Pathological fracture of the femoral neck as the first manifestation of osteonecrosis of the femoral head.

We describe two cases of pathological fracture of the femoral neck occurring as the first manifestation of osteonecrosis of the femoral head (ONFH). No abnormal findings suggestive of ONFH were identified on the radiographs for either of the patients, and the fractures occurred like spontaneous fractures without any trauma or unusually increased activity. The patients' medical history, age, and good bone quality suggested ONFH as a possible underlying cause of the fractures. If we had not suspected ONFH as a predisposing condition, these minimally displaced fractures might have been fixed internally with multiple pins, and this would have led to nonunion or collapse of the femoral head. To avoid inappropriate treatment, ONFH should be considered as a predisposing factor in pathological fractures of the femoral neck.