Improperly placed acetabular component in THA could lead to dislocation, abnormal stress concentration and increased wear of the lining. For patients with acetabulum bone defect, medially and inferior placed acetabular component could broaden the contact area between bone and prosthesis so that decreased contact stress and better clinical outcome can be expected. Orientation of placed acetabular also influences its stress distribution and wear markedlyM.o st researchers recommend that the acetabular component should be placed at 40 45 for abduction and 5 20 for anteversion.