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.

Abstract: Acetrabular cup as part of a hip joint prosthesis is composed of an outer support ring and a plastic inner socket insertable into the support ring. The acetabular cup includes a covering cap provided with at least one metal surface which covers the part of the inner socket not surrounded by the support ring and whose metal outer contour supplements the socket to give it the spherical shape of an essentially closed hemisphere or spherical cap.