Abstract: A prosthesis component for implantation into a bone canal has a tapered diaphyseal segment with one or more ridges, the ridges arranged coaxially from the distal to the proximal end of the diaphyseal segment of the component. Each ridge has a sharp longitudinal edge and at least one transverse sharp leading edge which forms a step that cuts into bone adjacent to the bone canal during implantation. The amount of taper of the outer dimensions of the ridges is controlled by the number and size of the steps and corresponds to an amount of taper of a bone canal into which the component is to be implanted. The outer edges of the ridges are parallel to the central longitudinal axis of the prosthesis component or divergent from this axis no more than 3.degree. from distal to proximal. In one embodiment the cross-sectional shape of the component is generally rectangular and in another, the cross-sectional shape is generally cylindrical.