Prosthetic joint

Abstract

A joint prosthesis comprising, e.g., a femoral component and a tibial component. The medial and lateral condylar articular surfaces may have substantially uniform and equal radii from full extension to about 90° of flexion. From 90°, the lateral condylar articular surface has a smaller radius than the medial condylar articular surface such that the medial condyle gradually becomes increasingly more proud than the lateral condyle to facilitate internal rotation of the tibia at deep flexion. Also, the tibial articular component may include a post intermediate the medial and lateral compartments that engages a cam on the femoral articular component between the medial and the lateral condylar articular surfaces. The cam and post become congruent at flexion angles of approximately 70° flexion and mate symmetrically during the first 20°-30° of further flexion, and then mate asymmetrically at greater degrees of flexion to force internal rotation of the tibia.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS[0001]This application is a divisional of U.S. application Ser. No. 13 / 358,777, filed Jan. 26, 2012, the entire disclosure of which is fully incorporated herein by reference.FIELD OF THE INVENTION[0002]The present invention relates generally to total joint replacement orthopedic prosthetics. More particularly, the invention relates to a total knee replacement (TKR) implant for use total knee arthroplasty (“TKA”).BACKGROUND OF THE INVENTION[0003]Disease and trauma affecting the articular surfaces of a joint, such as the knee joint, often are treated by surgically replacing the articular surfaces of the bones that meet at the joint, such as the femur and tibia of the knee joint, with prosthetic femoral and tibial implants, referred to as total knee replacements (“TKR”).[0004]In total knee replacement (TKR) surgery, a surgeon typically will surgically resect the distal end of the patient's femur (typically at a base angle orthogonal to the mechani...

AI Technical Summary

Benefits of technology

The present invention is a total joint replacement prosthesis that helps increase flexibility of the joint and more closely emulate its natural movement. It includes features such as medial and lateral femoral condylar articular surfaces with equal radii up to about 90 degrees of flexion, and a ridge and groove design that forces internal rotation of the tibia relative to the femur and prevents posterior subluxation of the tibia. The invention also includes a femoral articular component with a ridge positioned intermediate the medial and lateral condyles and a mating groove disposed between the medial and lateral tibial articular surfaces.

Problems solved by technology

In a natural knee, the relative movement of the femur, tibia, and patella (the knee cap) is a complex combination of flexion-extension, translation, and rotational movements in all six degrees of freedom and is difficult to emulate with a prosthesis.

However, current technology and materials for prosthetic knee articular components are not sufficiently advanced to provide shape change functionality.

Also, most TKR implants do not provide an extension-flexion range anywhere near the roughly 165° range of motion of a natural knee.

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