Endoprosthetic elbow joints

In an elbow joint in the form of an endoprosthesis having at least one hinge joint provided with anchoring shanks of which one is to be connected to the humerus and the other is to be connected to the ulna of a patient, and a hinge pin which connects the shanks together and defines the axis thereof, the hinge joint having a central mounting bore extending through its mounting parts for receiving said hinge pin, the axis of the hinge joint taking the place of the flexing and extending axis of the natural arm, the improvement which comprises

• a rotary humeroradial joint connected to the hinge joint on the side thereof on which the patient's radius is situated, said rotary humeroradial joint being connected on its hinge side to the humeral section of the hinge joint and being provided with a spigot-like connecting member, on the side thereof adjacent the patient's radius, and a sleeve to be anchored in the radius and rotatably mounted therein with respect to said connecting member for engaging the latter and thereby transmitting forces from the radius to said rotary humeroradial joint,
• said rotary humeroradial joint having in its mating region, at least on the side adjacent the radius, a spherical surface which covers the angular range of flexible movement of the patient's natural arm, and the upper end of said radius sleeve being provided with a joint cavity, the surface of which slides on said spherical surface as a mating surface, whereby said rotary humeroradial joint has at least two degrees of freedom, one of which allows pivoting movement of said rotary humeroradial joint by a radius shank thereof about the flexing and extending axis of the hinge joint, and of which the other allows rotary movement by said radius shank about the longitudinal axis of the patient's radius, and a further degree of freedom which allows axial movement by said radius shank along the longitudinal axis of the patient's radius.