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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. A method is described for inserting the tapered prosthesis whereby the central medullary canal of the diaphyseal portion of the bone is broached such that the sharp edges of the steps cut a groove in the surfaces of the bone and thus engage the dense bone of the inner surface of the diaphyseal medullary canal to resist torsional loads applied to the prosthesis.

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