2006 Volume 1 Issue 1 Pages 195-203
Over 7000 patients are suffering from osteonecrosis of the femoral head annually in Japan. The patients have to undergo surgical treatments if the femoral head collapsed. The mechanism of femoral head collapse is still unclear, although morphological and mechanical changes in the necrotic hard bones or the reparative soft tissues have been believed to cause this collapse. We analyzed three-dimensional morphological and mechanical changes in the metaphyseal cancellous bone during bone regeneration after traumatic osteonecrosis of young rat femoral head using a micro-CT. Morphological indices and apparent modulus were calculated based on parallel plate model and finite element model, respectively. Bone volume, trabecular thickness, and apparent modulus initially decreased on day 7 after osteonecrosis, and they gradually increased during regenerating process. These findings indicate that the structural rigidity of cancellous bone in the regenerative area transiently decreases after osteonecrosis. These changes possibly induce femoral head collapse. The reparative area should be a target to treat osteonecrosis of the femoral head.
