Universal joint prosthesis

A universal joint prosthesis comprising:

• a hollow cup shaped cap, said cap having an outer surface and an inner surface, said inner surface being configured for attachment to a bone, said outer surface forming a section of a spherical surface and said cap having a cap axis;
• a plurality of projections positioned along a circumference of said inner surface, pairs of adjacent projections being arranged to define an indentation between each said pair of projections, said indentations defining a substantially acute angled dado profile in a cross-section perpendicular to said cap axis, a subset of said plurality of projections each define a through hole, each through hole having a hole axis line in a plane which passes through said cap axis;
• first and second stems having an end rigidly connected to said cap and extending from said cap into an inner space defined by said inner surface, said first and second stems being substantially straight and having an axis substantially parallel to said cap axis, said first and second stems being each formed as a sleeve and each sleeve having another end projecting out of said inner space, said each another end being opened, said each sleeve defining perforations.

A universal joint prosthesis comprising:

• a hollow cup shaped cap having an outer surface and an inner surface, said inner surface being configured for attachment to a bone, said outer surface forming a section of a spherical surface and said cap having a cap axis, said outer surface is formed of an outer material and said inner surface is formed in a major part of an inner material, said outer material includes one of ceramic and an alloy having cobalt as a main component, said inner material includes one of titanium, a titanium alloy and a mixture of tantalum and zirconium;
• a plurality of projections positioned along a circumference of said inner surface, said plurality of projections are shaped to include an undercut in a cross-section perpendicular to said cap axis, said plurality of projections being formed of said inner material;
• a stem having an end rigidly connected to said cap and extending from said cap into an inner space defined by said inner surface, said stem being substantially straight and having an axis substantially parallel to said cap axis, said stem being formed as a sleeve and has another end projecting out of said inner space, said another end being opened, said sleeve defining perforations, said stem being formed of said inner material.

A universal joint prosthesis comprising:

• a hollow cup shaped cap, said cap having an outer surface and an inner surface, said inner surface being configured for attachment to a bone, said cap having a cap axis;
• a plurality of projections positioned along a circumference of said inner surface, said plurality of projections being arranged on said inner surface in a plurality of rows, each of said plurality of rows being located in planes substantially parallel to said cap axis, each of said projections defining a hole and two undercuts, said hole of each of said projections having a hole axis substantially parallel to said cap axis, said two undercuts being positioned on opposite sides of said projection in a plane passing through said cap axis and said hole axis of a respective projection.