Chondronecrosis of the hip. The protective role of the ossific nucleus in an animal model.

The presence of the ossific nucleus and its role in reducing the risk of ischemic necrosis in developmental dysplasia of the hip remains a matter of controversy. Ischemic necrosis of the pre-osseous capital femoral epiphysis, defined as chondronecrosis, was evaluated in a rabbit model. Histologic evidence of chondronecrosis after casting in maximum abduction was greater in 1-day-old New Zealand White rabbits before the radiographic appearance of the ossific nucleus, compared with 16-day-old New Zealand White rabbits with an ossific nucleus already present. This preliminary study supports the hypothesis that the ossific nucleus may decrease the risk of intracapsular compressive ischemic injury to the developing capital femoral epiphysis in a rabbit model.