Fig. 1

Greater trochanter classification system adapted from human THR. On the craniocaudal radiograph (frontal plane), the anatomic axis of the femur was first determined. Two additional axes were created parallel to the anatomic axis. The first of these axes was placed tangential to the periosteal surface of the lateral cortex at the femoral isthmus, while the second was placed tangential to the endosteal surface of the lateral cortex at the femoral isthmus. These three parallel axes created four zones for trochanter classification (Grade I-IV) from the lateral to medial direction. The medial-most aspect of the greater trochanter was used as the reference point for classification