Abstract: A prosthesis includes an elongated shaft terminating in a proximal end and a distal end. The shaft has a center axis and an outer surface provided with grooves having side walls forming an essentially wedge-shaped cross section terminating in a bottom edge line. The grooves extend substantially longitudinally on the outer surface from the proximal end to the distal end in a substantially uniform density. The bottom edge lines are oriented toward the center axis, whereby a separate imaginary plane longitudinally dividing each groove contains both the center axis and the respective bottom edge line. The number of grooves in an imaginary angular sector, having a vertex line coinciding with the center axis, increases with increasing distance of the outer surface from the center axis. The proximal end has an enlarged surface region and the grooves extend from the distal end upward toward the enlarged surface region.