Kyocera Corporation

University of California

Ian C Clarke

Hirokazu Amino

Harlan C Amstutz

Yoshinori Shiraiwa

An artificial knee joint comprising a femur member to be secured to the distal portion of a femur and a tibia member to be secured to the proximal portion of a tibia, wherein the femur member is made of alumina ceramics or zirconia ceramics, and the tibia member is a combination of a sliding section made of high-density polyethylene and a seat section made of titanium, titanium alloy, cobalt-chromium alloy or stainless steel. With this joint, the service life of the tibia member can be extended significantly. This disclosure also includes a modified embodiment of the above-mentioned artificial knee joint that includes reinforcing ribs with a special cross sectional shape to increase resistance against bending force applied to the femur member.

Artificial knee joint

An artificial hip joint of the type wherein a metal stem is fitted into the tapered hall of a ceramic stem head via a tapered cone in the stem, the hip joint being characterized in that the tapered stem engages the tapered hall in the deeper portion of the tapered hall, whereby the compression strength (fracture load) of the stem head is improved. Deep engagement of the tapered stem within the tapered hall is accomplished by, for example, making the angle of the taper of the tapered cone slightly smaller than that of the tapered stem. Preferably, the angle of taper of the tapered cone is smaller than that of the tapered hall by about 40 minutes or less. In addition, the diameter at the base of the hall is enlarged to form a cavity.

Artificial hip joint

In an artificial hip joint, in which a tapered cone of a metallic stem is inserted into a tapered hole of a ceramic stem head to be fixed, a truncated conical sleeve having a thickness of 50 .mu.m to 5.0 mm is compressedly held between a wall surface of the tapered hole and an outer circumferential surface of the tapered cone such that they are taperedly engaged with each other. With this artificial hip joint, an increased strength of the stem head, easy production, miniaturization, increased useful life time, safety in use, and the protection of the tapered cone are achieved.

A complete shoulder joint replacement includes a metal ball and stem for securing at the upper end of the upper arm bone or humerus, with the shape of the ball being spherical at the top and of elliptical cross-section at the juncture with the surface of the upper arm bone; and a concave plastic prosthesis having a keel of generally elliptical cross-sectional configuration matching the shape of the corresponding glenoid recess in the scapula, or shoulder bone. The metal prosthesis which is secured in the upper arm or humerus has a rounded metal stem with a longitudinal rib to prevent rotation and three fins under the head to further assist fixation. The matching glenoid prosthetic replacement is elliptical, both at the articulating surface and within the glenoid recess, to conform to the natural shape of the joint. Fixation grooves encircle the fixation keel, and the keel may be clipped off at the fixation grooves to accommodate various depths of the glenoid recess in the scapula bone. The glenoid prosthesis may be either relatively open, which is the preferred configuration, or somewhat hooded, depending on the strength and development of the 'rotator cuff,' the musculature and associated ligaments and the like which hold the relatively unconstrained shoulder joint in position.

Natural shoulder joint prosthesis

In the replacement of the hip joint, full access to the hip joint is obtained by separating the trochanter, a large protruberance on the upper portion of the upper leg bone, or femur, from the remainder of the femur, and the subsequent dislocation of the hip joint. Following dislocation, a minimum amount of bone is removed from the femoral ball and sufficient bone is removed from the socket to accommodate the minimum thickness surface replacement elements. A thin hollow inert metal ball or shell member having an outer diameter close to that of the original hip joint is then cemented onto the upper end of the femur, and an ultra high molecular weight polyethylene cup is cemented into the hip bone socket, with acrylic bone cement. To achieve maximum strength with minimum thickness, both the metal and plastic surface elements, although spherical at their mating surfaces, are thicker at their maximum load bearing points toward the top, and are of lesser thickness elsewhere. The two joint surface elements which are both generally hemispherical, have inner and outer surfaces which are both eccentric and asymmetric, with the thicker portion of the plastic liner being about 45.degree. off the central hemispherical axis, and the thicker portion of the metal shell being its upper portion.

Growing community of inventors

Santa Monica, CA, United States of America

Ian C Clarke