This study focuses on the effect of the hydroxyapatite coating with BoneMaster on the fixation of the hip prosthesis in primary hip alloplasty. A hemispheric joint cup of the type Exceed cup (Biomet) characterized by a porous surface of titanium plasma spray is used. The surface is coated with hydroxyapatite deposited electrochemically (BoneMaster) and will be compared with an identical cup without hydroxyapatite.