Hard substance multi-hooded enarthrodial joint implant

A hard substance joint head for an enarthrodial joint implant having a hard substance double-hooded articular cup, which comprises a head body that is a suitable biocompatible, rigid, hard, strong material other than ceramic, configured generally in a shape of a truncated sphere;

• a generally spherical articulation surface on the head body;
• and a truncation to the head body forming a truncated surface in which resides a blind frustoconical hole for receipt of a trunnion of a stem, wherein the truncated surface is at a central truncation distance extending from a peak of the spherical articulation surface to a center of the truncated surface, wherein the central truncation distance is perpendicular to the truncated surface and is about from 60% to 85% of the head diameter;
• the joint head is configured for insertion into and retention by the hard substance double-hooded articular cup that is adapted and configured to be fixed when implanted into a patient such that the cup is fixed with respect to the patient directly or with respect to a backing shell in which the cup resides when the backing shell is present and fixed directly to the patient, which has an articular surface upon which the articulation surface of the joint head can articulate, and which has a margin generally about a hemisphere and two and only two generally opposing hoods that are marginally extended continuations of superior about one-half of cup containment of a sufficient magnitude to reduce an overall dimension of socket outlet to less than a hemisphere, which can embrace and contain the joint head when the joint head is inserted into the cup, and wherein there is no securing member present for resistance against any likelihood of cracking, fracture, or other failure of the hard substance by application of outwardy displacing force on the hoods.

A hard substance enarthrodial joint implant device comprising at least one of A) a double-hooded articular cup of a first hard substance that is a first suitable biocompatible, rigid, hard, strong material;

• and B) an insert having a head of a second hard substance that is a second suitable biocompatible, rigid, hard, strong material with an articulation surface therefor—wherein;
• the cup includes a head-receiving cup made of the first hard substance, which is adapted and configured to be fixed when implanted into a patient such that the cup is fixed with respect to the patient directly or with respect to a backing shell in which the cup resides when the backing shell is present and fixed directly to the patient, which has an articular surface upon which the articulation surface of the head can articulate, and which has a margin generally about a hemisphere and two and only two generally opposing hoods that are marginally extended continuations of superior about one-half of cup containment of a sufficient magnitude to reduce an overall dimension of socket outlet to less than a hemisphere, which can embrace and contain the head when the head is inserted into the cup;
• the insert includes a joint head made of the second hard substance, which has a head body configured generally in a shape of a truncated sphere;
• a generally spherical articulation surface on the head body;
• and a truncation to the head body forming a truncated surface in which resides a blind hole for receipt of a trunnion of a stem, wherein the truncated surface is at a central truncation distance extending from a peak of the spherical articulation surface to a center of the truncated surface, wherein the central truncation distance is perpendicular to the truncated surface;
• and the head can be inserted into and retained by the hard substance double-headed articular cup when the head is inserted into the cup;
• the first and second hard substances are the same as or different from the other, with, at least one of the first and second hard substances being as follows:
• in all enarthrodial joint applications, alumina, a silicon nitride ceramic, or a zirconia ceramic other than MgO-TTZ;
• and
• provided that the device is an enarthrodial joint component or ensemble other than that for a hip, MgO-TTZ;
• and
• there is no securing member present for resistance against any likelihood of cracking, fracture, or other failure of the hard substance by application of outwardy displacing force on the hoods.