Subchondral Insufficiency Fracture of the Femoral Head Caused by Excessive Lateralization of the Acetabular Rim

Figure 1

Initial radiograph and magnetic resonance imaging (MRI) of the left hip. (a) Anteroposterior view of the left hip shows acetabular overcoverage due to extended lateralization of the acetabular margin (white arrow). (b) T1-weighted image shows bone marrow edema with diffuse low intensity expanding from the lateral aspect of the femoral head to the intertrochanteric area. An irregular, serpentine, low intensity band (white dotted arrow) is present in the subchondral area. (c) Short-tau inversion recovery (STIR) image shows high signal intensity corresponding to the area of low intensity in (b). Black asterisks indicate the bone marrow edema of the femoral head and intertrochanteric area. (d) No apparent labral tear at the extended rim was observed but the labrum was relatively small and thin on the T1-weighted image (white arrow).