Replacements for bicondylar joints in human limbs

Abstract

A surgical prosthesis or implant for replacing the natural components of a bicondylar joint in a human limb (leg or arm). Thus, a natural knee or elbow joint consists of two pairs of coacting load-bearing condyles. The prosthetic implant has two pairs of coacting male and female condylar components. The male and female components which replace the natural lateral condyles are spherical or spheroidal in shape to simulate a ball and socket joint, while the male and female components which replace the natural medial condyles are constituted by a rib or ridge and a groove. Both the rib and the groove are curved, in a plane normal to the general axis of the limb when straight or extended, to an arc of a circle centered on the center of articulation of the ball and socket, and are also curved in a plane parallel to the limb, the radius of the crest of the rib being less than the radius of the coacting base of the groove. Both male components and both female components can be formed on respective rigid carriers, or they may optionally be separate for individual fixation to the patient's limb.

I claim: 
     
       1. A replacement assembly for a bicondylar joint articulating two members of a human limb comprising two pairs of coacting male and female load-bearing condylar components,   the male components consisting of one spherical or spheroidal protruberance and one arcuate ridge having a curvature in each of two planes at right angles, one of said planes being normal to the general axis of the limb when straight and the other being parallel to the said axis,   the female components consisting of one spherical or spheroidal socket adapted to coact with the correspondingly shaped male component, and one arcuate groove being a curvature in each of the said two planes,   the curvature of the arcuate ridge and the arcuate groove in the plane normal to the general axis of the limb being an arc of a circle struck about the centre of the sphere represented by the spherical or spheroidal components.   
     
     
       2. A replacement assembly as claimed in claim 1 wherein the curvature of the crest of the ridge in the plane parallel to the limb is less than that of the base of the arcuate groove in the same plane. 
     
     
       3. A replacement assembly as claimed in claim 1 wherein the male components are formed integrally on a common carrier, and the carrier is adapted to be secured to the limb. 
     
     
       4. A replacement assembly as claimed in claim 1 wherein the female components are formed integrally on a common carrier, and the carrier is adapted to be secured to the limb. 
     
     
       5. A replacement assembly as claimed in claim 1 wherein the components representing the condyles on one half of the joint are of metal and the coacting components are at least coated with a low-friction synthetic plastic material. 
     
     
       6. A replacement knee joint assembly comprising lateral and medial pairs of coacting condylar components, the lateral pair comprising a male femoral component in the form of a spherical or spheroidal protruberance and a female tibial component in the form of a coacting spherical or spheroidal socket, and the medial pair comprising a male femoral component in the form of a ridge having a curvature in a plane normal to the axis of the femur and a curvature in a plane parallel to the axis of the femur and a female tibial component in the form of a coacting groove having a curvature in a plane normal to the axis of the tibia and a curvature in a plane parallel to the axis of the tibia, the curvatures in the planes normal to the axes of the femur and the tibia being arcs of circles of the same radius struck about the effective centre of rotation of the lateral condylar components. 
     
     
       7. A replacement knee joint assembly as claimed in claim 6 having integral fermoral condylar components united on the anterior side by a forward and upward curved trochlear extension the anterior surface of which has a shallow groove for locating the patella. 
     
     
       8. A replacement elbow joint as claimed in claim 1 having integral male condylar components for fixation to the humerus and separate female condylar components for fixation to the radius and ulna respectively. .Iadd. 9. A replacement assembly for a bicondylar joint articulating two members of a human limb comprising two pairs of coacting male and female load-bearing mechanical condylar components, the male components consisting of one spherical or spheroidal protruberance and one arcuate ridge having a curvature in each of two planes at right angles, one of said planes being normal to the general axis of the limb when straight and the other being parallel to the said axis, one of the female components being provided with a spherical or spheroidal socket adapted to coact with the correspondingly shaped male component and the other of the female components being provided with one arcuate groove having a curvature in at least one of the said two planes, the curvature of the arcuate ridge and the arcuate groove in the plane normal to the general axis of the limb being an arc of a circle struck about the center of the sphere represented by the spherical or spheroidal components. .Iaddend. .Iadd. 10. A replacement assembly as claimed in claim 9 wherein said at least one of the said two planes is the plane normal to the general axis of the limb. .Iaddend..Iadd. 11. A replacement assembly as claimed in claim 9 comprising a common carrier supporting the male components, the carrier being adapted to be secured to one of the members of the limb. .Iaddend..Iadd. 12. A replacement assembly as claimed in claim 1 comprising a common carrier supporting the female components, the carrier being adapted to be secured to one of the members of the limb. .Iaddend..Iadd. 13. A replacement assembly as claimed in claim 9 wherein one pair of said components is of metal and the coacting pair of components includes a lining of a low-friction synthetic plastic material. .Iaddend. .Iadd. 14. A replacement elbow joint as claimed in claim 9 having integral male condylar components for fixation to the humerus and separate female condylar components for fixation to the radius and ulna respectively. .Iaddend..Iadd. 15. A replacement knee joint assembly comprising lateral and medial pairs of coacting mechanical condylar components, the lateral pair comprising a male femoral component in the form of a spherical or spheroidal protruberance and a female tibial component in the form of a coacting spherical or spheroidal socket, and the medial pair comprising a male femoral component in the form of a ridge having a curvature in a plane intersecting the axis of the femur and a curvature in a second plane intersecting the first said plane and extending in generally the same direction as the axis of the femur and a female tibial component in the form of a coacting groove having a curvature in a plane intersecting the axis of the tibia, the curvatures in the planes intersecting the axes of the femur and the tibia being arcs of circles of the same radius concentric with the effective center of rotation of the lateral condylar components. .Iaddend..Iadd. 16. A replacement knee joint assembly as claimed in claim 15 comprising a forward and upward curved trochlear extension, said femoral condylar components being united on the anterior side by said trochlear extension the anterior surface of which has a shallow groove for locating the patella. .Iaddend.