The preoperative planning for total hip replacement is an aspect crucial for the outcome of operation. In these days, the planning is carried out by referring to medical images in twoor three-dimensions, and the geometrical fitting at the operation is examined in detail a priori. It, however, is not straightforward to examine the mechanical fitting at the stage of preoperative planning. Computational stress and strain analyses are providing some insights for mechanical fitting at the time of operation and for the short term stability but little for the long term mechanical fitting in which the bone loss is a critical feature. This study is designed to explore a biomechanical index to examine the difference of bone loss after total hip replacement based on different feasible plans considered by surgeons, by means of computational biomechanics simulation. Method