Necrosis of the head of the femur occurs less often if the fracture of the transcervical neck is immediately and accurately reduced and adoquately immobilized.

In the experiments carried out by the authors, necrosis with collapse of the weight-bearing portion of the cortex of the head occurred in two of six cases following accurate reduction of the fracture and pinning of the fragments, although the fracture united. In these two cases the head of the femur may have been viable when union occurred, but, with partially depleted blood supply, the minimal traumata of continued use and weight-bearing may have resulted in the necrosis and disintegration.

The prognosis for survival of the head of the femur is definitely less satisfactory if the reduction of the fracture is not anatomically correct or if pinning of the fragments is not adequate for complete immobilization.

Death of the head of the femur when the fracture was neither reduced nor immobilized was found to occur in nine of twelve hips studied. It is possible that weight-bearing activity and friction between the fragments may have ruptured blood vessels that were left intact after fracture in a portion of the posterior capsule. However, this theory does not explain the difference in incidence of necrosis in cases in which the head was pinned without accurate reduction and in those in which the head was pinned in an anatomically correct position.