The element comprises a columnar portion 4 and a convergent portion 12 having a gradually reduced cross-section in the direction of insertion such as a pointed or rounded tip. A central portion of the element is made from a metal or dense ceramic material and a surface portion 5 is made from a dense or porous biocompatible material such as glass ceramics or a calcium phosphate compound e.g. hydroxyapatite or fluoroapatite. Substantially the entire element may be of dense hydroxyapatite. The columnar portion may have a circular, square or rectangular cross-section and may have a groove or grooves configured as a spiral, rings or longitudinal recesses. A plurality of the elements may be inserted in an acetabulum to increase bone density prior to attachment of an acetabular cup. <IMAGE>
