Four weeks after the injection, both the femur and humerus were histopathologically examined for the presence of osteonecrosis, and the size of the marrow fat cells were measured. The incidence of osteonecrosis was 37 out of 48 rabbits (77%). The size of the marrow fat cells increased significantly more in the rabbits with ostconecrosis than in either the rabbits without osteonecrosis (P < 0.0001) or the control rabbits (P < 0.0001) and in the rabbits without osteonecrosis than in the control rabbits (P < 0.05). These results indicate that the enlarged marrow fat cells may contribute to the development of corticosteroid-induced osteonecrosis in rabbits.