Abstract
Although late segmental collapse of the femoral head sometimes follows intracapsular fracture of the femoral neck, the mechanism of this lesion is not well understood. We obtained T1-weighted magnetic resonance imaging (MM) images of the femoral head after fracture of the femoral neck and classified the signals into four patterns to investigate the sequential changes of the femoral head. The T1 -weighted MM images obtained initially after femoral neck fracture showed a normal pattern in 10 of the 15 hip joints studied, a homogeneous pattern in one hip joint, an inhomogeneous pattern in three hip joints, and a band pattern in one hip joint. MM images obtained subsequently still showed the normal signal pattern in eight of the 10 hip joints which had shown the normal pattern in the first MM, while two of the 10 joints subsequently showed a band pattern. The joint with the homogeneous pattern in the first MM subsequently showed a band pattern. Of the three joints with an inhomogeneous pattern in the first MM, two joints showed a subsequent band pattern, and the other a normal pattern. The joints which showed a band pattern continued to show a similar band pattern. Eventually, all hip joints studied showed a normal or band pattern within six months after intracapsular fracture of the femoral neck. The joints which showed a band pattern in the first MM continued to show a similar band pattern in the subsequent MM, without any change. Collapse occurred in one hip joint which showed an extensive band pattern. Plain X-rays showed collapse of one of the joints with a band pattern in the MM image. It was therefore suggested that necrosis may be present histologically in the femoral head after fracture of the femoral neck even when no abnormalities are present in plain X-rays. Based on the above results, it is considered necessary to follow-up patients with femoral neck fracture with MRI for at least six months until the normal or band pattern is observed. Since hip joints with an extensive band pattern are susceptible to collapse, it is neces-sary to monitor such patients carefully.
