Endoprosthesis for a hip joint, especially for the hip joint of a human being

Claim 1

A femur head cap for a hip joint endoprosthesis which can be implanted without cement, comprising: an inner plastic shell to be placed on a femur head, said inner shell including a top section the inner surface of which conforms to the end face of the femur head and the outer surface of which is generally hemispherically shaped, and a jacket extending from said top section for fitting about a treated circumferential surface of the femur head, the inner surface of said jacket conically narrowing in the direction away from said top section, said inner shell having a slot which extends between the free edge of said jacket and the center of said top section to enable said jacket to expand to slip over the largest diameter of the femur head when said inner shell is placed over the femur head; and a metallic outer shell having a generally hemispherical inner surface which corresponds to the outer surface of said top section of said inner shell so that said outer shell can be fitted over said top section, said outer shell also having a generally hemispherical outer surface wherein the height of said outer shell as measured from the free end plane to the center of the outer surface of said outer shell is less than the radius of curvature of the outer surface of said outer shell, said outer shell including an end section adjacent the free end thereof for engaging the outer surface of said jacket of said inner shell, the inner surface of said end section conically narrowing in the direction toward the free end of said outer shell, and a pin extending from the center of the inner surface of said outer shell for engaging said inner shell when said outer shell is fitted over said inner shell to operatively align both of said shells.