Total hip joint replacement

A set of artificial ball and socket hip joint surface units comprising:

• an entirely thin walled asymmetric, eccentric substantially hemispherical, biologically inert metal shell having a smooth spherical exterior surface, and a grooved and dimpled internal surface, free of inwardly directed extended protrusions;
• the upper side of said shell to be located on the load bearing portion of the joint being substantially thicker than the lower side of said shell;
• and
• a plurality of thin asymmetric eccentric substantially hemispherical inert plastic liners, each having a smooth internal spherical surface to match the exterior surface of said shell with minimum clearance, each said liner having a thicker area on its upper side to be located at the upper load bearing portion of the joint, each of said liners being of a different thickness to approximate the amount of bone which may be removed from the hip socket, to locate the artificial hip joint in substantially the original hip joint diameter, each said liner being provided with external irregularities for locking each said liner in place.

An artificial surfacing for hip joints for mounting on the upper end of the femur comprising:

• a thin eccentric, asymmetric substantially hemispherical, biologically inert metal shell having a smooth spherical exterior surface, and an internal surface which includes interlocking recesses and grooves;
• said metal shell having an upper side wall which is substantially thicker than its lower side wall,
• the maximum thickness of said metal shell being less than 10 millimeters;
• and
• said metal shell having a spherical extend slightly greater than hemispherical, and being provided with an inner groove extending generally parallel to its edge to facilitate firm securing of the shell in position, and said shell being free of inwardly directed extended protrusions, whereby said shell will interlock with but not divide or compartmentalize cement with which it may be used.

A method of total hip joint replacement involving a minimum removal of bone from a patient's hip joint surfaces comprising:

• dislocating the hip joint to expose the diseased joint surfaces;
• reaming a minimum amount of diseased bone from the surface of the head of the femur with precision cylindrical and tapered reamers, and from the surface of the pelvis hip joint socket to expose health firm bone surfaces,
• selecting a thin asymmetric, eccentric, substantially hemispherical biologically inert metal shall having an inner diameter matched to the size of said cylindrical and tapered reamers, and an outer diameter substantially equal to the original diameter of the mating ball and socket surfaces of the patient's hip joint, and with the inner surface of said metal shell being free of inwardly directed extended protrusions;
• cementing said thin metal shell over the head of the femur, with the thicker portion of the metal shell located at the superior or load bearing area of the head of the femur;
• selecting an asymmetric eccentric substantially hemispherical high strength biologically inert plastic liner having an inner diameter giving minimum clearance relative to the outer diameter of said metal shell, and having a thickness approximately equal to the thickness of the diseased bone layer which was removed;
• cementing said plastic liner into the hip socket with the thicker portion of said liner being oriented at the superior or load bearing area of the socket;
• and
• engaging said metal shell and plastic liner.