Fig. 1

Postoperative measurement: the distance between the center of rotation of the healthy femoral head to the vertical line across the midpoint of pubic symphysis (a1); the distance between the center of the prosthesis femoral head to the vertical line across the midpoint of pubic symphysis (a2); the diameter of the healthy femoral head (b1); the diameter of the prosthesis femoral head (b2); the thickness of the teardrop(c); the distance between the medial edge of prosthesis femoral head and the medial edge of the acetabular cup (d); the distance between the medial edge of the acetabular cup and the medial edge of teardrop (e)