Spherical knee joint prosthesis

A replacement knee prosthesis assembly for replacing an earlier implanted prosthesis, the replacement prosthesis comprising:

• a tibial implant and a femoral implant cooperatively configured to enable a first and a second articulation between said tibial implant and said femoral implant,
• said femoral implant comprising a bicondylian part comprising a pair of condyles disposed so as to define an intercondylian notch and a posteriorly extending hemispherical cavity central of the pair of condyles, and
• said tibial implant comprising a tibial base, a catch mounted to said tibial base, and at least one disc removably mounted to said tibial base and on which said pair of condyles is rotatably slidable to provide said first articulation,
• said catch comprising an end portion, and a spherical head having a conical cavity for accommodating the end portion of the catch and rotatably accommodated within said central cavity of said pair of condyles so as to provide said second articulation, and
• said spherical head being selected from a set of heads whose cavities have different opening angles in order to permit the heads to ride higher or lower on the catch due to the different size cavities, and therefore an adjustment of the height of said spherical articulation for obtaining a proper ligamentary tension.

A replacement knee prosthesis kit assembly for replacing an earlier implanted prosthesis, the replacement prosthesis comprising:

• a tibial implant and a femoral implant cooperatively configured to enable a first and a second articulation between said tibial implant and said femoral implant,
• said femoral implant comprising a bicondylian part comprising a pair of condyles disposed so as to define an intercondylian notch and a posteriorly extending hemispherical cavity central of the pair of condyles, and
• said tibial implant comprising a tibial base, a plurality of ball joint members mounted to said tibial base, and at least one disc removably mounted to said tibial base and on which said pair of condyles is rotatably slidable to provide said first articulation,
• said ball joint members being formed with a spherical head rotatably accommodated within said central cavity of said pair of condyles so as to provide said second articulation, and
• said ball joint member being formed in a plurality of heights and a plurality of tibial plates being formed in a plurality of thicknesses corresponding to the heights of the ball joint member in order to permit the heads to ride higher or lower on the ball joint member and therefor an adjustment of the height of said spherical head for obtaining a proper ligamentary tension.

A replacement knee prosthesis kit for replacing an earlier implanted prosthesis to enable a surgeon to adjust ligamentary tension, the kit comprising:

• a tibial implant comprising a tibial stem adapted to be introduced into the intramedullar canal of a tibia, and a tibial base attached to the stem and comprising a slide member,
• a set of tibial plates formed in a progression of thicknesses, each said tibial plate having a pair of conjugated surfaces and adapted to be received on the tibial base,
• a femoral implant comprising a stem attached to a pair of condyles and suitably shaped to slide and be articulated upon the conjugated surfaces, said condyles forming a hemispherical cavity, and
• a set of ball joint members formed in a progression of heights corresponding to respective of the tibia plates, each said ball member comprising a base plate member adapted to be slidably received in said slide member, and a spherical articulation head sized to be received in said cavity,
• said articulation heads being adapted to ride higher or lower on the tibial plate and therefor permit an adjustment of the height of said spherical articulation head whereby a surgeon can adapt a prosthesis to each patient without having to change the tibial stem for obtaining a proper ligamentary tension.