Avascular necrosis associated with fractures of the femoral neck in children: histological evaluation of core biopsies of the femoral head.

There is no well-documented effective treatment for avascular necrosis following fractures of the femoral neck in children. Six children who suffered avascular necrosis following these fractures were treated with a long period of non-weight bearing. We tried to predict the advisable period of non-weight bearing by histological finding on core biopsy taken from the femoral head and present long-term follow-up results. The time interval for the biopsy ranged from 4 to 21 months after injury. Two specimens obtained within 1 year after injury showed total necrosis. The other four specimens taken more than 1 year after injury showed partial repair. Two specimens obtained from patients who had minimally displaced fractures also revealed necrotic tissue. Four patients were initially placed non-weight bearing for over 1 year. Two patients started weight bearing immediately after surgery, and late segmental collapse occurred within 1 year. They were then placed non-weight bearing for a further period in excess of 1 year. All patients, including those who had severely displaced fractures, avoided severe collapse of the femoral head. To avoid severe collapse of the femoral head due to avascular necrosis after pediatric femoral neck fractures, a long period of non-weight bearing of at least 1 year may be recommended treatment.