[Spontaneous epiphyseal injury as a complication of a simple bone cyst of the femoral neck? Case report and review of the literature].

A case of a spontaneous epiphyseal injury of the femoral neck in an 8-year-old boy is reported. The same boy had been seen 8 months before for a pathological fracture caused by a simple bone cyst of the femoral neck on the same side. At the second visit the boy showed spontaneous severe pain of the hip, and radiography was performed under the presumed diagnosis of a slipped capital femoral epiphysis. However, it demonstrated a separation through the growth plate cranially and a fracture through the metaphysis inferiorly, leading to the differential diagnosis of a Salter-Harris type II fracture despite a nontraumatic patient history.A review of the literature failed to reveal a similar report of simultaneous occurrence of a simple bone cyst and epiphyseal injury of the femur. However, slipping of the proximal humeral epiphysis in connection with a simple bone cyst has been described by some authors. We propose a pathophysiological model for the simultaneous occurrence of epiphyseal injury and a simple bone cyst. Physeal involvement by a simple bone cyst and varus deformity of the femoral neck could cause weakening of the growth plate and predispose for epiphyseal injury. Based on these findings, we suggest that a simple bone cyst of the proximal femoral metaphysis can develop into a severe condition. Children presenting with this clinical picture should be treated vigorously and monitored for the development of complications leading to epiphyseal injury.