Loop-up X-ray View of Osteonecrosis of Femoral Head

It is well known that in femoral head osteonecrosis patients, necrosis and collapse are usually located in the anterosuperior portion of the femoral head. We evaluated the usefulness of a “look-up” plane X-ray view of osteonecrosis for early detection of femoral head collapse. We examined 20 joints in 17 patients. Osteonecrosis was classified into four stages according to radiographic signs (demarcation line, crescent line, collapse and joint space narrowing). Eight joints were classified as stage 2 and 12 joints as stage 3. Collapse, crescent line and demarcation line were evaluated on three types of radiographs; ordinary anteroposterior (AP) and lateral views and the “look-up” view. Seventeen of the 20 hips clearly showed more than 2mm collapse on the “look-up” view. The incidence of clear collapse was higher than that on the AP view. The incidence of crescent line was also higher. There were no significant differences in the demarcation line between the look-up view and AP view. Magnetic resonance imaging and tomography are useful and routinely used to define necrotic lesions. However, the “look-up” view is a simple and inexpensive method for the early detection of femoral head collapse in osteonecrotic patients.