Based on a 20 years old concept, the GAIA stem allows to obtain an optimal primary and secondary stability. Primary stabilityThe GAIA femoral stem has a strong primary stability due to quadrangular section with double taper on the proximal part, reducing constraints on the diaphyseal part. Secondary stability .The bone anchorage guarantees the secondary stability of the GAIA stem. This anchorage is obtained by the horizontal and vertical macrostructures, and also by the hydroxy apatite and titanium coating