ANIMAL MODELS

SERIAL MRI IN A NON-TRAUMATIC RABBIT OSTEONECROSIS MODEL

Takashi Sakai, Nobuhiko Sugano, Takashi Tsuji, Takashi Nishii, Nobuo Nakamura, Hideki Yoshikawa, Kenji Ohzono
Dept of Orthopaedic Surgery, Osaka University Medical School, Suita, Osaka, Japan

We investigated the time-dependent natural course of experimental osteonecrosis using serial repetitive MRI in a non-traumatic rabbit serum sickness osteonecrosis model. Some necrotic lesions were detected at 1 week (3 of 16 femora with necrotic lesions) and some in the metaphysis were detected by 12 weeks (2 of 6 femora with lesions) on non-enhanced images. On contrast-enhanced MRI, extravasation of the erythrocytes was detected at 72 hours (7 of 26 femora with lesions) as a small, focal enhanced area. Necrotic lesions were detected in all abnormal femora by 6 weeks (16 of 16 femora with lesions) as focal, homogeneously or inhomogeneously enhanced areas. Reparative tissue replaced with new vascular and trabecular formation in necrotic areas was detected as an extended marginal enhanced area at 12 weeks. These results suggest that the enhancement patterns on contrast-enhanced MRI may provide helpful information about the developmental and reparative process of clinical osteonecrosis.