This paper aims to present an approximate mechanical description for a specific class of bone replacement materials. A porous type of them is studied because such replacements are of increasing importance in orthopedic surgery. One of the most important benefits of such implants is that their supposed mechanical properties (stress-strain distribution under various in vivo loading conditions) are assumed to be similar to the mechanics of real bones. The investigation encounters both scanning electron-microscopy (to present micro-structural geometry of a specimen) and standard thrust tests. Then from the experimental force-displacement curve we try to find a material model (constitutive equation) to give similar qualitative behavior. The results show the essential role of the geometry of micro-structures in modelling.