Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2002-11-19
2004-08-03
Stewart, Alvin (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S020140
Reexamination Certificate
active
06770099
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates generally to orthopedic prosthetic devices. More specifically, the invention relates to a femoral orthopedic knee implant for use in conjunction with a total knee arthroplasty (“TKA”), wherein the femoral component is designed to accommodate a broader range of knee flexion than femoral components known in the art.
2. Description of the Related Art
Disease and trauma affecting the articular surfaces of the knee joint are commonly effectively treated by surgically replacing the articulating ends of the femur and tibia with prosthetic femoral and tibial implants, referred to as total knee replacements (“TKR”). These implants are made of materials that exhibit a low coefficient of friction as they articulate against one another so as to restore normal, pain free, knee function.
As a knee joint moves through a ROM, the angle of the distal femur relative to the mechanical axis of the person's leg changes. During high flexion, this change is even more pronounced. For example, as a person's natural knee is moved through a ROM from about 0° to about 155°, the angle of femoral rotation about the transverse axis which is perpendicular to the mechanical axis of the person's leg may move from about 10° at to about 30°.
Most TKRs, however, include femoral components that are designed to accommodate knee joint articulation from a position of slight hyper extension to approximately 115° to 130° of flexion. However, the healthy human knee is capable of a range of motion (“ROM.”) approaching 170° of flexion, and a ROM in around 155° is required for deep kneeling and squatting as may be required during some sporting, religious or cultural events.
There is a need, therefore, for an improved TKR femoral component that accommodates knee °flexion, under optimal conditions, of more than 130° (“high flexion”).
SUMMARY OF THE INVENTION
The present invention comprises, in one embodiment thereof, an improved femoral prosthesis for a TKR. The femoral component of the TKR comprises an internal non-articulating bone contacting surface adapted to receive a resected distal femur. In a preferred embodiment, the bone contacting surfaces of the femoral component include anterior, distal, and posterior chamfer surfaces, which may further comprise bone growth promoting surfaces attached thereto.
The femoral component further comprises anterior, distal, medial posterior and, lateral posterior articulating portions, referred to herein as medial and lateral posterior condyles. The medial and lateral condyles each comprise a unique “height.” The height of each condyle is measured from a line tangent to the distal articulating surface to the proximal tip of a particular condyle. The differences in the medial and lateral condylar height of a prosthetic femoral component according to the present invention permit a larger angle of femoral rotation in a TKR about the mechanical axis of a patient's leg. In addition, the extent to which the medial aspect of the lateral femoral condyle extends into the intercondylar region of the femoral prosthetic component is reduced in the present invention to accommodate high flexion.
An advantage of the present invention is that it allows greater rotation of the distal femur about a leg's mechanical axis. This greater rotation is necessary to, and therefore accommodates, high flexion in a patient's knee.
Other advantages and features of the present invention will be apparent to those skilled in the art upon a review of the appended claims and drawings.
REFERENCES:
patent: 5549688 (1996-08-01), Ries et al.
patent: 5681354 (1997-10-01), Eckhoff
patent: 6056779 (2000-05-01), Noyer et al.
patent: 6123729 (2000-09-01), Insall et al.
patent: 6152960 (2000-11-01), Pappas
patent: 6235060 (2001-05-01), Kubein-Meesenburg et al.
patent: 6402786 (2002-06-01), Insall et al.
Andriacchi Thomas
Donkers Ron
Harris James
Patmore Audrey
Steffensmeier Scott
Feuchtwang Jonathan D.
Stewart Alvin
Zimmer Technology Inc.
Zimmer Technology, Inc.
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